Studies Of The Modification Of POSS Via Click Reaction And The Properties Of Its Composites With PMMA And Silicone

Polyhedral oligomeric silsesquioxane (POSS) has the characteristic of organic-inorganichybrid structure, nano size, structure designability, high thermal stability, which give POSSbased polymers good thermal properties, flame retardance, good mechanical properties,dielectric properties, showing promising usage in the field of aerospace, porous materials,dielectric materials, biological and medical materials, etc. At present, POSS research hasbecome a hot spot in international and domestic. It not only has academic value, but also greatvalue of application.In this paper, POSS with eight vinyl groups(OvPOSS) was prepared byhydrolysis-condensation method, and then modified with with KH-580through the thiol-eneclick chemistry to obtain two noval kinds of POSS with different functionalgroups(POSS-E24, POSS-E12). The structure and properties of the products werecharacterized by FT-IR, NMR, Maldi-TOF MS, XRD, GPC, TG, etc.1H/29Si NMR resultsshowed single Si atom chemical environment which indicate that OvPOSS had cage structure;MS showed that OvPOSS had eight vinyl groups; XRD and TG show that OvPOSS had theproperties of high crystallinity and high thermal stability. Through FT-IR, NMR, GPC, wecould see POSS-E24had the ethoxy groups, and the vinyl groups in OvPOSS werecompletely reacted; POSS-E12had the ethoxy and vinyl groups, and the vinyl groups inOvPOSS were partly reacted which is strictly follow the reaction ratio. TG showed the twokinds of POSS had high thermal stability.Second, composites of POSS with room temperature vulcanized silicone rubber PDMSwere prepared: POSS-E24/PDMS, POSS-E12/PDMS. POSS improved the crosslinkingdensity as crosslinking point. SEM showed POSS existed as micron microspheres coated withPDMS.2.5wt%POSS-E24maked PDMS tensile strength and surface hardness increasedrespectively by78%,55%, the initial thermal decomposition temperature promoted19℃,50%weight loss temperature promoted74℃;2.5wt%POSS-E12maked PDMS tensile strength andsurface hardness increased respectively by61%,50%, the initial thermal decompositiontemperature declined19℃,50%weight loss temperature promoted66℃. POSS-E24hadbetter effect on PDMS than POSS-E12.Third, composites of OvPOSS, POSS-E12with PMMA were prepared by free radicalpolymerization. XRD and SEM showed OvPOSS crystallized seriously and dispersed badly inPMMA. While POSS-E12existed as uniform dispersed nano-sized microspheres. At1.0% POSS-E12, the initial decomposition temperature increased64.3℃, the maximumdecomposition temperature increase80.9℃. TG-IR showed POSS-E12delayed the time ofMMA generation from the degradation of PMMA.