Hybrid organic/inorganic polymers have been prepared
incorporating fluoroalkyl-substituted bisphenol groups linked using oligosiloxane spacers.
These hydrogen-bond acidic
materials have glass-to-rubber transition temperatures below room
temperature and are
excellent sorbents for basic vapors. The physical properties such
as viscosity and refractive
index can be tuned by varying the length of the oligosiloxane spacers
and the molecular
weight. In addition, the materials are easily cross-linked to
yield solid elastomers. The
potential use of these materials for chemical sensing has been
demonstrated by applying
them to surface acoustic wave devices as thin films and detecting the
hydrogen-bond basic
vapor dimethyl methylphosphonate with high sensitivity. It has
also been demonstrated
that one of these materials with suitable viscosity and refractive
index can be used to clad
silica optical fibers; the cladding was applied to freshly drawn fiber
using a fiber drawing
tower. These fibers have potential as evanescent wave optical
fiber sensors.
Four hydrogen bond acidic polymers are examined as sorbent layers on acoustic wave devices for the detection of basic vapors. A polysiloxane polymer with pendant hexafluoro-2-propanol groups and polymers with hexafluorobisphenol groups linked by oligosiloxane spacers yield sensors that respond more rapidly and with greater sensitivity than fluoropolyol, a material used in previous SAW sensor studies. Sensors coated with the new materials all reach 90% of full response within 6 s of the first indication of a response. Unsupervised learning techniques applied to pattern-normalized sensor array data were used to examine the spread of vapor data in feature space when the array does or does not contain hydrogen bond acidic polymers. The radial distance in degrees between pattern-normalized data points was utilized to obtain quantifiable distances that could be compared as the number and chemical diversity of the polymers in the array were varied. The hydrogen bond acidic polymers significantly increase the distances between basic vapors and nonpolar vapors when included in the array.
A series of novel hyperbranched hydrogen-bond acidic polymers for surface acoustic wave (SAW) sensor applications were prepared by functionalizing hyperbranched polycarbosiloxanes or polycarbosilanes with phenol or hexafluoro-2-propanol groups. Starting polymer, sensor polymer, and reagent structures were confirmed by IR, 1 H, 13 C, and 29 Si NMR, SEC, or GCMS as appropriate. The hyperbranched sensor polymers were coated onto 500 MHz SAW platforms and their responses to the nerve agent simulant dimethyl methylphosphonate (DMMP) were studied. The hyperbranched sensor polymers with phenol groups gave very high initial responses to DMMP which dropped to 30% of the initial levels over a period of 6 months, and the hyperbranched sensor polymers with hexafluoro-2-propanol groups gave lower initial responses that did not change with time. Hence, the long-term performances of hyperbranched phenolic sensor polymers and hyperbranched hexafluoro-2-propanol sensor polymers were found to be comparable.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.