含不同偶氮苯端基支化聚N-异丙基丙烯酰胺的制备及响应行为

Prepartion and Responsive Behavior of the Branched Poly( N-Isopropylacrylamide)( PNIPAM)Endcapped with Different Azobenzene Groups

分别以3种不同结构的偶氮苯为引发剂,N,N’-亚甲基双丙烯酰胺为支化单体,氯化亚铜(CuCl)/三(2-二甲氨基乙基)胺(Me6TREN)为催化体系,通过原子转移自由基聚合(ATRP)制备了含有不同偶氮苯端基的支化聚异丙基丙烯酰胺(PNIPAM)。研究了紫外光辐照对聚合物最低临界溶解温度(LCST)的影响,采用动态光散射研究了支化PNIPAM在水溶液中的自组装行为。结果表明,偶氮苯端基结构不仅影响聚合物的LCST,且在紫外光照射后发生不同的变化,其中AZO-PNIPAM的LCST无变化(27℃)、HOOC-AZO-PNIPAM的LCST升高1℃(30.5℃~31.5℃),而CH3O-AZO-PNIPAM的LCST却降低了1℃(25.5℃~24.5℃),并且3种聚合物表现出不同的自组装行为。

Branched poly( N-isopropylacrylamide)( PNIPAM) endcapped with different azobenzene structures were synthesized via atom transfer radical polymerization( ATRP) using three different initiators( AZO-Br,CH3O-AZO-Br and HOOC-AZO-Br),N,N'-methylene bisacrylamide( MBA) as branching monomer,and CuCl /tris[2-( dimethylamino) ethyl]amine( Me6TREN) as catalyst. The effects of UV irradiation on the lower critical solution temperature( LCST) of polymers were studied through dynamic light scattering( DLS),which reveals the self-assembly behavior of branched PNIPAM in aqueous solution. The results show that the azobenzene structure affects the LCST of PNIPAM after UV irradiation,the LCST of AZO-PNIPAM is a constant( 27 ℃),the LCST of PNIPAM-AZO-COOH increases 1 ℃( 30.5 ℃ ~31. 5 ℃) and the LCST of CH3O-AZO-PNIPAM decreases 1 ℃( 25. 5 ℃ ~ 24. 5 ℃) during UV irradiation,the three polymers represent different self-assembly behavior.