Abstract
The measurement of the mechanical properties of conjugated polymers can reveal highly relevant information linking optoelectronic properties to underlying microstructures and the knowledge of the glass transition temperature (T-g) is paramount for informing the choice of processing conditions and for interpreting the thermal stability of devices. In this work, we use dynamical mechanical analysis to determine the T-g of a range of state-of-the-art conjugated polymers with different degrees of crystallinity that are widely studied for applications in organic field-effect transistors. We compare our measured values for T-g to the theoretical value predicted by a recent work based on the concept of effective mobility zeta. The comparison shows that for conjugated polymers with a modest length of the monomer units, the T-g values agree well with theoretically predictions. However, for the near-amorphous, indacenodithiophene-benzothiadiazole family of polymers with more extended backbone units, values for T-g appear to be significantly higher, predicted by theory. However, values for T-g are correlated with the sub-bandgap optical absorption suggesting the possible role of the interchain short contacts within materials' amorphous domains.