Inter-Chain Entanglements

A value of T2 at the maximum, (T2s)max, is related to the molecular mass of the network chains between chemical crosslinks and trapped chain entanglements [49]. At higher values of Vs, T2 decreases until the state of equilibrium swelling is reached. This decrease in T2 is thought to reflect the increase in the inter-chain proton dipole-dipole interactions as a result of the network chain elongation following a progressive increase in the solvent fraction in a swollen gel [20]. 

The number density of network strands determines and the plateau modulus caused by inter-chain entanglements is Cg. This plateau modulus is understood on a molecular level by imagining surrounding chains confining each network strand to an effective tube. 

In this case, weak cohesive inter-chain forces [3,53] and physical entanglement [54] maintain the structure of the imprinted binding sites. The imprinted structure in this second strategy is inherently less robust because it relies on a multitude of noncovalent interactions. However, this strategy also has the synthetic advantage that the matrix can be imprinted using covalent cross-linking as shown in Fig. 1(c). 

A discussion of this subject is presented below. The additional oMitribution GX is said to arise from permanently trapped (inter-chain) entanglements in the network. Linear polymers of high molecular wd t exhibit a storage modulus G (constant over a wide range of frequencies This plateau modulus... 

It is useful to summarize here the most important types of results on model networks which have led to the conclusion s that inter-chain entangle-... 

Hoffmann has attempted to estimate the magnitude of Me directly from the structure (246). He suggests that entanglements comprise a special class of inter-molecular contacts in which one chain is looped tightly around another, and in which the four strands leading away from this contact are oriented such that the loop resists rapid deformations in the manner of a cross-link. His estimation of the concentration of such arrangements in polyethylene goes as follows. 

---