Study Of The Active Groups Terminated Ladder-like Polyphenylsilesequioxanes And Their Block Copolymers

The general formula of polysilsesquioxanes is (RSiO1.5) n (R: hydrogen, alkyl, aryl or organic group). One of the polysilsesquioxanes which has a molecular structure of the ladder-like silsesquioxane, is composed by two main chains of Si-O-Si, linked by oxygen as bridges. It belongs to a kind of novel polymer materials and has a series of good physical characteristics because of its special structure.Active chain groups terminated ladder-like polyphenylsilsesquio-xane (Ph-T) was firstly synthesized by a improved method. Then, a block copolymer, called polyphenylsilsesquioxane-dimetheylsioxane, was prepared through ring-opening polymerization with a ring monomer DMC.1. Phenyltrichlorosilane(PTCS) was employed as to synthesize phenyl-T by the hydrolysis and condensation reaction in a closed reactor and thyl ether were used as solvent. Ladder-like polyphenylsilses-quioxane was prepared through condensation and rearrangement of prepolymer. The structure was characterized by FT-IR, XRD and 29Si-NMR, which showed the ladder-like molecular structure of the product. A thermal gravimetric analysis was given, demonstrating a good heat resistance.2. The influence of reaction conditions on the synthesis of Ph-T was studied. It was found that the appropriate level of the solvent and water to monomers ratio (4:1and3:1)) could lead to a high yield of the prepolymer, while the temperature was less than15℃.3. The influence factors were measured in the condensation stage by molecular weight. It can be concluded that the best conditions for the preparation of Ph-T were like this:the catalyst concentration is2‰wt, reaction time is one hour, and the temperature is250℃.4. Active chain groups terminated ladder-like polyphenylsilsesquioxane was used as initiator. The copolymer polyphenylsilsesquioxane-dimetheylsioxane, with Ph-T as middle and dimethylsiloxane as arm, was prepared through ring-opening polymerization. We studied the effect of the polar regulator DMAc on the reaction rate. The reaction mechanism was studied and the structure of the product was characterized.