对苯撑乙烯撑寡聚物-b-聚乙二醇的合成及结晶驱动自组装行为

Synthesis and Crystallization-Driven Self-Assembly of Oligo(p-phenylenevinylene)-b-Poly(ethylene glycol)

通过多步合成分别得到具有3、4和5个重复单元末端炔基的对苯撑乙烯撑寡聚物(OPV)。利用铜催化的叠氮-炔环加成反应制备得到含有不同OPV链长的对苯撑乙烯撑寡聚物-b-聚乙二醇(OPV-b-PEG)。紫外-可见吸收和荧光发射光谱的研究结果表明:OPV的链长会显著影响OPV-b-PEG的溶液行为。由于OPV3-b-PEG115和OPV4-b-PEG115中OPV的重复单元较少,导致其自组装的结晶驱动力不够,因此以单分子的状态溶解在正丁醇中;而对于OPV5-bPEG115,OPV5链段在正丁醇中形成了H-聚集体。利用透射电子显微镜和原子力显微镜系统地考察了OPV5-b-PEG115在乙醇、异丙醇和正丁醇中的自组装行为,结果表明OPV5-b-PEG115自组装形成长达数微米、宽度均一的纤维状胶束。虽然利用"自晶种"策略所制得的纤维状胶束的平均长度随退火温度的提高而增长,但所得胶束的长度分布较宽。

Monodisperse aldehyde-terminated oligo(p-phenylenevinylene)(OPV) with 3, 4 and 5(trimer, tetramer and pentamer) repeated units were synthesized. Upon a functionalization reaction, alkynyl-terminated OPV was synthesized.Following the conjugation with N3-terminated poly(ethylene glycol)(PEG) through Cu-catalyzed alkyne-azide cycloaddition reaction, OPV-b-PEG was obtained. UV/Vis absorption and Fluorescence spectrometry analyses showed that the length of OPV segment dominated the solubility of OPV-b-PEG. Due to the weak driving force for the aggregation of OPV segments in butanol, OPV3-b-PEG115 and OPV4-b-PEG115 were not able to aggregate and dissolved in butanol at molecular level. On the contrary, OPV5-b-PEG115 was capable of self-assembling, leading to formation of long fiber-like micelles in ethanol,isopropanol and butanol where OPV segments self-assembled into H-aggregation. The resulting micelles presented uniform width and length, particularly, the length can reach several micrometers. Although the average length of fiber-like micelles obtained via "self-seeding" during crystallization-driven self-assembly was increased with temperature, the length distribution was rather broad.