Recent developments in polymer dynamics investigations of architecturally complex systems

Abstract: The tube model for linear and branched architectures is nowadays able to predict in high precision the linear viscoelastic relaxation time spectrum. For linear chains, the involved time scales fit to the commonly accessible dynamic scattering techniques. This makes it possible to microscopically investigate the correlation between structures and relaxation processes. In branched systems, however, the hierarchical nature of relaxations limits direct investigation via these microscopic methods as the dynamic processes are prolongated to much longer relaxation times that are no more accessible to usual dynamic scattering methods. A way to overcome this difficulty is offered by the use of static small angle neutron scattering. Here, the combination of annealing and quenching steps after a step deformation provides unique information of the structure at particular times along the relaxation spectrum. This, however, necessitates the availability of architecturally clean and specifically deuterium labelled model polymers due to the sensitivity of the scattering method. Therefore, we outline in this contribution first the current status on the synthesis and analysis of such compounds with relation to neutron scattering. Secondly, we present exemplary neutron scattering results from in situ stress relaxation studies inside the neutron beam on linear and H-shaped branched polymers which were molecularly designed to highlight specific relaxation processes. We discuss the relevance of the tube model parameters in linear and non-linear studies. [Copyright &y& Elsevier]