PeopleMichael Lang , Jens-Uwe Sommer , Ron Dockhorn
IntroductionCross-linking of polymers leads to a combination of liquid properties (viscosity) and solid-state properties (shape stability, stability in solvents). In modern polymer research, cross-linking processes are applied to control materials properties in combination with structure-forming preparation and self-organization processes. Even though rubber elasticity has been investigated since more than one century, convincing theoretical models that address all the possible structure-property relationships are not at hand. This is due the random cross-linking topology which results from the stochastic cross-linking process and leads to frozen-in disorder and heterogeneities. In particular, swelling properties of networks and multi-axial deformations of polymer networks are not fully understood yet.
We analyze the structure of networks using computer simulations. In particular, entanglements between overlapping chains are in the focus of our study. Furthermore, the homogeneity assumption made in essentially all theories is challenged by scattering experiments and computer simulations of swollen networks. We want to include an analysis of static polymer density fluctuations in swollen networks into the theoretical description of network swelling. Networks formed from branched polymers or ring polymers (Olympic gels) are investigated by simulations and analytical models. Moreover, charge effects as they are in particular important for bio-compatible gels are considered. Networks formed in thin polymer films such as in polymer brushes are also studied.
Analysis of entanglement length and segmental order parameters in polymer networks
Phys. Rev. Lett. 104 (2010) 177801
On the Structure of Star-Polymer Networks
Macromolecules 44 (2011) 9464