首页> 外文期刊>Langmuir: The ACS Journal of Surfaces and Colloids >Reversible photoswitchable wettability in noncovalently assembled multilayered films
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Reversible photoswitchable wettability in noncovalently assembled multilayered films

机译:非共价组装的多层薄膜中可逆的光开关润湿性

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摘要

Reversible and irreversible photoinduced changes in surface wettability were observed in noncovalently assembled multilayered films. The multilayered films studied were fabricated from a self-assembled monolayer (SAM) consisting of 4-(10-mercaptodecyloxy)pyridine-2,6-dicarboxylic acid on gold, Cu(II) ions complexed to the pyridine head group of the SAM, and either cis- (film 1) or trans- (film 2) stilbene-4,4'-dicarboxylic acid complexed to the Cu(II) ions. Irradiation of film 1 at wavelengths corresponding to the absorption band of the cis-stilbene isomer resulted in an irreversible chemical change and an irreversible increase in wettability, as indicated by surface contact angle and grazing incidence IR measurements. However, no evidence for cis-/trans-photoisomerization was observed. Films 3 and 4, similar to films 1 and 2 in that they consist of an underlying SAM, an intermediate layer consisting of Cu(II) ions, and either cis- or trans-stilbene-4,4'-dicarboxylic acid as the capping ligand, were fabricated with a mixed SAM that contained both 4-(10-mercaptodecyloxy)pyridine-2,6-dicarboxylic acid and 4-tert-butylbenzenethiol. Irradiation of these films at wavelengths corresponding to stilbene isomer absorption bands resulted in reversible cis- to trans- (film 3) and trans- to cis- (film 4) photoisomerization and reversible switching of the surface wettability between a low wetting state (cis-stilbene) and a high wetting state (trans-stilbene). The difference in observed behavior between films 1 and 2 and films 3 and 4 is attributed to the greater surface spacing afforded by the mixed monolayer, which allows greater conformational flexibility and lowers the steric barriers to isomerization.
机译:在非共价组装的多层膜中观察到表面润湿性的可逆和不可逆的光诱导变化。研究的多层膜是由自组装单层(SAM)制成的,该层由在金上的4-(10-巯基癸氧基)吡啶-2,6-二羧酸,与SAM的吡啶头基络合的Cu(II)离子组成,以及与Cu(II)离子络合的顺式(薄膜1)或反式(薄膜2)二苯乙烯-4,4'-二羧酸。如表面接触角和掠入射IR测量所指示,以与顺式-二苯乙烯异构体的吸收带相对应的波长照射膜1导致不可逆的化学变化和润湿性的不可逆增加。但是,没有观察到顺-/反-光异构化的证据。薄膜3和4与薄膜1和2相似,因为它们由下面的SAM组成,中间层由Cu(II)离子组成,并且顺式或反式-苯乙烯-4,4'-二羧酸作为封端用包含4-(10-巯基癸氧基)吡啶-2,6-二羧酸和4-叔丁基苯硫醇的混合SAM制备了配体。在与二苯乙烯异构体吸收带相对应的波长下辐照这些薄膜会导致可逆的顺式至反式(薄膜3)和反式至顺式(薄膜4)光异构化,并且表面润湿性在低润湿状态之间可逆转换(顺式1,2-二苯乙烯)和高润湿状态(反二苯乙烯)。膜1和2与膜3和4之间观察到的行为差异归因于混合单层所提供的更大的表面间距,这允许更大的构象柔性并降低了异构化的空间障碍。

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