Epoxy-Based Azopolymers with Enhanced Photoresponsive Properties Obtained by Cationic Homopolymerization

Azopolymers are highly versatile materials due to their unique photoresponsive properties. In this contribution, a novel azo-modified epoxy network is synthesized by cationic homopolymerization with boron trifluoride monoethylamine (BF3. MEA) complex as initiator. The effect of the addition of a fixed content of amino-functionalized azo chromophore, Disperse Orange 3, into the polymer matrix is studied in detail. First of all, the thermal curing cycle is optimized by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) measurements. Then, the resulting bulk azo-modified epoxy networks are characterized by means of thermogravimetric analysis (TGA), FTIR, DSC, UV-vis spectroscopy, and rheological measurements. Finally, the optical response of thin films of these materials is determined. The results evidence that azo-modified epoxy networks obtained by cationic polymerization with optimized curing cycle display high Tg values, high maximum photoinduced birefringence, fast writing speed, and exceptionally high remnant anisotropy. Therefore, this material is a promising candidate to be used for optical storage applications.