Eric Fossum

Synthesis of Block, Graft and Star Polymers from Inorganic Macroinitiators

Recent advances in the synthesis of block, graft and star polymers containing inorganic macromolecular species are described. Anionic copolymerization techniques were used in the formation of diblock copolymers of poly(styreneblock-methylphenylsilylene) and poly(isopreneblock-methylphenylsilylene) by the ring-opening polymerization of 1,2,3,4-tetramethyl-1,2,3,4tetraphenylcyclotetrasilane initiated by living anionic polystyrene and isoprene respectively. Hydrosilation of an attachable initiator onto telechelic vinyl- or hydrosilyl-terminal or -pendant poly(dimethylsiloxane) (PDMS) yielded a PDMS macroinitiator. This macroinitiator was used in atom transfer radical polymerization (ATRP) of styrene and isobornyl acrylate to produce ABA triblock copolymers. As a model for graft copolymers from a polyphosphazene backbone, chemical transformation of hexachlorocyclotriphosphazene resulted in hexafunctional molecules containing either benzyl bromide or bromopropionyl moieties. The initiator 1,1,3,3,5,5-hexakis[4-(2bromopropionyloxymethyl)phenoxy]cyclotriphosphazene was used in the ATRP of styrene to yield a polymer with a narrow, monomodal molecular weight distribution. Chain extension of this star polymer with isobornyl acrylate is also described. # 1998 John Wiley & Sons, Ltd.

SYNTHESIS AND CHARACTERIZATION OF POLYSTYRENE-BLOCK-POLY(METHYLPHENYLSILYLENE) AND POLYISOPRENE-BLOCK-POLY(METHYLPHENYLSILYLENE)

Abstract Polystyrene/poly(methylphenylsilylene) and polyisoprene/poly(methylphenylsilylene) block copolymers were prepared by two independent methods. Subsequent additions of solutions of cyclotetrasilanes in benzene to the living ends of the polystyrene and polyisoprene resulted in the formation of well-defined block copolymers with narrow molecular weight distributions ( M w / M n 1 H and 29 Si NMR, GPC, DSC and elemental analysis.

Microstructure in the Ring Opening Polymerization of Cyclotetrasilanes

Abstract Cyclotetrasilanes with methyl and phenyl substituents Si4MenPh8-n (n=3,4,5,6) have been prepared by dearylation of octaphenylcyclotetrasilane and subsequent nucleophilic displacement with methylmagnesium bromide. All monomers are sufficiently strained to be polymerized to high molecular weight linear polysilanes. Ring Opening Polymerization, ROP, of cyclotetrasilanes proceeds with considerable stereoselectivity and regioselectivity. Silylcuprates lead to two inversions of configuration at both the attacked Si atom and at the newly developed active center. The assignment of 29Si NMR signals for poly(methylphenylsilylene) to heterotactic (−38.5 ppm), syndiotactic (−39.0 ppm) and isotactic (−41.0 ppm) triads has been determined based on the polymerization of various mixtures of stereoisomers