Multiple Internal Reflection IR Spectroscopy Research Articles

Low-temperature plasma surface modification of textiles made from natural fibers and advanced technologies

Processes that occur in natural fibers during glow-discharge plasma treatment are considered. A study of the plasma etching kinetics, capillarity changes, the fiber surface (using electron microscopy and attenuated total multiple internal reflection IR spectroscopy), and the principal mechanical and other properties demonstrated that modification and degradation affect the fiber surface layers. It is evident that the surface membranes of flax and wool fiber cells are damaged. Important reaction pathways are processes involving the transformations of free radicals. Plasma treatment of gray linen fabric leads to degradation and modification of impurities, thereby opening an opportunity for accelerating the laborious bleaching process and making it environmentally more benign. The enhancement of the sorption-diffusion properties by plasma treatment makes it possible to intensify the dyeing and printing processes.

The use of low-temperature plasmas in wool finishing

Processes that occur in wool fiber under the action of a glow-discharge plasma were considered. The kinetics of plasma etching, the amino acid compositions of whole fiber and separated cuticle elements, the surface of fiber (using scanning electron microscopy and attenuated total multiple internal reflection IR spectroscopy), as well as the electrosurface, friction, and other properties, were studied. These studies demonstrated that undergoing degradation and modification were primarily the fiber cuticle and its proteins and, particularly, lipids. Important reaction paths were processes involving the transformations of free radicals. Cystine, peptide, alanine, and glycine radicals were identified on the basis of EPR spectra. Plasma treatment enhanced the wettability of wool and the diffusion of dyes into fibers upon dyeing and printing and decreased the felting ability. This treatment did not impair the physicomechanical, heat-insulation, and thermal properties of wool. However, the resulting changes somewhat decreased the hydrophilicity of wool after plasma treatment.

MIRIRS studies of the growth of Si and Si-Ge alloys from molecular precursors

The adsorption of hydrogen and disilane on Si(100), Ge Si(100) and Si− Ge Si(100) surfaces, and the evolution with temperature of these adsorption systems, has been followed by multiple internal reflection IR spectroscopy (MIRIRS). The initial dissociative adsorption of disilane at 300 K is similar on both Si and Ge surfaces, but the presence of surface germanium opens up a much more facile route for monohydride decomposition and hydrogen desorption.

Photosynthetic membranes IV: kinetic investigation of photoinitiated grafting and photo-cross-linking of an epoxydiacrylate resin onto cellulose

Photochemical grafting onto cellulose and successive photo-cross-linking of 2.00 – 37.00 mg cm −2 of an epoxydiacrylate prepolymer based on glycidyl ether of bisphenol A, containing 25 wt./wt.% trimethylolpropane triacrylate, were investiated kinetically at 30 °C in the presence of 1,2-diphenyl-2,2-dimethoxyethanone as a photoinitiator, with the weight concentration ratio of photoinitiator to prepolymer varied between 0.070 and 1.115. Irradiations were carried out polychromatically, in air or under a stream of nitrogen, with incident radiation of flux I ranging from 2.1 × 10 −8 to 20.5 × 10 −8 einsteins s −1 cm −2. Graft yields as a function of irradiation time were determined gravimetrically: two consecutive kinetic processes were observed which had rates linearly dependent on I. The quantum yields Φ 1 of the first constant-rate period showed a linear dependence on photoinitiator concentration, while the quantum yields Φ 2 for the second constant-rate process showed an inverse dependence on n/S (moles of prepolymer initially deposited per unit apparent cellulose surface). Kinetic analysis of the degree of unsaturation by multiple internal reflection IR spectroscopy was carried out in parallel and the results indicated that a structure with one pendant acrylate group per monomer unit may be assigned to the grafted polymer. At longer irradiation times, further decrease in unsaturation resulting from photo-cross-linking was observed which had a rate linearly dependent on I 0.5, suggesting a bimolecular termination for this process. In the light of this information, the mechanism of photografting of poly-functional acrylate monomers onto polymeric surfaces is discussed.

Study of the acid?Base interaction in the sulfuric acid-ethyl acetate system by multiple internal reflection IR spectroscopy

1. Using the method of MFTIR IR spectroscopy at 30°C, the equilibrium concentrations of acid, ester, and the products of their interaction in the binary liquid system H2SO4-CH3COOC2H5 were determined. Depending on the molar ratios of components the products of combination may have the composition B·2H2SO4, B·H2SO4, and 2B·H2SO4. 2. In the concentration regions of H2SO4 close to absolute, the complexes B·2H2O4 and B·H2SO4 are practically completely ionized. In dilute H2SO4 solutions in ester, primarily molecular complexes are contained. In solutions of equimolar composition complexes with proton transfer predominate.