可光、化学降解聚苯乙烯的合成与性能研究

Photo-and Chemo-Degradable Polystyrene Containing o-Nitrobenzyl Ester and Trithiocarbonate Moieties

通过1,3-二碘甲基-2-硝基苯与双(2-甲基丙酸)三硫代碳酸酯的高效聚酯化反应合成了主链中含有邻硝基苄酯和三硫代碳酸酯基团的聚合物,以其作为大分子链转移剂,进行苯乙烯的可逆加成断裂链转移(RAFT)聚合,获得了多嵌段聚苯乙烯.大分子链转移剂和多嵌段聚苯乙烯的结构及分子量通过核磁氢谱(1H-NMR)和凝胶渗透色谱(GPC)进行了表征.考察了多嵌段聚苯乙烯溶液和固态的降解性能及热性能.实验结果表明,多嵌段聚苯乙烯不仅在紫外辐照条件下可发生光降解,而且也可通过胺解和水解反应进行降解.热重分析(TGA)和示差扫描量热(DSC)结果显示,邻硝基苄酯基团和三硫代碳酸酯基团的引入,对于多嵌段聚苯乙烯玻璃化转变温度和热稳定性并没有明显的影响.

The extensive use of polystyrenes led to the accumulation of plastic waste because of the non-degradability in natural circumstance, which has caused serious environmental impacts, dubbed ＂white pollution＂. Therefore, it is highly desirable to design and prepare degradable polystyrenes. A new macromolecular chain transfer agent was designed and synthesized by polyesterfication of the monomer with dicarboxylic groups, S,S＇-bis（a,a＇-dimethyl-a＂-acetic acid）-trithiocarbonate, and the monomer with diiodine groups, 1,3-bis（iodo- methyl）-2-nitrobenzene. Then, multiblock polystyrenes （PS） containing o-nitrobenzyl ester and trithiocarbonate moieties as photosensitive units in the main chain weresuccessfully synthesized by reversible addition-fragmentation chain transfer （RAFT） polymerization of styrene in the presence of the macromolecular chain transfer agent. Moreover, the photodegradation behavior of the multiblock PS in tetrahydrofuran and in solid state was examined under ultravioletray （UV） irradiation at room temperature in air atmosphere. The structure and molecular weight of the macromolecular chain transfer agent and the block polymer were characterized by nuclear magnetic resonance （-H-NMR） and gel permeation chromatography （GPC）. The molecular weight and molecular weight distribution of the macromolecular chain transfer agent were 8400 and 1.8, respectively. The kinetics of RAFT polymerization of styrene was studied, and it was found that the polymerization was a first-order reaction with respect to monomer concentration. The photodegradation and chemical degradation behaviour were investigated through -H-NMR, ultraviolet-visible spectroscopy （UV-Vis） and GPC analyses. The results demonstrated that the multiblock polystyrenes could be degraded into separate PS blocks, not only by UV light, but also by hydrolysis or amiolysis of the ester and trithiocarbonate groups. In addition, thermal properties of the multiblock PS were measured by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA） under a nitrogenatmosphere. The glass transition temperature and the maximum rate of the decomposition of the multiblock PS appeared respectively at 97 and 385℃. The result of thermal analysis indicated that the thermal properties of the multiblock PS are very similar to those of conventional polystyrene.