Leaf litter decomposition is largely effected by the enzymatic action of fungal colonizers of leaf material. Microscopic attenuated total reflectance (ATR) infrared spectroscopy would be a useful tool to evaluate changes in leaf litter carbohydrate chemistry over time during the colonization process at the scale of resolution of the fungal hyphae. This paper reports the first studies to use microspectroscopy in the mid-infrared (IR) region to perform analyses within an area of 250 × 250 μm to gain spectra of single species of sugars and complex carbohydrates (cellulose, hemicellulose, lignin) to identify characteristic IR reflectance peaks and to be able to separate the species in complex media. Changes in leaf surface carbohydrate chemistry were interpreted from spectra obtained from leaf material that underwent the following: (1) treatment with acetone (to remove surface waxes), (2) treatment with enzymes, and (3) observation after colonization by fungi. Analysis of spectra obtained from random locations or from the same points on the leaf surface over time permitted changes in carbohydrate chemistry to be detected. Comparative analysis of spectra was carried out by using time-series analysis of variance of selected characteristic peak heights and multivariate statistics.
Sulfonium precursor routes are the most popular synthetic routes to light-emitting poly(p-phenylene vinylene) (PPV) thin films. These routes involve a high-temperature solid-state thermal
elimination reaction which yields PPV from its water-soluble precursor. The quality of PPV and hence
its ultimate properties have a strong dependence on the polymerization parameters and thermal
elimination conditions. The elimination reaction remains less understood. In this report, we have
qualitatively and quantitatively analyzed the thermal elimination reaction using TGA, DSC, MTGA, TG-IR and transmission IR. The qualitative analysis focuses on identification of the underlying reactions
and establishing the reaction sequence and reaction mechanisms. The quantitative analysis, on the other
hand, focuses on the determination of the kinetic parameters of these reactions. The effect of heating
rate and reaction environment on the luminescent properties of PPV have also been investigated.
Poly@-phenylenevinylene) can be loosely viewed as a regular copolymer of polyacetylene and poly@-phenylene). Here, the electronic structures of polyacetylene, poly@-phenylene), and poly@-phenylenevinylene) have been studied using ultraviolet photoelectron spectroscopy and quantum chemical calculations baaed upon the valence effective Hamiltonian method. Excellent agreement between theory and experiment allows for a detailed description of the evolution of the electronic structure in this polymer series.
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