Study Of Crystal Modification And Phase Transition Behavior Of Solution Cast P3OT Film

In this paper, we studied the regio-regular poly (3-octylthiophene)(rr-P3OT) film and phase change behavior under different conditions byDSC、WAXD and FTIR.The research found that P3OT form Ⅰ′crystal can be obtained atthe appropriate annealing temperature. This new modification is similarwith the conventional form I, but with closer layer packing and higherstructural ordering. Moreover, it exhibits a distinct characteristic IR bandat826cm-1. The endothermic phenomenon around87°C is observed asheating the solution cast P3OT film with form Ⅰ′modification, which canbe assigned to the form Ⅰ′-to-form I transition. By temperature dependentIR spectroscopy, it is revealed that the stacking modes for both the octyl side chains and the conjugated backbones are rearranged in the process ofthis crystal phase transition.For the solubility of P3OT sample under the different solvents whichhave the different boiling point and the relative solubility parametercharacteristics, we found that P3OT thin film can form different crystalstructure by the different methods. The study found that the P3OT filmhad been formed the Form Ⅱ crystal via secondary film processing usingthe dry film method with chloroform as the solvent and CS2as the steam.However, it did not appear P3OT Form Ⅱ crastal when used chloroformas a solvent and used the chloroform as the steam treatment, whilemaking the conventional crystal modification Form I by controlling therapid evapor system. Thus, we found that CS2was the good solvent of theP3OT and could change the crystal structure through the comparison ofdifferent solvents.In order to study the change of P3OT film crystal infraredspectroscopy with the low temperature, we conducted the low andchange temperature FTIR experiment to the P3OT sample which was prepared by the method of the low temperature solvent annealing. Theexperiment found that P3OT octyl side chain conformational had changeda lot with the temperature.The changes were mainly the offset of the peakposition for the main chain and the small π-π interaction.