Study On Morphology And Thermal Properties Of PMMA-POSS Hybrid Materials

Polyhedral oligomeric silsesquioxane (POSS) is surface-functionalized nanoparticles andhas three-dimensional polyhedral structure in space, which is made of the―core‖of theinorganic and―shell‖of organic. The chemical composition of core is (SiO3/2)n, which a Siatom is connected to an organic group. The space distance of POSS nanoscaleorganic-inorganic hybrid molecules between the Si-O-Si bond is0.5nm, and the two adjacentdistance between the organic group is1.5～3.0nm. POSS can be prepared by chemical orphysical methods due to its miscellaneous properties and nanoscale features. Studies on theperformance of POSS-modified polymers indicated that the incorporation of POSS into apolymer matrix can improved significantly properties.In this artcle, the structure and morphology of octavinyl POSS were characterized.PMMA-OVPOSS hybrid materials were prepared by blend method with octavinylPOSS.PMMA-OVPOSS hybrid polymers were prepared by UV polymerization method usingmethacrylphenyl polyhedral oligomeric silsesquioxanes. Study introduction of POSS on thestructure, morphology and thermal properties, following major elements：OctavinylPOSS had a hexahedral crystal structre by FT-IR,1H NMR,29SiNMR andXRD analysis. The hexahedral crystal structure of OVPOSS can be directly observed by TEM,and the size of octavinylPOSS was found to be different in its TEM image because ofmolecular aggregation. OVPOSS aggregates were separated and formed small sizeaggregation when OVPOSS was introduced into PMMA resin. The DSC curve investigatesthat there were two glass transition temperatures in110℃and220℃when OVPOSS contentup to3wt%. It indicated that significant phase separation was happened in PMMA-OVPOSShybrid material in high OVPOSS content by FOX and Gordon-Taylor formulathe.A series of hybrid polymers based on methacrylphenyl polyhedral oligomericsilsesquioxanes (MA-POSS) and methylmethacrylate (MMA) were rapidly synthesized viaUV photopolymerization through a (2,4,6–trimethylbenzoyl) diphenylphosphine oxide-initiated reaction. The structure and morphology of hybrid polymers were characterizedvia Fourier-transform infrared spectroscopy,1H NMR, gel permeation chromatography andX-ray diffraction,, which confirmed that MA-POSS cage could be successfully incorporatedinto the polymethylmethacrylate (PMMA) chain with pendant structure. Mn of the hybridpolymers increased with the MA-POSS feed ratio in the polymerization. The increasing of thePDI was more likely to be determined by an increase of the compositional polydispersity ofcopolymers with higher content in MA-POSS. A different size was also found in theMA-POSS TEM image. The size observed was from150nm to680nm, and the average sizeof the molecule was300nm. And TEM image revealed that PMMA-MAPOSS hybridpolymers were some small chains, the size of MA-POSS, which ranged from60nm to90nm.PMMA-MAPOSS films were analysed by AFM. With the MA-POSS content increasing, theaverage thickness of the PMMA-MAPOSS films was improving from177～232nm, and theaverage roughness (Ra) of films was improving from4.591～10.27nm. Similar andhomogeneous surfaces without any noticeable domains can be observed. The SEMmicrographs show a featureless morphology, indicating no phase separation or evidence ofMA-POSS aggregates within the limits of SEM detection. In addition, DSC, TGA and DTGresults showed that the glass transition temperature and melting point were increasing withMA-POSS was introduced into PMMA polymer. It implies that enough POSS can restrain thehybrid polymer side ester group scission from breaking and the incorporation of POSS isbeneficial for improving the thermal stability of the hybrid polymers.