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

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.