Synthesis of Chain End Functionalized Multiple Hydrogen Bonded Polystyrenes and Poly(alkyl acrylates) Using Controlled Radical Polymerization

Abstract

Hydrogen bonding uracil functionalized polystyrenes and poly(alkyl acrylate)s were synthesized via stable free radical polymerization. Quantitative chain end functionalization was achieved using novel uracil containing TEMPO- and DEPN-based alkoxyamine unimolecular initiators. Polymerizations were conducted at 130 °C and yielded functionalized homopolymers with narrow molecular weight distributions (Mw/Mn ∼ 1.20) and predictable molecular weights. Polymerizations of both n-butyl acrylate and styrene using the DEPN- and TEMPO-based alkoxyamines resulted in molecular weight control over a wide range of conversions. Terminal functionalization of poly(alkyl acrylate)s with hydrogen bonding groups increased the melt viscosity at temperatures below 80 °C, which was defined as the dissociation temperature, and as expected, the viscosity approached that of the nonfunctional analogues above this temperature. The hydrogen bonding effect was also evident in thermal (DSC) analysis and 1H NMR spectroscopic investigations, and low molar mass polystyrenes exhibited glass transition temperatures that were consistent with a higher apparent molar mass. 1H NMR spectroscopy confirmed the presence of a single hydrogen bonding group at the chain terminus, which was consistent with a well-defined initiation process for two families of novel alkoxyamines.