Inter-polymer interactions

Inter-polymer interactions Some polymers have weak forces between their polymer chains, whereas some have stronger forces. This inter-polymer force is decided by van der Waals forces. PE has a relatively weak van der Waals force while PVC has stronger ones. 

These factors are not acting independently and have been seldom analysed. The structure and molecular weight of a polymer affect the solubility of polymer and consequently the solvent effects. The polymer chain conformation which is certainly a function of solvent and temperature will then influence both intra- and inter-polymer interactions. 

In polymer science and technology, linear, branched and crosslinked structures are usually distinguished. For crosslinked polymers, insolubility and lack of fusibility are considered as characteristic properties. However, insoluble polymers are not necessarily covalently crosslinked because insolubility and infusibility may be also caused by extremely high molecular masses, strong inter-molecular interaction via secondary valency forces or by the lack of suitable solvents. For a long time, insolubility was the major obstacle for characterization of crosslinked polymers because it excluded analytical methods applicable to linear and branched macromolecules. In particular, the most important structural characteristic of crosslinked polymers, the crosslink density, could mostly be determined by indirect metho ds only [ 1 ], or was expressed relatively by the fraction of crosslinking monomers used in the synthesis. 

The properties of polymer materials can e greatly extended by blending two or more homopolymers together. Blends may be classified as compatible or incompatible - although this does depend on the dimensions being considered. Compatibility is influenced by the molecular weight of the homopolymers and is enhanced in practice by incorporation of block copolymers and other compatibilizers. The effects of radiation on blends depend on the degree of compatibility and the extent of inter-molecular interaction (physically and chemically) between the different types of homopolymers. 

The precipitation of a polymer can be regarded as a solvophobic phenomenon the interactions between polymer and solvent molecules are diminished by lowering the temperature or adding nonsolvent until they are weaker than the intra- and inter-molecular interactions between polymer segments. If the thermodynamic quality of the solvent has decreased beyond a certain limit, the macromolecules associate and... 

With monomeric molecules, the aggregation number of micelles is determined by equilibrium thermodynamics. In polymeric molecules, however, topological constraints are imposed on the system. If the degree of polymerization exceeds the aggregation number of the monomeric micelle, unsaturated sites of the polymeric molecules become available (directed to the aqueous phase) and inter-molecular interactions (agglomeration) occur. In the case of polymer with Mw= 6.23x105, typical surfactant behavior was found. 

Most of the studies on polymers such as polyamides in solution are limited because the insolubility of these polymers in common solvents. This fact makes their characterization very difficult [87] The degree of order or crystallinity shown by these polymers caused by intra- and inter- chain interactions affect their solubility and their general properties. 

Finally, it should be stressed that photoluminescence has usually a larger quantum yield in solution than in the solid state27. In the latter case, inter-chain interactions appear to quench the luminescence properties through a mechanism that is not fully understood yet. In this context, it is, however, useful to note that the possibility that the polaron-excitons evolve into excimers28 is ruled out by the absence of Stokes shifts in good-quality PPV oligomer and polymer samples14. 

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