Synthesis and characterizations of two stimuli sensitive polymer gels

Depending on the lower energy demands of today, stimuli-responsive sensitive polymer gels are alternatives to conventional methods which are used in separations processes for industrial applications. Temperature sensitive gels which can respond to temperature changes can be prepared using redox-initiator system and hydrophilic and acrylic monomers via lower temperature polymerization. Temperature sensitive N-isopropylacrylamide gels swell and deswell at 33-34 °C and they and it can be prepared as block or particule forms without functional groups for derivatizing. In this study, N-isopropylacrylamide (Nipa), 2-hydroxyethylmethacrylate (Hema), acrylic acid (AA), acrylic amid (AAm) were used as monomers. During polymerization potassium persulfate and Tetramemylethylendiamine (TEMED) were added to monomers mixture as a redox iniator system and temperature sensitive gels poly(Nipa-Hema), poly(Nipa-AA), pH and temperature sensitive gels poly(Nipa-Hema-AAm) were synthesized. N,N,N,N methylenebisacrylamide (MBAM) was used as the crosslJnking agent. Depending on temperature and pH, swelling, deswelling and equilibrium absorption behaviors of the synthesized gels in different mixture systems were investigated as a function of time. Water, ethyl alcohol-water, ethyl acetate - water, N,N-Dimethyacetamide (NDMAM), N,N Dimethy acetamide-water, pH=4 and pH=10 tampon mixtures were used as mixture systems. Variations in the absorption, swelling and deswelling behavior of the above mentioned gels in above mentioned mixtures were investigated due to the changes in tile ratio of monomers in gel composition, amount of crosslinking agent and neutralization degree of acrylic acid. Effect of the gel composition to its selective absorption in the mixtures was also investigated. In addition the concentration and the molecular weight of the poly(ethylene glycol) (PEG), use to obtain porous structures during polymerization, were varied to determine its effect on the swelling, deswelling and the separation behaviors of the gels. It was observed that temperature sensitive poly(Nipa-Hema) gels were sensitive composition variations in NDMAM-water mixture systems. These gels were selective to alcohol in ethyl alcohol-water mixtures and its selectivity behaviour was affected by the gel composition. It was also observed that molecular weight of the PEG affected the swelling and deswelling behaviours of poly(Nipa-Hema) gels. It was observed that selectivity behaviour of temperature sensitive poly(Nipa-AA) gels in ethyl alcohol-water mixtures were effected by neutralization degree of acrylic acid. Poly(Nipa-AA) gels do not cause any composition change in ethyl acetate-water mixture via absorption. Swelling and deswelling behaviours of poly(Nipa-AA) gels were effected by the neutralization degree of acrylic acid. Temperature and pH sensitive poly(Nipa-Hema-AAm) gels were found to be selective to alcohol in ethyl alcohol-water mixture and were selective to water in ethyl acetate-water mixture. Selectivity behaviour of the gels were affected by the gel composition and molecular weight of PEG's used during polymerization.