【作者】 张磊；

【导师】 崔元臣；

【作者基本信息】 河南大学 ， 高分子化学与物理， 2013， 博士

【摘要】 酶作为催化剂在有机合成中已经得到了较为广泛的研究，但酶催化聚合反应的研究相对较少。酚类化合物在过氧化物酶的催化下可以发生聚合反应，这是一种不使用有毒单体甲醛、且在温和条件下得到酚聚合物的新方法，近年来吸引了众多学者的关注。本文在水相胶束体系中，以辣根过氧化物酶为催化剂，成功实现了苯酚的酶催化聚合。由于不使用有机溶剂，该反应体系中酶催化剂的高活性得以保持，酶用量少、反应速率快，表现出高效、低成本、绿色环保的特点，使酶催化苯酚聚合反应的实用性能大大提高。在表面活性剂用量由0.1g增加到0.4g的过程中，苯酚聚合物的产率逐渐增加，最终达95%左右。在水相胶束体系中，苯酚的酶催化聚合反应还可以在较宽的pH值范围内进行，具有较好的酸碱耐受性。通常情况下，在水相胶束体系中只能得到溶解性较差的聚合产物，胶束的盐效应使得在pH=8的磷酸氢二钾-柠檬酸缓冲溶液中，可以得到在丙酮、四氢呋喃、二甲亚砜、DMF等溶剂中可溶的聚苯酚。在此缓冲溶液中，十二烷基苯磺酸钠用量由0.3g增加到0.5g时，反应产率由54.5%增加到80.6%，质均分子量由3.5×10~4增加到8.0×10~4。而反应温度由20℃增加到50℃时，聚合物的分子量逐渐增加，但聚合反应产率先增加后减少。苯酚聚合物的分解温度在300℃以上，表现出较好的热稳定性。以苯酚聚合物为载体制备了一种新型结构的负载型钯配合物催化剂，用于催化芳基碘、芳基溴及活化芳基氯的Heck反应，产率在80%以上。该配合物可重复用于催化碘苯与苯乙烯的反应，重复使用5次，反应产率仍达90.8%。在水相胶束体系中，进行了4-甲基苯酚的酶催化聚合，反应产率大于90%，所得产物为平均聚合度小于10的低聚物，这是分子链末端的酚羟基易转化为醌式结构造成的。由于分子量较低且含有甲基，4-甲基苯酚聚合产物在200℃左右即开始分解。4-甲基苯酚低聚物具有与天然多酚类化合物类似的结构，表现出较好的抗自由基性能，清除DPPH自由基和ABTS阳离子自由基的Ic50分别为33.3mg/L和3.4mg/L，与性能较好的天然化合物（芦丁、松脂醇等）的抗自由基性能相当。由于合成方法简单、在空气中长期稳定，无刺激性气味，4-甲基苯酚低聚物作为抗氧化剂具有较好的应用前景。在有机溶剂和磷酸盐缓冲溶液（pH=7）的混合体系中，以辣根过氧化物酶为催化剂，得到了4-氯苯酚和4-溴苯酚聚合物（产率在60%左右）。改变有机溶剂种类对聚合反应产率影响不大，但聚合物的分子量变化较大，以甲醇为有机溶剂，4-氯苯酚和4-溴苯酚聚合产物分子量较低，质均分子量在2.0×10~4以下。有机溶剂和缓冲溶液配比改变时，聚合物的产率和分子量均受到较大的影响。4-氯苯酚和4-溴苯酚聚合物对DPPH自由基和ABTS阳离子自由基均表现出一定的抑制作用，4-氯苯酚聚合物清除DPPH自由基和ABTS阳离子自由基的Ic50分别为240mg/L和11.1mg/L。而4-溴苯酚聚合物清除两种自由基的Ic50分别为365mg/L和23.5mg/L，其抗自由基性能稍弱于4-氯苯酚聚合物，可能是由于溴原子半径较大，形成空间位阻，不利于聚合物链与自由基相互作用造成的。更多还原

【Abstract】 Enzymes used as catalyst in organic synthesis were investigated extensively; however, there arerelatively less reports on polymerization catalyzed by enzyme. Polymerizations of phenol compounds canbe performed by using peroxidase as catalyst. The finding has attracted many scholars’ attention because itprovides a new method for producing phenol polymers under mild conditions without formaldehyde.In this paper, polymerization of phenol catalyzed by horseradish peroxidase was performed smoothly inaqueous micelle system. Due to no organic solvent added, the high catalytic activity of horseradishperoxidase is maintained. Tiny amount of enzyme is used but the reaction rate is very fast in aqueousmicelle system. The novel reaction system holds advantages of high efficiency, low cost and environmentalbenign. As a result, the practical performance of the enzymatic phenol polymerization will be enhancedgreatly. The yield of the phenol polymer increases by increasing the amount of surfactant from0.1to0.4g,and the final yield is up to95%. The phenol polymerization catalyzed by horseradish peroxidase in aqueousmicelle system can be performed effectively over a wide pH range from4to10and shows good acid-alkalitolerance. Phenol polymer obtained in aqueous micelle system often exhibits poor solubility. Interestingly,phenol polymer shows good solubility in acetone, THF, DMSO and DMF can be prepared inphosphate-citric acid buffer (pH=8) because of the salt effect on micelle. The yield of the phenol polymerobtained in the buffer increases from54.5%to80.6%when the dosage of sodium dodecyl benzenesulfonate rises from0.3g to0.5g. Meanwhile, the weight-average molecular weight of the polymerincreases from3.5×10~4to8.0×10~4. When the reaction temperature rises from20℃to50℃, the averagemolecular weight of the polymer increases but the yield increases first, and then decreases. The decomposition temperature of the soluble phenol polymer is higher than300℃and shows good thermalstability. A novel supported palladium complex catalyst is synthesized by using the obtained phenolpolymer as carrier. Heck reactions of aryl iodides, aryl bromides or activated aryl chlorides can becatalyzed by the complex smoothly and the yields of the product are higher than80%. The complex can bereused for Heck reaction of iodobenzene with styrene and yield of90.8%is obtained at the cycle of five.Enzymatic polymerization of p-cresol can also be performed smoothly in aqueous micelle system and theyield of the product is higher than90%. The average degree of the product is less than10probably due tothe phenol structure at the end of the molecular chain turns into quinine structure. p-Cresol oligomerdecomposes at200℃because of the low molecular weight and the presence of methyl. The structure of thep-cresol oligomer is very similar to the natural polyphenolic compounds, and also shows good free radicalscavenging activities. The concentration in mg/L that p-cresol oligomer inhibits free radical by50%(Ic50)was calculated and the result is33.3mg/L (for DPPH free radical) and3.4mg/L (for ABTS cation freeradical) respectively. The free radical scavenging activity is comparable with natural compound (rutin orpinoresinol) showing good performance. The synthetic method of p-cresol oligomer is very simple. Inaddition, it shows good stability in air and has no stimulating smell. As a result, p-cresol oligomer has goodapplication prospect as a novel antioxidant.p-Chlorophenol polymer and p-bromophenol polymer with moderate yields are synthesized in themixture of organic solvent and phosphate buffer (pH=7) by using horseradish peroxidase as catalyst. Thetype of the organic solvent has little effect on the polymer yield; nevertheless, the molecular weight of thepolymer varies greatly. p-Chlorophenol polymer and p-bromophenol polymer with weight-averagemolecular weight less than2.0×10~4are produced by choosing methanol as organic solvent. The volumeratio of organic solvent to buffer has great effect on the yield and molecular weight of the polymer. Ic50of p-chlorophenol polymer for DPPH free radical and ABTS cation free radical is240mg/L and11.1mg/Lrespectively. Under the same reaction conditions, Ic50of p-bromophenol polymer for DPPH free radical andABTS cation free radical is365mg/L and23.5mg/L respectively. It is obvious that the free radicalscavenging activity of p-bromophenol polymer is poorer than p-chlorophenol polymer. The reason isprobably due to the steric effect related to the larger bromine atom preventing the interaction of polymerchain with free radicals.更多还原