Preparation Of Polycarbonate/SiO₂ Hybrid Materials Based On Quadruple Hydrogen Bonding

In 1997,Meijer reported the 2-ureido-4-[1H](Upy)pyrimidone with feature of forming quadruple hydrogen bonds,and proved its ability of assembling into supramolecular polymer through self-recognition.There is no need to synthesize different components of recognition units because of the characteristic of self-recgonition to form quadruple hydrogen bonds.Moreover,the Upy units can be used to prepare relatively stable supramolecular polymers due to the high self polymerization constant.In order to investigate the interfacial binding force of quadruple hydrogen bonds between particles and matrix resin in hybrid materials,supramolecular polymer/nanosilica hybrid materials were prepared by blending Upy functionalized nanosilica with Upy end-capped supramolecular polymer.The main researchs of this work are as follows:(1)The Upy functionalized hexamethylene monoisocyanate(Upy-HDI)was synthesized and used as end-capping agent of polycarbonatediol and HDI extended polyurethane oligomer.Supramolecular polymers were obtained by introducing Upy-HDI at the chain-ends.FTIR and NMR spectra were used to analyse the structure of the synthesized molecules.GPC analysis showed that the Upy-HDI end-capped supramolecular polymers can be assembled to form higher molecular weight polymers by quadruple hydrogen bonds.DSC analysis showed that the glass transition temperature of the Upy end-capped supramolecular polymers was greatly improved comparing with their precursors.A regular microcrystalline region was formed from the ?-? stacking of Upy dimers and the reconstruction of microcrystalline region after thermal destruction was strongly dependent on the time.DMA analysis showed that the Upy-HDI end-capped supramolecular polymers exhibited thermoplastic rubber properties at room temperature,and the content of Upy units in the system had a great influence on the storage modulus.Optical microscopy and tensile test were used to evaluate the self-healing properties of quadruple hydrogen bonded supramolecular polymers.The results showed that the crystallite formed by the stacking of Upy dimers was dissociated at a relatively high temperature,which greatly influenced the self-healing temperature.(2)The Upy functionalized isophorone monoisocyanate(Upy-IPDI)was synthesized and used as the surface modification of nanosilica.The existence of Upy units on the surface of nanosilica was verified by FTIR spectrum.Furthermore,thermogravimetric analysis showed that the thermal decomposition of Upy-IPDI was in the temperature range of 225-350?,and the grafting rate of Upy-IPDI on the surface of nanosilica was 11.03%.The contact angle and scanning electron microscopy showed that the surface of Upy modified nanosilica showed strong hydrophobicity.The water contact angle on the surface of Upy modified nanosilica could up to 142 o due to the low surface energy.Scanning electron microscopy analysis revealed that excellent dispersion of Upy modified nanosilica possessed in strong polar DMF,but poor dispersion in weak polar toluene which resulted a porous surface after the solvent being dried.(3)The hybrid materials of Upy-IPDI modified nanosilica bonding with Upy-IPDI end-capped supramolecular polycarbonate were prepared by simple mechanical blending.Scanning electron microscopy image of sample containing 5wt% Upy modified nanosilica showed that nanoparticles could be evenly distributed in the supramolecular polycarbonate matrix.DMA analysis showed that Upy modified nanosilica had more obvious enhancement on the glass transition temperature than the amino silane coupling agent modified nanosilica.Tensile tests showed that the tensile stress increased by 292% and young's modulus increased by 198% with the addition of 5wt% Upy modified nanosilica.