Sol–gel preparation and photophysical properties of pseudo-interpenetrating polymer networks based on poly(3-alkylthiophene)/polysiloxane glass

In this work poly(3-hexadecylthiophene) (P3HDT) was dispersed in a polysiloxane polymer network and in a hybrid organic inorganic copolymer network polysiloxane/(3-mercaptopropyl)trimethoxysilane (3MPTMOS) using the sol–gel process. Spectroscopic analysis in the ultraviolet–visible region as a function of temperature shows that the tetraethoxysilane/poly(3-hexadecylthiophene) (TEOS/P3HDT) pseudo-interpenetrating polymer network (pseudo-IPN) has emission band centered at 5400±75 Å at 25°C which we attribute to P3HDT. At 100°C this emission band intensity decreases by almost half and has blue shift to 5000±100 Å. As the temperature is further increased an increase in the intensity of this 5000±100 Å band is observed. On the other hand the TEOS-3MPTMOS/P3HDT pseudo-IPN has an emission maximum at 5000±100 Å at 25°C and instead of a blue shift an unusual red shift to 5800±100 Å is observed as the temperature increases. Using sol–gel processing techniques we have prepared a new type of luminescent glass composite with luminescence properties covering a region of the visible spectrum from 4000 to 7000 Å. The control of the electronic and optical properties we explain by the interaction and geometric restriction imposed by the inorganic host matrix together with the thermochromic properties of P3HDT.