Modification of epoxy-novolac resins with polysiloxane containing nitrile functional groups: synthesis and characterization

Synthesis of the statistical epoxidized polycyanopropylmethylsiloxane-co-polydimethylsiloxanes (PCPMS-co-PDMS) has been demonstrated. The modified polysiloxanes were prepared via a two-step method; (1) the ring-opening polymerization of octamethylcyclotetrasiloxane (D4) and tetramethylcyclotetrasiloxane (D4H), (2) hydrosilylation reaction of the polysiloxane prepolymers with allyl cyanide and allyl glycidyl ether. Molar ratios of D4H and D4 were varied to produce the modified polysiloxanes with differences in polarity. 1H-NMR, 29Si-NMR, 13C-NMR and FTIR were used to monitor the formation of the modified polysiloxanes and DSC was used to study their thermal behaviors (Tg, −118 to −68 °C). The use of the modified polysiloxanes as an elastomeric component in epoxy-novolac networks was also investigated. TEM and their transition temperatures suggested that the epoxy-novolac networks with high content of PDMS modifiers exhibited microphase separation. The fracture toughness properties of the networks with the polysiloxane modifiers were improved over the controls without polysiloxanes.