Лако-красочные материалы — производство

Different molecular mechanics systems and programs exist. There are programs that allow simultaneous variation of bonds and bond angles as well as allowing bond rotation, and there are programs in which instead all the covalent bond lengths and bond angles between covalently bonded atoms are fixed to specific values without allowance for their adjust­ment or […]

A. Pizzi Ecole Nationale Superieure des Technologies et Industries du Bois, Universite de Nancy l, Epinal, France I. INTRODUCTION Molecular mechanics in the broader sense of the term is a computational technique which is, among other things, particularly suited for determining at the molecular level the interactions at the interface of well-defined polymers. It has […]

In this short review, we have presented some results on the behavior of polymer solutions close to surfaces in the context of adhesion phenomena. The emphasis has been placed on the interaction between two flat parallel solid surfaces induced by a polymer solution and more specifically on the bridging effect between the surfaces due to […]

The equilibrium interaction between two parallel surfaces mediated by a polymer solution can be studied within the mean field approximation [34]. The polymer in the gap between the two surfaces is in equilibrium with a reservoir that fixes its chemical potential. One first determines the concentration profiles and then calculates the free energy. The interaction […]

The whole discussion of polymer adsorption so far makes the fundamental assumption that the layer is at thermodynamic equilibrium. The relaxation times measured experi­mentally for polymer adsorption are very long and this equilibrium hypothesis is in many cases not satisfied [29]. The most striking example is the study of desorption: if an adsorbed polymer layer […]

The mean field theory allows the calculation of many physical properties of adsorbed polymer layers. For most experimental situations it gives a good qualitative description, but it is known not to be quantitative as it implicitly ignores the concentration fluctuations associated with the excluded volume interaction. A simple strategy is to assume that the mean […]

In a mean field approach, the interaction between one chain and all the other chains of the adsorbed layer is approximated by a mean field potential proportional to the local con­centration U(z) = kTvc(z) and the average conformation of one chain is calculated in this potential. The conformation of one chain is characterized by the […]

When all the monomers adsorb on a solid surface, a rather dense adsorbed layer is formed in the vicinity of the surface even if the bulk solution is dilute. This layer is rather thick due to the formation of large loops by the chains on the surface (although far thinner than a dense grafted layer). […]

The interaction between two surfaces each carrying a grafted polymer layer of thickness H is repulsive [15]. If the distance h between the surfaces is larger than 2H, the polymer layers do not overlap and the force between the surfaces owing to the polymer vanishes. If the distance h is smaller than 2H, the two […]

A sketch of a polymer brush is shown in Fig. 1. We call a the graft density or the number of grafted chains per unit area of the surface. Each chain has N monomers. In a dilute solution the chain radius of gyration, R, is R ~ N1/2a for Gaussian chains in a в solvent […]