A TEMPERATURE AND pH DOUBLE SENSITIVE CHOLESTERIC POLYMER FILM FROM A PHOTOPOLYMERIZABLE CHIRAL HYDR

来源 :Chinese Journal of Polymer Science | 被引量 : 0次 | 上传用户:dongchangnie
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In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal (Ch-LC) monomers mixture containing a photopolymerizable chiral H-bonded assembly (PCHA). The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green/yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Additionally, the selective reflection band (SRB) of the cholesteric polymer film in solution with pH > 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH < 7 hardly changed. This pH sensitivity in solutions with pH > 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by―OH and―K + ions in the alkaline solution. In contrast, it couldn’t happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical/photonic papers, optical sensors and LCs displays, etc. In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal (Ch-LC) a photopolymerizable chiral H-bonded assembly (PCHA). The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green / yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Yet, the selective reflection band (SRB) of the cholesteric polymer film in solution with pH> 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH <7 hardly changed. This pH sensitivity in solutions with pH> 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by-OH and-K + ions in the alkaline solution. In contrast, it could not happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical / photonic papers, optical sensors and LCs displays, etc.
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