Thermal Properties of Poly(3-(2′-Ethyl)Hexylthiophene): Study with a Real-Time Combination of Synchrotron X-Ray Scattering and Ultrafast Chip Calorimetry

Abstract

Here we report on reorganization on heating of a perspective organic semiconductor poly(3-(2′-ethyl)hexylthiophene) (P3EHT). P3EHT is an analogue of a well-known poly(3-hexylthiophene) (P3HT), which has comparable optoelectronic properties and the advantage of a lower processing temperature. The processes of structural reorganization during heating of P3EHT have been explored with a combination of synchrotron X-ray scattering and ultrafast chip calorimetry. The signature of reorganization has been identified from an increase of d-spacing of 100 peak of the P3EHT unit cell. It was observed that reorganization operates during heating of P3EHT at conventional rates of a DSC experiment (i.e., at 10 deg/min), whereas it is largely suppressed at a heating rate of 100 deg/s. Despite the absence of reorganization at high heating rates the calorimetric curves exhibit pronounced double melting, which corroborates the model of the negative pressure building up during crystallization of semi-rigid chain polymers.