MONOLAYERS OF MULTICHAIN MOLECULES - A MONTE-CARLO STUDY

The aim of this work is to understand how the chain orientational orde r in monolayers depends on intramolecular connectivity. Therefore mono layers of one-, two-, three-, and four-chain flexible molecules have b een simulated using the Monte Carlo technique. The chains are linked u p in the head group region. Three- and four-chain molecules can have b oth: linear rigid as well as flexible head groups. The simulations wer e carried out within a lattice model on the simple cubic lattice. Only the excluded volume effect was taken into account. For the calculatio n of the orientational order we used end-end vectors of each chain in the molecule and vectors pointing from the centre of mass of the whole molecule to the centre of mass of the head group. If the chains in th e molecules have equal lengths the degree of order calculated from end -end vectors is neither influenced by connectivity in the head group r egion nor by the flexibility of the head group. The degree of order ba sed on the centre of mass vectors clearly indicates an effect of the i ntramolecular connectivity and for short chains also an influence of t he flexibility of the head groups.