Jong Myung Park

Dual temperature and thiol-responsive POEOMA-multisegmented polydisulfides: Synthesis and thermoresponsive properties

New thermoresponsive polydisulfides of POEOMA multiblocks linked with disulfide bonds having redox-responsive properties are reported. These POEOMA-multisegmented polydisulfides were synthesized by a new method employing a combined RAFT/aminolysis and reversible thiol-disulfide redox reaction that centers on the synthesis of new disulfide-labeled difunctional RAFT agent. RAFT polymerization proceeded in living fashion, yielding well-defined POEOMA copolymers with middle disulfides and terminal RAFT species. They were then used as precursors for thiol-disulfide polyexchange induced by aminolysis and reductive reaction followed by oxidation: these polydisulfides with different molecular weights and end groups exhibited tunable thermoresponsive properties and thiol-responsive degradation.

Synthesis and Characterization of Poly(Oligoethyleneglycol Methacrylate)-g-TiO2 Nanocomposites via Surface-Initiated ARGET ATRP

Poly(oligoethyleneglycol methacrylate) (POEGMA) covalently attached to TiO2 nanoparticles (NPs) were synthesized by the surface-initiated ARGET ATRP. The growth of polymer chains from the surface of ATRP-initiator functionalized nanoparticles was achieved under mild condition by using copper (II) as a catalyst and zerovalent copper (Cu0) or L-ascorbic acid (AsAc) as reducing agents. The as-synthesized nanocomposites were characterized by FT-IR, TGA, FE-SEM and TEM analyses. FT-IR results suggested the formation of polymer chains covalently attached to the TiO2 nanoparticles. The nanoparticles were found to be imbedded in polymer matrices as revealed by TEM and FE-SEM images. TGA curves demonstrated that AsAc afforded the faster grafting rate over Cu0.

Effect of Solvent Vapor on the Morphology of Fluorinated Block Copolymer Films from Different Casting Solvent

Poly(ethylene oxide)-b-poly(1H,1H-dihydroperfluorooctyl methacrylate) (PEO-b-PFOMA) micellar films were cast from chloroform or α,α,α-trifluorotoluene (TFT) with different copolymer concentrations, followed by TFT or PF-5080 vapor treatment. Though their initial morphologies were different, finally the same patterns were obtained under TFT or PF-5080 vapor with varying the annealing time. The time dependent phase behavior was examined at different stages.