N-(2-hydroxypropyl)methacrylamide-b-4-vinylpyridine (HPMA-b-VP) copolymer synthesis via RAFT method and characterization

This study aimed at synthesis and characterization of amphiphilic block copolymers by one of the living/controlled polymerization methods, named as Reversible Additional-Fragmentation Chain Transfer Polymerization (RAFT), as potential carriers for gene or drug delivery.The carrying systems formed by polymers which have amphiphilic properties came out as an effective method for the delivery of hydrophobic drugs to the cells. In addition, positively charged polymeric carriers allow DNA to enter cells as well as show great potential in drug delivery. However, physicochemical properties of synthetic polymers to be used in these studies are in great importance for efficiency and reproducibility. Therefore new methods for the synthesis of monodisperse polymers have been gaining significance in this area.Living/Controlled radical polymerization techniques have a great deal of attention because of their versatility in the production of complex macromolecular architectures with pre-estimated molecular weights and very narrow molecular weight distribution. These methods allow us to synthesize polymers various architectures (block, gradient, graft, star), monodisperse and functional.Here, poly(HPMA-b-VP) copolymer was synthesized via RAFT polymerization by which controlled structure and Mn are possible. First, N-(2-hyroxypyropyl) methacrylamide monomer was synthesized. Then suitable RAFT agent and monomer/RAFT agent/initiator ratio were determined by changing monomer/CTA/initiator ratios. Then poly(HPMA) homopolymer synthesized with chosen RAFT agent and ratio. In adiditon to the conventional heating, these reactions were also carried out by microwave heating and effect of microwave irradiation was investigated. In the following step, poly(HPMA-b-VP) copolymers were synthesized by using vinyl pyridine monomer and poly(HPMA) homopolymer as a macroCTA. Reaction kinetics of synthesized polymers were examined by using conversion (gravimetrically) and molecular weight data (by GPC). Structural and functional characterizations were determined by FT-IR and H-NMR. Then, quaternization was applied to the copolymers by using an alkyl halide to obtain permanent positive charge on the chains. In addition, the micelle formation capability, charge and size of amphiphilic polymers were examined by Zetasizer.According to the results, poly(HPMA-b-VP) copolymer was successfully synthesized via RAFT method in a controlled molecular weight and narrow size distribution. It was shown that these amphiphilic polymers have micelle-forming ability and can be partially positively charged. Therefore, these polymers have a great potential to be used in drug or gene delivery. It has been planning to study the applications of these carriers to elucidate their effectiveness in corresponding systems.