Synthesis and characterization of amphiphilic, zwitterionic polymers and the study of solution behavior upon addition of surfactant

Kathryn Marie Johnson

Abstract

A novel series of hydrophobically modified water-soluble polyzwitterions incorporating acrylamide and N,N-dimethyl-N-3' -(N ' acryloyl) aza-tridecyl) ammonio propane sultone (DAATAPS) 8 was synthesized. Free radical micellar polymerization techniques were utilized to target copolymers containing a 99:1 molar ratio of these respective monomers. The surfactant-to-monomer ratio (SMR of betaine-to-sodium dodecyl sulfate) was varied to control microstructural architecture. An analogous carboxybetaine polymer series was synthesized containing acrylamide and 3-(N,N-dimethyl-N-3 ' -(N' acryloyl)aza-tridecyl) ammonio butanoate (DAATAB) 11 . Viscosity profiles of both the sulfobetaine and carboxybetaine copolymers indicate that low SMR values result in more effective associative thickening behavior, and addition of NaCl produces negligible change in the solution viscosity of all polymers due to the low betaine concentration. Interactions of the amphiphilic polymers with added surfactant were studied utilizing Triton X-100, N-dodecyl-N,N-dimethylammonio-1-propanesulfonate (SB3-12), sodium dodecyl sulfate (SDS), and dodecyltrimethylammonium bromide (DTAB). Polymers synthesized at low SMR values (and likely blocky microstructures) were found to be the most responsive to surfactant. SDS was found to exert the greatest effect on viscosity when added to these polymers below c*. Also, novel acrylamide-based terpolymers containing acrylamide, butylphenylacrylamide, and either 3-(2-acrylamido-2-methylpropanedimethylammonio)-1-propanesulfonate (AMPDAPS) 8 or 4-(2-acrylamido-2-methylpropyldimethylammonio) butanoate (AMPDAB) 11 were successfully synthesized using micellar techniques. Viscosity profiles of the sulfobetaine polymers indicate larger viscosity values above c* for HSB5 17-5 , while those for HSB25 17-25 remained below acrylamide viscosity values. The addition of NaCl has a negligible effect on most sulfobetaine polymers; however, carboxybetaine polymers are responsive, with most showing an initial decrease, then subsequent increase. The effect of pH on the sulfobetaine polymers is negligible due to the low pK a of the sulfonate ion. In contrast, all carboxybetaine polymers are responsive to pH, with HCB25 22-25 showing complex behavior. All hydrophobically modified polymers were shown to interact with surfactant through viscometry and surface tension analyses. All surfactants studied produced viscosity changes consistent with a generally accepted model. SDS was found to have the greatest effect on viscosity behavior, followed by SB3-12 and DTAB, then Triton X-100. Surface tension experiments generally corroborate viscosity indications of surfactant-polymer interactions. However, the surface tension profiles of polymer-DTAB interaction are complex and do not follow anticipated trends.