Copolymer, infrared

Spectroscopic analyses are widely used to identify the components of copolymers. Infrared (IR) spectroscopy is often sufficient to identify the comonomers present and their general concentration. Nuclear magnetic resonance (NMR) spectrometry is a much more sensitive tool for analysis of copolymers that can be used to accurately quantify copolymer compositions and provide some information regarding monomer placement. 

The starting materials were low and medium molecular weight copolymers. Infrared spectra of the products from the Schmidt reaction show a high degree of conversion. The yields of the oximes and subsequent Beckmann rearrangements are also high. 

Polymer blends are mixtures of polymeric materials and consist of at least two polymers or copolymers. Infrared spectroscopy is now quite a commonly used technique for examination of the interactions in polymer blends [9, 10]. If two polymers are immiscible, the infrared spectrum should be the sum of the spectra of the two components. Phase-separation implies that the component polymers in the blend will have an environment similar to the pure polymers. If the polymers are miscible, there is the possibility of chemical interactions between the individual polymer chains. Such interactions may lead to differences between the spectra of the polymers in the blend and the pure components. Generally, wavenumber shifts and band broadening are taken as evidence of chemical interactions between the components in a blend and are indicative of miscibility. 

Panyszach and Kovar [125] have shown that results accurate to within 2.5% can be obtained in determinations by FTIR of the butadiene content of styrene - butadiene copolymers. Infrared methods are reported to have serious disadvantages when applied to the determination of unsaturation in vulcanisates [126-130]. 

Nitrile Styrene-acrylonitrile copolymer Infrared spectroscopy 205,206... 

Waldman D A, Kolb B U, McCarthy T J and Hsu S L 1988 Infrared study of adsorbed monolayers of poly(styrene-propylene sulphide) (PS-PPS) block copolymers Polym. Mater. Sc/. Eng. 59 326-33... 

Most of the experimental information concerning copolymer microstructure has been obtained by physical methods based on modern instrumental methods. Techniques such as ultraviolet (UV), visible, and infrared (IR) spectroscopy, NMR spectroscopy, and mass spectroscopy have all been used to good advantage in this type of research. Advances in instrumentation and computer interfacing combine to make these physical methods particularly suitable to answer the question we pose With what frequency do particular sequences of repeat units occur in a copolymer. 

Alternation is usually above 90%. Nearly perfect alternation of isomeric units in a ca 1 1 monomer ratio has been confirmed by infrared spectroscopy. Bands at 733 and 721 cm have an intensity proportional to the concentration of (CH2) groups (n = 4 and <6, respectively) present in a copolymer containing 46 mol % tetrafluoroethylene intensity decreases with increasing concentration of fluorinated monomer. 

The incidence of these defects is best determined by high resolution F nmr (111,112) infrared (113) and laser mass spectrometry (114) are alternative methods. Typical commercial polymers show 3—6 mol % defect content. Polymerization methods have a particularly strong effect on the sequence of these defects. In contrast to suspension polymerized PVDF, emulsion polymerized PVDF forms a higher fraction of head-to-head defects that are not followed by tail-to-tail addition (115,116). Crystallinity and other properties of PVDF or copolymers of VDF are influenced by these defect stmctures (117). 

Tosi, C. and Ciampelli, F. Applications of Infrared Spectroscopy to Ethylene-Propylene Copolymers. Vol. 12, pp. 87-130. 

Mori, S., Wada, A., Kaneuchi, F., Ikeda, A., Watanabe, M., and Mochizuki, K., Design of a highly sensitive infrared detector and application to a high-performance size exclusion chromatography for copolymer analysis, /. Chromatogr., 246, 215, 1982. 

The methyl ester gives rise to a fairly sharp singlet at 3.59 ppm, and the ester carbonyl exhibits an infrared band at 1730 cm"1. The MM content of the copolymer is easily ascertained by integration of the 1H NMR spectrum and may be corroborated by elemental analysis. 

Many characteristic molecular vibrations occur at frequencies in the infrared portion of the electromagnetic spectrum. We routinely analyze polymers by measuring the infrared frequencies that are absorbed by these molecular vibrations. Given a suitable calibration method we can obtain both qualitative and quantitative information regarding copolymer composition from an infrared spectrum. We can often identify unknown polymers by comparing their infrared spectra with electronic libraries containing spectra of known materials. 

In the case of heterogeneous polymers the experimental methods need to be refined. In order to analyze those polymers it is necessary to determine a set of functions / (M), which describe the distribution for each kind of heterogeneity i This could be the mass distributions of the blocks in a diblock copolymer. The standard SEC methods fail here and one needs to refine the method, e.g., by performing liquid chromatography at the critical point of adsorption [59] or combine SEC with methods, which are, for instance, sensitive to the chemical structure, e.g., high-pressure liquid chromatography (HPLC), infrared (IR), or nuclear magnetic resonance spectroscopy (NMR) [57],... 

A combination of infrared spectroscopy with size exclusion chromatography has a wide application range in the characterization of copolymers, adhesives, impurity profiling in polymers and branching in polyolefines [60-65]. Commonly, the solvent used as a mobile phase absorbs strongly in the... 

Coleman and Sivy also used an infrared transmission cell to undertake degradation studies under reduced pressure on a series of poly(acrylonitrile) (ACN) copolymers [30-33]. Thin films prepared from a polymer were mounted in the specially designed temperature-controlled cell mounted within the infrared spectrometer. The comparative studies were made on ACN copolymers containing vinyl acetate [30,32], methacrylic acid [30,31] and acrylamide [30,33]. The species monitored was the production of the cyclised pyridone structure. This was characterised in part by loss of C=N stretch (vC = N) intensity at 2,240 cm-1 accompanied by the appearance and increase in intensity of a doublet at 1,610/1,580 cm-1. 

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