EVALUATION BY IR SPECTROSCOPY

The efficiency of various substituted benzophenones for initiating the photopolymerization of multifunctional monomers in condensed phase was evaluated by IR spectroscopy from conversion versus exposure time kinetic curves. The best results were obtained with diphenoxy- benzophenone (DPB) associated to an hydrogen donor, like methyl- diethanolamine, for a one to one mixture of hexanetfrol-diacrylate (HDDA) and of a polyurethane-diacrylate (Actilane 20 fix)m SNPE). Figure 1 shows some typical polymraization profiles obtained for a 30 im thick film exposed, in the presence of air, to the UV radiation of a medium pressure mercury lamp at a light intensity of 1.5 X lO einsteins l cm-2. 

Sassi and Chanzy subjected nanocrystals, from Valonia and tunicin, to both homogenous and heterogeneous acetylation [51]. The acetyl content was evaluated by IR spectroscopy. In both methods, acetylation essentially took place at the surface of the crystals. However, in homogenous acetylation, the crystal diameter was drastically reduced, indicating that sufficiently acetylated cellulose chains located in the surface dissolved in the reaction medium. In heterogeneous acetylation the acetylated cellulose remained insoluble and surrounded an unreacted core of cellulose crystals. 

As revealed by IR-spectroscopy, the attachment of the polymer proceeds via acylation of aminopropyls absorbances of both amides (1650 cm-1) and esters (1740 cm-1) contribute to the spectrum of polyacrylate-coated aminopropyl-Aerosil (specific surface area 175 m2/g) [55], During the reaction, the accumulation of p-nitrophenyl ester groups in the support is accompanied by the liberation of p-nitrophenol into the contacting solution. Thus, the evaluation of the conformational state of adsorbing macromolecules can be performed by the simultaneous study of both processes by UV-spectroscopy as shown in Fig. 7. Apparently, at... 

To determine the conformation of adsorbed polymers the fraction of adsorbed polymer segments (p) and the fraction of the occupied surface sites (6) are often measured. Fontana and Thomas2 were the first to measure p and 6 by IR spectroscopy. At present, the application of IR spectroscopy is limited to finely divided substrates, e.g. nonporous silica, and requires that the surface area and the number of surface sites (e.g. the silanol groups) per unit area are accurately known in advance. The adsorbed amount T of polymer per surface site can be determined from adsorbance A(g/cm2) and the total area of the adsorbent. However, it can also be evaluated from the ratio 6/p. 

Photoinitiator concentration 1 mol% of benzophenone moieties in the HDDA/APDG mixture. Irradiation performed by a medium-pressure linear (15 cm) Hg lamp (5(X) W) on a 10 pm thick liquid film between two NaCl discs located at a distance of 20 cm Half-time of the process as determined by IR spectroscopy Polymerization rate evaluated at ti/2 and expressed as % conversion over time... 

Polymerization conditions see Table 1 Half-time of the process, as determined by IR spectroscopy Polymerization rate evaluated at ti/2 and expressed as % conversion over time... 

Determined by IR spectroscopy. Irradiation conditions see Table 1 Evaluated by microwave dielectrometry. Irradiation conditions see Table 2 Benzophenone moiety concentration in the HDDA/APDG and HDDA/BA mixtures 1 mol% Half-time of the curing process... 

The success of the PVA crosslinking, as well as the success of the dispersion of Co(acac)2 and Co(acac)2trien NaY in the polymeric matrix, were evaluated by FTIR spectroscopy, using a Bio-Rad FTS 155 FT-IR spectrometer. The amount of acid groups in the PVA/SSA matrix was measured by using a classic titration with 0.1 MNaOH... 

The mono- and bimetallic substituted MCM-41 catalysts with cobalt, vanadium or lanthanum have been prepared by direct synthesis or impregnation and characterized by various techniques, such as XRD, N2 adsorption-desorption, SEM, TEM and TGA. The catalytic activity in the selective oxidation of styrene with H2O2 has been evaluated. Adsorption of benzene and ammonia on the mono- and bimetallic mesoporous molecular sieves with cobalt and vanadium has been studied by IR spectroscopy and the results have been correlated with their catalytic properties and the characteristics of the structure. Co-incorporated catalysts prepared by direct synthesis show to be very active and selective. 

The kinetics of ultrafast polymerization of acrylic monomers exposed to UV radiation or laser beams has been investigated by IR spectroscopy. An 8 fold increase of the cure speed was observed by using diphenoxybenzophenone as photoinitiator instead of benzophenone. llie reactivity of polyurethane-acrylate or epoxyacrylate systems was markedly improved by adding acrylic monomers that contain carbamate or oxazolidone groups and which impart both hardness and flexibility to the cured polymer. Time-resolved infirared spectroscopy was used to directly record the actual polymerization profile for reactions taking place within a fraction of a second upon UV or laser exposure. Comparison with other techniques of real-time analysis show the distinct advantages of this method for an accurate evaluation of the important kinetic parameters and of the dark polymerization which develops just after the irradiation. 

Analysis. The extent of the polymerization process was evaluated quantitatively by IR spectroscopy (Perkin Elmer spectrophotometer, model 781) by monitoring the decrease of the sharp peak centered at 812 cm- (twisting vibration of the acrylic CH2 = CH bond) which occurs after a given UV exposure. This analytical method has proved very valuable for measuring the polymerization rate of reactions which develop in the millisecond time scale 51. but it suffers the major disadvantage of requiring tedious point by point measurements. 

A new method for measuring diffusion coefficients by IR spectroscopy was developed by Karge and Niessen [158],Niessen [132] and Karge et al. [939]. The change in the intensities of bands typical of molecules migrating inside a zeolite structure during their uptake or desorption were measured by FTIR spectroscopy under high time-resolution as a fimction of small partial pressure jumps and at various temperatures. An appropriate method of evaluation of the time-resolved spectra was developed on the basis of solutions of Fick s second diffusion law provided by Crank [940]. As an example,Fig. 53 illustrates an uptake experiment with benzene (B) as the adsorbate and H-ZSM-5 as the adsorbent. 

If the substituents are not stable during acid hydrolysis or methanolysis, the complementary substitution pattern can be determined after permethylation, as already noted. Examples are organic (acetates) and inorganic esters (sulfates), and benzyl and silyl ethers. " Such an approach was applied as early as 1964 to vinyl starches."" In contrast to the direct determination of the substituent pattern, incomplete methylation and consequently erroneous evaluations cannot be recognized from the product pattern obtained in the indirect methods. If the average DS is known from an independent determination, it allows at least a certain control. Therefore, the absence of OH absorption should be carefully monitored by IR spectroscopy. 

IR spectroscopic method is developed for evaluating the porosity (concentration and size of pores) in polymers. PE and PAN films of various porosity are prepared from the solutions in liquid and solid paraffins. The concentration and maximum pore size in the bulk and in a surface layer of the samples are determined by IR spectroscopy in the transmission and reflection modes, respectively. The results obtained are in agreement with the data of optical and atomic force microscopy. 12 refs. RUSSIA... 

A special device is designed to study the effect of pressure on the kinetic behaviour of a commercial phenolic resin by IR spectroscopy (FTIR). Accurate and reproducible spectra are generated, the characteristic IR peaks assigned and the reaction kinetics evaluated by monitoring the rates of peak disappearance. The pressure has the effect to increase both reaction rate and maximum conversion value. 6 refs. 

The hardening of the boundary layer of epoxy and polyester compositions was studied by IR spectroscopy (of repeatedly disturbed total internal reflection—RDTIR) on a UR-20 spectrometer. A KRS-5 prism N =18, C = 45°) and a germanium prism N =14, C = 45°) were used for simulation of the substrate surface. The thickness of a polymer layer was 0.5-1 nm for the element made of germanium and 2-3 nm for KRS-5. Inhibition of polyester resin polymerization by atmospheric oxygen was eliminated by applying a polyethylene film to the surface of a system to be hardened. The thickness of the applied epoxy and polyester composition was up to 20-30 nm. To evaluate the glass-transition temperature and the polymer-solvent interaction parameter, we used reversed-phase gas chromatography. Basalt-1 and basalt-2 (see below) served as fillers and as a model substrate. The... 

Measurement by IR spectroscopy is potentially promising and semi-quantitative evaluations are possible. IR methods suffer from two main drawbacks absence of suitable calibration, and thermal history effects. The second limitation is the change induced in the infrared spectrum hy thermal history effects. Thus, the IR bonds used to measure isotacticity are bonds sensitive to the formation of regular isotactic helices rather than isotacticity. As such, IR absorbance will be dependent on pretreatment and annealing, which determine the conformation and morphology of polymer chains. 

Polymers formed by the ring-opening metathesis polymerisation (ROMP) reaction [54] exhibit a wide variety of microstructures which may be evaluated by specctroscopic techniques. The first ROMP polymers were analysed by IR spectroscopy [55], but that can only determine the absolute stereochemistry of... 

Reactive compatibilization of engineering thermoplastic PET with PP through functionalization has been reported by Xanthos et al. [57]. Acrylic acid modified PP was used for compatibilization. Additives such as magnesium acetate and p-toluene sulfonic acid were evaluated as the catalyst for the potential interchange or esterification reaction that could occur in the melt. The blend characterization through scanning electron microscopy, IR spectroscopy, differential scanning calorimetry, and... 

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