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- Title
Light and Temperature as Dual Stimuli Lead to Self-Assembly of Hyperbranched Azobenzene-Terminated Poly(N-isopropylacrylamide).
- Authors
Wenyan Huang; Jing Yang; Yunqing Xia; Xuezi Wang; Xiaoqiang Xue; Hongjun Yang; Guifang Wang; Bibiao Jiang; Fang Li; Komarneni, Sridhar
- Abstract
Hyperbranched poly(N-isopropylacrylamide)s (HBPNIPAMs) end-capped with different azobenzene chromophores (HBPNIPAM-Azo-OC3H7, HBPNIPAM-Azo-OCH3, HBPNIPAM-Azo, and HBPNIPAM-Azo-COOH) were successfully synthesized by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide using different azobenzene-functional initiators. All HBPNIPAMs showed a similar highly branched structure, similar content of azobenzene chromophores, and similar absolute weight/average molecular weight. The different azobenzene structures at the end of the HBPNIPAMs exhibited reversible trans-cis-trans isomerization behavior under alternating UV and Vis irradiation, which lowered the critical solution temperature (LCST) due to different self-assembling behaviors. The spherical aggregates of HBPNIPAM-Azo-OC3H7 and HBPNIPAM-Azo-OCH3 containing hydrophobic para substituents either changed to bigger nanorods or increased in number, leading to a change in LCST of -2.0 and -1.0 °C, respectively, after UV irradiation. However, the unimolecular aggregates of HBPNIPAM-Azo were unchanged, while the unstable multimolecular particles of HBPNIPAM-Azo-COOH end-capped with strongly polar carboxyl groups partly dissociated to form a greater number of unimolecular aggregates and led to an LCST increase of 1.0 °C.
- Subjects
AZOBENZENE; ACRYLAMIDE; CHROMOPHORES; POLYMERIZATION; ATOM transfer reactions; MOLECULAR weights
- Publication
Polymers (20734360), 2016, Vol 8, Issue 5, p183
- ISSN
2073-4360
- Publication type
Article
- DOI
10.3390/polym8050183