Seminarium Fizyki Materii Skondensowanej

We use grand canonical Monte Carlo simulation paired with multiplehistogram reweighting, hyperparallel tempering and finite size scaling toinvestigate the structure and phase behaviour of monolayers of diblockcopolymers. The chain molecules are arranged on the square lattice and weconsider both fully flexible and rod-coil polymer models. We investigatehow the length of the polymer and the segment-segment interactions affectthe phase behaviour of the adsorbed molecules. When the interactionsbetween the unlike segments are weaker than the interactions betweenthe segments of the same type we find that the order-disorder phasetransition can be either first-order or continous. The resulting topologyof the phase diagram involves either a triple point, critical end-point ora tricritical point. The mechanism of the order-disorder transitioninvolves the formation of domains resembling those observed during thespinodal decomposition process. The domains subsequently merge and arrangeinto lamellae. These observations are supported by integral geometryanalysis. When the interactions between the unlike segments are enhancedwith respect to the interactions between the segments of the same type,for the rod-coil molecules we observe the formation of a novel hairpinchessboard ordered structure. The resulting phase diagram is of theswan-neck type.