Synthesis, Characterization And Application Of Polyhedral Oligomeric Phenylsilsesquioxane Derivatives

Polyhedral oligomeric silsesquioxane (POSS) as a kind of organic-inorganic hybridmaterial at molecular scale has good toughness and processability of organic phase and rel-ative high rigidity, dimensional stability and thermostability of inorganic phase. The incor-poration of POSS in polymers not only improves the thermal stability and the mechanicalproperty of matrix, but aslo brings some unique properties. Therefore, the development ofnovel POSS and POSS based polymer composites has important academic significance andpractical value.In this article, the Fridel-Crafts sulfonylation reaction was firstly utilized to synthesizephenyl-POSS derivative. Polyhedral oligomeric octadiphenylsulfonylsilsesquioxane (OD-PSS) and octamethyldiphenylsulfonylsilsesquioxane (OMDPSS) were synthesized viaFriedel-Crafts sulfonylation reactions, and synthesized sulfonate-containing polyhedral ol-igomeric silsesquioxane (S-POSS) via sulfonation reaction. The structures and properties ofthe phenyl-POSS derivatives were characterized by Fourier transform infrared spectroscopy,nuclear magnetic resonance(NMR), matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry (MALDI-TOF-MS), elemental analysis and thermograv-imetric analysis, and so on. Then the POSS derivatives were used to prepare POSS basedpolymer composites. The epoxy resin based composites and polycarbonate/S-POSS com-posite were prepared. The appearance, thermal property, flame retardancy and mechanicalproperty of the composites were studied. The specific research contents and results are asfollows:(1) ODPSS was synthesized from octaphenylsilsesquioxane (OPS) and benzenesul-fonyl chloride by one-step method with a yield of89%. The structure of ODPSS has beencharacterized, and the results suggested that ODPSS had eight metasubstitution octadi-phenylsulfonyl groups. TGA uncovered the high thermal stability of ODPSS in both nitro-gen and air. The temperature of5%weight loss of ODPSS was at515°C in nitrogen and491°C in air. By changing the solvent, catalyst, reaction time and molar ratio of reactants,the optimal reaction conditions were determined, the reaction mechanism was analyzed anda sulfonylation model of OPS was established. The triclinic crystal of ODPSS was culti-vated, and its crystal structure was investigated. ODPSS and its synthesis method have been applied for national patent, and the patent application number is201310149158.0.(2) In order to further improve the solubility of phenyl-POSS derivatives in organicsolvents, OMDPSS was synthesized from OPS and tosyl chloride by one-step method witha yield of81%. The structure of OMDPSS has been characterized, and the results suggestedthat the position of the substituents of benzene was not changed with increasing the volumeof sulfonyl group. TGA showed that the temperature of5%weight loss of OMDPSS was at428°C in nitrogen and401°C in air. OMDPSS exhibits much better solubility than OPS andODPSS in dichloromethane, dimethyl sulfoxide, N,N-dimethylformamide, and so on. Thegood solubility offers great potential for OMDPSS to evenly incorporate into polymersthrough physical mixing.The triclinic crystal of OMDPSS was cultivated, and its crystalstructure was investigated.(3) Take advantage of the sulfonation of octaphenylsilsesquioxane by chlorosulfonicacid, the S-POSS was synthesized successfully. Its structure was characterized, and the re-sults suggested that S-POSS had eight metasubstitution sulfonate groups. TGA uncoveredthe high thermal stability of S-POSS, the temperature of5%weight loss of S-POSS was at539°C and the residue yield was63%at850°C in nitrogen.(4) A series of EP/ODPSS composites were prepared, and the thermal property, flameretardancy and tensile strength of the composites were improved with the addition of OD-PSS. The LOI value was26.0%and the self-extinguishing phenomenon was observed inthe UL-94test for the resins loading with2.5wt%ODPSS. The peak of heat release rate(p-HRR) and total heat release (THR) of composites were reduced significantly in conecalorimeter test with increasing the ODPSS content. The p-HRR was reduced by63%andthe THR was reduced by28%with7.5wt%ODPSS loading.(5) A series of EP/OMDPSS composites were prepared. OMDPSS could evenly dis-perse into the EP matrix, and the compatibility between OMDPSS and EP matrix was betterthan ODPSS.Thermal property and flame retardancy of the composites were improved withthe addition of OMDPSS. The LOI value was25.1%and the self-extinguishing phenome-non was observed in the UL-94test for the resins loading with2.5wt%OMDPSS. In conecalorimeter test, the p-HRR was reduced by39%and the THR was reduced by28%with1wt%OMDPSS loading. Because OMDPSS was dispersed in nanoscale in the composites,the efficient and stable thermal-oxidative insulation char layer was formed to improve theefficiency of flame retardancy. (6) To compound ODPSS and DOPO, a series of EP/ODPSS/DOPO composites wereprepared, and the flame retardancy of composites was improved significantly. The mixtureof ODPSS and DOPO had a remarkable synergistic effect on retarding flame of the EPcomposites. The LOI value of EP/2.5wt%ODPSS/2.5wt%DOPO composite was29.8%andthe UL-94rating was V-0(3.2mm). In cone calorimeter test, the p-HRR was reduced by47%and the THR was reduced by27%. An obvious synergistic effect between ODPSS andDOPO can be described as following: DOPO promotes the char layer formation rate andinhibits complete combustion in vapor phase while ODPSS improves the stability of charlayer. The tensile strength and modulus of EP/2.5wt%ODPSS/2.5wt%DOPO were im-proved by23%and28%, respectively.(7) A series of PC/S-POSS composites were prepared. The temperature of5%weightloss of PC/2.5wt%S-POSS was decreased by56°C in nitrogen, but the flame retardancywas improved significantly. The LOI value of PC/2.5wt%S-POSS composite was increasedto33.3%and the UL-94test reached V-0rating (3.2and1.6mm). The cone calorimeter testresults revealed that S-POSS could promote the composite degradation to form the intu-mescent char layer in the condensed phase.