Siloxyl and Hydroxyl functionalized polymers by atom transfer radical polymerization

Abstract

The syntheses of siloxyl and hydroxyl chain end functionalized polystyrene and poly(methyl methacrylate) by Atom Transfer Radical Polymerization (ATRP) were effected by the following methods: (a) α-Siloxyl functionalized polymers were prepared in quantitative yields via a one-pot ATRP synthesis method for the polymerization of styrene or methyl methacrylate using a new siloxyl functionalized initiator adduct, formed in situ by the reaction of (1-bromoethyl)benzene with 1-(4-t-butyldimethylsiloxyphenyl)-1- phenylethylene in the presence of CuBr/bpy or CuBr/PMDETA as catalysts in diphenyl ether at 90 -110 oC. The polymerizations proceeded via controlled living radical polymerization methods and α-siloxyl functionalized polymers with predictable number average molecular weights (Mn = 1.8 x 103 - 17.40 x 103 g/mol), narrow molecular weight distributions (Mw /Mn = 1.03 - 1.41) and regiospecificity of the functional groups were obtained in quantitative yields. Similarly, the one-pot ATRP synthesis method for the preparation of α-bis(siloxyl) functionalized polymers were effected by the initiation of styrene or methyl methacrylate polymerization with a new bis(siloxyl) functionalized initiator adduct, formed by the in situ reaction of 1,1-bis(4-t-butyldimethylsiloxylphenyl)- ethylene with (1-bromoethyl)benzene in the presence of CuBr/bpy or CuBr/ PMDETA as catalytic systems in diphenyl ether at 90 -110 oC. Each polymerization reaction proceeded via a controlled living fashion to afford quantitative yields of the corresponding α-bis(siloxyl) functionalized polymers with predictable number average molecular weights (Mn = 1.7 X 103 - 15.00 x 103 g/mol), narrow molecular weight distributions (Mw /Mn = 1.03 - 1.35) and good control of chain end functionality.

The acid catalyzed hydrolysis of α-siloxyl and α-bis(siloxyl) chain end functionalized polymers afforded the corresponding α-hydroxyl and α-bis(hydroxyl) chain end functionalized polymers, respectively. Polymerization kinetic data was employed to determine the controlled/living character of each ATRP reaction leading to the formation of different siloxyl functionalized chain end functionalized polymers. Polymerization kinetic measurements show that the polymerization follows first order rate kinetics with respect to monomer consumption and the number average molecular weight increases with percentage monomer conversion, resulting in the formation of polymers with narrow molecular weight distributions. Thin layer chromatography (TLC), 1H and 13C Nuclear Magnetic Resonance Spectrometry (NMR), Fourier Transform Infrared Spectroscopy (FTIR), Size Exclusion Chromatography (SEC), Gas Chromatography (GC) and non - aqueous titrations were used to determine the structures and purity of the siloxyl functionalized initiator precursors as well as the siloxyl and hydroxyl functionalized polymers.