Living Radical Copolymerization Of Styrene And Maleic Anhydride

Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the newest developed living radical polymerization. Major advantages of the RAFT polymerization compared with other living/controlled free radical polymerization are not only easy transplant based on prescription and processes of traditional free radical polymerization but also suitability with a very wide variety of monomers. Moreover, well-pleasing polymerization rate can be obtained and specific copolymer with well-defined structure can be produced. The objective of this work should be to study the controlled behavior of RAFT thermal copolymerization of styrene (St) and maleic anhydride (MAn), and then apply this technique for the synthesis of styrene and maleic anhydride copolymers (SMA) with controlled sequence.Two RAFT agents bis(thiobenzoyl) disulfide (BTBD) and 1-phenylethyl phenyldithioacetate (PEPDA) with different chain transfer constant were synthesized. Both gas chromatography and mass spectrum, *H NMR and 13C NMR spectroscopy were used to confirmed the structure of the RAFT agents.Before investigating SMA thermal copolymerization, thermal bulk homopolymerization of styrene was studied in the presence of either BTBD or PEPDA as RAFT agent. Kinetic studies show that PEPDA is a more efficient RAFT agent and can result in well controlled polymerization than BTBD. The molecular weight of obtained polystyrene increases linearly with the overall conversion and agrees with the theoretically predicted molecular weight. The molecular weight distribution tends to be narrower as well as 1.05 with the conversion increases. Good linear relationship between ln([M]o/[M]) and polymerization time reveals that the concentration of propagating radicals is constant. The effect of polymerization temperature and RAFT agent content on kinetics was also investigated. Temperature has a significant force on polymerization rate. On the contrary, change in RAFT agent content make polymerization rate little difference. However, it determines the predetermined molecular weight and its distribution.Controlled living radical thermal bulk copolymerization of St and MAn in the presence of PEPDA as RAFT agent was successfully realized. However, adjustable ranges of polymerization temperature and RAFT agent content should be limited than that of aboved styrene polymerization for well living behavior. Different feed addition processes of St-MAn copolymerization such as batch, sequential addition of monomer and semi-batch addition of monomer can produce some novel diblock so much astriblock copolymers combined with various sequence structures involved polystyrene block and alternating or random SMA copolymer block. During the batch copolymerization, rate of copolymerization is boosted up significantly and MAn is preferentially consumed by St and MAn alternating copolymerization. When MAn is consumed up, the rate is slowed down, and then homopolymerization of styrene continues to ultimately produce copolymers with both St-alt-MAn block and St rich block shown as P(St-alt-MAn)-b-PS structure. The molecule weight polydispersity of obtained diblock copolymer has lower than 1.2. When the method of sequential addition of monomer is used, St-MAn copolymers with diblock (PS-b-P(St-alt-MAn)) and triblock (PS-b-P(St-alt-MAn)-b-PS) can be obtained by controlling addition moment and consumption rate of MAn. And then the polydispersity just is 1.15. The PS-b-P(St-co-MAn) diblock and PS-b-P(St-co-MAn)-b-PS triblock copolymer can be synthesized by semi-batch feed process utilizing starve-state addition of MAn. The molecule weight distribution of ultimately obtained copolymers has not higher than 1.2. To sum up, theoretically, multi-block SMA copolymers with various monomer sequence distribution can be obtained just by change of feed condition.Study on the thermal property of obtained multi-block SMA copolymers shows that the beginning and the ending point of the glass transition temperature are related with the polystyrene block and the SMA copolymers bl...