Synthesis, Characterization, and Aqueous Solution Behavior of Electrolyte- and pH-Responsive Carboxybetaine-Containing Cyclocopolymers
Document Type
Article
Publication Date
12-30-2003
Department
Polymers and High Performance Materials
Abstract
A novel pH- and salt-responsive carboxybetaine monomer, 4-(N,N-diallyl-N-methylammonio)butanoate (2), was prepared and cyclocopolymerized with the cationic monomer N,N-diallyl-N,N-dimethylammonium chloride (3) in 0.5 M NaCl aqueous solution (pH = 7.0) using 2-hydroxy-1-[4(hydroxyethoxy)phenyll-2-methyl-1-propanone (Irgacure 2959) as the free-radical photoinitiator. The molar feed ratio of 2:3 was varied from 100:0 to 0:100 with the total monomer concentration held constant at 2.5 M. Cyclopolymerization to five-membered ring structures common to diallylammonium salts was confirmed by C-13 NMR spectroscopy. Reactivity ratio studies indicate that 2 and 3 copolymerize in a nearly ideal fashion (r(1) = 0.86, r(2) = 0.99). Weight-average molecular weights and second virial coefficients vary from (6.0 to 12.8) x 10(4) g mol(-1) and (1.62 to 5.36) x 10(-4) mL Mol g(-2), respectively. Dilute solution viscosity behavior depends on copolymer composition, ionic strength, and pH. Copolymers with a large excess charge exhibit typical polyelectrolyte behavior, while those with balanced charge exhibit "anti-polyelectrolyte" behavior reported for zwitterionic (co)polymers. The polymers studied here are closely analogous cyclocopolymers we prevoiusly reported containing sulfobetaine mer units.(25) Unlike solutions of sulfobetaine-containing polymers, soltuions of poly(2-co-3) remain soluble at very low ionic strength even up to 100% incorporation of 2. Additionally, while the sulfobetaine systems are insensitive to pH, solutions of poly(2-co-3) exhibit a pH-dependent viscosity. All the copolymers have an apparent pK(a) of similar to3.6. Copolymers with 2 incorporations of 28 mol % and above have viscosity responsiveness between pH values of 2.5 and 4.5. The maximum pH response was achieved for solutions of poly(2-co-3) containing 37 and 56 mol % of the carboxybetaine monomer 2.
Publication Title
Macromolecules
Volume
36
Issue
26
First Page
9710
Last Page
9715
Recommended Citation
Thomas, D. B.,
Vasilieva, Y. A.,
Armentrout, R. S.,
McCormick, C. L.
(2003). Synthesis, Characterization, and Aqueous Solution Behavior of Electrolyte- and pH-Responsive Carboxybetaine-Containing Cyclocopolymers. Macromolecules, 36(26), 9710-9715.
Available at: https://aquila.usm.edu/fac_pubs/3125