Journal of Polymer Science Part A: Polymer Chemistry
Zeynep Beyazkilic, Muhammet U. Kahveci, Binnur Aydogan, Baris Kiskan, Yusuf Yagci
A new class of polybenzoxazine precursors of combined molecular structure of benzoxazine in the open and ring form, thiol and allyl groups has been developed. Thermally curable benzoxazine networks were obtained by simultaneous photoinduced thiol-ene and Catalytic Opening of the Lateral Benzoxazine Rings by Thiols (COLBERT). The thiol-ene reactions were initiated by photolysis of a benzoin type free radical photoinitiator, 2, 2-dimethoxy-2-phenyl acetophenone (DMPA), and the competing COLBERT reaction was triggered by thiol compound, 1,2-ethanedithiol, present in the reaction mixture. The extent of reactions was evaluated by conducting experiments both under UV irradiation and in dark using model benzoxazine compounds. The precursor soft films (pre-P(B-ala-DTE)) were prepared by irradiating solutions of diallyl functional benzoxazine (B-ala), 1,2-ethanedithiol and DMPA in a minimal amount of chloroform. The obtained pre-P(B-ala-DTE) films were then cured through thermally activated ring opening reaction of remaining benzoxazine groups yielding a more rigid and tough film. Thermal and mechanical properties of the films were investigated by DSC, DMA and TGA and compared with a typical polybenzoxazine, P(B-ala).