Synthesis and characterization of poly(methyl acrylate) grafted from poly(thiophene) to form solid-state fluorescent materials

This paper describes the synthesis and characterization of graft copolymers having a poly(thiophene) (PT) backbone with poly(methyl acrylate) (pMA) sidearms. Thiophene monomer containing a protected alcohol group was prepared and polymerized via the McCullough method to yield regioregular PT. The backbone was then functionalized to contain an atom-transfer radical polymerization (ATRP) initiator at approximately 90% of the repeat units as determined through H-1 NMR analysis, yielding 2,5-poly(3-[1-ethyl-2-(2-bromopropionate)]thiophene). From these initiator sites, MA was polymerized to yield well-defined polymer brushes. The addition of the sidearms to the thiophene backbone resulted in twisting of the backbone as a result of steric effects, which caused a decrease in conjugation length of the PT. In the solid state, the sidearms trap the PT in a "solution-like" conformation. In addition, these arms serve to separate PT chains and disrupt the ordered array usually seen in regioregular PT. With a lower conjugation length and isolated PT chains, the material achieved a photoluminescent yield of up to 40% in the solid state.