Analysis of natural and synthetic polymers by analytical chemical chromatographic and spectroscopic methods.

摘要

Polymer analysis is important in industrial product development, quality control, and forensic analysis of trace evidence. Analytical pyrolysis (Py) enables characterization of the chemical structure of polymers by thermal fragmentation of microgram sample amounts to produce characteristic products, which are separated and identified by gas chromatography/mass spectrometry (GC/MS). Fourier transform infrared (FTIR) spectroscopy, which measures 1R radiation transmitted or absorbed at characteristic vibrational frequencies for the functional groups present, is another common approach for polymer characterization. Ultraviolet-visible (UV-VIS) and fluorescence microspectrophotometry are useful for analysis of highly conjugated chemical additives ( e.g., dyes) on polymeric substances, such as fibers. Absorption of UV-VIS radiation causes pi and nonbonding electronic transitions, while fluorescence occurs when light is emitted at longer wavelengths than the absorbed radiation.;Thermal stability of nonyl and ethylhexyl substituents in polymeric poly( p-phenyleneethynylene)s was investigated by sequential automated pyrolysis over a range of temperatures. Degradation rates and activation energies were obtained using the Ericsson and Guggenheim methods; activation energies for the two substituted polymers were not significantly different at the 95% confidence level.;Py-fast GUMS and FTIR were applied to rapid forensic identification of automobile tires. Attenuated total reflectance was employed to facilitate FTIR analysis of the non-transparent polymers. Linear discriminant analysis (LDA) of spectra from three tire manufacturers produced 98% cross-validated classification accuracy. Natural and synthetic fibers were also analyzed by laser Py-fast GC/time-of-flight MS and FTIR microscopy. LDA of pyrolysis and spectral data achieved 93% and 97% cross-validated classification accuracy, respectively.;Three mounting media (glycerin, Norland Optical Adhesive 65, Permount RTM) were evaluated for forensic UV-VIS and fluorescence microspectroscopy of dyed textile fibers. PermountRTM has many advantages including ease of use, low cost, and suitability for long-term storage and polarized light microscopy measurements. The discrimination of dyed fibers using UV-VIS and fluorescence microspectroscopy was also evaluated.;Bipolar membranes consist of polymeric materials for removing salts by applying a direct current to stacked anion/cation exchange membranes, where water splitting occurs to produce acids and bases. Production of these membranes normally involves syntheses using highly carcinogenic substances. A safe chloromethylation and amination process was developed for producing anion-exchange membranes for bipolar membranes.