Electrolyte and pH Responsive Surfactant Association in Ionic Semi-Interpenetrating Networks Containing Cellulose or Chitin Synthesized in Lithium Chloride N,N-Dimethylacetamide

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Polymers and High Performance Materials


Semi-interpenetrating networks (SIPNs) of N,N-dimethylacrylamide (DMAm)-N,N-dimethylamino-ethylacrylamide (DMAEAm), or N,N-dimethylacrylamide (DMAm)-2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) containing cellulose or chitin were synthesized in 9% LiCl-N,N-dimethylacetamide (DMAc). The SIPNs were formulated to contain (1, 2, or 5% w/w) cellulose or 0.8% w/w chitin. Control systems (without polysaccharide) were also synthesized in 9% LiCl-DMAc. An acrylamide (Am)AMPS hydrogel was synthesized for comparison with the SIPN composites. The swelling behavior of these materials was investigated as a function of pH (DMAEAm-containing networks) or electrolyte concentration (AMPS-containing networks). The DMAm-AMPS materials were found to have higher equilibrium water content (EWC) values in deionized water than the DMAm-DMAEAm materials. The EWC of the DMAm-DMAEAm materials was largest between pH 4 and 5 due to the protonation of the tertiary amine, with the chitin-containing material exhibiting the largest EWC. The DMAm-AMPS materials exhibited a decrease in EWC values with an increase in electrolyte concentration. Polymer-surfactant interactions were shown to exist for surfactants of opposite charge of the ionic mer units incorporated into the polymeric network. Surfactant sequestration by the polysaccharide-containing materials was greater than that of the control gels; however, the rates of surfactant binding were lower. Release of the bound surfactant was achieved by the disruption of the charge-charge interactions by changing the pH of the medium (DMAEAm-containing networks) or by the addition of electrolyte (AMPS-containing networks). The DMAm-DMAEAm SIPNs released only 4% of the surfactant originally sequestered. By contrast, the DMAm-AMPS SIPNs released approximately 80%. The control Am-AMPS hydrogel-surfactant complex collapsed in the presence of electrolyte, and no surfactant was released from the complex. (C) 1999 John Wiley & Sons, Inc.

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Journal of Applied Polymer Science





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