Polymer network, dynamic

The main postulate on which exposition of material in the present section is based is the dynamic polymer network concept [1]. This concept assumes that molecular and structural characteristics of crosslinked polymer networks are defined not only by the chemical constitution of their chains, but also by boundary conditions (e.g., crosslinking density), external influence (for example, tension strain) and so on. 

In the present section notions of the amorphons state structure of a cluster model of polymers [7, 8] were used for the description of a change in nucleation mechanism and melting temperature of an oriented PCP. These notions are developed in the dynamic polymer network concept, since supramolecnlar (more precisely, snprasegmental) structure changes, described by a cluster model, are a logical result of changes on the molecular level, which are due to network tension (see Table 4.1). The cluster model application allows the physical effects predicted within the frameworks of general thermodynamic theory to be concretised and identified and also to be described quantitatively. 

To understand the global mechanical and statistical properties of polymeric systems as well as studying the conformational relaxation of melts and amorphous systems, it is important to go beyond the atomistic level. One of the central questions of the physics of polymer melts and networks throughout the last 20 years or so dealt with the role of chain topology for melt dynamics and the elastic modulus of polymer networks. The fact that the different polymer strands cannot cut through each other in the... 

Candau, S., Bastide, J. und Delsanti, M. Structural. Elastic and Dynamic Properties of Swollen Polymer Networks. Vol. 44, pp. 27—72. 

Subsequent work by Johansson and Lofroth [183] compared this result with those obtained from Brownian dynamics simulation of hard-sphere diffusion in polymer networks of wormlike chains. They concluded that their theory gave excellent agreement for small particles. For larger particles, the theory predicted a faster diffusion than was observed. They have also compared the diffusion coefficients from Eq. (73) to the experimental values [182] for diffusion of poly(ethylene glycol) in k-carrageenan gels and solutions. It was found that their theory can successfully predict the diffusion of solutes in both flexible and stiff polymer systems. Equation (73) is an example of the so-called stretched exponential function discussed further later. 

S Candau, J Bastide, M Delsanti. Structural, elastic and dynamic properties of swollen polymer networks. Adv Polym Sci 44 27-73, 1982. 

The paper is organized in the following way In Section 2, the principles of quasi-elastic neutron scattering are introduced, and the method of NSE is shortly outlined. Section 3 deals with the polymer dynamics in dense environments, addressing in particular the influence and origin of entanglements. In Section 4, polymer networks are treated. Section 5 reports on the dynamics of linear homo- and block copolymers, of cyclic and star-shaped polymers in dilute and semi-dilute solutions, respectively. Finally, Section 6 summarizes the conclusions and gives an outlook. 

Crosslinked polymer networks formed from multifunctional acrylates are completely insoluble. Consequently, solid-state nuclear magnetic resonance (NMR) spectroscopy becomes an attractive method to determine the degree of crosslinking of such polymers (1-4). Solid-state NMR spectroscopy has been used to study the homopolymerization kinetics of various diacrylates and to distinguish between constrained and unconstrained, or unreacted double bonds in polymers (5,6). Solid-state NMR techniques can also be used to determine the domain sizes of different polymer phases and to determine the presence of microgels within a poly multiacrylate sample (7). The results of solid-state NMR experiments have also been correlated to dynamic mechanical analysis measurements of the glass transition (1,8,9) of various polydiacrylates. 

Polymers dynamics of polymer chains microviscosity free volume orientation of chains in stretched samples miscibility phase separation diffusion of species through polymer networks end-to-end macrocyclization dynamics monitoring of polymerization degradation... 

Yount WC, Loveless DM, Craig SL. SmaU-molecule dynamics and mechanisms underlying the macroscopic mechanical properties of coordinatively cross-hnked polymer networks. J Am Chem Soc 2005a 127 14488-14496. 

Muller M, Seidel U, Stadler R. Influence of hydrogen bonding on the viscoelastic properties of thermoreversible networks analysis of the local complex dynamics. Polymer 1995 36 3143-3150. 

Keywords Block copolymers Chirality Dynamic kinetic resolution copolymer Kinetic resolution Polymer networks... 

In accordance with theoretical predictions of the dynamic properties of networks, the critical concentration of dextran appears to be independent of the molecular weight of the flexible polymeric diffusant although some differences are noted when the behaviour of the flexible polymers used is compared e.g. the critical dextran concentrations are lower for PEG than for PVP and PVA. For ternary polymer systems, as studied here, the requirement of a critical concentration that corresponds to the molecular dimensions of the dextran matrix is an experimental feature which appears to be critical for the onset of rapid polymer transport. It is noteworthy that an unambiguous experimental identification of a critical concentration associated with the transport of these types of polymers in solution in relation to the onset of polymer network formation has not been reported so far. Indeed, our studies on the diffusion of dextran in binary (polymer/solvent) systems demonstrated that both its mutual and intradiffusion coefficients vary continuously with increasing concentration 2. ... 

This is the fundamental equation to describe the kinetics and dynamics of polymer networks in a liquid. The left-hand side of Eq. (3.4) represents the acceleration term, whereas the first two terms of the right-hand side represent the elastic term. The last term of the right-hand side is the contribution of the friction between the network and solvent molecules. In most cases, however, the acceleration term is much smaller than the other terms. Thus one obtains... 

Takserman-Krozer.R., Ziabicki.A. General dynamic theory of macromolecular networks. IL Dynamics of network deformation. J. Polymer Sci. Part A-2 8, 321-332... 

The results obtained by the present mechanical measurements are also consistent with the previous experimental results of the dynamic light scattering studies of the collective diffusion coefficient of gels and the rheological studies of the shear modulus of gels. The studies published by different researchers indicate that the concentration dependence of the collective diffusion constant of the polymer networks of gel and that of the elastic modulus are well represented by the following power law relationships [2, 3, 5]... 

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