Preparation Of Amphiphilic Block Copolymer PSt-b-PVP By Initiation Of Cerium Salt In Micellar Solution And The Study On Its Self-Assembly Behavior

The amphipathicity and microcosmic segregation of Amphiphilic blockpolymer make it special on physicochemical property and self-assembly behavior, greatly used on lots of science and technology fields. In the micellar solution, free radical polymerization was used to prepare the block copolymer of hydroxyl-terminated (PSt-OH) and N-vinyl pyrrolidone (NVP), and study its self-assembly behavior. The system and method were hardly reported, so its are fresh in area of preparing Amphiphilic blockpolymer.The emulsion polymerization of styrene (St) was first carried out by initiating of H2O2/Fe2+ redox initiation system, and polystyrene with hydroxyl group as end group, PSt-OH, was obtained. FTIR,DSC were adopted to characterize the chemical structure and thermal behavior of PSt-OH;GPC was adopted to characterize the molecular weight and its distribution; Viscometricmethod was adopted to detect the intrinsic viscosity[η]. Subsequently, the macromolecules PSt-OH were solubilizated in the micellar solution of sodium dodecylsulfate (SDS), and the block polymerization of N-vinylpyrrolidone (NVP) in the aqueous solution at the end group of PSt-OH was initiated by Cerium ammonium sulfate, resulting in the amphiphilic block copolymer PSt-b-PVP. FTIR, 1H-NMR, GPC and DSC were adopted to characterize the chemical structure, molecular weight distribution and thermal behavior of PSt-b-PVP; ultraviolet spectrophotometry was used to measure the cotent of PVP. The experimental results show that by the oxidation action of cerium (Ⅳ) salt, free radicals can be produced at the sites of the hydroxyl groups of PSt-OH, which are solubilized in the micellar solution of SDS, and the block copolymerization of NVP can be favorably realized. With the copolymerization time increase, the content of PVP block is increased.Self-assembly behavior of copolymers were determined by surface tension and fluorescence probe technique: (1) surfactivity and critical associating concentration (CAC) was determined by Surface tension ,and the content of PVP to the CAC andγCAC was research; (2) the hydrophobic associating properties of copolymer PSt-b-PVP was explored by pyrene fluorescence probe. The experimental results show that amphiphilic blockpolymer will happen to self aggregation, and to reduce the surface tension; the mensuration result of surface tension and fluorescence probe technique are accordance: when the content of PVP block increased in the amphiphilic blockpolymer PSt-b-PVP, The CAC and surface tensionγCAC increase too.