Polymers molecular interaction

PHOTOISOMERIZATION AND PHOTO-ORIENTATION OF AZO DYE IN FILMS OF POLYMER MOLECULAR INTERACTION, FREE VOLUME, AND POLYMER STRUCTURAL EFFECTS... 

Photoisomerization and Photo rientation of Azo Dye in Films of Polymer Molecular Interaction, Free Volume, and Polymer Structural Effects... 

Intra-polymer molecular interactions Some polymer chains are soft (such as PE, where the polymer chain is easily rotated) and some stiff (like PVC, where it is more difficult to rotate the polymer chain). It is intra-polymer adjacent elemental interactions that decide if a long chain polymer is soft , hard , or something in between. 

It is possible to chemically string chains of different polymers together (forming block copolymers or through randomised copolymerisation) or physically melt different polymers into a blend to gain beneficial synergised properties. These altered properties are also determined by the above two factors, ie, intra- and inter-polymer molecular interactions. These are the fundamental characteristics of polymer interactions at molecular scales. 

In polymer solutions and blends, it becomes of interest to understand how the surface tension depends on the molecular weight (or number of repeat units, IV) of the macromolecule and on the polymer-solvent interactions through the interaction parameter, x- In terms of a Hory lattice model, x is given by the polymer and solvent interactions through... 

The viscosity of a polymer solution is one of its most distinctive properties. Only a minimum amount of research is needed to establish the fact that [77] increases with M for those polymers which interact with the solvent to form a random coil in solution. In the next section we shall consider the theoretical foundations for the molecular weight dependence of [77], but for now we approach this topic from a purely empirical point of view. 

In this equation, % is a proportionality factor known as the bead-solvent friction coefficient which purports to account in some kind of average way for the complex molecular interactions as the polymer segments (schematized by the bead) move about in the solvent. Following Stokes law of drag resistance, this friction coefficient is usually given as = 67trisa, with a equal to the bead radius. 

From the weak dependence of ef on the surrounding medium viscosity, it was proposed that the activation energy for bond scission proceeds from the intramolecular friction between polymer segments rather than from the polymer-solvent interactions. Instead of the bulk viscosity, the rate of chain scission is now related to the internal viscosity of the molecular coil which is strain rate dependent and could reach a much higher value than r s during a fast transient deformation (Eqs. 17 and 18). This representation is similar to the large loops internal viscosity model proposed by de Gennes [38]. It fails, however, to predict the independence of the scission yield on solvent quality (if this proves to be correct). 

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