Alexey Polotsky, Sérvice de Physique de l'Etat Condensé CEA/Saclay, France
Polymer brushes — layers of polymer chains densely grafted onto impenetrable surface — attract much attention and are intensively studied in the last three decades. This interest is motivated by the large numbers of systems and situations where brush and brush-like structures can be observed.
Polymer brushes formed by chains capable to liquid-crystalline (LC) ordering represent an individual class of systems and problems in this area. In the present talk, the results of the theoretical study of a planar polymer brush formed by freely-joined chains of rigid segments and immersed into a solvent will be presented. Free brush as well as brush deformation via external normal and lateral force will be considered. All three situations can be treated in the framework of the single approach considering the solvent quality and the values of the applied normal and lateral force as "external" parameters governing the conformational behaviour of the brush.
It will be shown that a deterioration of the solvent quality and a deformation by normal (compression) and lateral (shear) external force can cause brush transition into ordered LC state. Depending on the brush parameters, such as chain grafting density, rigid segment's length and the solvent quality (in the case of the brush deformation), LC transition can be of jump-like or continuous. Brush characteristics in the transition point as well its critical behaviour will be discussed.