Alcohophilic Gels: Polymeric Organogels Composing Carboxylic and Sulfonic Acid Groups

Polymeric organogels based on acrylic acid (AA) and sodium allyl sulfonate (SAS) were prepared through solution polymerization using a persulfate initiator and a polyethylene glycol diacrylate (PEGDA) cross-linker. FTIR spectroscopy, elemental, and rheological analyses were used for a preliminary characterization. Thermo-mechanical analysis was also carried out for characterizing samples. Glass transition temperature (T-g) of copolymer was decreased after acid treatment which could be attributed to detachment of ion pairs during the post-treatment. Due to counterion binding of Na+ to form ionomer, the poly(AA-SAS) gels showed no polyelectrolyte behavior to have high swelling capacity in conventional alcohols, i.e., ethanol and methanol. It was postulated that modification via removing Na+ could help breaking ion pair aggregates which leads to swelling enhancement. Thus, poly(AA-SAS) was treated with hydrochloric acid to remove (Na+) counterions. This modification led to the gel transform from ionomer regime to a polyelectrolyte regime in which free mobile ions were existed in the network. The gel swelling capacity was increased due to raise of mobile ions after the treatment. It was found that both of the acid concentration and treatment time had constructive influence on the gel alcohophilicity. The acid-treated samples could imbibe ethanol and methanol as high as 25.8 and 39.5 g/g, respectively. They may be superior candidates for applications such as pharmaceuticals gels and fire starters. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 3350-3356, 2011