Spectroscopic analysis of polymers

Spectroscopic methods are finding increasing use in the characterization and analysis of polymers. All of the methods that are employed were developed initially for use with low-molar-mass materials and they have been extended for the analysis of polymers. The spectrum obtained for a particular polymer is often characteristic of that polymer and can therefore be used for identification purposes. Polymer spectra can be surprisingly simple given the complex nature of polymer molecules and they are often similar to the spectra obtained from their low-molar-mass counterparts. This can make the analysis of the spectra a relatively simple task allowing important spectral details to be revealed. In fact, certain information can only be obtained using spectroscopic methods. For example, nuclear magnetic resonance (n.m.r.) is the only technique that can be used to measure directly the tacticity of a polymer molecule. 

Since the spectroscopic techniques applied to polymers are normally adaptations of conventional methods, the details of each method will not be discussed as they can readily be found in standard texts. 

It is possible to use i.r. spectroscopy for structural characterization as well as identification. For example, in certain copolymers it is possible to determine quantitatively the composition of the copolymer from the intensities of specific absorption bands. The characteristic nitrile band can be used in the analysis of samples of acrylonitrile-butadiene-styrene copolymer. It is also possible to determine the relative amounts of d5-l,4, trans-1,4 and 1,2 addition in polybutadiene (Section 2.5.4) from the relative strengths of specific absorption bands. 

spectra of crystalline polymers tend to be sharper and more well-defined than those of their amorphous counterparts. In the case of polyethylene terephthalate certain bands have been found to be characteristic of the crystalline form of the polymer and others are found to be due to vibrations in amorphous polymer. This is because the molecules are all trans in the crystals whereas gauche conformations can exist in amorphous regions. The different conformations give rise to bands with different frequencies of absorption in the i.r. spectrum. 

The better definition of spectra from crystalline polymers can give an indication of polymer tacticity since atactic polymers are generally non-crystalline and there are certain polymers such as poly(methyl methacrylate) and polypropylene in which specific absorption bands can be assigned to the presence of molecules with particular types of tacticity. Some idea of the tacticity for samples of these polymers can, therefore, be obtained from measurements of the strength of the absorption of the relevant bands, but in general this method is not as accurate as n.m.r. for tacticity determination. 

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H. Ishida, "Quantitative Surface FT-IR Spectroscopic Analysis of Polymers," Rubber Chem. Technol.. 60. 497-554 (1987). 

Oligomeric hindered amine light stabilisers, such as Tinuvin 622 and Chimassorb 944, resist satisfactory analysis by conventional HPLC and have required direct UV spectroscopic analysis of a polyolefin extract [596], PyGC of an extract [618,648], or SEC of an extract [649]. Freitag et al. [616] determined Tinuvin 622 in LDPE, HDPE and PP by saponification of the polymer dissolution in hot toluene via addition of an... 

The infrared spectrum (v(CO) 2046 and 1969 cm 1) was again consistent with the presence of the desired polymer-bound complex, [Ir(CO)2I2]. ICP mass spectroscopic analysis of the metal loaded resins showed the metal contents to be 0.56-0.66 % (Rh) and 0.79-0.86 % (Ir) by weight. These values are in line with the observation that virtually all the metal complex is taken up from solution under the conditions of these loading experiments, and that 15-20% of the pyridinium sites are loaded with metal in the products. 

For a number of years, polymers such as polyimide, have been subjected to widespread research, because of their increasing importance as dielectric materials for the fabrication of microelectronic devices (1). In particular, the adhesion of metal or polyimide films deposited on polyimide substrates and vice versa, is of considerable importance in most applications, and many studies ranging from adhesion testing to detailed spectroscopic analysis of interfaces have been reported previously (2,3.. 5.6). 

T. Turquois, S. Acquistapace, F. Arce Vera, and D. H. Welti, Composition of carrageenan blends inferred from 13C-NMR and infrared spectroscopic analysis, Carbohydr. Polym., 31 (1996) 269-278. 

Polymerization of propylene with complex 5 (Table 4) at atmospheric pressure produces an atactic polypropylene having the same features regarding the temperature and Al Zr ratio as for ethylene. The H and 13C-NMR spectroscopic analysis of polypropylene reveals only vinyl/isopropyl, but no vinylidene/n-propyl, end groups, similar to the polymers obtained with zirconocenes [67,68]. Polymers with these end groups may be formed from at least three different mechanisms. The first involves an allylic C-H activation of propylene, the second, a /1-methyl elimination, and the third, a /1-hydrogen elimination from a polymer chain in which the monomer inserts in a 2,1 fashion [69]. Since in the... 

The materials analyzed were blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) in various ratios. The two components are miscible in all proportions at ambient temperature. The photooxidation mechanisms of the homo-polymers PS and PVME have been studied previously [4,7,8]. PVME has been shown to be much more sensitive to oxidation than PS and the rate of photooxidation of PVME was found to be approximately 10 times higher than that of PS. The photoproducts formed were identified by spectroscopy combined with chemical and physical treatments. The rate of oxidation of each component in the blend has been compared with the oxidation rate of the homopolymers studied separately. Because photooxidative aging induces modifications of the surface aspect of the material, the spectroscopic analysis of the photochemical behavior of the blend has been completed by an analysis of the surface of the samples by atomic force microscopy (AFM). A tentative correlation between the evolution of the roughness measured by AFM and the chemical changes occurring in the PVME-PS samples throughout irradiation is presented. 

Specific spectroscopic techniques are used for the analysis of polymer surface (or more correctly of a thin layer at the surface of the polymer). They are applied for the study of surface coatings, surface oxidation, surface morphology, etc. These techniques are typically done by irradiating the polymer surface with photons, electrons or ions that penetrate only a thin layer of the polymer surface. This irradiation is followed by the absorption of a part of the incident radiation or by the emission of specific radiation, which is subsequently analyzed providing information about the polymer surface. One of the most common techniques used for the study of polymer surfaces is attenuated total reflectance in IR (ATR), also known as internal reflection spectroscopy. Other techniques include scanning electron microscopy, photoacoustic spectroscopy, electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy, secondary ion mass spectroscopy (SIMS), etc. 

Einfeldt, J., Meipner, D., Kwasniewski, A., and Einfeldt, L. Dielectric spectroscopic analysis of wet and well dried starches in comparison with other polysaccharides, Polymer, 42, 7049, 2001b. 

A dynamic method for acquiring and treating infrared spectroscopic data from the imidization of a number of polyimide systems is presented. In situ FT-IR analysis of polymer reactions is preferred when doing comparitive studies on a number of polymer systems. For systems where these reactions occur at relatively high temperatures, it is often difficult to obtain good isothermal data for determining kinetic parameters. Kinetic data for several polyimide systems are shown and compared. 

The mass spectroscopic analysis of the gases formed in thermal development of the UV exposed poly(l-butene sulfone)/pyridine N-oxide revealed only 1-butene and S02 as the products, which indicated depolymerization of the polymer initiated by energy transfer form the sensitizer. These photosensitized poly(olefin sulfones) are not suitable for dry etching processes, and they are not reactive ion etching resistant. Resists made of poly(olefin sulfones) and novolac resins which will be described next are CF plasma etch resistant with reasonable photosensitivities. 

During the past five decades, spectroscopy has moved out from the laboratories of physicists and theoretical chemists into every area of analysis and chemical research. Applications vary from routine, single data point measurements for control of plant streams to structural analysis of complex molecules and conformational analysis of polymers. Enhancement of the sensitivity of all spectroscopic methods has been achieved through computer-assisted data handling. It is possible to find structural differences in polymers under different degrees of stress and to analyze for very low levels of chemical structures at surfaces and interfaces. For difficult structure determinations, data from several spectroscopic disciplines may be combined and require months or years of research. 

The cis- and trans-1,4-polybutadienes used in this work were obtained from The B. F. Goodrich Research and Development Center, Brecksville, OH, and had initial cis/trans ratios of 98/2 and 2/98, respectively. The procedures for the photosensitized oxidation of purified samples of the 1,4-polybutadienes, using visible light and methylene blue, chlorophyll and Rose Bengal as sensitizers, the procedures for the reduction of the hydroperoxidized polymers to the corresponding alcohols, as well as the procedures for the spectroscopic analysis of the reaction products, were similar to those described previously (8). 

Zhou, Y. T., Wu, S. X., and ConticeUo, V. P. Genetically directed synthesis and spectroscopic analysis of a protein polymer derived from a flageUiform silk sequence. Biomacromolecules 2, 111-125 (2001). 

IR spectroscopy is one of the most powerful spectroscopic tools available for the analysis of polymer systems (a.l). IR spectroscopy is molecularly specific with high sensitivity. It is based on the absorption or attenuation by matter of electromagnetic radiation of a specified motion of chemical bonds. Through quantum physics, nature defines the absorption modes, their locations in the frequency spectrum and the amount of energy absorbed by each molecule. The absorbance at a characteristic frequency is a measure of the concentration of the chemical species being probed in the sample. 

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