Texture of Polymers

the physical structure of polymeric bodies that is caused by various types of order of macromolecules. In polymers in the amorphous state, the macromolecules exhibit short-range order, which because of their large dimensions and lower mobility becomes detectable in considerably larger volumes and persists longer than in amorphous low-molecular-weight substances. Comparison of the cluster formation of liquids with the structure of amorphous polymeric materials has led the Soviet scientists V. A. Kargin, A. I. Kitaigorodskii, and G. L. Slonimskii to the hypothesis that the simplest forms of texture in the amorphous state of polymers are globular or fibrillar (bundle) aggregates of macromolecules, which are long-lived fluctuation formations of large dimensions. These very simple formations, which are formed even by the action of weak (van der Waals) forces, are capable of aggregating into more complex, still little studied forms of texture in the presence of strongly interacting groups (for example, ionic groups). The texture of amorphous polymers becomes less developed and more mobile upon transition from the vitreous state through the hyperelastic into the viscous-flow state.

Aggregation of macromolecules in polymers in the crystalline state leads to the formation of various types of crystallites, which are one of the simplest forms of texture. The crystallites in turn combine to yield more complex forms of texture (for example, fibrils, spherulites, and spherulite concretions in the form of bands and lamina). Direct observation of such forms is possible in many cases using electron or optical microscopy.

Differences in the texture appreciably affect the physical properties of polymers, which therefore are not determined only by their chemical structure. Controlled changes in the texture, which may be produced by thermal, mechanical, and other types of action, have a significant effect on the properties of the polymeric material and are widely used in industry (in production of high-strength fibers and films and in modification of plastics). Changes in the texture of polymeric articles during their use is one cause of their aging.