Surface structure, mechanics and rheology of amphiphilic polymer conetworks on different length scales*

In order to allow the simultaneous transport of hydrophilic and hydrophobic substances, networks with fine-structured hydrophilic and hydrophobic components are requested. Amphiphilic polymer co-networks (ACNs) can be tailored to create gels that selectively swell or collapse in different solvents with the corresponding polarity and greatly impact transport properties through these networks. 

This study focuses on the relation between structure, swelling abilities and mechanical/rheological properties of films of ACNs.^1,2 First, the correlation between different synthesis strategies for gel films and their resulting properties will be described. Secondly, the effect of solvents of different polarity on the swelling ability will be presented on different length scales. For this purpose, topology and near surface structure are studied with atomic force microscopy (AFM). We also put special emphasis on the determination of mechanical and rheological properties laterally and orthogonally to the gel surface by carrying out dynamic AFM indentation experiments. In order to evaluate heterogeneities the mechanical and rheological behavior at the interface of the ACNs will be presented on various length scales (nm - µm). The study shows that the synthesis strategy has a strong effect on the gel structure and on nano/microrheological properties. The structure and rheology of gel films will be compared with results obtained of the respective bulk gel phase.