Water-soluble polymers. 77. Amphoteric cyclocopolymers with sulfobetaine units: Phase behavior in aqueous media and solubilization of p-cresol in microdomains
Polymers and High Performance Materials
A novel series of cyclocopolymers containing the ps-responsive hydrophobic monomer, N,N-diallyl-N-methylamine (DAMA), and the sulfobetaine monomer, 3-(N,N-diallyl-N-methylammonio)-propanesulfonate (DAMAPS), have been prepared in 0.5 M NaCl aqueous solution (pH = 4.0) using 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure 2959) as the free-radical photoinitiator. The feed ratio of DAMA:DAMA:DAMAPS was varied from 100:0 to 0:100 mol % with the total monomer concentration held constant at 2.5 M. C-13 NMR data indicate that the resulting polymers maintain the five-membered-ring structure in the cis conformation common to cyclized diallylammonium salts. Reactivity ratio studies predict that the sulfobetaine monomer is incorporated randomly along the polymer backbone. Weight-average molecular weights and second virial coefficients vary from (4.00 to 8.42) x 10(4) and (2.14 to 4.62) x 10(-4) mt mol g(-2), respectively. Solution behavior is dependent upon pH as determined by turbidimetric titration, steady-shear viscometry, and equilibrium surface tensiometry. At high degrees of ionization, the copolymers assume an extended conformation due to the charge-charge repulsions along the copolymer backbone. As the molar incorporation of the sulfobetaine increases, the copolymer assumes a more globule-like conformation due to zwitterionic interactions. With decreasing degree of ionization of the DAMA units, hydrophobic associations increasingly dominate the solution behavior. For copolymers with a low incorporation of the sulfobetaine, chain collapse leading to phase separation occurs. However, at higher incorporations, the sulfobetaine acts as a hydrophilic segment to limit hydrophobic packing and minimizes the chain collapse. Equilibrium dialysis experiments demonstrate that these ps-reversible microdomains can be used to control the sequestration of organic foulants and thus have potential application as polymeric surfactants in micellar enhanced ultrafiltration processes for water purification.
McCormick, C. L.
(2000). Water-soluble polymers. 77. Amphoteric cyclocopolymers with sulfobetaine units: Phase behavior in aqueous media and solubilization of p-cresol in microdomains. MACROMOLECULES, 33(8), 2944-2951.
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