From Hyperbranched to Crosslinked Polymers by Atom Transfer RadicalPolymerization

摘要

Atom Transfer Radical Polymerization, ATRP, has provided for the control of freeradical polymerizations. The polymers which are obtained by this technique have predefined molecular weights, DP = delta(M) sub o/ (I) sub o, and low polydispersities, Mw/Mn < 1.3. This technique involves the homolytic abstraction of a halogen from an organohalide initiator by Cu (I) salts. The resulting organic radical initiates a radical polymerization which is reversibly deactivated by Cu (II) X. By use of an AB2 type monomer, where A is a halogen atom and B2 is the monomer double bond, it possible to synthesize hyperbranched polymers. One such monomer is p-chloromethylstyrene, p-CMS. The chlorine group can be abstracted to form a radical while the double bond can be polymerized. Homopolymerization of this monomer by ATRP has resulted in the synthesis of hyperbranched polystyrene. Copolymerization of p-CMS (2%) with styrene has resulted in the synthesis of branched polystyrene. However, when greater than 10% p-CMS was used, or the reaction was conducted for long reaction times, gels were formed. The synthesis of these materials and their characterization will be discussed.