双烯烃橡胶复分解-加氢制备端羧基聚烯烃

Synthesis of Carboxyl-terminated Polyolefins via Metathesis Degradation-hydrogenation of Diene Rubbers

采用烯烃复分解法,以双烯烃橡胶为原料,在Grubbs II代催化剂和链转移剂(马来酸)的作用下制得相应的端羧基聚二烯烃,通过对甲苯磺酰肼/三正丙胺试剂对其进一步加氢得到端羧基聚烯烃.主要研究了反应时间、反应温度、橡胶中双键/催化剂摩尔比、橡胶中双键/链转移剂摩尔比等因素对产物分子量及分子量分布的影响.通过核磁共振氢谱(1H-NMR)和碳谱(13C-NMR)、红外光谱(FTIR)、凝胶渗透色谱仪(GPC)、热重分析(TGA)和示差扫描量热分析(DSC)对产物的结构和性能进行了测试表征.结果表明,通过调整橡胶中双键/催化剂的摩尔比或橡胶中双键/链转移剂的摩尔比可以调控产物的分子量.另外,采用该方法制得的端羧基聚丁二烯具有较高的反式1,4-结构含量,与原料相比其顺式1,4-结构含量大幅下降,从而对产物的性能产生一定影响;而以异戊橡胶为原料时并没有观察到该现象.端羧基聚二烯烃经加氢反应后转变成端羧基聚烯烃,具有更好的热稳定性.该方法合成步骤简单,产物分子量可控,为功能材料的制备提供了新的可能.

The carboxyl-terminated polydiene is a kind of widely used telechelic liquid rubber,which is commonly used as adhesive for solid rocket propellant,material bonding,sealant,electric insulation or as modifier of epoxy resins.Taking diene rubbers as raw materials,the carboxyl-terminated polydienes were synthesized via olefin metathesis degradation of diene rubbers catalyzed by Grubbs II catalyst(G2)in the presence of maleic acid as a chain transfer agent(CTA).The carboxyl-terminated polyolefins were further prepared by the subsequent chemical hydrogenation with p-toluenesulfonyl hydrazide/tri(n-propyl)amine reagents.The influences of reaction conditions on the molecular weight and molecular weight distribution of products,including reaction time,reaction temperature,molar ratios of C=C/catalyst and C=C/chain transfer agent,were investigated.The results indicated that the molecular weight of products could be controlled by varying the molar ratio of C=C/catalyst or C=C/chain transfer agent.It turned out that the catalyst was highly active for the metathesis degradation of diene rubbers even if there was no existence of chain transfer agents.The structures of carboxyl-terminated polydienes and polyolefins were characterized by nuclear magnetic resonance spectroscopy(1 H-NMR)and carbon spectrum(13 C-NMR),infrared spectroscopy(FTIR)and gel permeation chromatography(GPC)and their thermal properties were investigated by thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).It’s worth noting that the trans-1,4 content of carboxyl-terminated polybutadiene via metathesis degradation greatly increased and the corresponding cis-1,4 content decreased,thus affecting the properties of polymers.After hydrogenation,the carboxyl-terminated polyolefins had better thermal stability than the carboxyl-terminated polydienes.