U.S. patent application number 15/282175 was filed with the patent office on 2017-02-16 for process for making a poly(zwitterion/dianion).
This patent application is currently assigned to KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS. The applicant listed for this patent is KING ABDULAZIZ CITY FOR SCIENCE AND TECHNOLOGY, KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS. Invention is credited to SHAIKH ASROF ALI, SHAMSUDDEEN ABDULLAHI HALADU.
Application Number | 20170044277 15/282175 |
Document ID | / |
Family ID | 53480994 |
Filed Date | 2017-02-16 |
United States Patent
Application |
20170044277 |
Kind Code |
A1 |
ALI; SHAIKH ASROF ; et
al. |
February 16, 2017 |
PROCESS FOR MAKING A POLY(ZWITTERION/DIANION)
Abstract
A zwitterionic monomer and corresponding cyclopolymerized
polyzwitterion (.+-.) (PZ) (i.e. poly(Z-alt-SO.sub.2). Phosophonate
ester hydroloysis in PZ gave a pH-responsive polyzwitterionic acid
(.+-.) (PZA). The PZA under pH-induced transformation was converted
into polyzwitterion/anion (.+-.-) (PZAN) and polyzwitterion/dianion
(.+-.=) (PZDAN).
Inventors: |
ALI; SHAIKH ASROF; (DHAHRAN,
SA) ; HALADU; SHAMSUDDEEN ABDULLAHI; (DHAHRAN,
SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS
KING ABDULAZIZ CITY FOR SCIENCE AND TECHNOLOGY |
DHAHRAN
RIYADH |
|
SA
SA |
|
|
Assignee: |
KING FAHD UNIVERSITY OF PETROLEUM
AND MINERALS
DHAHRAN
SA
KING ABDULAZIZ CITY FOR SCIENCE AND TECHNOLOGY
RIYADH
SA
|
Family ID: |
53480994 |
Appl. No.: |
15/282175 |
Filed: |
September 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14144094 |
Dec 30, 2013 |
9481765 |
|
|
15282175 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08F 8/12 20130101; C08G
75/22 20130101; C08F 26/06 20130101; B01D 2321/168 20130101; C08G
75/205 20130101; C08G 75/20 20130101; B01D 65/02 20130101; C08F
226/06 20130101; C08F 26/04 20130101; C08F 8/44 20130101; C08F
226/04 20130101 |
International
Class: |
C08F 8/44 20060101
C08F008/44; C08F 8/12 20060101 C08F008/12 |
Claims
1-4: (canceled)
5: A process for making a poly(zwitterion/dianion) having the
following formula: ##STR00007## where n is an integer of 10 or
greater, the process comprising: copolymerizing a monomer of
formula (I) with SO.sub.2 in the presence of a polymerizing agent
to form a copolymer comprising alternating units of the monomer of
formula (I) and SO.sub.2, ##STR00008## wherein R is a C.sub.1 to
C.sub.6 alkyl group or a C.sub.6-C.sub.12 aryl group or an H group,
treating the copolymer with an acid solution to hydrolyze the
P(O)(OR).sub.2 groups of the copolymerized monomer units of formula
(I) to form groups of formula P(O)(OH).sub.2, then deprotonoating
the P(O)(OH).sub.2 groups with an alkaline solution to form the
poly(zwitterion/dianion).
6: The process of claim 5, wherein n is the number of repeating
units in the range of 20-1,500.
7: (canceled)
8: The process of claim 1, wherein the polymerizing agent is
tert-butyl hydroperoxide.
9: The process of claim 1, wherein the polymerizing occurs in a
solution of dimethylsulfoxide.
10: The process of claim 1, wherein the polymerizing agent is
azobisisobutyronitrile.
11: The process of claim 1, wherein the alkaline solution is an
aqueous solution of NaOH.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of Ser. No.
14/144,094, now allowed.
BACKGROUND OF THE INVENTION
[0002] Technical Field
[0003] The present invention relates to a zwitterionic monomer, a
polyzwitterion synthesized from the zwitterionic monomer, a
pH-responsive polyzwitterionic acid synthesized from the
polyzwitterion, a polyzwitterion/anion and polyzwitterion/dianion
synthesized from the polyzwitterionic acid, and the corresponding
methods by which each compound and polymer is formed and use of the
polyzwitterionic acid as an antiscalant.
[0004] Description of the Related Art
[0005] The "background" description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the presently named inventors, to the extent it is described in
this background section, as well as aspects of the description
which may not otherwise qualify as prior art at the time of filing,
are neither expressly or impliedly admitted as prior art against
the present invention.
[0006] The architecture of Butler's cyclopolymers from
diallylammonium salts (Butler G B. Cyclopolymerization and
cyclocopolymerization. New York: Marcel Dekker; 1992; Kudaibergenov
S, et al.; Polymeric betaines: synthesis characterization and
application. Adv. Polym Sci 2006; 201:157-224; Singh P K, et al.;
Zwitterionic polyelectrolytes: A review. E-Polymers 2007; 030:
1-34; Jaeger W, et al.; Synthetic polymers with quaternary nitrogen
atoms-Synthesis and structure of the most used type of cationic
polyelectrolytes. Prog Polym Sci 2010; 35:511-77--each incorporated
herein by reference in its entirety) has been Recognized as the
eighth major structural type of synthetic polymers (Butler G B.
Cyclopolymerization. J Polym Sci Part A: Polym Chem 2000;
38:3451-3461; McGrew F C. Structure of synthetic high polymers. J
Chem Ed. 1958; 35:178-186--each incorporated hereinby reference in
its entirety). These ionic polymers have found manifold
applications in industrial processes. Use of sulfur dioxide in the
cyclopolymerization protocol provides value added diallyl ammonium
salts/S02 copolymers (Ali S A, et al.; Comparative solution
properties of cyclocopolymers having cationic, anionic, witterionic
and zwitterionic/anionic backbones of similar degree of
polymerization. Polymer 2012; 53:3368-3377; Abu-Thabit N Y, et al.;
Phosphonobetaine/sulfur dioxide copolymer by Butler's
cyclopolymerization process. Eur Polym J 2011; 47:1113-23; Ali S A,
et al.; Synthesis and comparative solution properties of single-,
twin, and triple-tailed associating ionic polymers based on
diallylammonium salts. J Polym Sci Part A Polym Chem 2006; 44:5480
94; Umar Y, et al.; The effects of charge densities on the
associative properties of a pH responsive hydrophobically modified
sulfobetaine/sulfur dioxide terpolymer. Polymer 2005;
46:10709-17--each incorporated herein by reference in its
entirety). The nitrogen center in the repeat unit may bear a
positive charge as in cationic polyelectrolytes (+). Alternately,
the nitrogen center may act as the cationic part of a
polyzwitterion (.+-.) containing carboxylate, phosphonate or
sulfonate as the negative centers or be the cationic part of a
polyampholyte (+-) having a polymer chain containing equal or
unequal amounts of opposite charges (Abu-Thabit, N Y, Al-Muallem H
A, Ali S A. The pH-responsive Cycloterpolymers of
Diallyldimethylammonium chloride,
3(N,N-Diallylammonio)propanesulfonate, and Sulfur dioxide. J Appl
Polym Sci 2011; 120:3662-73--incorporated herein by reference in
its entirety). Strong intragroup, intra- and interchain
electrostatic dipole-dipole attractions among the dipolar motifs in
polyzwitterions (PZs) lead to a collapsed or globular conformation
which can undergo a globule-to-coil transition
("antipolyelectrolyte" effect) in salt (e.g. NaC) solutions owing
to the disruption of the network of ionic cross-links (Wielema T A,
et al.; Zwitterionic polymers--I Synthesis of a novel series of
poly(vinylsulphobetaines). Effect of structure of polymer on
solubility in water. Eur Polym J 1987; 23:947-50; Salamone J C, et
al.; Aqueous solution properties of a poly(vinyl imidazolium
sulphobetaine. Polymer 1978; 19:1157-62; Dobrynin A V, et al.;
Flory Theory of a Polyampholyte Chain. J Phys II 1995; 5: 677-95;
Higgs P G, et al.; Theory of Polyampholyte Solutions. J Chem Phys
1991; 94:1543-54--each incorporated herein by reference in its
entirety). More effective screening of the positive centers in a
(.+-.) PZ by Cl-- ions as compared to the screening of the negative
charges by Na+ ions results in each dipolar zwitterionic motif
having a net negative charge, repulsion among which leads to chain
expansion (Corpart J, Candau F. Aqueous solution properties of
ampholytic copolymers prepared in microemulsions. Macromolecules
1993; 26:1333-1343; Skouri M, et al.; Conformation of neutral
polyampholyte chains in salt solutions: a light scattering study.
Macromolecules 1994; 27:69-6--each incorporated herein by reference
in its entirety). PZs can serve as an excellent polar host matrix
owing to their high dipole moments (Yoshizawa M, et al.; Molecular
brush having molten salt domain for fast ion conduction. Chem.
Lett. 1999; 889-90--incorporated herein by reference in its
entirety). The pH-responsive biomimic PZs have been utilized in
various fields including: medical (Chan G Y N, et al.; Approaches
to improving the biocompatibility of porous perfluoropolyethers for
ophthalmic applications. Biomaterials 2006;
27:1287-95--incorporated herein by reference in its entirety),
nanotechnology tools (You Ye-Zi, et al.; Directly growing ionic
polymers on multi-walled carbon nanotubes via surface RAFT
polymerization. Nanotechnology. 2006; 17:2350-4--incorporated
herein by reference in its entirety), cosmetics and pharmaceuticals
(Kudaibergenov, SE. Polyampholytes: Synthesis, Characterization,
and Application. Plenum Corporation; New York: 2002; Salamone J C,
et al.; In: Encycl Polym Sci Eng. Mark, H F, Bikales N M,
Overberger, C G, Menges G, Kroschwitz J I. Eds.; John Wiley &
Sons, Inc: New York; 1987: 11, 514-30; Mumick P S, Welch P M,
Salazar L C, McCormick C L. Water-soluble copolymers. 56. Structure
and solvation effects of polyampholytes in drag reduction.
Macromolecules 1994; 27:323-31--each incorporated herein by
reference in its entirety), procedures for DNA assay (Filippini D,
et al.; Computer screen photo-assisted detection of complementary
DNA strands using a luminescent zwitterionic polythiophene
derivative. Sensors and Actuators B. 2006; 113:410-8--incorporated
herein by reference in its entirety), chelation of toxic trace
metals (Ni, Cu, Cd, and Hg) in wastewater treatment, drilling-mud
additives (Zhang L M, et al.; New water-soluble ampholytic
polysaccharides for oilfield drilling treatment: a preliminary
study. Carbohydr Polym 2001; 44:255-260-incorporated herein by
reference in its entirety), and water in oil emulsions (Didukh A G,
et al.; Oil Gas 2004; 4:64-75-incorporated herein by reference in
its entirety).
[0007] When the monomer which represents repeating units of the
polymer contains an ammonium group and a matching anionic group, it
belongs to the betaine family and the charges form an inner salt. A
distinctive feature of the polymers of the invention is that they
are electrically neutral polymers even though the betaine groups
have both positive and negative charges. The positive charge is
provided by a quaternary ammonium function, and the negative charge
is provided by a sulfonate (sulfobetaines) or phosphonate
(phosphobetaines) group.
[0008] Some copolymers were obtained by copolymerization of
acrylamide with carboxybetaine type monomers. Their properties in
solution greatly depend on the pH value and they are incompatible
with the desired properties. In fact, at a low pH value, the
protonation of the carboxylate functions leads to the loss of the
zwitterionic character and the copolymer behaves like a cationic
polyelectrolyte, thus sensitive to the presence of salt in
particular.
[0009] The polybetaines described here have the advantage of
keeping their zwitterionic character within a wide pH range.
Certain acrylaride and sulfobetaine copolymers have already been
described, but they result from synthesis processes carried out in
the presence of salts, which is of notable importance for the
structures obtained.
BRIEF SUMMARY OF THE INVENTION
[0010] The foregoing paragraphs have been provided by way of
general introduction, and are not intended to limit the scope of
the following claims. The described embodiments, together with
further advantages, will be best understood by reference to the
following detailed description taken in conjunction with the
accompanying drawings.
[0011] One embodiment of the disclosure includes a zwitterionic
monomer.
[0012] Another embodiment includes a method for synthesizing and
copolymerizing the zwitterionic monomer to form a polyzwitterion
(.+-.) (PZ) containing a repeating unit of a diallylammonium group
containing both diethylphosphonate and sulfonate functionalities,
and a sulfur dioxide unit.
[0013] Another embodiment includes a method in which hydrolysis of
the phosphonate ester in the (.+-.) (PZ) forms a pH-responsive
polyzwitterionic acid (.+-.) (PZA).
[0014] Another embodiment includes a method in which the (.+-.)
(PZA) undergoes pH-induced transformation and is converted into a
polyzwitterion/anion (.+-.-) (PZAN) and a polyzwitterion/dianion
(.+-.=) (PZDAN).
[0015] Another embodiment includes using the (.+-.) (PZA) as an
antiscalant in a reverse osmosis desalinization plant to inhibit or
treat the formation of a scale.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A more complete appreciation of the disclosure and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0017] FIGS. 1A-1C show .sup.1H NMR spectra of the corresponding
polymers in (+NaCl) in D.sub.2O;
[0018] FIGS. 2A-2C show .sup.13C NMR spectra of the corresponding
polymers in (+NaCl) in D.sub.2O;
[0019] FIG. 3 shows a TGA curve of PZ 5;
[0020] FIG. 4 shows a diagram demonstrating the viscosity behavior
in 0.1 M NaCl of different polymers;
[0021] FIG. 5 shows a diagram demonstrating the viscosity behavior
in salt-free water of different polymers;
[0022] FIG. 6 shows a diagram demonstrating the viscosity behavior
in 0.1 M NaCl of different polymers;
[0023] FIG. 7 shows a plot for the apparent (a) log K.sub.1 versus
degree of protonation (.alpha.) and (b) log K.sub.2 versus .alpha.
for (.+-.-) PZAN 7 in salt-free water and 0.1 M NaCl;
[0024] FIG. 8 shows a graph demonstrating the reduced viscosity
(.eta..sub.sp/C) at 30.degree. C. of a solution solution of polymer
PZA 6 in 0.1 N NaCl; and
[0025] FIG. 9 shows the precipitation behavior of a supersaturated
solution of CaSO.sub.4 in the presence (20 ppm) and absence of PZA
6.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0026] Referring now to the drawings, wherein like reference
numerals designate identical or corresponding parts throughout the
several views. The disclosure includes the zwitterionic monomer 4
having the following structure (I):
##STR00001##
[0027] Zwitterionic monomer 4 of formula (I) is a cationic
nitrogen-containing compound bonded to two allyl units. The
nitrogen atom is further bonded to phospho- and sulfopropyl groups.
The formula for each phosophonate group is (--P(O)(OH).sub.2 or
--P(O)(OR.sub.2) where the "R" group may be the same or different
and is preferably a C.sub.1-C.sub.6 alkyl or C.sub.6-C.sub.12 aryl
group selected from the group consisting of methyl, ethyl, propyl,
butyl, pentyl, or hexyl or the aryl groups selected from the group
consisting of phenyl, tolyl, xylyl, mesityl, naphthyl, biphenyl and
any isomers thereof. "R" may be substituted or unsubstituted.
Preferably the "R" group of the phosphonate group is an ethyl
group.
[0028] The copolymerization of the zwitterionic monomer 4 with
SO.sub.2 to obtain (.+-.) PZ 5, a precursor to pH-responsive
polyzwitterion acid (.+-.) (PZA) 6, is presented in Scheme 1. The
pH-induced dissociation of dibasic acid (.+-.) (PZA) 6 leads to
polyzwitterion/anion (PZAN) (.+-.-) 7 and polyzwitterion/dianion
(PZDAN) (.+-.=) 8 whose structures are akin to the type 1 polymers
having repeating units with charge asymmetry. The
cyclopolymerization protocol has documented very few such
copolymers of the type 1 bearing (.+-.-) or (.+-.=) ionic traits on
the polymer chains (Mazumder M A J, et al.; Synthesis and solution
properties of a new poly(electrolyte-zwitterion). Polymer 2004;
45:125-32; Ali, M M, et al.; Polymerization of functionalized
diallyl quaternary salt to poly(ampholyte-electrolyte). Polymer
2000; 41:5591-600; Ali S A, et al.; J Appl Polym Sci, DOT:
10.1002/app.38835--each incorporated herein by reference in its
entirety). Cyclopolymers 4-8 having phophonate, sulfonate as well
as a SO.sub.2 spacer in the same repeating unit is also presented
in Scheme 1 where the alkoxy group of the phosphonate is described
as an ethoxy group, other alkoxy groups may be used in place of the
ethoxy group.
##STR00002##
[0029] As depicted in Scheme 1, a polymer 1 serves as a generic
model for the polymers polyzwitterion (PZ) 5, polyzwitterionic acid
(PZA) (ZH.sub.2.sup..+-.) 6, poly(zwitterion/anion) (PZAN)
(ZH.sup..+-.-) 7, and poly(zwitterion/dianon) (PZDA) (Z.sup..+-.-)
8 that are formed from zwitterionic monomer 4. Polymer 1 has the
following structure:
##STR00003##
[0030] Polymer 1 includes repeating units of a five-membered
heterocyclic ring having a nitrogen atom bonded to a linking unit
comprising a phosphonate group with the formula for each
phosphonate group being --P(O)(OH).sub.2 or --P(O)(OR).sub.2 where
the "R" group is preferably an alkyl or aryl group selected from
the group consisting of methyl, ethyl, propyl, butyl, pentyl, or
hexyl or the aryl groups selected from the group consisting of
phenyl, tolyl, xylyl, mesityl, naphthyl, biphenyl and any isomers
thereof. "R" may be substituted or unsubstituted. Preferably the
"R" group of the phosphonate group is an ethyl group.
[0031] The phosphonate and linking groups can be further
represented in polymer 1 as --(CH.sub.2).sub.x-A.sup.n-. More
specifically, the variable "x" represents the number of methylene
units, and "x" is 3. The group "A.sup.n-" represents a phosphonate
group. Variable "n.sup.-" represents the charge value of the
corresponding phosphonate group and also the coefficient
representing the number of atoms of the cationic counter ion having
a single charge (the number of counter ions having double charge
would therefore be only 1/2 of the number of counter ions having a
single counter ion). The "n" represents the number of repeating
units of the corresponding polymer and "n" is at least 10,
preferably at least 15, 20, 40, 80, or 100. In one aspect of the
invention the polymer is a homopolymer that includes repeating
units consisting of only the five-membered ring and the SO.sub.2
groups, with the polymer alternately having one or more different
terminal units. More preferably, "n" is in the range of 20-1,500;
40-1,400; 80-1,300; or 100-1,200. Cationic materials such as
Kt.sup.+, Cu.sup.+, or Li.sup.+ and dicationic materials such as
Ca.sup.2+, Cr.sup.2+, Cu.sup.2+, Fe.sup.2+, Pb.sup.2+, Mg.sup.2+,
Mn.sup.2+, Hg.sup.2+, Sr.sup.2+, Sn.sup.2+, or Zn.sup.2+ may be
used in place of Na.sup.+.
[0032] The nitrogen atom included in the five-membered heterocyclic
ring is also bonded to a linking unit comprising a sulfonate group
with the formula (--SO.sub.3). The sulfonate group and linking
groups can be further represented in polymer 1 as
--(CH.sub.2).sub.y--B.sup..crclbar. in polymer 1. The variable "y"
represents the number of methylene units, and "y" is 3. The
variable "B" represents the sulfonate group.
[0033] A sulfur dioxide group (--SO.sub.2--) is further bonded to
the five-membered heterocyclic ring through a linking group
(--CH.sub.2). In one embodiment of the invention, the copolymer
includes only repeating units of a diallylammonium unit and a
SO.sub.2 unit.
[0034] As further depicted in Scheme 1, a solution of the monomer
2, which is a tertiary amine, diethyl
3-(diallylamino)propylphosphonate, is treated with a cyclic
sulfonate ester of a hydroxy sulfonic acid 3, more preferably in
the form of propane sultone to yield a monomeric zwitterion 4. The
treatment of monomer 2 with ester 3 yields the resultant anionic
sulfonate material and thus balances the cationic charge of the
nitrogen atom of the 5-membered heterocyclic ring. The monomeric
zwitterion 4 is the monomer 3-[diallyl
{3-(diethoxyphosphoryl)propyl} ammonio]propane-1-sulfonate. The
monomer is a cationic nitrogen-containing compound bonding to units
where the phosphoryl group consists of the formula
C--P(O)(OR).sub.2 where the "R" group is preferably an alkyl group
selected from the group consisting of methyl, ethyl, propyl, butyl,
pentyl, or hexyl or an aryl group selected from the group
consisting of phenyl, tolyl, xylyl, mesityl, naphthyl, biphenyl and
any isomers thereof. Preferably the "R" group of the phosphonate
group is an ethyl group.
[0035] The monomeric zwitterion 4 is then treated with a
polymerizing agent and SO.sub.2. The polymerizing agent includes
but is not limited to a peroxide solution, more preferably a
tert-butyl hydroperoxide solution (TBHP), which acts to initiate
cyclopolymerization of the zwitterionic monomer 4 to yield a
polyzwitterion 5. The polyzwitterion 5 contains the core structure
following the model of polymer 1, further including the phosphoryl
group with the formula C--P(O)(OR).sub.2 where the "R" group is
preferably an alkyl group selected from the group consisting of
methyl, ethyl, propyl, butyl, pentyl, or hexyl or the aryl groups
consisting of phenyl, tolyl, xylyl, mesityl, naphthyl, biphenyl and
any isomers thereof. Preferably the "R" group of the phosphonate
group is an ethyl group.
[0036] The polyzwitterion 5 is then treated with a solution of
water and a concentrated inorganic acid, more preferably HCl, to
yield a polyzwitterionic acid (PZA) (ZH.sub.2.sup..+-.) 6, which
contains two hydroxy groups in the formula of the phosphonate
group. (PZA) (ZH.sub.2.sup..+-.) 6 contains the structure following
the model of polymer 1, further including the phosphonate group in
the form of C--P(O)(OH).sub.2. Polyzwitterionic acid 6 may be used
as an antiscalant in reverse osmosis plants against mineral scales
such as CaCO.sub.3, CaSO.sub.4, Mg(OH).sub.2.
[0037] Treatment of (PZA) (ZH.sub.2.sup..+-.) 6 with an alkaline
material, e.g. NaOH, KOH, Ca(OH).sub.2 and the like, deprotonates
one of the hydroxy groups of the phosphonate group to provide a
polymeric material having an anionic charge. The anionically
charged derivative of (PZA) (ZH.sub.2.sup..+-.) 6 is shown as
poly(zwitterion/anion) (PZAN) (ZH.sup..+-.-) 7.
[0038] Upon further treatment of (PZAN) (ZH.sup..+-.-) 7 with
additional base, the anionic oxygen atom of the phosphonate group
forms a (Na.sup.+-O) complex bonded to the phosphorus atom to yield
a dianionic charge. The dianionically charged derivative of the
(PZAN) (ZH.sup..+-.-) 7 is shown as poly(zwitterion/dianon) (PZDA)
(Z.sup..+-.=) 8.
[0039] Both (PZAN) (ZH.sup..+-.-) 7 and (PZDA) (Z.sup..+-.=) 8 may
also be used as antiscalants in reverse osmosis plants against
mineral scales that contain mineral compounds such as CaCO.sub.3,
CaSO.sub.4, Mg(OH).sub.2.
[0040] The dianionically charged monomer 11 (Z.sup..+-.=) and the
dianionically charged polymer 12 (Z.+-.=) are comparative examples
to PZDAN (Z.sup..+-.=) 8. Both monomer 11 and polymer 12 do not
contain the SO.sub.2 repeating unit present in the copolymer PZDAN
(Z.sup..+-.=) 8.
[0041] The synthesis of monomer 4 preferably occurs by the method
of (Haladu S A, Ali S A. J Polym Sci Part A: Polym Chem:
Submitted--incorporated herein by reference in its entirety):
2,2'-Azoisobutyronitrile (AIBN) from Fluka A G (Buchs, Switzerland)
was crystallized (ethanol-chloroform). Dimethylsulfoxide (DMSO),
dried over calcium hydride overnight, was distilled (bp
64-65.degree. C. at 4 mmHg). A Spectra/Por membrane (MWCO of
6000-8000 from Spectrum Laboratories, Inc) was used for
dialysis.
[0042] The cyclopolymerization of the monomer 4 preferably occurs
by the following method: in a typical cyclopolymerization (see
Table 1, entry 3), adsorption of SO.sub.2 (20 mmol) in a solution
of monomer 4 (7.95 g, 20 mmol) in DMSO (7.2 g) was followed by the
addition of initiator (AIBN) (80 mg). The reaction mixture under
N.sub.2 in a closed flask was stirred at 60.degree. C. for 20 h.
Within 30 min, the magnetic bar stopped stirring with the
appearance of a transparent thick gel. At the end, the hard
polymeric mass was crushed to powder with the aid of acetone,
soaked in methanol, filtered, and washed with hot (50.degree. C.)
acetone to obtain copolymer (.+-.) PZ 5 (8.0 g, 87%). The thermal
decomposition: brown color at 270.degree. C. and black at
290.degree. C. (Found: C, 41.3; H, 7.2; N, 2.9; S, 13.6%.
C.sub.16H.sub.32NO.sub.8PS.sub.2 requires C, 41.64; H, 6.99; N,
3.03; S, 13.89%); .nu..sub.max(KBr): 3447 (br), 2985, 1651, 1486,
1370, 1316, 1217, 1100, 1043, 966, 788, 732 cm.sup.-1.
.delta..sub.P (202 MHz, D.sub.2O): 30.81 (s). .sup.1H and .sup.13C
NMR spectra of PZ 5 are shown in respective FIGS. 1 and 2.
[0043] Conversion of PZ 5 to PZA 6 preferably occurs by the
following method: PZ 5 (5.0 g, 10.8 mmol) (entry 3, Table 1) was
hydrolyzed in water (30 mL) and HCl (40 mL) at 90.degree. C. for 24
h. During dialysis of the homogeneous mixture (24 h), the polymer
separated within 1 h as a gel which redissolved after 3 h. The
resulting polymer solution was freeze-dried to obtain (.+-.) PZA 6
as a white solid (4.2 g, 96%). The thermal decomposition: the color
changed to dark brown and black at 275.degree. C. and 285.degree.
C., respectively; (Found: C, 35.2; H, 6.2; N, 3.3; S, 15.5%.
C.sub.12H.sub.24NO.sub.8PS.sub.2 requires C, 35.55; H, 5.97; N,
3.45; S, 15.82%); .nu..sub.max (KBr): 3445 (br), 2971, 2928, 1643,
1471, 1411, 1311, 1215 (br), 1132, 1042, 982, 932, 789, 733
cm.sup.-1. .delta..sub.P(202 MHz, D.sub.2O): 25.52 (s). The .sup.1H
and .sup.13C NMR spectra of PZA 6 are shown in FIGS. 1 and 2.
TABLE-US-00001 TABLE 1 Copolymerization.sup.a of monomer 3 with
sulfur dioxide. Intrinsic.sup.c Entry Monomer DMSO Initiator.sup.b
Yield viscosity No. (mmol) (g) (mg) (%) (dL g.sup.-1) M.sub.W
(PDI).sup.d 1 10 3.6 30 93 0.517 2 10 3.6 50 92 0.578 1.37 .times.
10.sup.5 2.1 3 20 7.2 80 87 0.901 2.44 .times. 10.sup.5 2.2
.sup.aAn equimolar mixture of monomer 4 and SO.sub.2 was
polymerized at 60.degree. C. for 20 h.
.sup.bAzobisisobutyronitrile. .sup.cViscosity of 1-0.0625% polymer
solution in 0.1N NaCl at 30.degree. C. was measured with Ubbelohde
Viscometer (K = 0.005718). .sup.dPolydispersity index.
A 2% (w/w) mixture of 5 or 6 in a solvent was stirred at 70.degree.
C. for 1 h and the solubility behavior was then checked at
23.degree. C. (Table 2). The solubility behaviors are given in
Table 2.
TABLE-US-00002 TABLE 2 Solubility.sup.a,b of PZ 5 and PZA 6.
Solvent .epsilon. PZ 5 PZA 6 Formamide 111 + + Water 78.4 + +
Formic acid 58.5 + + DMSO 47.0 + - Ethylene glycol 37.3 + - DMF
37.0 - - Methanol 32.3 - - Triethylene glycol 23.7 - - Acetic acid
6.15 + - .sup.apolymer (2% w/w) mixture in water was heated at
70.degree. C. for 1 h and then cooled to 23.degree. C. .sup.b+
indicates soluble, `-` indicates insoluble. .sup.c5% (w/w of PZA 6
was insoluble in water.
[0044] Polymer PZA 6 (25 mg, 5 wt %) is insoluble in water (0.5 mL)
but soluble in excess water (1.0 mL). A solution of PZA 6 (30 mg,
0.0617 mmol) in 1.04 M HCl (2.30 mL) was titrated with salt-free
water until cloudiness. The first appearance of cloud required
addition of water (1.35 mL). At this point the concentration of the
polymer and HCl are calculated to be 0.0169 and 0.655 M HCl,
respectively. Continued addition of water (50.5 mL) leads to
disappearance of the cloudy mixture to colorless solution. That
translates into the solubility of 0.00114 M polymer in 0.0442 M
HCl.
[0045] The first and second step protonation constants, K.sub.1 and
K.sub.2, of polymer 8 [ZH.sub.2.sup..perp.] were determined by
potentiometric titrations under N.sub.2 in CO.sub.2-free water as
described elsewhere using PZA 6 [ZH.sub.2.sup..+-.] in salt-free
water or 0.1 M NaCl.sup.- (200 mL) (Tables 3 and 4) of (Al-Muallem
H A, Wazeer M I M, Ali S A. Synthesis and solution properties of a
new pH-responsive polymer containing amino acid residues. Polymer
2002; 43:4285-95--incorporated by reference herein in its
entirety). The Log K.sub.1 of --PO.sub.3.sup.2- (in 8) and Log
K.sub.2 of --PO.sub.3H-- (in 7) are calculated at each pH value by
the Henderson-Hasselbalch eq 2 (Scheme 1) where the ratios
[ZH.sup..+-.-].sub.eq/[Z].sub.o and
[ZH.sub.2.sup..+-.].sub.eq/[Z].sub.o represent the respective
degree of protonation (.alpha.). The [ZH.sup..+-.-].sub.eq and
[ZH.sub.2.sup..+-.].sub.eq are the equilibrium concentrations of
the first (7) and second (6) protonated species and [Z].sub.o is
the initial concentration of the repeating units.
[0046] For the determination of log K.sub.2 of --PO.sub.3H.sup.-
(i.e. [ZH.sup..+-.-]) using titration of polymer 6
[ZH.sub.2.sup..+-.] with NaOH, [Z].sub.o and
[ZH.sub.2.sup.+].sub.eq are related by
[ZH.sub.2.sup.+].sub.eq=[Z].sub.o--
C.sub.OH.sup.---[H.sup.+]+[OH.sup.-], where C.sub.OHH.sup.-,
[H.sup.+] and [OH.sup.-] represent the added concentration of NaOH,
and [H.sup.+] and [OH.sup.-] describe the equilibrium
concentrations as calculated from the pH values (Felty W K.
Intuitive and general approach to acid-base
equilibriumcalculations. J Chem Educ 1978; 55(9):576; Barbucci R,
Casolaro M, Ferruti P, Barone V, Lelji F, Oliva L.
Properties-structure relationship for polymeric bases whose
monomeric units behave independently towards protonation.
Macromolecules 1981; 14:1203-9--each incorporated herein by
reference in its entirety). The log K.sub.1 for the first step
protonation of --PO.sub.3.sup.2- (i.e. [Z.sup..+-.=]) was
calculated using volume of the titrant after deducting the
equivalent volume from the total volume. In this case, .alpha.
represents the ratio [ZH.sup..+-.].sub.eq/[Z].sub.o whereby
[ZH.sup..+-.--].sub.eq equals [Z].sub.o--
C.sub.OH.sup.---[H.sup.+]+[OH.sup.-].
[0047] The linear regression fit of pH vs. log
[(1-.alpha.)/.alpha.)] (eq 2, Scheme 1) gave `n` and log K.sup.o,
the respective slope and intercept. The apparent basicity constants
K.sub.i is described by eq 3 (Scheme 1) where log K.sup.o=pH at
.alpha.=0.5 and n=1 in the case of sharp basicity constants.
Simultaneous protonation of the three basic sites: --PO.sub.3.sup.-
(log K.sub.1.apprxeq.+8), --PO.sub.3H.sup.- (log
K.sub.2:.apprxeq.+3) and --SO.sub.3.sup.- (log K.sub.3:
.apprxeq.-2.1) (Guthrie J P. Hydrolysis of esters of oxy acids: pKa
values for strong acids. Can J Chem 1978; 56:2342-54--incorporated
herein by reference in its entirety) is least likely due to
differences of their basicity constants by about 5 orders of
magnitude (vide infra). The basicity constant log K of any base B
is the pK.sub.a of its conjugate acid BH.sup.+.
[0048] Inhibition of calcium sulfate (gypsum) scaling by PZA 6 was
carried out using supersaturated solution of CaSO.sub.4 containing
Ca.sup.2+ (3.times.866.7 mg/L i.e., 2600 mg/L) and SO.sub.4.sup.2-
(3.times.2100 mg/L i.e. 6300 mg/L) where a typical analysis of a
reject brine at 70% recovery from a Reverse Osmosis plant revealed
the presence of 866.7 mg/L and 2100 mg/L Ca.sup.2+ and
SO.sub.4.sup.2-, respectively (Butt F H, et al.; Pilot plant
evaluation of advanced vs. conventional scale inhibitors for RO
desalination. Desalination 1995; 103:189-198--incorporated herein
by reference in its entirety). The concentration of reject brine
(i.e., concentrated brine (CB)) is denoted as 1CB.
[0049] The evaluation of the newly developed scale inhibitor PZA 6
was performed in 3 CB solutions supersaturated with respect to
CaSO.sub.4 as confirmed from solubility data of CaSO.sub.4. To a
solution of 6 CB calcium chloride (60 mL) containing PZA 6 (40 ppm
i.e. 40 mg/L) at 40.degree. C..+-.1.degree. C. was added quickly a
preheated (40.degree. C.) solution of 6 CB sodium sulfate (60 mL).
The resultant 3 CB solution containing 20 ppm of PZA 6 was stirred
at 300 rpm using a magnetic stir-bar, and conductivity measurements
were made at an interval of every 10 min initially to quantify the
effectiveness of the newly developed antiscalant. The drop in
conductivity indicates the precipitation of CaSO.sub.4. Induction
time was measured with a decrease in conductivity when
precipitation started. Visual inspection was carefully done to see
any turbidity arising from precipitation.
[0050] Copolymerization of zwitterion monomer 4 and SO.sub.2
afforded alternate polyzwitterion (PZ) 5 in excellent yields
(Scheme 1). An initiator concentration of 4 mg/mmol monomer (entry
3, Table 1) gave the copolymer having the highest intrinsic
viscosity [.eta.]. PZ (.+-.) 5 was hydrolyzed in HCl/H.sub.2O to
give PZA (.+-.) 6 which on neutralization with 1 and 2 equivalents
of NaOH is expected to generate polyzwitterion/anion (PZAN) (.+-.-)
7 and polyzwitterion/dianion (PZDAN) (.+-.=) 8.
[0051] PZ 5 was observed to be stable up to around 266.degree. C.
as evident from the thermogravimetric analysis (TGA) curve (FIG.
3); an initial loss of 5% was attributed to the loss of moisture.
FIG. 3 is a TGA curve of PZ 5. The first steep weight loss of 40%
in the temperature range 266-320.degree. C. range was due to the
combined losses of sulfopropyl moiety (26%) and SO.sub.2 (14%). The
second gradual loss of 36% in the 320-800.degree. C. range was the
result of decomposition of the phosphonate ester functionality and
the release of H.sub.2O, NO.sub.x and CO.sub.2 gases
(Martinez-tapia HS, Cabeza A, Bruque H, Pertierra P, Garcmh S,
Aranda M A G. Synthesis and Structure of
Na.sub.2[(HO.sub.3PCH.sub.2).sub.3NH] 1.5H.sub.2O: The First
Alkaline Triphosphonate. J Solid State Chem 2000;
151:122-9--incorporated herein by reference in its entirety). The
remaining mass of 19% is attributed to P.sub.2O.sub.5.
[0052] The PZ 5 and PZA 6 were found to be soluble in protic
solvents having higher dielectric constants (Table 2). Even though
PZs are usually insoluble in salt-free water, the water-solubility
of the current polymers is attributed to the steric crowding which
makes it difficult for the negative charges in sulfonate to move
closer to positive nitrogens to impart effective zwitterionic
interactions (Haladu, S. A. Ali, S. A. cyclopolymerization protocol
for the Synthesis of a New Poly(electrolyte-zwitterion) Containing
quaternary nitrogen, carboxylate, and sulfonate functionalities.
Eur Polym J 2013; 49:1591-600; Monroy Soto V M, Galin J C.
Poly(sulphopropylbetaines): 2 Dilute solution properties. Polymer
1984; 25:254-62--each incorporated herein by reference in its
entirety).
[0053] A 5 wt % (.+-.) PZA 6 in salt-free water remained
heterogeneous while it became homogeneous when diluted to 2.5 wt %.
The heterogeneous mixture became homogeneous in the presence of 0.1
M NaCl; however dilution of the homogeneous salt-added solution
with salt-free water did not bring back the turbidity. For the
pK.sub.a value of 3.61 of --PO.sub.3H.sub.2 (vide infra) it was
calculated that (.+-.) PZA 6 will be dissociated to (.+-.-) PZAN 7
to the extent of 4.4 mol % and 6.1 mol % in respective 5 wt % and
2.5 wt % solution in salt-free water. Greater participation of the
zwitterionic/anionic (.+-.-) motifs in the dissociated form thus
makes the polymer soluble in 2.5 wt % solution. Note that the
presence of NaCl increases the solubility as a result of increased
dissociation; for a pK.sub.a value of 2.98 (vide infra) in 0.1 M
NaCl, the percent dissociation was calculated to be 8.8 mol % and
12 mol % in 5 wt % and 2.5 wt % solution. The presence of NaCl not
only increases the dissociation, it also helps break up
zwitterionic interactions thereby increasing its solubility.
[0054] Interestingly it was observed during the dialysis of PZA 6
in 6.9 M HCl, precipitation of the polymer occurred within 1 h and
its dissolution after 3 h. On further investigation it was observed
that PZA 6 (30 mg, 0.0617 mmol) remained soluble in 1.04 M HCl
(2.30 mL); titration with water (1.35 mL) led to cloudiness. The
polymer (0.0169 M) thus became insoluble in the presence of 0.655 M
HCl. Continued addition of water (50.5 mL) to the cloudy mixture
leads to a colorless solution at a polymer and HCl concentrations
of 0.00114 M and 0.0442 M, respectively. The equilibria presented
in Scheme 2 may explain the solubility behavior.
##STR00004##
[0055] Scheme 2 describes the effect of (PZA) (ZH.sub.2.sup..+-.) 6
under pH-induced equilibration. For example, the reaction of (PZA)
(ZH.sub.2.sup..+-.) 6 with an inorganic acid or an organic acid
such as HCl. HBR, HI or H.sub.2SO.sub.4, more preferably the acid
being HCl, results in a soluble cationic polyelectrolyte (CPE)
(ZH.sub.3.sup.+) 13, in which the sulfonate group of the (PZA)
(ZH.sub.2.sup..+-.) 6 is protonated to yield a sulfonic acid that
is connected to the five-membered heterocyclic ring through an
alkylene group. Further, dialysis of (CPE) (ZH.sub.3.sup.+) 13
deprotonates the sulfonic acid and regenerates the (PZA)
(ZH.sub.2.sup..+-.) 6. Extended dialysis without the presence of
HCl yields a soluble dissociated acid polyzwitterion/anion (PZA)
(ZH.sup..+-.-) 14, in which the one of the hydroxy groups of the
phosphonate group is deprotonated to provide a polymeric material
having an anionic charge.
[0056] While the undissociated (.+-.) PZA 6 by virtue of being
zwitterionic is insoluble in neutral water, the presence of HCl
pushes the equilibrium towards water-soluble cationic
polyelectrolyte (CPE) (+) 13 which upon extended dialysis is
transformed to water-insoluble undissociated (.+-.) PZA 6 with the
depletion of HCl. Continued dialysis in the absence of HCl
establishes the equilibrium: 614 in which increased dilution pushes
the equilibrium towards (.+-.-) PZAN 14 in which the anionic
portion of the zwitterion/anion motifs leads to greater solubility
as a result of increased hydration of the expanded polymer
backbone.
[0057] The strong IR adsorptions around .apprxeq.1216 cm.sup.-1 and
.apprxeq.1042 cm.sup.-1 indicate the presence of sulfonate and
phosphonate groups in PZ 5 and PZA 6. The two strong bands at
.apprxeq.1315 cm.sup.-1 and .about.1100 cm.sup.-1 were assigned to
the asymmetric and symmetric vibrations of SO.sub.2 unit. The
P.dbd.O absorption peaks appeared at 985 (in PZ 5) and 982
cm.sup.-1 (in PZA 6). FIGS. 1A-1C and FIGS. 2A-2C show the
respective .sup.1H and .sup.13C NMR spectra of 4-6. The complete
disappearance of any alkene proton or carbon signals ascertains
that the termination happens via chain transfer and/or coupling
process (Pike R M, Cohen R A. Organophosphorus polymers I.
Peroxide-initiated polymerization of diethyl and diisopropyl
vinylphosphonate. J Polym Sci 1960; 44:531-8; Butler G B, Angelo R
J. Preparation and Polymerization of Unsaturated Quaternary
Ammonium Compounds. VIII. A Proposed Alternating
Intramolecular-Intermolecular Chain Propagation. J Am Chem Soc
1957; 79:3128-3131--each incorporated herein by reference in its
entirety). The absence of the ester group (OCH.sub.2CH.sub.3)
indicate its removal by hydrolysis as shown in the spectra of 6
FIG. 1C and FIG. 2C. FIGS. 1A-1C are .sup.1H NMR spectrum of (a) 4,
(b) 5, and (c) 6 (+NaCl) in D.sub.2O. FIGS. 2A-2C are .sup.13NMR
spectrum of (a) 4, (b) 5, and (c) 6 (+NaCl) in D.sub.2O. The
stereochemistry of the substituents at C.sub.b,b in the polymers as
cis and trans in a 75/25 ratio is similar to earlier findings.
[0058] Eq. 4 was developed to give a mathematical expression to
rationalize the solution behavior of symmetrically or
asymmetrically charged ionic polymers (Everaers R, Johner A, Joanny
J-F. Complexation and precipitation in polyampholyte solutions.
Europhys Lett 1997; 37:275-280; Candau F, Joanny J-F. In: Salamone
J C, editor. Polyampholytes (Properties in Aqueous Solution). Boca
Raton, Fla.: CRC Press; 1996 p. 5462-76. vol. 7; Wittmer J, Johner
A, Joanny J-F. Random and alternatingpolyampholytes. Europhys Lett
1993; 24(4):263-268--each incorporated herein by reference in its
entirety).
v * = - .pi. ( fI B ) 2 .kappa. S + 4 .pi. I B .DELTA. f 2 .kappa.
S 2 ( 4 ) ##EQU00001##
where f is the total fraction of charged monomers, .DELTA.f is the
charge imbalance, I.sub.B is the Bjerrum length, and .kappa..sub.S
is the Debye-Huckel screening parameter. For symmetrically charged
polymers i.e. polymers having equal number of charges of both
algebraic signs, the second term in eq. 4 is eliminated by virtue
of .DELTA.f=0. In this case the negative excluded volume (v*)
indicates contraction to a collapsed coil. The second term in eq 4
describes the shielding of the Coulombic repulsive interactions as
a result of .DELTA.f.noteq.0. In the event of charge imbalance as
well as domination of second term over the first, the positive
electrostatic excluded volume (v*) leads to expansion to a
semicoil.
[0059] The dependence of viscosity of behavior of (.+-.) PZ 5 on
the concentration of NaCl is shown in FIG. 4. FIG. 4 is a graph
using an Ubbelohde Viscometer at 30.degree. C. that shows the
viscosity behavior of (.+-.) PZ 5 in .box-solid. 1 M NaCl,
.quadrature. 0.5 M NaCl, .tangle-solidup. 0.1 M NaCl, and
.quadrature. salt-free water. (Polymer used from entry 3, Table 1).
The intrinsic viscosity [.eta.] in 0 M (salt-free water), 0.1 M,
0.5 M and 1.0 M NaCl was measured to be 0.697, 0.901, 0.988, and
1.03 dL/g, respectively. For the electroneutral (.+-.) PZ 5 with
.DELTA.f=0, the viscosity values increases with the increase in
salt concentrations. The Cl.sup.- ions effectively shield or bind
the positive nitrogens whereas Na.sup.+ with its large hydration
shell cannot reach close enough to shield the anionic charges thus
resulting in negation of the eletroneutrality of (.+-.) PZ 5. A net
negative charge on (.+-.) PZ 5 thus brings the first as well as
second terms in eq 4 to be reckoned thereby making the .DELTA.f
lesser negative with the increase of NaCl concentrations. This
leads to increase in the viscosity values in compare to viscosity
in salt-free water. Note that the jump in the [.eta.] values from
salt-free-water to 0.1 M NaCl is much greater than when the solvent
is changed from 0.1 M to 0.5 or 1 M NaCl. Lesser changes in the
viscosity values at the higher concentrations of salt (0.5 M or
more) is attributed to the near completion of screening of the
zwitterionic motifs resulting in insignificant electrostatic
contribution to the polymer size.
[0060] FIG. 5 shows the viscosity behavior of 5-8 in salt-free
water. FIG. 5 is a graph using an Ubbelohde Viscometer at
30.degree. C. that shows the viscosity behavior in salt-free water
of: (a) .box-solid. (.+-.=) PZDAN 8, (b) .quadrature. (.+-.-) PZAN
7, (c) .tangle-solidup. (.+-.) PZ 6 and (d) .DELTA. (.+-.) PZ 5.
(All polymers are derived from entry 3, Table 1) [Inset describes
the viscosity plot in the dilution range 0.0625-0.0156 g/dL].
Rather than a polyzwitterion, viscosity plots of 6-8 resemble that
of a polyelectrolyte i.e. concave upwards. Increase of reduced
viscosity with decreasing concentrations of polymer (.+-.) PZA 6
and (.+-.-) PZAN 7 is attributed to their increased dissociation to
the zwitterionic/anionic motifs of (.+-.-) PZAN 7 and
zwitterionic/dianionic motifs of (.+-.=) PZDAN 8, respectively.
Note that (.+-.) PZA 6 has much higher viscosity values than that
of (.+-.) PZA 6 as a result of the acid dissociation (FIG. 5).
[0061] Based on the pK.sub.a value of 2.98 in 0.1 M NaCl (vide
infra), the extent of dissociation of --PO.sub.3H.sub.2 of (.+-.)
PZA 6 to --PO.sub.3H-- of (.+-.-) PZAN 7 in solutions having
polymer concentration of 1, 0.5, 0.25 and 0.125 g/dL is determined
to be 19, 25, 34, and 44 mol %, respectively.
[0062] FIG. 6 is a graph using an Ubbelohde Viscometer at
30.degree. C. that shows the viscosity behavior in 0.1 M NaCl of:
.box-solid. (.+-.=) PZDAN 8, .quadrature. 1:1 (.+-.-) PZAN
7/(.+-.=) PZDAN 8; .tangle-solidup. (.+-.-) PZAN 7, .DELTA. 1:1
(.+-.) PZA 6/(.+-.-) PZAN 7, and (.+-.) PZA 6 (all polymers are
derived from entry 3, Table 1). The viscosity plot (FIG. 6) of 7
remains linear since the weak acidity of --PO.sub.3H-- (pK.sub.a:
7.9) in 7 leads to insignificant level of dissociation to
--PO.sub.3.sup.2- of (.+-.=) PZDAN 8: the percent dissociation
remains 0.07-0.2 mol % in the concentration range 1-0.125 g/dL. For
a pK.sub.a value of 3.61 in salt-free water (vide infra), the
corresponding respective percent dissociation is determined as 9.5,
13, 18, and 25 mol %, which are less than that in 0.1 M NaCl.
Inspection of FIGS. 5 and 6 reveals that the polelectrolyte effect
in 6 is more pronounced in salt-free water than in 0.1 M NaCl,
while the opposite behavior was expected since the increased
dissociation to (.+-.-) 7 in 0.1 M NaCl should lead to higher
values for the .DELTA.f owing to the presence of higher percentage
of charge asymmetric zwitterionic/anionic motifs (.+-.-). As
discussed earlier, the importance of the second term in eq 4
increases with the increasing .DELTA.f values. However, the lower
viscosity values in 0.1 M NaCl is attributed to the greater
contraction of the polymer chain by shielding of the
(.+-.)--PO.sub.3H-- anions by Na.sup.+ ions (polyelectrolyte
effect) than the expansion caused as a result of disruption of
zwitterionic interactions.
[0063] FIG. 6 displays the viscosity plots for the polymers 5-8
having identical number of repeating units. Conversion of (.+-.)
PZA 6 by addition of 0.5, 1.0, 1.5, and 2 equivalents of NaOH to
1:1 (.+-.) PZA 6/(PZAN) (.+-.-) 7, (PZAN) (.+-.-) 7, 1:1 (PZAN)
(.+-.-) 7/(PZDAN) (.+-.=) 8, and (PZDAN) (.+-.=) 8, respectively,
results in the increase in viscosity values as a result of
increasing concentration of the anionic portions. The anionic
motifs thus dominate the viscosity behavior.
[0064] The basicity constant log K.sub.1 for the protonation of the
--PO.sub.3.sup.2- (in 8)) in salt-free water and 0.1 M NaCl were
determined to be 9.51 and 7.90, respectively (Table 3), while log
K.sub.2 for the respective protonation of the --PO.sub.3H.sup.- (in
7) were found to be 3.61 and 2.98 (Table 4). The log K values are
thus found to be higher than those of the corresponding monomers 10
and 11 (Scheme 1). All the n.sub.i values of greater than 1
ascertain the "apparent" (Barbucci R, Casolaro M, Danzo N, Barone
V, Ferruti P, Angeloni A. Effect of different shielding groups on
the polyelectrolyte behavior of polyamines. Macromolecules 1983;
16:456-62--incorporated herein by reference in its entirety) nature
of the basicity constants as evident from Tables 3 and 4 and also
demonstrated in FIG. 7, which reveals a decrease in log K with the
increase in .alpha. as a direct consequence of a decrease in the
electrostatic field force that encourages protonation. FIG. 7 is a
plot for the apparent (a) log K.sub.1 versus degree of protonation
(.alpha.) (entry 3, Table 3) for (.+-.=) PZDAN 8 and (b) log
K.sub.2 versus .alpha. for (.+-.-) PZAN 7 in salt-free water and
0.1 M NaCl (entry 3, Table 4). Unlike monomer the basicity constant
of a repeating unit in polymer is influenced by the nature of the
charges on the neighboring units. It is to be noted that for 11, n
values of .apprxeq.1 for both log K.sub.1 and log K.sub.2 in
salt-free water as well as 0.1 M NaCl is expected for a small
monomer molecule (Tables 3 and 4). Table 3 is shown below.
TABLE-US-00003 TABLE 3 Details for the First Protonation of Monomer
ZDA (Z.sup.+ =) 11 and Polymer PZDAN 8 (Z.sup.+ =) at 23.degree. C.
in Salt-Free Water. ZH.sub.2.sup..+-. or Z.sup.- C.sub.T .sup.a run
(mmol) (mol L.sup.-1) .alpha.-range pH-range Points .sup.b Log
K.sub.i.sup.o c n.sub.i .sup.c R.sup.2, .sup.d ##STR00005## Polymer
in Salt-Free water 1 0.1759 (ZH.sub.2.sup..+-.) -0.1016 0.79-0.14
8.77-10.42 14 9.47 1.18 0.9992 2 0.2467 (ZH.sub.2.sup..+-.) -0.1016
0.89-0.13 8.57-10.51 15 9.54 1.15 0.9974 3 0.3244
(ZH.sub.2.sup..+-.) -0.1016 0.87-0.14 8.58-10.45 17 9.52 1.16
0.9970 Average 9.51 (4) 1.16 (2) Log K.sub.1 e = 9.51 + 0.16 log
.left brkt-top.(1 - .alpha.) / .alpha..right brkt-bot. Monomer in
Salt-Free water: Log K.sub.1 .sup.e = 7.53 Polymer in 0.1 M NaCl 1
0.1995 (ZH.sub.2.sup.+) -0.1016 0.78-0.13 7.20-9.14 14 7.90 1.54
0.9904 2 0.2486 (ZH.sub.2.sup..+-.) -0.1016 0.80-0.13 7.15-9.17 17
7.91 1.42 0.9917 3 0.3034 (ZH.sub.2.sup..+-.) -0.1016 0.86-0.15
6.80-8.92 18 7.88 1.39 0.9980 Average 7.90 (2) 1.45 (8) Log K.sub.1
.sup.e = 7.90 + 0.45 log [(1 - .alpha.) / .alpha.] Monomer in 0.1 M
NaCl: Log K.sub.1 .sup.e = 7.12 .sup.a (-)ve values describe
titrations with NaOH. .sup.b data points from titration curve.
.sup.c Standard deviations in the last digit are given under the
parentheses. .sup.d R = Correlation coefficient. .sup.e log K.sub.i
= log K.sub.i.sup.o + (n - 1) log [(1 - .alpha.) / .alpha.].
[0065] Table 4 is shown below.
TABLE-US-00004 TABLE 4 Details for the Second Protonation of
Monomer ZDAN (Z.sup..+-. =) 11 and Polymer PZDAN 8 (Z.sup..+-. =)
at 23.degree. C. in Salt-Free Water. ZH.sub.2.sup..+-. or Z.sup.-
C.sub.T .sup.a run (mmol) (mol L.sup.-1) .alpha.-range pH-range
Points .sup.b Log K.sub.i.sup.o c n.sub.i .sup.c R.sub.2, d
##STR00006## Polymer in Salt-Free water 1 0.1759
(ZH.sub.2.sup..+-.) -0.1016 0.53-0.23 3.44-4.70 15 3.55 2.13 0.9986
2 0.2467 (ZH.sub.2.sup..+-.) -0.1016 0.53-0.21 3.56-4.97 16 3.64
2.25 0.9980 3 0.3244 (ZH.sub.2.sup..+-.) -0.1016 0.59-0.18
3.25-5.10 18 3.63 2.17 0.9970 Average 3.61 (5) 2.18 (6) Log K.sub.2
.sup.e = 3.61 + 1.18 log [(1 -.alpha.) / .alpha.] Monomer in
Salt-Free water: Log K.sub.2 .sup.e = 2.74 Polymer in 0.1 M NaCl 1
0.1995 (ZH.sub.2.sup..+-.) .sup.f -0.1016 0.54-0.20 2.90-3.73 15
2.97 1.24 0.9929 2 0.2486 (ZH.sub.2.sup..+-.) .sup.f -0.1016
0.56-0.18 2.92-3.88 18 3.02 1.22 0.9906 3 0.3034
(ZH.sub.2.sup..+-.) .sup.f -0.1016 0.58-0.16 2.81-3.95 19 2.94 1.29
0.9925 Average 2.98 (4) 1.25 (4) Log K.sub.2 .sup.e = 2.98 + 0.25
log [(1 - .alpha.) / .alpha.] Monomer 11 in 0.1 M NaCl:: Log
K.sub.2 .sup.e = 2.90 .sup.a (-)ve values describe titrations with
NaOH. .sup.b data points from titration curve. .sup.c Standard
deviations in the last digit are given under the parentheses.
.sup.d R = Correlation coefficient. .sup.e log K.sub.i = log
K.sub.i.sup.o + (n - 1) log [(1 + .alpha.) / .alpha.]. .sup.f
titration was carried out in the presence of 1.5-2 mL of 0.1222 M
HCl to attain the required values of the .alpha..
[0066] The higher basicity constants in salt-free water compared to
values in 0.1 M NaCl could be attributed to the entropy effects
associated with the greater release of water molecules from the
hydration shell of the repeating unit that is being protonated in
the former medium (Barbucci R, Casolaro M, Ferruti P, Nocentini M.
Spectroscopic and calorimetric studies on the protonation of
polymeric amino acids. Macromolecules 1986;
19:1856-61--incorporated herein by reference in its entirety). The
higher viscosity values in salt-free water (FIG. 5, inset) than in
0.1 M NaCl (FIG. 6) in the dilute solution range 0.03125-0.0625
g/dL ascertains the polymer backbone is highly extended and as such
more hydrated in the formnner medium. A similar concentration range
was used for the determination of basicity constants.
[0067] The higher degree of contraction in salt-free water reflects
greater changes in the hydration number which results in
entropy-driven greater basicity constants. The highest
polyelectrolyte index with a n value of 2.18 is associated with the
progressive transformation of (.+-.-) 7 to electroneutral (.+-.) 6
in salt-free water (Table 4) (FIG. 5, inset) during which the
negative charges are less accessible to protonation as a result of
their being increasingly buried in the globular conformation of
polymer backbone having ionic motifs of 6. In 0.1 M NaCl on the
other hand the 7 to 6 transformation is associated with a lesser
change in viscosity values (FIG. 6) in the dilute solutions hence
lesser changes in hydration.
[0068] FIG. 8 is a graph that displays the reduced viscosity
(.eta..sub.sp/C) at 30.degree. C. of a 0.0247 M (i.e. 1 g/dL)
solution of polymer PZA 6 in 0.1 N NaCl ( ) versus equivalent of
added NaOH at 23.degree. C. Distribution curves (dashed lines) of
the various ionized species calculated using eq 2 and pH of the
solutions in 0.1 N NaCl at 23.degree. C. FIG. 8 displays a
viscometric titration of a 0.0247 M (i.e. 1 g/dL) solution of the
polymer PZA 6 in 0.1 M NaCl with NaOH at 23.degree. C. FIG. 8 also
includes the distribution curves of various ionic specie
ZH.sub.2.sup..+-. (PZA 6), ZH.sup..+-.- (PZAN 7) and Z.sup..+-.-
(PZDAN 8) as calculated from the basicity constants (vide supra)
and pH values. The reduced viscosity increases with the increase in
concentration of added NaOH owing to increasing repulsions among
the excess negative charges as a result of transformation of
zwitterionic species (.+-.) to progressively increasing
zwitterionic/anionic (.+-.-) or zwitterionic/dianionic (.+-.=)
species.
[0069] Operation of desalination plants is often plagued by
precipitation (scale formation) of CaCO.sub.3, CaSO.sub.4,
Mg(OH).sub.2, etc. Inhibition of growth rate of crystal formation
by commonly used anionic antiscalants like poly(phosphate)s,
organophosphates, and polyelectrolytes (Gill J S. A novel inhibitor
for scale control in water desalination. Desalination 1999, 124,
43-50; David H, Hilla S, Alexander S. State of the Art of Friendly
"Green" Scale Control Inhibitors: A Review Article. Ind Eng Chem
Res 2011; 50:7601-7--each incorporated herein by reference in its
entirety) is attributed to their ability to sequestrate polyvalent
cations and alter the crystal morphology at the time of nucleation
(Davey R J. The Role of Additives in Precipitation Processes,
Industrial Crystallization 81, Eds. S. J. Jancic and E. J. de Jong,
North-Holland Publishing Co; 1982:123-135; Spiegler K S, Laird A D
K. Principles of Desalination, Part A, 2nd edn., Academic Press;
New York: 1980--each incorporated herein by reference in its
entirety).
[0070] The reject brine in the Reverse Osmosis process has
dissolved salts which precipitate in the event of exceeding their
solubility limits. Antiscalant behavior of a supersaturated
solution of CaSO.sub.4 containing 2600 ppm of Ca.sup.2+ and 6300
ppm of SO.sub.4.sup.2- was investigated using conductivity
measurements of 3CB solutions in the absence and presence of in the
presence of 20 ppm of PZA 6. The results are given in Table 5 and
FIG. 9. Table 5 is shown below.
TABLE-US-00005 TABLE 5 Concentration of Ca.sup.2+ at various times
at 50.degree. C. in the absence.sup.a and presence.sup.a of
antiscalant additive PZA 6 (20 m/L). Solution.sup.a Blank with
Inhibitor solution.sup.a Scale Time Ca.sup.2+ Ca.sup.2+ Inhibition
(min) (mg/L) (mg/L) (%) 0 19.97 19.97 -- 500 19.90 16.71 97.9 890
19.48 16.48 86.0 .sup.aboth solution contained Ca.sup.2+ and
SO.sub.4.sup.2- at a concentration of 3 times the concentration of
concentrated brine (CB) i.e. [Ca.sup.2+] = mg/L and
[SO.sub.4.sup.2-] = mg/L
[0071] A drop in conductivity is indicative of precipitation of
CaSO.sub.4. Note that precipitation started immediately in the
absence of antiscalant (FIG. 9a: Blank). FIG. 9 is a graph that
shows the precipitation behavior of a supersaturated solution of
CaSO.sub.4 in the presence (20 ppm) and absence of PZA 6. To our
satisfaction, there was no considerable change in conductivity for
about 500 min, registering a 98% scale inhibition as calculated
using eq 5:
% Scale Inhibition = [ Ca 2 + ] inhibited ( t ) - [ Ca 2 + ] blank
( t ) [ Ca 2 + ] inhibited ( t 0 ) - [ Ca 2 + ] blank ( t ) .times.
100 ##EQU00002##
where [Ca.sup.2+].sub.inhibited (t.sub.0.sub.) is the initial
concentration at time zero, [Ca.sup.2+].sub.inhibited (t) and
[Ca.sup.2+].sub.blank (t) are the concentration in the inhibited
and blank solutions at time t. It is assumed that the conductance
is proportional to the concentration of the ions. Usually a
residence time of .apprxeq.30 min for the brine in osmosis chamber
is required. It is worth mentioning that neither monomers 4 and 9
nor polymer 5 gave any effective inhibition; since screening
experiments based on visual inspection revealed that under the same
conditions the system becomes cloudy within 1 h.
[0072] Some properties of monomer 11, homopolymer 12 and copolymer
8 are given in Table 6 for the sake of comparison. Table 6 is shown
below.
TABLE-US-00006 TABLE 6 Comparative properties of monomer (.+-. =)
11, homo-(.+-. =) 12 and cyclopolymer (.+-. = ) 8. Log
K.sup.o.sub.1 Log K.sup.o.sub.2 (n.sub.1).sup.a (n.sub.2).sup.a
Salt-free 0.1M Salt-free 0.1M IE.sup.b Polymer [.eta.] Sample
H.sub.2O NaCl H.sub.2O NaCl (h) yield (dL g.sup.-1).sup.c M.sub.W
Mono- 7.53 7.12 2.74 2.90 -- -- -- -- 11.sup.d (1) (1) (1) (1)
Homo- 9.32 8.19 3.26 2.83 98% 76% 0.186 4.37 .times. 10.sup.4
12.sup.d (1.33) (1.53) (2.16) (1.60) (8.3 h) Co-8 9.51 7.90 3.61
2.98 .apprxeq.100% 87% 2.47 2.44 .times. 10.sup.5 (1.16) (1.45)
(2.18) (1.25) (45 h) .sup.an values are written in parentheses.
.sup.b1E referes to CaSO.sub.4 scale inhibition efficiency with
time written in parentheses. .sup.cViscosity of 1-0.0625% polymer
solution in 0.1M NaCl was measured with Ubbelohde Viscometer (K =
0.005718) at 30.degree. C.
[0073] Copolymer 8, obtained in higher yield, has much higher
intrinsic viscosity and molar mass as compared to homopolymer 12.
Both the polymers have similar values for the basicity constants
(log K) and polyelectrolyte index (n) even though the copolymer has
an additional electron-withdrawing SO.sub.2 spacer separating the
repeating units. This is not surprising since the spacer group is
very far away from the location of the negative charges on the
phophonate units. One notable exception is the antiscalant behavior
of the polymers, the homopolymer with low molar mass performed
better than the copolymer having much higher molar mass.
[0074] Cocyclopolymerization of and SO.sub.2 afforded the
cyclocopolymer PZ 5 in excellent yields. The PZ 5 represents the
first example of a poy(zwitterions 4-alt-SO.sub.2) (via Butler's
cyclopolymerization protocol) containing phosphonate and sulfonate
groups in the same repeating unit. The pH-responsive (.+-.) PZA 6
derived from (.+-.) PZ 5 was used to investigate pH-dependent
solution properties that involved its conversion to (.+-.-) PZAN 7
and (.+-.=) PZDAN 8 all having identical degree of polymerization.
The apparent basicity constants of the --PO.sub.3.sup.2- and
--PO.sub.3H.sup.- group in (.+-.-) PZAN 7 and (.+-.=) PZDAN 8 have
been determined. PZA 6 at a concentration of 20 ppm was found to be
an effective antiscalant in the inhibition of the formation of
calcium sulfate scale. The corrosion inhibition activities of both
the homo- and copolymer using mild steel in several media are
currently under investigation in our laboratory.
* * * * *