In Situ Monitoring the Thermal Degradation of PCPDTBT Low Band Gap Polymers with Varying Alkyl Side-Chain Patterns

Abstract

The degradation pattern of a series of low band gap PCPDTBT polymers under thermal stress is investigated by in situ UV-vis and FT-IR techniques combined with thermal degradation analysis. Thermogravimetric analysis is used to predetermine the decomposition intervals, revealing that thermolysis occurs in two stages. TG-TD-GC/MS shows that loss of the alkyl side chains predominantly happens within the first temperature regime and degradation of the polymer backbone occurs thereafter. UV-vis spectroscopy is used to monitor the evolution of the optical properties upon heating, reflecting the thermal stability of the conjugated backbone, whereas FT-IR spectroscopy is applied to evaluate the chemical changes under thermal stress, with an emphasis on the polymer periphery. The influence of the side chains and possible defects, dependent on the synthesis protocol applied, on the thermal stability of the final polymers is discussed and is related to the application of said materials in organic photovoltaics. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4912-4922