外端为偶氮苯基团的聚酰胺-胺树枝状分子对光和H^＋的响应行为  

PHOTO AND H^+ DUAL-RESPONSIVE BEHAVIORS OF AZOBENZENE-SHELLED POLY(AMINOAMINE) DENDRIMERS

作　　者：高敏[1] 王冰冰[1] 贾欣茹[1] 李武松[1] 旷桂超[1] 危岩 

机构地区：[1]北京大学化学与分子工程学院高分子科学与工程系高分子化学与物理教育部重点实验室,北京100871 [2]Department of Chemistry,Drexel University,Philadelphia,PA 19104,USA

出　　处：《高分子学报》2008年第1期32-40,共9页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号20574001、20640420562)资助项目

摘　　要：合成了1到5代外端修饰有偶氮苯基团的聚酰胺-胺(PAMAM)树枝状分子.H-NMR、FTIR和元素分析等表明得到了目标产物,外端接枝率在70%~90%.结构分析表明经修饰的PAMAM分子在3代和4代之间存在一个结构转变.UV-Vis和H-NMR分析结构显示,在中性条件下,Gn-azo表现出类似于小分子偶氮苯基团的光响应行为.而在酸性条件下,偶氮苯基团的顺反异构转化率较质子化前低.包裹及释放实验表明,虽然G4-azo包裹水杨酸分子的能力弱于G4PAMAM,但它对于客体小分子具有缓释作用,光照使偶氮苯基团发生由反式到顺式的异构转化之后,缓释效应更明显.A series of azobenzene functionalized poly（aminoamine）dendrimers （Gn-azo （n = 1 -5））and thecorresponding model compounds were synthesized and characterized by ^1H-NMR,^13C-NMR, FTIR and elemental analysis, and the photo- and H^＋ - responsive behaviors of these dendrimers were studied through UV-Vis and HNMR spectroscopy. It was found that the graft ratios of these azobenzene-shelled dendrimers were in the range of 70% -90%. A structural transition occurred between the third （G3-azo）and the fourth （G4-azo）generation, indicating that a relative open and loose structure of lower generation dendrimers became a dense spherical structure at higher generations. Therefore, the fourth （G4-azo）and the fifth （G5-azo）generation modified PAMAM dendrimers are ideal nano-containers that can encapsulate guest molecules. The modified dendrimers （Gn-azo（ n = 1 - 5））exhibited the similar photo-responsive behaviors to azobenzene itself. Under 365 nm UV-light irradiation, the intensity of the π-π^＋ band at 336 - 348 nm decreased, and the intensity of the n-π^＋ band at 440 - 443 nm increased. The case was reverse under visible-light irradiation. 1H-NMR results indicated that Gn-azo dendrimers could be protonized when adding trifluoroacetic acid （TFA） into the chloroform solution of Gn-azo. It was also found that the protonated and non-protonated dendrimers showed different behaviors in response to UV-light. The ratio oftrans-cis isomerization of the azobenzene chromophores was lower in protonated form when compared to that in nonprotonated form. It might be due to that the N = N group of azobenzene on the periphery was also protonized under the TFA environment. Moreover, the ratio of trans-cis isomerization decreased with the generation increasing, which might be owing to the structure and size of dendrimers. The encapsulation ability of azobenzene-shelled G4 dendrimer decreased relative to the unmodified G4 dendrimer, but the release of salicylic acid was indeed slowed down becauseof t

关 键 词：光响应 H^+响应 偶氮苯 PAMAM树枝状分子 

分 类 号：O633.22[理学—高分子化学]