中文摘要：

以4，4’－二羟乙氧基偶氮苯（BHEAZO）为引发剂引发对二氧环己酮（PDO）开环聚合，与羧基化的单羟甲基聚乙二醇（mPEG）偶联，制备了具有光响应性的两亲性三嵌段共聚物mPEG—BHEAZO—PPDO—mPEG，并对其纳米聚集体的光响应行为进行了研究．采用紫外可见光谱（uV—Vis Spectroscopy）研究了纳米聚集体水溶液的吸光度随着光照时间的变化；用动态光散射（DLS）研究了辐射波长对纳米聚集体的粒径及粒径分布的影响；结合透射电子显微镜（TEM）的研究结果，提出了对纳米聚集体在不同波长光照下聚集行为改变的机理，即反式结构共平面的共轭体系更易形成稳定的低能级电子离域状态，从而使得纳米聚集体之间通过竹．盯堆积作用形成微聚集现象．

英文摘要：

A photo-responsive amphiphilic triblock copolymer has been synthesized. The hydrophobic segment of copolymer was prepared by ring-openi,g polymerization of p-dioxanone （PDO） using 4, 4＇-bis- （hydroxyethylether） azobenzene （BHEAZO） as an initiator and stannous 2-ethylhexanoate [ Sn（Oct）2 ] as a catalyst. The hydroxyl terminated poly（p-dioxanone） （PPDO） precursors were then coupling-reacted with the carboxyl group terminated hydroxymethyl polyethylene glycol （mPEG-COOH） to give the mPEG-BHEAZO- PPDO-mPEG triblock copolymer. The photo-responsive behavior of the copolymer was studied by UV-Vis spectroscopy, dynamic laser scattering （DLS） and transmission electron microscopy （TEM）. The configurational change of the azobenzene group contained in the copolymer nano-aggregate was investigated by the UV-Vis spectroscopy. The absorbance of the nano-aggregate aqueous solution increased with the growth of the irradiation time. The size of nano-aggregate particle and particle size distribution after exposure to light with different wavelengths were measured by DLS. The size of the copolymer nano-aggregate after exposure to 450 nm light was getting bigger than that to 365 nm,and the size distribution was getting wider at the same time. The TEM images of the nano-aggregate aqueous solution were consistent with the DLS results. According to the analyses above, a bypothetie mechanism was proposed for explaining the changes of the nano-aggregates after exposure to lights with different wavelengths. A single nano-aggregate particle easily tended to aggregate with the particles nearby since the trans configuration of azobenzene groups in the copolymer was more likely to form a stable electron delocalization state of low level,which could lead to a stonger π-π stacking effect.