Abstract
Strong polyampholytes comprising cationic vinylbenzyl trimethylammonium chloride (VBTAC) bearing a pendant quaternary ammonium group and anionic sodium p-styrenesulfonate (NaSS) bearing a pendant sulfonate group were prepared via reversible addition-fragmentation chain-transfer polymerization. The resultant polymers are labelled P(VBTAC/NaSS)n, where n indicates the degree of polymerization (n = 20 or 97). The percentage VBTAC content in P(VBTAC/NaSS)n is always about 50 mol%, as revealed by 1H NMR measurements, meaning that P(VBTAC/NaSS)n is a close to stoichiometrically charge-neutralized polymer. Although P(VBTAC/NaSS)n cannot dissolve in pure water at room temperature, the addition of NaCl or heating solubilizes the polymers. Furthermore, P(VBTAC/NaSS)n exhibits upper critical solution temperature (UCST) behavior in aqueous NaCl solutions. The UCST is shifted to higher temperatures by increasing the polymer concentration and molecular weight, and by decreasing the NaCl concentration. The UCST behavior was measured ranging the polymer concentrations from 0.5 to 5.0 g/L.
Highlights
Stimuli-responsive polymers change their physical and chemical properties in response to changes in external conditions such as temperature, pH, solvent ionic strength, light irradiation, and the application of electric and magnetic fields
upper critical solution temperature (UCST) polymers become soluble upon heating, and this quality has the potential to be exploited in biomedicine as a means for Polymers 2019, 11, 265; doi:10.3390/polym11020265
NaSS monomers at two different of we introduce strong polyampholytes prepared via reversible addition-fragmentation addition-fragmentation chain-transfer chain-transfer (RAFT) that exhibit polymerization (DP), i.e.,prepared
Summary
Stimuli-responsive polymers change their physical and chemical properties in response to changes in external conditions such as temperature, pH, solvent ionic strength, light irradiation, and the application of electric and magnetic fields. Phase diagram analysis can differentiate thermo-responsive polymers into lower or upper critical solution temperature (LCST or UCST) types by the position at which the miscibility gap is observed, i.e., at high or low temperature, respectively [8,9]. UCST behavior in water to the strong interactions between the groups charged[18,19]. Few studies in the literature have addressed the controlled of polyampholytes or ofidentifying and maintaining ratiosthe of proper anionic andofcationic radical polymerization polyampholytes or identifyingthe andproper maintaining ratios anionic monomers. Andare anionic sodium p-styrenesulfonate wellover thestyrene-type polymerization of a polyampholyte has over a strong on its UCST known monomers [24,29].
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