Dielectric relaxation spectroscopy is a powerful technique which allows one to study the local and cooperative chain dynamics of polymers both in the liquid and solid state, across an extremely wide range of frequencies (10^-2 - 10⁹ Hz). We will present DRS-results obtained on a series of quite different polymer systems based either on permanent (covalent) chemical networks or on reversible or temporary physical networks.

We will demonstrate that - among the various relaxation processes possible - in particular the -relaxation, which reflects the dynamic glass transition, is quite sensitive to the degree of intermolecular interactions created by permanent or temporary crosslinks. This sensitivity manifests itself by two characteristics:

1. the a-peak broadens on its low frequency side with increasing crosslink density
2. the temperature dependence of its mean relaxation time _a - usually described by a WLF or VFT relation - changes from a strongly curved dependence (weak interactions) to an almost Arrhenius-like dependence (strong interactions). The universality of this dual behaviour will be illustrated by results from: side-chain liquid crystalline polymers, linear polymer electrolytes containing coordinated Li-O complexes and H-bonded supramolecular polymers. The results will be discussed in the framework of theoretical concepts for cooperative relaxation phenomena