The Study Of Controlled/Living Free Radical Polymerization And Its Application

Controlled / living free radical polymerization have recently attracted considerable attention and there have been numerous studies in the field of macromolecules. There are many methods to synthesis polymer, such as living ring opening polymerization , living anionic polymerization, living cationic polymerization, nitroxide-mediated polymerization, reversible addition-fragmentation chain transfer polymerization and atom transfer radical polymerization and so on.In this paper, a series of polystyrene, poly(4-vinylpyridine), polystyrene-block-poly(4-vi-nylpyridine) (PS-b-P4-VP) were synthesized by using living free radical polymerization initiated by benzoyl peroxide (BPO) in the presence of 4-hydroxyl-2, 2, 6, 6-tetramethylpiperridine-oxyl-l(HTEMPO.). The polystyrene and diblock copolymers were characterized by gel permeation chromatography (GPC) and fourier transform infrared spectroscopy (FTIR). The morphologies of PS/P4-VP/P(St-b-4-VP) was imaged by atomic force microscope(AFM). Experimental results have showed that the polymerization of styrene has "living" nature, the molecular polydispersities of synthesized polystyrene is in the range of 1.15 to 1.25. The polystyrene with "living" ends can initiate the living free radical polymerization of 4-vinylpyridine in the presence of 4-hydroxyl-2, 2, 6, 6-tetramethylpiperridine-oxyl-1 to sequentially form the polystyrene-block-poly- (4-vinylpyridine) with molecular polydispersities in the range of 1.12 to 1.35 and molecular weight in the range of 14000 g/mol to 20000g/mol. The structure of diblock was determined by FTIR. The diblock polymerization (PS-b-P4-VP) is good compatibiliers for PS and P4-VP.On the other hand, a new method of fabricating a brush-like polystyrene layer anchored on the surface of the silicon substrate was described, which involves three steps, namely (i) the attachment of 3-methacryloxypropyltrimethoxysilane onto the silicon surface;(ii) the reaction of vinyl moiety at another extremity of the anchored 3-methacryloxypropyltri-methoxysilane to 4-Hydroxyl-2, 2, 6, 6-tetramethyl-1-piperidinyloxy (HTEMPO.) catalyzed by Benzoyl Peroxide (BPO);(iii) living free radical graftingpolymerization in the presence of HTEMPO. The controllable living free radical polymerization permits accurate control of both the molecular weight and the polydispersity. X-photoelectron spectroscopy measurement proved that the alkoxyamine initiator layer was formed on the silicon surface. XPS and Ellipsometry measurements showed that the polymers' chains were covalently anchored onto the silicon surfaces. The thickness of the grafted polymer layer can be accurately manipulated by altering the polymerization time. The new method allows synthesizing random copolymer and block copolymers by the sequential growth of monomers from the substrate surface.