Structural and thermal behavior of poly(3-octylthiophene): a DSC, C-13 MAS NMR, XRD, photoluminescence, and Raman scattering study

This work tries to give an answer to questions persisting over a decade in literature, concerning poly(3-alkylthiophene)s: polymorphism and phase stability related to the molecular masses, their distribution, the degree of regioregularity, the length of the side chain, and its nature. In fact we have studied, by means of five different techniques, the structural and thermal behavior of poly(3-octylthiophene) prepared by Ni catalyzed polymerization. A different thermal behavior for the rod-like conjugated backbone and for the side chains has been found having a strong influence both on the structural arrangement and the photoluminescence properties of the polymer. A thermal transition occurring at 84°C was found to correspond to the trans to gauche transition in the side chain conformations without a relevant change in the conjugated backbone planarity.