Repulsion chain segments

Figure 10.67 indicates the probable distribution of a silicone containing the optimum content of aminoethyliminopropyl groups when applied to a polyester fibre surface. In this case the attachment is through hydrophobic polymer-fibre interaction and the mobility of the silicone chain segments is increased by electrostatic repulsion between neighbouring cationic groups. Dependence of softness of the treated polyester fabric on the proportion of... 

It is however possible to find conditions, called unperturbed or theta conditions (because for each polymer-solvent pair they correspond to a well-defined temperature called d temperature) in which a tends to 1 and the mean-square distance reduces to Q. In 6 conditions well-separated chain segments experience neither attraction nor repulsion. In other words, there are no long-range interactions and the conformational statistics of the macromolecule may be derived from the energy of interaction between neighboring monomer units. For a high molecular weight chain in unperturbed conditions there is a simple relationship between the mean-square end-to-end distance < > and the mean-... 

Because of the van der Waals interactions, the plates attract a larger number of polymer segments into the gap between the plates than when there are only electrostatic interactions with the chain segments. As a result, the interaction between plates, with the latter at constant electrical potential, becomes more attractive at distances larger than about 12 A than when the van der Waals interaction is neglected (Fig. 2). This behavior occurs because (p2 increases and hence the number of bridges increases. The force between plates at distances smaller than 12 A becomes, however, more repulsive when the van der Waals interaction is taken into account than when it is neglected. This increased repulsion can be attributed to the third term in Eq. (17), which provides a positive contribution to the force and becomes dominant at short distances. 

The bonds of the polymer molecule have been considered thus far as volumeless lines in space. In contradistinction, the bonds of real polymer molecules occupy flnite volumes in space. The repulsion between segments that are far removed from one another along the contour of the chain but spatially contiguous will cause the polymer chain to expand beyond the unperturbed dimensions. The magnitude of this dimensional expansion is measured by the intramolecular expansion factor a... 

Compared with linear cousins having the same molecular weight, chains with complex topology are usually more compact. The smaller size causes the chains to experience less mechanical force. On the other hand, extremely compact structure increases the repulsive interactions between chain segments, which leads to additional tension in the chains. The mechanical stability of the whole macromolecules is the balance of the two effects. 

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