Structure polymer, analytical tools

The availability of these novel enzymes, next to the known pectic enzymes, offer new opportunities to use them as analytical tools in revealing the structure of oligo- and polysaccharides [31,32]. In contrast with frequently used chemical degradation methods, which usually have a poor selectivity, these enzymes act in a deflned way. To be able to recognize different structural units within the polymer, endo-acting types of enzyme are preferred, although accessory enzymes might be essential as well [30]. 

NMR spectroscopy is one of the most widely used analytical tools for the study of molecular structure and dynamics. Spin relaxation and diffusion have been used to characterize protein dynamics [1, 2], polymer systems[3, 4], porous media [5-8], and heterogeneous fluids such as crude oils [9-12]. There has been a growing body of work to extend NMR to other areas of applications, such as material science [13] and the petroleum industry [11, 14—16]. NMR and MRI have been used extensively for research in food science and in production quality control [17-20]. For example, NMR is used to determine moisture content and solid fat fraction [20]. Multi-component analysis techniques, such as chemometrics as used by Brown et al. [21], are often employed to distinguish the components, e.g., oil and water. 

As the majority of stabilisers has the structure of aromatics, which are UV-active and show a distinct UV spectrum, UV spectrophotometry is a very efficient analytical method for qualitative and quantitative analysis of stabilisers and similar substances in polymers. For UV absorbers, UV detection (before and after chromatographic separation) is an appropriate analytical tool. Haslam et al. [30] have used UV spectroscopy for the quantitative determination of UVAs (methyl salicylate, phenyl salicylate, DHB, stilbene and resorcinol monobenzoate) and plasticisers (DBP) in PMMA and methyl methacrylate-ethyl acrylate copolymers. From the intensity ratio... 

Polymer degradation, which reflects changes in the properties of polymers due to chemical processes that occur as a function of a complex set of environmental conditions, is a challenging topic of great fundamental and technological importance. Historically, materials were used long before their properties were fully understood. In recent years, analytical tools such as microscopy, imaging, and computational techniques have made possible the determination of structural and functional details of materials, some of which are hard to obtain by other methods. 

We begin with a short introduction to provide polymer chemists who may be new to the field of electrophoresis with a brief background concerning electrophoretic separation and characterization. Those who wish to obtain an in-depth understanding of the theory or detailed practical techniques are referred to textbooks/monographs on this subject [1-6]. Next, the advantages of gel electrophoresis as an analytical tool, and the structural requirements regarding dendrimers as electrophoretic analytes are discussed. Finally, studies directed at... 

Mass spectrometry is an indispensable analytical tool in chemistry, biochemistry, pharmacy, and medicine. No student, researcher or practitioner in these disciplines can really get along without a substantial knowledge of mass spectrometry. Mass spectrometry is employed to analyze combinatorial libraries [1,2] sequence biomolecules, [3] and help explore single cells [4,5] or other planets. [6] Structure elucidation of unknowns, environmental and forensic analytics, quality control of drugs, flavors and polymers they all rely to a great extent on mass spectrometry. [7-11]... 

Both solution-state and solid-state NMR spectroscopy are important analytical tools used to study the structure and dynamics of polymers. This analysis is often limited by peak overlap, which can prevent accurate signal assignment of the dipolar and scalar couplings used to determine structure/property relationships in polymers. Consequently, spectral editing techniques and two- or more dimensional techniques were developed to minimize the effect of spectral overlap. This section highlights only a few of the possible experiments that could be performed to determine the structure of a polymer. 

Combination of static and dynamic laser light scattering is also useful to determine not only the size distribution but also the particle structure of polymer colloids such as the adsorbed surfactant layer thickness [73] and the formation of nanoparticles [74,75]. A recently developed method of determining the density of polymer particles is outlined below to illustrate the usefulness of laser light scattering as a powerful analytical tool for investigating more sophisticated colloidal problems [76-78]. 

An important objective in materials science is the establishment of relationships between the microscopic structure or molecular dynamics and the resulting macroscopic properties. Once established, this knowledge then allows the design of improved materials. Thus, the availability of powerful analytical tools such as nuclear magnetic resonance (NMR) spectroscopy [1-6] is one of the key issues in polymer science. Its unique chemical selectivity and high flexibility allows one to study structure, chain conformation and molecular dynamics in much detail and depth. NMR in its different variants provides information from the molecular to the macroscopic length scale and on molecular motions from the 1 Hz to 1010 Hz. It can be applied to crystalline as well as to amorphous samples which is of particular importance for the study of polymers. Moreover, NMR can be conveniently applied to polymers since they contain predominantly nuclei that are NMR sensitive such as H and 13C. 

PAL has become well established as an analytical tool in polymer characterization. The results of PAL studies on polymers have led to many important insights into the relationship between microscopic structure at a nanoscale and bulk properties of many polymers. The usefullness of the technique is seen in the fact that a large number of polymer systems have been studied in recent years. 

By scanning the temperature in a filament pyrolyser, the technique allows the separation of non-polymeric impurities from a polymer or composite material. Time-resolved filament pyrolysis has a series of useful applications as an analytical tool or even in some structure elucidations. As an example, it can be used [48] to differentiate the existence of more labile groups in a polymer structure. A typical variation of the total ion trace in a time-resolved pyrolysis MS for a composite material is shown in Figure 5.4.3. 

The intention of the author was to provide information on pyrolysis for a wide range of readers, including chemists working in the field of synthetic polymers as well as for those applying pyrolysis coupled with specific analytical instrumentation as an analytical tool. Some theoretical background for the understanding of polymer structure using analytical pyrolysis is also discussed. The book is mainly intended to be useful for practical applications of analytical pyrolysis in polymer identification and characterization. 

Analytical pyrolysis has a number of characteristics that can make it a very powerful tool in the study of polymers and composite materials. The technique usually requires little sample and can be set with very low limits of detection for a number of analytes. For Py-GC/MS the identification capability of volatile pyrolysate components is exceptionally good. A range of information can be obtained using this technique, including results for polymer identification, polymer structure, thermal properties of polymers, identification of polymer additives, and for the generation of potentially harmful small molecules from polymer decomposition. In most cases of analysis of a polymer or composite material, the technique does not require any sample preparation, not even solubilization of the sample, which may be a difficult task for the type of materials analyzed. The analysis can be easily automated and does not require expensive instrumentation (beyond the cost of the instrument used for pyrolysate analysis). 

The applicability of nanocasting as an analytical tool has been demonstrated [38] by comparing the silica structures obtained from the lyotropic phase, which has been crosslinked using y-rays, in order to provide sufficient mechanical stability to allow thin-sectioning, with those of a silica nanocast obtained from a lyotropic phase of the same composition (Fig. 7). The similarity between the structures is striking. A reference sample was prepared by filHng the pore system of the crosslinked polymer gel with sihca and subsequent calcination. The pictures prove without doubt that the sol-gel process indeed does not have any structurally disrupting effect on the hquid crystalhne phase [38]. 

Giorgio Montaudo, Ph.D. is a Professor of industrial chemistry at the Department of Chemistry, University of Catania, Italy and Director of the Institute for Chemistry Technology of Polymeric Materials of the National Cormcil of Research of Italy, Catania. Dr. Montaudo received a Ph.D. in chemistry from the University of Catania. He was a postdoctoral associate at tire Polytechnic Institute of Brooklyn (1966) and at tire University of Michigan (1967-68 and 1971) and he was a Humboldt Foundation Fellow, 1973 at Mainz University. Dr. Montaudo has been active in the field of the synthesis, degradation, and characterization of polymeric materials. A major section of his activity has been dedicated to develop mass spectrometry of polymers as analytical and structural tools for the analysis of polymers. He is tire author of more than 300 publications in international journals and chapters in books. 

It is clear from this brief overview that analytical pyrolysis can be a useful analytical tool for both qualitative and quantitative analysis of large macromolecules. Treatment of nonvolatile samples such as synthetic polymers and natural biopolymers using pyrolysis/GCMS can yield much information about volatiles and structure and provide a characteristic fingerprint of the macromolecule. 

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