The Polymerizations Of Styrene In The Presence Of Novel Initiators And Nitroxide Stable Radicals

In this thesis,two novel nitroxide stable radicals,2,2,6,6-tetramethyl-4-(d-(+)-10-camphorsulfonyl)-1-piperidinyloxy (CS-TEMPO) and 2-bromo-propionic acid 1-oxy-2,2,6,6-tetramethyl-piperidin-4-yl ester (Br-TEMPO), were synthesized and used to the polymerizations of styrene. The polymerizations of styrene were carried out in three cases as below: (1) 2-mercaptobenzothiazole(MBT) was used as an initiator for the stable free radical polymerization of styrene in the presence of TEMPO ; (2) CS-TEMPO was used as a mediator for bulk polymerization of styrene initiated by BPO, TETD and thermal initiation, respectively. The specific rotation of the polymer was measured. Successful chain extension reaction was also carried out using the obtained polymer as mediator with the butyl acrylate; (3) Br-TEMPO was used as mediator for bulk polymerization of styrene initiated by BPO, TETD and thermal initiation, respectively. The obtained polymer can be used as macro-initiator to synthesize block polymer via atom transfer radical polymerization (ATRP) and nitroxide mediated radical polymerization (NMRP). All of the results showed that the polymerizations proceeded in a controlled/"living"way, i.e., the kinetics presented approximately first-order plots and the molecular weights (Mn) of the polymers increased linearly with monomer conversion. Furthermore, in the first case, the results also showed that the rate of polymerization decreased obviously with increasing the molar ratio of [TEMPO] 0 / [MBT] 0. As the ratio was larger than 1, the molecular weight distributions of the polymers maintained nearly 1.3. In the second case, the obtained polymer showed a good specific rotation. Increasing the number average molecular weights of the polymer decreased the value of specific rotation of the polymer. In the last case, Br-TEMPO was used to mediate the polymerization of styrene via NMRP, and the obtained polymers can easily and efficiently be used as the initiator for ATRP of butyl methylacrylate (BMA) and methyl methacrylate (MMA) in the presence of CuCl / PMDETA at 70 ℃. By the further chain-extension of obtained PSt-b-PMMA using styrene as the monomer via NMRP, the triblock copolymer of PSt-b-PSt-b-PMMA can be prepared. Furthermore, using MMA as the monomer and the PSt-b-PBMA as the macro-initiator via an ATRP way, the triblock copolymer PSt-b-PBMA-b-PMMA can also be obtained. It is an alternative method to synthesize the triblock copolymer of ABC style or A2B style.