Atom transfer radical polymerization of (meth)acrylates from poly(dimethylsiloxane) macroinitiators

The atom transfer radical polymerization (ATRP) of (meth)acrylates from poly(dimethylsiloxane) (PDMS) macroinitiators is described. Hydrosilylation of commercially available difunctional hydrosilyl terminal PDMS (M-w/M-n > 1.3) with allyl- or 3-butenyl 2-bromoisobutyrate resulted in the macroinitiators. Linear semilogarithmic kinetic plots were obtained for the ATRP of acrylates and methacrylates. A nonlinear dependence of molecular weight on conversion was ascribed to a high concentration of low molecular weight chains not readily observed in the size exclusion chromatograph using THF as eluent. Well-defined monofunctional, low-polydispersity PDMS macroinitiators were synthesized by the anionic ring-opening polymerization of hexamethylcyclotrisiloxane. ATRP of acrylates and methacrylates from those compounds showed linear increases in Mn with conversion, demonstrating the effectiveness of ATRP to synthesize a variety of inorganic/organic polymer hybrids. A monofunctional poly(styrene-b-dimethylsiloxane) macroinitiator was used to initiate ATRP of n-butyl acrylate and methyl methacrylate, resulting in ABC organic/inorganic/organic hybrid triblock copolymers.