A Novel Hyperbranched Polysiloxane Containing Epoxy and Phosphaphenanthrene Groups and its Multi-Functional Modification of Cyanate Ester Resin

Abstract A novel hyperbranched polysiloxane containing epoxy and phosphaphenanthrene groups (EP-HPSi) was synthesized through a ring-open reaction between P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and epoxy group of a hyperbranched polysiloxane. EP-HPSi was used to modify cyanate ester (CE) resin. The influences of the content of EP-HPSi in modified CE resin system as well as the molar ratio between DOPO and epoxy group on the structure and integrated performance of the EP-HPSi/CE system were systematically studied. Results show that EP-HPSi is a multi-functional flame retardant, which endows CE resin with not only outstanding flame retardancy, but also significantly increased toughness and stiffness. For example, EP-HPSi/CE system has a 40–80oC lower curing temperature than CE; moreover, the impact and flexural strengths of EP-HPSi/CE system are about 1.6–2.2 and 1.3 times higher than that of CE resin, respectively. These attractive integrated performances of EP-HPSi/CE system are attributed to the special structure of EP-HPSi, and its influence on the cross-linked network. This investigation suggests that the method proposed herein is a new approach to develop high performance flame retardant resins for cutting-edge industries, especially those that simultaneously have outstanding thermal resistance, toughness, and stiffness. [Supplementary materials are available for this article. Go to the Publisher's online edition of Soft Materials for the following free supplemental resource: Figure S1] Keywords: Cyanate esterHyperbranched polysiloxaneMechanical propertyMulti-functional flame retardantPhosphaphenanthrene Acknowledgments The authors thank Natural Science Foundation of China (21274104, 51173123), the Priority Academic Program Development of Jiangsu Higher Education Institutions, the Major Program of Natural Science Fundamental Research Project of Jiangsu Colleges and Universities (11KJA430001), and the Suzhou Applied Basic Research Program (SYG201141) for financially supporting this project.