Processible poly[(p-phenyleneethynylene)-alt-(2,5-thienyleneethynylene)]s of high luminescence: their synthesis and physical properties

Abstract

Several alternating copolymers, poly[(p-phenyleneethynylene)-alt-(2,5-thienyleneethynylene)]s (PPETEs), have been synthesized by using a Heck-type coupling reaction under mild conditions. The polymers are characterized by using 1H and 13C NMR, UV-VIS absorption and fluorescence spectroscopy. PPETEs produced under the mild conditions exhibit longer conjugation length (ca. 10nm in UV-VIS absorption lambda;max) than the same polymers synthesized at high temperature. The chain rigidity of the copolymers is moderate with Mark-Houwink constant alpha;=0.82-0.94, which is moderately higher than PTE 2 (alpha;=0.68) but significantly lower than PPE 3 (alpha;=1.92). The PL quantum efficiencies of PPETE copolymers are found to be phis;fl=0.37-0.48, which is comparable to PPE homopolymers and much higher than for PTE (phis;fl=0.18). Synthesis of copolymer PPETE thus successfully combines both the high luminescence of PPE and good solubility of PTE into a single polymer chain.-6