Cationic highly alcohol-swellable gels: synthesis and characterization

Cationic alcogels (alcohol-absorbing gels) based on acrylamide and methacrylamidopropyltrimethyl ammonium chloride (MAPTAC) were synthesized using solution polymerization in the presence of ammonium persulfate as an initiator and poly(ethylene glycol) diacrylate as a crosslinking agent. The swelling capacities of the gels in alcohols (i.e., methanol and ethanol) were investigated. The swelling capacities of the alcogels increased with increasing MAPTAC content, and the prepared gels had the ability to absorb up to 105.5 g/g methanol and 73.3 g/g ethanol, respectively. An ability to absorb more than 100 g/g of alcohol was only rarely observed. According to the results of rheological studies, the storage moduli of the ethanol-swollen gels were higher than those of the methanol-swollen gels, and enhancing the MAPTAC content caused the storage moduli of the gels to increase. Thermomechanical analysis was carried out to characterize the organogels. The values for the glass transition temperature (T-g) implied that the structural rigidity of the acrylamide homopolymer is higher than that of the poly(MAPTAC), which indicates that the presence of the MAPTAC units softens the system. The DMTA results showed that the intensity of the tan delta peak in the matrix region decreased with increasing MAPTAC content. Thus, acrylamide units are better than MAPTAC units at damping dynamic forces, which can be attributed to the greater chain mobility of acrylamide.