Preparation of Titanium-silphenylene-siloxane Hybrid Polymers with High Refractive Index,Transmittance,and Thermal Stability

Vinyl-containingtitanium-silphenylene-sioxane oligomers(O1,O2,O3,andO4)withdifferent molar ratios of titanium to silicon were successfully synthesized in high yields by nonhydrolytic sol-gel reaction,and the obtained four oligomers were further crosslinked with methylphenyl hydro-silicone oil(4)to form corresponding polymers(P1,P2,P3,and P4)by hydrosilylation reaction.Their structures were characterized with spectroscopic characterization techniques including FTIR,1H-NMR,and Raman spectroscopy.The effect of titanium element on crosslinking behavior,thermal resistance,refractive index,transparency,thermal aging stability,glass transition temperature,and surface properties of the polymers were studied.Compared with titanium-free polymer P1,the thermal resistance,refractive index,and thermal aging stability of titanium-silphenylene-siloxane polymers(P2,P3,and P4)were significantly improved.The titanium-silphenylene-siloxane polymers achieved a high refractive index(n=1.580-1.584)and thermostability(Tsd>500℃).In thermal aging,the polymers exhibited superior performances with high optical transparency(~90%at 450 nm)and exhibited high thermal stability(~84%at 450 nm after thermal aging at 150℃for 120 h).These data indicate that the polymers have potential application in optical materials such as LED encapsulants.

Self-healing Supramolecular Polymer Composites by Hydrogen Bonding Interactions between Hyperbranched Polymer and Graphene Oxide

A self-healing supramolecular polymer composite（HSP-GO） was designed and prepared via incorporation of modified graphene oxide to hyperbranched polymer by hydrogen-bonding interactions. The polymer matrix based on amino-terminated hyperbranched polymer（HSP-NH_2） was synthesized by carboxylation, Curtius rearrangement, and amination of hydroxyl-terminated hyperbranched polyester（HP-OH）, while the modified graphene oxide was prepared by transformation of hydroxyl to isocyanate and further to carbamate ester. Spectroscopic methods were utilized to characterize the obtained polymer composites. Stress-strain test was selected to carefully study the self-healing property of HSP-GO. It is found that a small amount of modified graphene oxide（up to 2 wt%） improves the glass transition temperature（T_g）, tensile strength, Young＇s modulus, and self-healing efficiency of the polymer composites. After healed at room temperature for 10 min, the addition of modified graphene oxide improves the self-healing efficiency to 37% of its original tensile strength. The experiment result shows that the self-healing efficiency is related to the density of hydrogen bonding site and the molecular movement.

Synthesis and Characterization of Carborane-containing Poly(hydroxy ethers) with Excellent Thermal Stability

o-Carborane-containing poly（hydroxy ethers）（P1, P2 and P3） were synthesized via ＂advancement reaction＂ of o-carborane-containing bisphenol（4） and diglycidyl ether of bisphenols（DGEBA and 1）. FTIR and 1^H^-, 13^C^-, and 11^ B-NMR were utilized to characterize the obtained polymers. TGA test was conducted under nitrogen and air. It is found that the shielding effect of carborane moiety on its adjacent aromatic structures contributes to high initial decomposition temperatures, while oxygen in air has an adverse effect on the initial decomposition temperature. The oxygen can combine with polymer chain to form peroxide and hydroperoxide groups, which are more reactive during the degradation process. Besides, o-carborane-containing poly（hydroxy ethers） have high char yield at elevated temperatures. The boron atom combines with oxygen from the polymer structure or/and from air, thus to form a three-dimensional network linked with B―O―B and B―C bonds, and retain the polymer weight to a large extent.