Synthesis and self-assembling of diblock copolymers containing a side-on liquid crystalline block and a pseudo-stilbene azobenzene block

Abstract

Liquid crystalline (LC) diblock copolymers containing a side-on LC block and a pseudo-stilbene azobenzene block were synthesized, and their self-assembling in water/tetrahydrofuran (THF) was investigated. Side-on LC monomer 4’’-methylacryloyloxybutyl 2,5-di(4’-butyloxybenzoyloxy) benzoate (4-MDBB) was synthesized, and then polymerized into P4MDBB through reversible addition-fragmentation chain transfer (RAFT) polymerization. A pseudo-stilbene azobenzene monomer 6-(N-methyl-N-(4-(4’-cyanophenylazo)phenyl)amino)hexyl methacrylate (6-NCN) was also synthesized. The diblock copolymers P4MDBB_m-b-P6NCN_n were obtained through the RAFT polymerization of 6-NCN by using P4MDBB as the chain transfer agent. The copolymers and the intermediates were confirmed by ¹H and ¹³C NMR spectra, FT-IR spectra, UV-Vis spectra, mass spectra, DSC analysis, POM observations, GPC tests and contact angle measurements. The diblock copolymers self-assembled upon adding water slowly into their THF solutions. The self-assembling and the corresponding assemblies were characterized by fluorescence spectra, laser light scattering experiments as well as TEM measurements. Results demonstrated that these diblock copolymers form spherical aggregates in water/THF, but the aggregates are un-stretchable upon irradiation with polarized light.

Keywords:

• liquid crystalline polymer
• block copolymer
• azobenzene
• self-assembling

Acknowledgements

The financial support from National Natural Science Foundation of China (Project No. 51603029) is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.