Formation and Structure of Amorphous Polymer Networks

The development of concepts concerning the formation and structure of three-dimensional network polymers was for a long time exclusively based on chemical considerations. It was assumed that these systems are formed from monomers or oligomers containing two or more reactive groups capable of 

On the other hand, a chemical network alone caimot explain the variety of network properties. Physical intermolecular polar interactions, donor-acceptor interactions, etc. play a very important role in network formation. In network systems capable of forming physical cross-links, the contribution of such Unks to the effective network density may be very significant [22]. It is known that the whole group of modern polymer materials, thermoelastoplas-tics, contain only physical cross-Unks. 

Frisch determines IPNs as topologically interpenetrating systems. According to Irzhak [25] the topological structure of a polymer is determined by the connectivity of the structural elements, and may be described as a graph independent of the real chemical and spatial structure and disposition of its elements in space. Topological knots are labile formations that reveal them- 

Unlike linear polymers, topological entanglements in cross-Hnked polymers affect not only dynamic, but also equihbrium mechanical properties. The equilibrium shear modulus at the temperature above glass transition consists of two components CTx estimated from the classical theory and Oy connected with the network topology [29]. The share of topological component depends on the chemical cross-hnking degree [48]. 

It may be suggested that, because it is not yet known whether IPNs follow either the lower (LOST) or upper critical solution temperatiue (UCST) phase diagram, the effect of temperature on miscibility cannot be established, since curing usually proceeds at elevated temperatures and estimation of miscibility is carried out at room temperatiue. 

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