Journal Article Amphiphilic gels of solvatochromic fluorescent poly(2-oxazoline)s containing D–π–A pyrenes

Chen, Chia-Hsiu  ,  Chen, Chia-Hsiu  ,  仁子, 陽輔  ,  Niko, Yosuke  ,  小西, 玄一  ,  Konishi, Gen-ichi

6 ( No. 49 )  , pp.42962 - 42970 , 2016-04 , RSC , 英国王立化学会
Herein, we report amphiphilic, fluorescent, solvatochromic poly(2-methyl-2-oxazoline) (POZO-py) and poly(2-ethyl-2-oxazoline) (PEtOZO-py), which contain D–π–A pyrene dye units in their side chains. These new fluorescent polymers display solvatochromism and bright fluorescence in a variety of solvents, ranging from toluene (475 nm) to methanol (515 nm) and water (535 nm). Furthermore, amphiphilic gels (amphigels) of POZO-py and PEtOZO-py were synthesized by cross-linking the amine sites of partially hydrolyzed POZO-py and PEtOZO-py. Amphigels were formed rapidly when bridging ethyleneimine moieties were used for POZO-py and PEtOZO-py. These amphigels swell in various solvents, resulting in a solvatochromic shifts of the fluorescence emission. We furthermore determined the relationship between the swelling process, the solvatochromic properties, and the polymer structure of the POZO-py and PEtOZO-py gels. The different swelling properties led to different amphigel structures in water and hence, to different maximum fluorescence wavelengths. For example, a POZO-py amphigel with 10% ethyleneimine bridging exhibited the same solvatochromic behavior as POZO-py in solution. These results are significant in order to evaluate the solvatochromic properties of pyrene chromophores in polymers and to investigate gel structures and functional group interactions in gels.

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