Chemical sensor, hydrogen bond

Fluorinated alcohols are not only interesting as model systems for weak hydrogen bonds with implications in the life sciences [254] and as chemical sensor materials [255], but also provide excellent reaction media [256, 257] and peptide solvents [258 260] with conformation-modulating properties. In both cases, molecular aggregates are thought to play an important role. One of the most widely used fluorinated alcohols is 2,2,2-trifluoroethanol, which will be in the focus of the following section. 

Absorption of a solute liquid or vapor into a polymer film can profoundly affect the viscoelastic behavior of the polymer. The magnitude of this effect depends on the nature of the solute/polymer interactions and on the amount of solute absorbed. The solute/polymer interactions can range fttun simple dispersion to hydrogen-bonding and other specific interactions. The extent of absorption can be described by the partition coefficient, AT, which quantifies the thermcxlynamic distribution of the solute between two phases (K = coiKentration in polymer divided by die concentration in the liquid or vapor phase in contact with the polymer). It has long been known that acoustic wave devices can be used to probe solubility and partition coefficients (53,67). Due to the relevance of these topics to chemical sensors, more comprehensive discussions of these interaction mechanisms and the significance of the partition coefficient are included in Chapter 5. 

Chemoselective hydrogen-bonded acid polymers are at the heart of many electronic nose chemical point detection sensor systems. These polymers selectively adsorb chemical agents or explosives over extended periods of time (minutes, hours, days). Relatively thick polymer films and/or hyperporous structures allow rapid vapor sorption. Material properties are selected to allow vapor sorption, but not desorption, at ambient conditions. Heating allows the trapped agent to be released for analyses. 

Biihlmann, P. Amemiya. S. Nishizawa, S. Xiao. K.P. Umezawa, Y. Hydrogen-bonding ionophores for inorganic anions and nucleotides and their application in chemical sensors. J. Incl. Phenom. Mol. Recognit. Chem. 1998. 32, 151-163. 

Design of Sorbent Hydrogen Bond Acidic Polycarbosilanes for Chemical Sensor Applications, Chapter 5... 

This work describes recent advances in the preparation of hydrogen bond acidic polycarbosilanes and their application as chemical sensor coatings. We have prepared hydrogen bond acidic polymers based on polycarbosilanes with the goal of improving upon the chemical and thermal properties of this class of functionalized polymer (3-5). Results pertaining to the preparation of selected model compounds are also described. 

Comparative chemical sensor vapor testing of the hydrogen bond acidic polycarbosilanes with polysiloxane analogues has shown a significant enhancement in sensitivity toward hydrogen bond basic vapors relative to the... 

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