Study On Synthesis And Thermal Property Of Multifunctional POSS Based PMMA Copolymers

Over the last decade,the preparation of hybrid organic-inorganic nanocomposites from polyhedral oligomeric silsesquioxane(POSS)derivatives has attracted much attention,owing to their excellent optical properties,thermal resistance,flame retardance,high hardness,and abrasion resistance.POSS is a category of organosilicon compounds with peculiar molecular structure.It has a well-defined cage-like molecule having an inorganic silica-like core surrounded by seven or eight organic hydrocarbon groups.The inorganic core provides it with high thermal stability,while the organic groups endow it with good compatibility with the organic matrix.Organic inorganic hybrid materials on molecular level with an inorganic silica-like core can be obtained using POSS as the precursor.The crosslinked polymers containing POSS are becoming a focus of research because of their unique performance in the field of catalyst,micro- and meso-porous and low dielectric materials.However,the synthetic technology of POSS,especially for multifunctional POSS still needs to be improved to promote the further study,development and application in the nanomaterial field.On consideration of this situation,the compound of octaphenyl silsesquioxane(OPS)is synthesized from phenyltrichlorosilane(C₆H₅SiCI₃),and the structure is characterized by FT-IR,²⁹SiMNR,elemental analysis method.The compound of polybromo polyhedral octaphenyl silsesquioxane(POSS-Br_m)is synthesized by the bromination of OPS,the controlled number of bromo is determined by ¹H-NMR.The compound of multicarboxyl polyhedral octaphenyl silsesquioxane(POSS-COOH_x)is finally synthesized by the BuLi-CO₂ reaction of POSS-Br_m,the controlled number of carboxyl is determined by the inverse acid-base titration method.Multiacrylate POSS is synthesized from POSS-COOH_x by the acyl chloride reaction and the esterification reaction,the structures are characterized by FT-IR. The synthesis of these new multifunction POSS provides a new approach to the extensive application of POSS in the Polymers,and having higher research value.In this paper,the influences of POSS on the thermal stabilities of the polymer are studied through the contrast experiment of modelmonomers.Different contents of POSS-Br₄ or POSS-HEMA_3.85are introduced into methacrylate(MMA)to obtain the polymethacrylate Blend or highly cross-linked polymethacrylates.The glass-transition temperature(T_g)and the decomposition temperature(T_d)of the polymer are determined by DSC and TGA.The results of experiment show that the existence of symbol can greatly improve the thermal stability of the polymers.In addition,multifunctional POSS offers access to highly cross-linked three-dimensional-nanocomposites by copolymerization with MMA.They form the larger mesh,besides the nanometer pore of POSS itself,so POSS based PMMA copolymers have the further research value.