58 research outputs found
Dynamics of end-linked star polymer structures
In this work we focus on the dynamics of macromolecular networks formed by
end-linking identical polymer stars. The resulting macromolecular network can
then be viewed as consisting of spacers which connect branching points (the
cores of the stars). We succeed in analyzing exactly, in the framework of the
generalized Gaussian model, the eigenvalue spectrum of such networks. As
applications we focus on several topologies, such as regular networks and
dendrimers; furthermore, we compare the results to those found for regular
hyperbranched structures. In so doing, we also consider situations in which the
beads of the cores differ from the beads of the spacers. The analytical
procedure which we use involves an exact real-space renormalization, which
allows to relate the star-network to a (much simpler) network, in which each
star is reduced to its core. It turns out that the eigenvalue spectrum of the
star-polymer structure consists of two parts: One follows in terms of
polynomial equations from the relaxation spectrum of the corresponding
renormalized structure, while the second part involves the motion of the spacer
chains themselves. Finally, we show exemplarily the situation for copolymeric
dendrimers, calculate their spectra, and from them their storage and the loss
moduli.Comment: 15 pages, 11 eps-figures include
Frequency Dispersion of Sound Propagation in Rouse Polymer Melts via Generalized Dynamic Random Phase Approximation
An extended generalization of the dynamic random phase approximation (DRPA)
for L-component polymer systems is presented. Unlike the original version of
the DRPA, which relates the (LxL) matrices of the collective density-density
time correlation fumctions and the corresponding susceptibilities of polymer
concentrated systems to those of the tracer macromolecules and so-called broken
links system (BLS), our generalized DRPA solves this problem for (5xL)x(5xL)
matrices of the coupled susceptibilities and time correlation functions of the
component number, kinetic energy and flux densities. The presented technique is
used to study propagation of sound and dynamic form-factor in disentangled
(Rouse) monodisperse homopolymer melt. The calculated sound velocity and
absorption coefficient reveal substantial frequency dispersion. The relaxation
time is found to be N times less than the Rouse time (N is the degree of
polymerization), which evidences strong dynamic screening because of interchain
interaction. We discuss also some peculiarities of the Brillouin scattering in
polymer melts. Besides, a new convenient expression for the dynamic structural
function of the Rouse chain in (q,p)-representation is found.Comment: 37 pages, 2 appendices, 48 references, 1 figur
Orientational mobility and relaxation spectra of dendrimers: Theory and computer simulation
Rotational and translational relaxation times of quasi-elastic and rigid dumbbells elastically bound to polymer network junctions
Theory of relaxation spectra and dielectric relaxation of rigid rodlike particles incorporated in a polymer network
Theory of relaxation spectra of polymer networks with interchain friction and long-range hydrodynamic interactions
Viscoelastic Dynamic Properties of Meshlike Polymer Networks: Contributions of Intra- and Interchain Relaxation Processes
Theory of ordering in three-dimensional polymer systems with local orientational-deformational interactions
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