Synthetic Method for a Highly Insulated Conjugated Polymer Using Host-Guest Bridged Pseudorotaxane as a Monomer

Abstract

Insulated conjugated molecular wires have attracted much attention because of their interesting optical and electronic behavior attributed to blocking the interchain interactions of conjugated molecular wires. Herein, we describe the novel synthetic method for a polyrotaxane as a highly insulated conjugated molecular wire using a pseudorotaxane as a monomer. The pseudorotaxane was prepared via double self-inclusion of symmetric oligo(phenyleneethynylene) derivatives attached with two cyclodextrins in aqueous MeOH. Formation of this pseudorotaxane was confirmed by 2D ROESY NMR spectroscopy in D2O:CD3OD = 1:1. Then formed pseudorotaxane was polymerized by Hay coupling reaction in aqueous MeOH. According to size-exclusion chromatography (SEC) analysis of the obtained polyrotaxane, the average molecular weight and the average repeating units were estimated as 119,000 and 43, respectively using polystylene as a calibration standard. The polyrotaxane was readily soluble in common organic solvents such as chloroform, ethylacetate and THF. Atomic force microscopy (AFM) images of the polyrotaxane on mica substrate indicated that the shape of a polyrotaxane was highly rigid linear and the chain length was above 200nm.