Structure and dynamics of polymers

For the investigation of polymer systems under spatial confinement, fluorescence microscopy is a powerful method providing valuable information with high sensitivity. A fluorescence microscopy technique with nanometric spatial resolution and nanosecond temporal resolution has been developed, and was used to study the structure and dynamics of polymer chains under spatial confinement a polymer chain in an ultra-thin film and a chain grafted on a solid substrate. Studies on the conformation of the single polymer chain in a thin film and the local segmental motion of the graft polymer chain are described herein. 

Lai, P. Y. and Binder, K. (1992) Structure and dynamics of polymer brushes near the theta point - a Monte-Carlo simulation. 

Krishnamoorti, R., Vaia, R.A. and Giannelis, E. (1996) Structure and dynamics of polymer-layered silicate nanocomposites. Chemistry of Materials, 8, 1728-1734. 

Among the experimental techniques for studying the structure and dynamics of polymers, neutron scattering plays a unique role for several reasons ... 

Pdtschke D, Ballauff M (2000) Structure and dynamics of polymer and colloidal systems. In Pecora R, Borsali R (eds) NATO ASI Studies (accepted)... 

Nuclear magnetic resonance (NMR) spectroscopy is a most effective and significant method for observing the structure and dynamics of polymer chains both in solution and in the solid state [1]. Undoubtedly the widest application of NMR spectroscopy is in the field of structure determination. The identification of certain atoms or groups in a molecule as well as their position relative to each other can be obtained by one-, two-, and three-dimensional NMR. Of importance to polymerization of vinyl monomers is the orientation of each vinyl monomer unit to the growing chain tacticity. The time scale involved in NMR measurements makes it possible to study certain rate processes, including chemical reaction rates. Other applications are isomerism, internal relaxation, conformational analysis, and tautomerism. 

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. 

Films of pure PPX and PPX composites with nanoparticles of various metals resulted from cryochemical solid-state synthesis were studied by the dielectric spectroscopy method [104], Dielectric spectroscopy has proven very useful for studying the structure and dynamics of polymer materials as well as the transport mechanism of charge carriers. To study features of the polymer structure dielectric test methods were used due to their high sensitivity to morphological changes. 

NMR has grown in importance over the last two decades as an important tool for characterizing the structure and dynamics of polymers, both synthetic and biosynthetic. Other reviews have appeared in the recent literature [1, 2]. This chapter will focus on both the characterization of structure and dynamics of biopolymers from spectra obtained without the use of magic-angle spinning. 

The structure and dynamics of polymer chains adsorbed on the surface of solids have been studied using spectroscopic methods such as IR, ESR and... 

Recently, high resolution NMR studies of solids have been realized by using advanced pulse and mechanical techniques, and so have provided a variety of structural and dynamic information about polymer systems. Further, it can be said that solid state NMR has provided characteristic information that cannot be obtained by other spectroscopic methods, and that it has become a very powerful means for elucidating the structure and dynamics of polymer systems. 

It has been demonstrated that solid state NMR spectroscopy provides useful information about the structure and dynamics of polymers in the bulk. At present, in polymer science, solid state NMR is recognized as one of the most powerful means for elucidating the structure and the dynamics of solid polymers in addition to X-ray diffraction. The history of solid state NMR, which has been used in polymer science, is very old. The appearance of new techniques in solid state NMR has certainly contributed to the development of polymer science and technology. 

The magnetic properties of polymers have historically not received nearly as much attention as their optical and electrical properties. This situation is quite understandable. Polymers with certain optical and/or electrical properties are often required, for a wide variety of technological applications. On the other hand, there are no major applications where any of the magnetic properties of a polymer is a key performance requirement. Magnetic properties are therefore far more often studied for the information and the insights that they provide about the structure and dynamics of polymers, instead of being utilized to screen polymers for specific applications. 

Fotiadou, S., Chrissopoulou, K., Frick, B., and Anastasiadis, S. H. 2010. Structure and dynamics of polymer chains in hydrophilic nanocomposites. Journal of Polymer Science. Pari B Polymer Physics 48 1658-1667. 

This volume consists of four parts. The first part is devoted to theoretical studies and computer simulations. These studies deal with the structure and dynamics of polymers adsorbed at interfaces, equations of state for particles in polymer solutions, interactions in diblock copolymer micelles, and partitioning of biocolloidal particles in biphasic polymer solutions. The second part discusses experimental studies of polymers adsorbed at colloidal surfaces. These studies serve to elucidate the kinetics of polymer adsorption, the hydrodynamic properties of polymer-covered particles, and the configuration of the adsorbed chains. The third part deals with flocculation and stabilization of particles in adsorbing and nonadsorbing polymer solutions. Particular focus is placed on polyelectrolytes in adsorbing solutions, and on nonionic polymers in nonadsorbing solutions. In the final section of the book, the interactions of macromolecules with complex colloidal particles such as micelles, liposomes, and proteins are considered. 

Recently, polymer nanocomposites based on clay minerals have attracted great interest from researchers, both in industry and in academia, because they often exhibit concurrent improvement in several properties of neat polymer. These improvements can include high moduli, increased strength and heat resistance, decreased gas permeability and flammability, and increased degradability of biodegradable polymers [7-12]. These materials have also been proven to be unique model systems to study the structure and dynamics of polymers in confined environments [20]. 

The information about the structure and dynamics of polymers that EPR can provide is very similar [19, 21]. For synthetic polymers, biopolymers, and supramo-lecular assembUes, nitroxide spin probes and spin labels are particularly useful [36]. In solution, their EPR spectra are governed by the g-factor and the hyperfine splitting (denoted as a) to the nucleus of the NO group. In solution, the former determines... 

The NMR sensitivity depends on the magnetogyric ratio and the natural abundance of the NMR active nuclei. Table 3.1 lists the properties of some of the nuclei that are of particular interest to polymer chemists. The sensitivity is highest for protons and fluorines, but nuclei such as carbon, silicon and phosphorus can be routinely studied. Deuterium and nitrogen have poor sensitivities, but they provide valuable insight into the structure and dynamics of polymers when isotopically enriched samples are prepared. 

It is the use of pulsed NMR that allows us to probe in detail the structure and dynamics of polymers. The polymer spin system can be perturbed with rf pulses and its return to equilibrium can be measured. The degree to which the spins are rotated by the rf pulses depends on the nuclei, the strength of the rf field, and the pulse length. The tip angle (6) is given by ... 

Two-dimensional NMR experiments can also be used in the solid state to study the structure and dynamics of polymers, and 2D solid-state NOESY has been used to provide a molecular-level assignment for the polyethylene a transition observed by dielectric and dynamic mechanical spectroscopy [32]. One proposal is that this transition can be assigned to chain diffusion between the crystalline and amorphous regions [33], Two peaks are observed in the C-CPMAS spectra of polyethylene that can be assigned to chains in crystalline and amorphous environments. Figure 3.27 shows the 2D spin exchange... 

The combination of various fluorescence techniques, such as steady-state and time-resolved fluorescence spectroscopy and fluorescence microscopy, can provide extremely important information on the structure and dynamics of polymer blends. Many relevant examples will be presented in this chapter, with particular emphasis being placed on the most recent investigations. 

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