Intra-polymer molecular interactions

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. 

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... 

The function Ym (like Yg) has the dimension (K kg moF1). The group increments for this function could be derived from the available literature data on crystalline melting points of polymers, totalling nearly 800. The quantity Ym (like Yg) does not show simple linear additivity due to intra- and inter-molecular interactions between structural groups. The available group contributions and their structural corrections are summarised in Table 6.8. We shall again discuss these data step by step. 

These results show that the absorption energy of a polydiacetylene extended chains in solution is 2.5 eV and that the Icwer values observed for crystals, polymer extract, films and rigid-planar conformation in solution reflect the structure imposed on the polymer by the intra- and inter-molecular interactions of the side-groups. While reasonable agreement has been obtained in some cases, using experimentally determined parameters, the details of the relationship between absorption energy and structure have yet to be worked out. 

The polar, ionic and even non-ionic head-group interactions of lipid membranes and other surfactants, (as indeed for many polymers and polyelectrolyte intra-molecular interactions) and the associated curvature at interfaces formed by such assemblies will be dependent on dissolved gas in quite complicated ways. Fluctuating nanometric sized cavities at such surfaces will be at extremely high pressure, (P = 2y/r, y= surface tension, and r the radius) resulting in formation of H and OH radicals. The immediate formation of Cl radicals and consequent damage to phospholipids offers em explanation of exercise-induced immunosuppression (through excess lactic acid CO2 production), perhaps a clue to the aging process. 

Abstract Atomic force spectroscopy (AFM)-based single-molecule force spectroscopy (SMFS) was invented in the 1990s. Since then, SMFS has been developed into a powerful tool to study the inter- and intra-molecular interactions of macro-molecules. Using SMFS, a number of problems in the field of supramolecular chemistry and mechanochemistry have been studied at the single-molecule level, which are not accessible by traditional ensemble characterization methods. In this review, the principles of SMFS are introduced, followed by the discussion of several problems of contemporary interest at the interface of supramolecular chemistry and mechanochemistry of macromolecules, including single-chain elasticity of macromolecules, interactions between water and macromolecules, interactions between macromolecules and solid surface, and the interactions in supramolecular polymers. 

Direct experimental verifications of the temperature dependences of the elastic moduli of perfect crystals of polyethylene in the chain-extended form, as represented in Table 4.3, present great difficulties, first because they relate to a perfect crystalline material and second because they are based on the anharmonic atomic interactions in such perfect material. Polymeric solids, even those that are highly crystalline, incorporate a variety of crystal imperfections that permit thermally assisted relaxations under stress. These dramatically attenuate the elastic properties that, at all but the lowest cryogenic temperatures, mask the temperature dependence of elastic interactions of the perfect crystal, particularly the stiffest intra-molecular interactions along the C—C backbone. In the vast majority of cases the elastic moduli of polymers reflect the soft intermolecular interactions, and the temperature dependence of these overwhelmingly dominates the intramolecular variety at all but the lowest temperatures. 

High molecular weight polymers, including proteins, also form surface mono-layer films. However, because of the length of the polymer molecules and the complex interactions involved in intra- and interchain interactions, the properties of such films are less distinct and more difficult to determine with... 

It should be noted that there have been attempts to produce molecular modeling results and simulations of high temperature polymer blends. The most extensive of these efforts was published by Jacobson et al. (1992). Those workers used a short chain molecular model that incorporates the effects of both inter- and intra-molecular interactions. Using that model, estimates of the net interaction energies for a series of high temperature polymer blends were calculated and used to predict miscibility. The results were in general agreement with experiments and were used to focus the direction of additional experimental work. 

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