Applications to Polymer Science

Abstract ESR spectroscopic applications to polymer science are presented. ESR parameters used for the molecular and material characterization of polymer materials are reviewed. It is emphasized that ESR studies of the polymer science are particularly effective in three areas. (1) Intermediate species such as free radicals produced in chemical reactions of polymer materials can be directly detected. (2) The temperature dependent ESR spectra of free radicals trapped in the polymer matrices are very effective for the evaluation of molecular mobility (molecular motion) of polymer chains. (3) The mobility of electron, the structure of solitons, and the doping behavior in conduction polymers can be observed in detail in order to clarify the mechanism of conduction. 

Electron spin resonance (ESR) spectroscopy has been used in polymer science for half a century. Two major areas have been investigated. One is the study of mechanisms of chemical reactions in polymerization and the effects of radiation. Intermediate species such as neutral and ionic radicals produced by exposure to ionizing radiation and ultraviolet light, mechanical fracture, deterioration of polymers and polymerization of monomers have been identified. Many kinds of reactions such as decay and conversion of the free radicals to different species, have also been observed. 

The other area has been the elucidation of relaxation phenomena of polymer chains by observing temperature and pressure dependent ESR spectra of radical species trapped in solid and liquid polymers. 

Polymer science has also been developing over this half century. Great progress has occurred in the field of functional polymers, biopolymers with concurrent advances in molecular design and molecular characterization. It can be expected that the ESR techniques will give valuable insight in the area of molecular characterization. It is well known that solid polymers have many kinds of structural heterogeneities which lead to phenomena like the distribution of relaxation times 

These characteristie features originate from the interaction between the electron spin and the nuclear spins and with other surrounding electron spins. It is well known that paramagnetie relaxation kinetics of radical species is closely related to relaxation phenomena of polymers. The electron spin echo (ESE) method can for example directly observe the relaxation behavior of electron spins. 

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T. Hatakeyama and F. X. Quinn, Thermal Analysis Fundamentals and Applications to Polymer Science, Chap. 4, Wiley, New York, 1994. 

Hatakeyama, T. and FIX. Quinn Thermal Analysis. Fundamentals and Applications to Polymer Science, 2nd Edition, John Wiley, Sons, Inc., New York, NY, 1999. 

Almost all of these examples involve diffusion of a chemical species measuring diffusion rates has long been a specialty of NMR spectroscopy. The studies of KBr and drawn polyethylene produced unique information in the latter case, the known orientation of the deuterium electric field gradient in C-D bonds is used to determine the orientation, with respect to the magnetic field, of a polymer chain of a uniaxially ordered polyethylene fiber. The real time imaging of the polymerization of methyl methacrylate is very interesting and may represent a major direction for NMR imaging applications to polymer science. 

Surface tensions of low-energy surfaces like many polymers are often determined from contact angle measurements. A review of the method and its application to polymer science was written by Koberstein [ 107], In equilibrium, the contact angle of a liquid drop on a solid surface is given by the Young equation ... 

T.P. Russell, X-ray and Neutron Reflectivity for the Investigation of Polymers. Mater. Sci. Reports 5 (1990) 171-271. (Basic theoretical and experimental concepts of specular reflection, and application to polymer science,)... 

Polymer chemistry is an important branch of science, and polymer analysis and characterization is a common subject in scientific literature. Analytical pyrolysis is one of many tools used particularly for polymer identification and for the evaluation of polymer thermal properties. Before a more in-depth discussion on analytical pyrolysis and its application to polymer science, some basic concepts regarding the chemistry of synthetic polymers will be briefly discussed. 

Evans, R. A. (2007) The rise of azide-alkyne 1,3-dipolar click cycloaddition and its application to polymer science and surface modification. Aust. J. Chem., 60, 384—395. 

Figure 10.3 DTA curve for a polymer sample under a constant heating rate. (Reproduced with permission from T. Hatakeyama and F.X. Quinn, Thermal Analysis Fundamentals and Applications to Polymer Science, 2nd ed., John Wiley Sons Ltd, Chichester. 1999 John Wiley Sons Ltd.)...

In this chapter, we present typical applications of ESR spectroscopy to polymer science, whieh include structures and molecular motions of polymer chains and chemical reactions in the polymer material. The first part deals with ESR parameters derived from speetra and the molecular information of polymer chains. In the second part, examples of applications to polymer science are introduced. In the following section, the close relations between structure, molecular motion and chemical reactions are discussed. The narrative will illustrate how these studies have made a considerable contribution to polymer physics and chemistry especially describing mechanisms of deteriorations, polymerization and relaxation phenomena of solid polymers. 

Several parameters can be derived from the ESR spectrum and be used for molecular characterization of polymer materials. The temperature and time dependent parameters reflect the dynamical behaviors of chemical reaction and physical properties in the polymer matrices. In the classification system used here the ESR parameters are divided into a group related to molecular characterization of polymer materials (A) and examples of applications to polymer science (B). 

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