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Amphiphilic Rod–Rod Block Copolymers Based on Phenylacetylene and 3,5-Disubstituted Phenylacetylene: Synthesis, Helical Conformation, and Self-Assembly

Author:
Chen, Junxian, Wang, Sheng, Shi, Ge, Wang, Rong, Cai, Siliang, Zhang, Jie, Wan, Xinhua
Source:
Macromolecules 2018 v.51 no.19 pp. 7500-7508
ISSN:
1520-5835
Subject:
catalysts, composite polymers, energy, hydrophilicity, hydrophobicity, micelles, polymerization, water content
Abstract:
A novel series of amphiphilic rod–rod block copolymers (PPAₘ-b-PrmEOₙ) based on achiral phenylacetylene (PA) and chiral 3,5-disubstituted phenylacetylene (rmEO) were synthesized through sequential living polymerizaitons using the catalyst Rh[C(C₆H₅)═C(C₆H₅)₂](nbd)(4-FC₆H₄)₃P (nbd = norbornadiene) (Rh-cat). The living nature of the polymerization of rmEO using Rh-cat was proved. These block copolymers consist of a hydrophobic achiral stretched cis–transoid helical PPA block and a hydrophilic one-handed contracted cis–cisoid helical PrmEO block. The amphiphilic block copolymers could self-assemble into well-defined aggregates in THF/H₂O. The effects of the composition of block copolymers, water contents, and initial copolymer concentration on the formation of aggregates were investigated. The block copolymers with short corona-forming blocks formed vesicles, while those with long corona-forming blocks formed novel multiarm worm-like micelles. As the water content increased, the aggregates transformed from the spherical micelles to worm-like micelles, and then the end-caps of the worm-like micelles fused together to form the multiarm worm-like micelles. The formation mechanism of the multiarm worm-like micelles was proposed by considering the large end-capping energy originating from the rigid conformation of the copolymers. Besides, the copolymers tend to form vesicles at high initial copolymer concentration.
Agid:
6151938