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Open AccessArticle

Influence of Cyclodextrins on Thermosensitive and Fluorescent Properties of Pyrenyl-Containing PDMAA

1
School of Chemistry and Materials Engineering, Fuyang Normal University, Fuyang 236037, China
2
Anhui Provincial Key Laboratory for Degradation and Monitoring of the Pollution of the Environment, Fuyang 236037, China
3
State Key Laboratory of Molecular Engineering of Polymers (Fudan University), Shanghai 200433, China
*
Author to whom correspondence should be addressed.
Polymers 2019, 11(10), 1569; https://doi.org/10.3390/polym11101569
Received: 31 August 2019 / Revised: 22 September 2019 / Accepted: 23 September 2019 / Published: 26 September 2019
(This article belongs to the Special Issue Stimuli Responsive Polymers II)
A series of pyrenyl-containing PDMAA copolymers were prepared by free radical copolymerization of dimethylacrylamide (DMAA) with pyrenebutanoyloxy ethyl methacrylate (PyBEMA). The structure of as-prepared copolymers was characterized by UV, FT-IR and 1H NMR spectroscopy. The effect of cyclodextrins (α-CD, β-CD and γ-CD) on the thermosensitivity and fluorescence of the copolymers in aqueous solutions were investigated. It was found that the as-prepared copolymers exhibit lower critical solution temperature (LCST)-type thermosensitivity. Cloud point (Tcp) decreases with the increasing molar content of PyBEMA unit in the copolymers. Tcp of the copolymers increases after the CD is added from half molar to equivalent amount relative to pyrenyl moiety, and that further adding twice equivalent CD results in a slight decrease in Tcp. The copolymers exhibit a pyrene emission located at 377 nm and a broad excimer emission centered at 470 nm. The copolymers in water present a stronger excimer emission (Intensity IE) relative to monomer emission (Intensity IM) than that in ethanol. The IE/IM values decrease after the addition of equivalent α-CD, β-CD and γ-CD into the copolymers in aqueous solution, respectively. The IE/IM values abruptly increase as the copolymers’ concentration is over 0.2 mg/L whether in ethanol solution or aqueous solution with or without CD, from which can probably be inferred that intra-polymeric pyrene aggregates dominate for solution concentration below 0.2 mg/L and inter-polymeric pyrene aggregates dominate over 0.2 mg/L. Furthermore, the formation of the CD pseudopolyrotaxanes makes it possible to form pyrene aggregates. For high concentration of 5 g/L, the copolymers and their inclusion complexes completely exhibit an excimer emission. The IE values abruptly increased as the temperature went up to Tcp, which indicates that the IE values can be used to research phase separation of polymers. View Full-Text
Keywords: poly(N,N-dimethylacrylamide); cyclodextrins; pyrene; thermosensitive polymers; fluorescence poly(N,N-dimethylacrylamide); cyclodextrins; pyrene; thermosensitive polymers; fluorescence
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Dong, Q.; Sun, C.; Chen, F.; Yang, Z.; Li, R.; Wang, C.; Luo, C. Influence of Cyclodextrins on Thermosensitive and Fluorescent Properties of Pyrenyl-Containing PDMAA. Polymers 2019, 11, 1569.

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