Multiple materials systems have been studied to better understand the chemistry that occurs at the molecular level. These materials either had dimensions on the nanometer length scale or had domains of nanometer size. Each of the systems had multiple components where there were one or more interfaces present. Solid-state NMR techniques were used to probe the compositions and structure of the interfaces of these materials in an effort to develop an understanding of the structure-property relationships.
Alumina nanofibers were produced by electrospinning using a stabilizer free precursor and calcination at intermediate temperatures. The nanofibers were shown to be reactive toward phosph(on)ate compounds with the detection of physisorbed and chemisorbed bridged aluminophosphate species. This reactivity toward chemical warfare simulants suggests their potential use in the decomposition of chemical warfare agents.
Materials for potential use as fuel cell membranes able to be operated in a high temperature, low humidity environment were studied. A hyperbranched polymer was successfully incorporated into Nafion® at ~7 wt%. The impregnation of the hyperbranched polymer was shown to improve the stability and proton conductivity of Nafion® at higher temperatures when in the absence of mobile water. A phosphazene trimer doped with phenylphosphonic acid was successfully dispersed into a polyimide film and there was shown to be an interaction of the trimer and phenylphosphonic acid.
Silica aerogel systems were characterized and TEOS-based aerogels treated with a polysilsesquioxane, TPOSS, was found to participate in condensation reactions via silanol groups, whereas when the TEOS/APTES-based aerogels were treated with epoxyPOSS it was observed that the epoxyPOSS grafted to the aerogel structures via reactions with amine groups of APTES. It was observed that small amounts of either POSS derivative significantly enhanced the hydrophobicity and the compressive strength and modulus of the resultant aerogels, without much change to the density. The molecules of silanol-POSS and a sorbitol derivative, di(benzylidene)sorbitol (DBS), were shown to be capable of forming several complex molecular adducts. Such complex formation occurred due to non-covalent interactions, such as hydrogen bonding. In the aluminosilicate aerogels the majority of the Si sites of the aerogel prepared from AlCl3 contained at least one Si-O-Al linkage and there was a distribution in the number of Al near each Si. When the aerogel was prepared from boehmite the material contained mostly a silica network and bulk alumina. The boehmite aerogels exhibited smaller shrinkage, lower physical density and higher porosity while the AlCl3 aerogels exhibits a higher mesopore volume and higher surface area.
The individual components that make up the tire, nylon cord, SBR rubber and the adhesive were all characterized and chemical shift assignments were made. Various composite materials were produced in order to be better able to observe the interactions occurring at the interface of the materials, specifically the interface of the RF component of the adhesive with nylon. The proposed the hydrogen bond between the RF component of the adhesive and the nylon was observed by using 2D HETCOR NMR.