Engineering molecular architecture of hydrophobically modified poly(N-isopropylacrylamide)

This project was carried out to engineer protein reactive N-isopropylacrylamide (NiPAM) polymers using methylmethacrylate (MMA) to exhibit a controlled lower critical solution temperature (LCST) and to improve their gel stability. A methodology for comb-type polymer (CP) synthesis was first developed. The effect of polymer architecture and molecular weight on polymer's physical properties (i.e., LCST and gel stability) was then investigated. It was found that the LCST of CP remained unchanged as mol% MMA was increased. In contrast, LCST of random polymer (RP) decreased with increasing mol% of MMA. However, the gels of low molecular weight (MW) CPs were more stable than those of RPs. For both types of polymers, gel stability improved with increase in MW. Gel stability of CP was independent of MMA side chain length, which was between 3 and 10 kD. Protein reactive ends of these polymers were obtained by using free radical initiator with protein reactive succinimide ends during the thermal polymerization process. These end-functionalized polymers showed capacity to conjugate to the model protein, albumin. Overall, this thesis showed that the temperature sensitive polymer with controlled architecture could be engineered. In the future, these polymers will be useful in delivering immunosuppressive protein in vivo.