Photosynthesis Of Polymer Networks With Controlled Properties By Dimerization Of Cinnamoyl Groups

Photosensitive monomers/polymers/copolymers containing a variable amount of cinnamoyl (Ci) groups ranging from 3 up to 480 per molecule were synthesized. These precursors were photocrosslinked by irradiation with UV light of wavelength 320-380 nm via the photodimerization of the Ci units. The evolution of conversion, gel fraction, modulus and T-g during irradiation was followed. Two types of photosensitive systems were studied: (i) a blend of photosensitive precursors of different functionality f(Ci) and (ii) copolymers with a different content of Ci units and T-g. The control of the precursors' structure and composition as well as photocuring time period make it possible to finely tune the properties of the formed polymer network films. The prepared photocrosslinked networks show a very broad range of thermomechanical properties with T-g from -25 degrees C up to 135 degrees C and moduli over a range of three orders of magnitude. (c) 2021 Society of Chemical Industry