Hydrosilylation has been carried out between Si-H terminated polydimethylsiloxanes with narrow molecular weight distribution and protected 3-allyloxy-l,2-propanediol, and after subsequently alcoholyzed, α-{3-[（2,3-dihydroxy）propoxy]propyl}-ω- butyl-polydimethylsiloxanes with varying number of （（Si（CH3）2-O） unit were obtained. At each step, the produced compounds were carefully characterized. The results showed that each step was successfully carried out and target products were achieved.
Xiao Li Zhan Zhen Huan Luo Qing Hua Zhang Bi Chen Feng Qiu Chen
Reversible addition fragmentation chain transfer(RAFT)mediated miniemulsion copolymerizations of butyl methacrylate with fluoroacrylate were carried out at 70 ℃ with potassium persulphate as initiator,and the kinetics of copolymerizations were investigated.Copolymer compositions at low conversion levels were determined by 1H NMR spectra techniques.In the presence of RAFT agent 2-cyanoprop-2-yl dithiobenzoate(CPDB),the copolymerization of BMA with FMA in miniemulsion exhibited typical features of a controlled mole-cular weights and narrow polydispersities.The reactivity ratios were evaluated by Kellen-Tudos(K-T)method,which yields the apparent reactivity ratios,rBMA=0.63 and rFMA=0.79.The results show that the monomer FMA with a fluorinated side chain is more reactive than BMA,and the copolymerizations have a tendency to alternate and to produce a higher FMA content in the copolymers.The spontaneous statistical copolymers with soft gradient shapes were obtained using variable initial ratios of BMA and FMA.
Cationic ring opening polymerization of octamethylcyclotetrasiloxane （Da） initiated by acid treated bentonite was investigated. The experimental conditions were chosen on the basis of preliminary experiments.Higher temperature was found beneficial for the reaction process while stirring intensity beyond a certain level showed no obvious effect on the reaction rate. Polymers were characterized by Fourier transform infrared, proton nuclear magnetic resonance （IH-NMR） and gel perneation chromotography. The width of molecular mass distribution was found ranging between 1.2 and 1.4, which is extraordinarlly narrow compared with that of cationic polymerizations reported elsewhere （〉 1.9）. The results were believed due to the absence of free proton and counter ion which simplifies the polymerization process and the huge steric hindrance provided by bentonite particles which keeps the propagation of polysiloxane onto the surface of bentonite particles in a much more regular way. A feasible mechanism is proposed and seems to be supported well by experiments. Additionally, from the results of α, ω-dihydrogen terminated polysiloxanes prepared, the possibility of applying this potential environmentally friendly heterogeneous catalyst in industrial polymerization of cyclosiloxanes is anticipated.
