Novel Hyperbranched Polysiloxane Liquid Crystalline And Its Multifunctional Modified Cyanate Ester Resin

As the representative of high performance thermosetting resins, cyanate(CE) resin has excellent integrated performance, including prominent thermal stability, low moisture absorption, good chemical resistance and outstanding dielectric properties, at the same time, it has great potential in the fields of aerospace, electronics and information, electrical insulation et al. However, the formation of triazine ring structure with high crosslinking density after the curing of CE resin made it have low load capacity, leading to low toughness of material. The traditional toughening CE resins are difficult to maintain excellent dielectric property and outstanding thermal property of original CE resins.Our research is aiming at preparing a novel toughened modifier that could obtain outstanding toughening effect without deteriorating the outstanding performances of CE resin. To be specific, a novel hyperbranched polysiloxane liquid crystalline(LCPSi) with terminal amino groups, flexible chain(polysiloxane backbone) and rigid chain(mesogenic unit) was designed and facilely synthesized through the hydrolysis of3-aminopropyltriethoxysilane and mesogenic unit 11[4’-cyano-(1,1-biphenyl)-4-oxy]undecanoate(CBU), and the structure and properties of LCPSi were fully characterized.Results show that LCPSi has wide liquid crystalline phase transition temperature range(85~220°C, ΔT=135°C), appropriate melting point and facile praparation process,overcoming the existed disadvantages including complicate preparation method,narrow liquid crystalline phase transition temperature range, mismatching with the prepolymerization temperature of thermally resistant thermosetting resins, no reactive terminal groups.In this subject, LCPSi was used for the first time to toughen CE resin, and a seris of LCPSi modified e CE(the weight ratio of epoxy and CE resin is 1:9) resin were prepared.Results show that LCPSi/e CE resin not only has prominent toughness, but also exhibits improved flexural modulus, thermostability and dielectric properties. The properties ofLCPSi/e CE resin are related to the contents of LCPSi and the integrated properties of modified resin have been improved at low content of LCPSi. Compared with e CE resin,the impact strength of 1.5LCPSi/e CE(the content of LCPSi is 1.5 wt%) increased about2.3 times and the initial thermal decomposition temperature(Tdi) at which the weight loss reaches 5 wt%) decreases by 18.9 °C compared with those of e CE resin; moreover, the dielectric constant and loss are just 78% and 45%(at 103Hz) of those of e CE resin.These super performances are proved to be resulted from the unique crosslinked network structure of LCPSi/e CE resins, demonstrating that LCPSi is an efficient multi-functional modifier and showing research and application potential.