UV absorption spectra of poly(methylphenylsilane) films were measured at varying temperatures from 25°C to 200°C and a new thermal hysteresis in UV absorption of the polysilane films was observed. Once a polysilane film was annealed above its glass transition temperature, its UV absorption spectrum greatly and irreversibly changed. In other words, the absorption spectrum intrinsic to a particular polysilane film is obtained only after it is annealed above its Tg. This thermal hysteresis is discussed in relation to the changes in the micrtoscopic free spaces and in the hole transport characteristics between the annealed and non-annealed polysilane films. We concluded that after a polysilane film is annealed above its Tg, there occurs an irreversible re-distribution of the σ-conjugated domains in a way as to increase their average size.
T. Dohmaru, K. Oka, T. Nakamura, H. Naito, "Thermal Hysteresis in UV Absorption of Polysilane Films" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP14), 1998, pp 544 - 547, https://doi.org/10.2352/ISSN.2169-4451.1998.14.1.art00052_2