含偶氮苯侧基接枝共聚物的可控合成及其光响应性能研究

Controlled Synthesis of Photoresponsive Graft Copolymers Containing Azobenzene Groups in Side Chains

以引发单体为基础,通过两种可控聚合方法,即原子转移自由基聚合(ATRP)和开环易位聚合(ROMP)的联用,合成一种新型侧链含偶氮苯基团的接枝聚合物刷.含叔溴的降冰片烯引发剂首先引发偶氮苯单体的ATRP反应,生成聚合物接枝链,每条接枝链上都带有偶氮苯基团;然后,将具有高环张力降冰片烯的ATRP聚合物作为大分子单体,在第三代Grubbs催化剂的引发下进行ROMP反应,生成结构明确的新型接枝共聚物.其主链每个单体单元上均含有一条带偶氮苯基团的接枝链.最后,研究此类接枝共聚物在紫外与可见光照射下的光响应性能,并用UV-Vis分光光度计研究其在溶液中的顺反异构化过程.

A novel photosensitive graft copolymer containing azobenzene chromophores in side chains was successfully achieved via the combination of two controlled polymerization methods, atom transfer radical polymerization （ATRP） and ring-opening metathesis polymerization （ROMP） with good control over the polymerization processes. ATRP of the azobenzene monomer initiated by an as-prepared inimer was first performed to generate a maeromonomer, which was used in subsequent ROMP catalyzed by Grubbs third generation catalyst. The well-defined graft copolymers with grafts bearing azobenzene groups distributed on the same unit along the backbone were finally obtained by aforementioned strategy. As compared with typical macroinitiator syntheses of graft copolymers, the macromonomer synthetic approach allowed for precise architecture control. The structure and molecular weight of the graft eopolymer were confirmed by MALLS-GPC andI H-NMR measurements. After ROMP,the molecular weight of the polymer was shifted to a high molecular weight position, and no peak attributed to the starting macromonomer was observed, indicating that the macromonomer had been completely converted to the graft copolymer. Besides, the obtained graft copolymer bearing azobenzene chromophores showed the reversible photoisomerization process upon irradiation with UV or visible light.