The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The first part of the paper describes how rigid rods, i.e., liquid crystal polymers can be used as a physical system whose glass transition can be investigated with confidence. For this system the position of the transition and the Volger-Fulcher Law by which it is approached can be derived. The second part discusses the physics of such molecules giving examples of their chemical structure...
The bond fluctuation model of polymer melts is presented as a reasonable compromise between simulation efficiency and realistic chemical detail. It is shown that inclusion of a potential energy that depends on the length of the effective bonds connecting the effective monomers easily creates a conflict between configurational entropy of dense packing and the energetic tendency of the bonds to stretch...
In this work, we focus on hierarchical relaxation in complex systems. Two means of describing relaxation are considered in detail: first, we use a microscopic model based on continuous-time random walk (CTRW) ideas; this procedure is efficient in describing photoconductive behavior and is used here also in the framework of polymer chain dynamics, by letting each bead move according to its own waiting-time...
An operational definition of the glass transition as the transition between the solid and liquid states of amorphous or partially ordered matter is given, particularly as it applies to flexible macromolecules. This is followed by a description of the basic observations of glass transitions via thermal analysis using calorimetry. Partial order is treated as it is found in semicrystalline, mesomorphic,...
Relaxation in largely strained permanent networks is described. With the aid of thermodynamics of irreversible processes a constitutive equation is formulated whereby the equilibrium states of references are given by the van der Waals network strain energy. A key observation is that the shape of the relaxation time spectrum does not depend on the strain, straintype, strain-rate, temperature or pressure...
To explore the physical content of the intuitive concept of dyanmic molecular cooperativity, as thematized in a famous paper of Adam and Gibbs [1], a class of lattice-gas and kinetic Ising models has been investigated [2–25]. The concept is thought to apply to the non-vibrational diffusive motion of molecules in supercooled liquids near the glass transition. The models made the intuitive idea concrete...
Various phase tranditions occurring in polymeric systems are reviewed from the standpoint of classic equilibrium thermodynamics. It is shown that classic rules are obeyed to a surprising degree of accuracy and provide a useful ordering principle. Transitions considered involve partial miscibility, crystallization, mesophase and compound formation. Simple molecular modeling already produces phase diagrams...
A survey for the osmotic equilibrium between solution and a pure solvent as well as for the swelling pressure eqilibrium between a gel and pure solvent is given, where phase transitions of the pure component are allowed to occur. The equilibrium temperature/concentration curves are presented for constant osmotic and swelling pressure respectively in the different phase ranges for crystalline, liquid...
We here review some of our recent results on fluid-like and crystalline ordered colloidal suspensions. We have investigated the structure and the dynamical properties of strongly interacting charged latex particles. The interaction can be varied experimentally over a wide range and in a precisely controlled way. It gives rise to pronounced correlations between the particles, leading to ordered mesosocpic...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.