Polymer near-infrared spectra

Gerasimov, T.G. and Snavely, D.L., Vibrational overtone spectroscopy of ethylene glycol diacrylate and ethylene glycol dimethacrylate, monomer and polymer, App/. Spectrosc., 56(2), 212-216, 2002. Snavely, D.L. and Angevine, C., Near-infrared spectrum of polybutadiene, J, Polym. ScL Part A, 34, 1669-1673, 1996. 

The new near infrared wave guide coupling technique can be used for the determination of the three dimensional refractive indices of films opaque in the visible region. This technique is appropriate for other electroactive polymer systems providing a window exists in the visible or near infrared spectrum where measurements can be made. Applying this technique to PANI films has clearly shown that spin coated films show some planar character in the thickness direction. Unidirectional stretching of freestanding spin-coated PANI film leads to increased orientation in the deformation direction, and conversion from a planar to a more uniaxial structure. Similar studies have been carried out on PANI films formed from NMP solutions.[ll]... 

A major objective of the current research programme is to extend the treatment of polymerization kinetics based on direct measurements of monomer and radical concentrations to crosslinking systems. Conventional methods for measurement of monomer concentrations are not suitable, as they require soluble polymer. We have been able to apply our procedure for utilizing the near-infrared spectrum of the C=C bond in methyl methacrylate to systems containing ethylene glycol dimethacrylate (EGDMA) [14]. 

Table VII the electron-beam exposure characteristics are given for the soluble poly (triphenylmethyl methacrylate-co-methyl methacrylate)s. The sensitivity on alkaline development was strongly influenced by the copolymer composition. The highest sensitivity was obtained on the copolymer containing 93.7 mol% methyl methacrylate. The copolymer of highest sensitivity showed the 7-value of 6.3, which was nearly twice as large as that for poly(methyl methacrylate). Formation of methacrylic acid units on exposure is obvious from the infrared spectrum. However, the mechanism of the occurrence should be different from the case of the a,a-dimethylbenzyl methacrylate polymer since there are no /3-hydrogen atoms in the triphenylmethyl group, and may be similar to the case of poly (methyl methacrylate). This will be explored in the near future.

The investigation of the 300 MHz spectrum of poly(3-methyl-l -butene) indicates that the conclusions drawn by previous workers (2—4) concerning the structures of the crystalline and amorphous polymers are essentially correct the crystalline polymer being almost entirely of the 1,3-structure and the amorphous polymer being a mixture of both 1,2- and 1,3-structures. Further, it has indicated that this method is useful for analysis of the composition of the polymer. Quantitative composition determination, however, has not been carried out, since it is felt that the accuracy of the previous estimates utilizing near infrared spectroscopy were satisfactory. 

Fiber optic sensors based on polymer swelling offer several potential advantages. They can be designed so that the optical measurement is separated from the polymer by a diaphragm so that the measurement can not be affected by the optical properties of the sample. Unlike fiber optic sensors based on indicator absorbance or luminescence, photodegradation is not a potential source of sensor instability. Measurements can be made in the near infrared region of the spectrum and take advantage of inexpensive components available for fiber optic communications. 

These devices are based on the anisotropic absorption of light. Usually molecular crystals exhibit this property and tourmaline is the classical example for this. For practical purposes, however, micro crystals are oriented in polymer sheets. Polymers containing chromophors become after stretching dichroic polarizers. The devices produced in this manner are called polawids. They have found a broad application in many technologies. Their application in spectroscopy is limited to the near ultraviolet and to the visible and near infrared range of the spectrum. In vibrational spectroscopy polaroids are employed as analyzers only for Raman spectroscopy. 

Polymers with a h degree of conjugation in the main diain. In these polymers the absorption extends well into the visible and in some cases into the near infrared region, especially when certain electron withdrawing groups are present. They are photoconductors in the visible region of the spectrum. 

It is known that the optical absorption which is the major drawback of the classical plastic materials such as PMMA, is dominated by the higher harmonics of the carbon-hydrogen stretching vibrations. The value of polymers from 2,2-dichlorovinyl chloroformates derivatives has to do with their lower optical absorption as compared to standard plastics in the visible and near-infrared regions of the spectrum (0.6 to 1.5 J.m). Some new 1,2-dichlorovinyl carbonates prepared by standard procedures in 90-95 % yield for that purpose are gathered in table 3-19 (Ref. 169). 

Both PPSe and PPTe turn black and undergo weight Increases of 20 and 150%, respectively, on exposure to Iodine, with the conductivity of the PPSe samples being no more than 10 H(ohm-cm) l while the PPTe samples had a conductivity range of 10 -10 ohm-cm)-- -. Electron transfer does not appear to be involved in the interaction of I2 with PPSe and PPTe since the solid state spectra show the maxima of the original polymers with long tails into the near infrared. In the case of PPTe, the interaction with iodine largely involves formation of a tetracoordinate diaryl tellurium diiodide (24). Reduction of this material with sodium sulfide (24) leads to-recovered PPTe, identified by its IR spectrum. 

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