Photoresponsive Spiropyran and DEGMA-based Copolymers with Photo-switchable Glass Transition Temperatures.

Herein, novel photo-responsive spiropyran-based P(DEGMA-co-SpMA) copolymers with variable percentages of spiropyran fractions are synthesized. The spiropyran group present in these polymers exhibited abilities of reversible photo-isomerism. Their photo-responsive, structural and thermal properties have been investigated and compared, using various characterization techniques. These light-responsive copolymers are found to exhibit photoswitchable glass transition temperature (Tg ), high thermal stability (Td > 250°C), instant photochromism as well as fluorescence, upon exposure to UV light. It is demonstrated that the Tg of these synthesized polymers increased when irradiated with UV light (λ = 365 nm), as a consequence of the photo-isomerization of incorporated spiropyran groups into its merocyanine form. This increase in Tg is attributed to an increase in polarity and a decrease in the overall entropy of the polymeric system when it switches from the ring-closed spiropyran form (less-ordered state) to the ring-opened merocyanine form (more-ordered state). Therefore, such polymers with a unique feature of photo-tunable glass transition temperatures provide the possibility to be integrated into functional materials for various photo-responsive applications. This article is protected by copyright. All rights reserved.