Thin Solid Films. 189 (I 990) 379-387 LANGMUIR-BLODGETT AND RELATED FILMS 379 GROWTH OF LARGE LIQUID CRYSTALLINE DOMAINS OF PHOSPHOLIPIDS AT AIR-WATER INTERFACES* M. FLijRSHEIMER AND H. MiiHWALD Universiry of’ Maim, Institufe of Physical Chemistry, Welder Weg II, 06500 Maim (F.R.G.) (Received August 10, 1989; accepted March 15, 1990) The fusion of condensed phase domains in a fluid environment in monolayers is studied. A system of electrodes permits the non-invasive and predetermined movement of single domains while the film is observed by fluorescence microscopy. Two domains fuse when they are brought into contact with special positions of their borderlines. The experiment yields information about the molecular structure of the domains and allows us to fabricate very large domains. The equilibrium size is estimated and verified. 1. INTRODUCTION The domain structure in a monofilm is determined by an interplay of four factors. (1) The line energy of the one-dimensional fluid-condensed interface enforces compact domain shapes. (2) The alignment of polar or charged molecules at the interface causes long- range electrostatic forces. Repulsive forces give rise either to finite domain sizes or to elongated domain shapes’-‘. Furthermore superlattices appear’,6. (3) The molecular symmetry and the compatibility of the hydrophilic and hydrophobic part of a molecule influence both maximal size and shape of the domains4*7-9. (4) The initial number of domains in a film compressed into the phase coexistence region is given by the nucleation conditions”. Until recently neither spontaneous fusions nor fissions ofcompact domains in a film were reported. Therefore it was argued that these domains possibly never show equilibrium sizes ‘i but only the sizes given by the non-equilibrium nucleation features and the degree of compression. After having demonstrated that monolayers can achieve states close to a global equilibrium by domain fission4**, in this work fusions are investigated. Using the example of the phospholipid L-c+ *Paper presented at the 4th International Conference on Langmuir-Blodgett Films, Tsukuba, Japan, 1989. 0040-6090/90/$3.50 0 Elsevier Sequoia/Printed in The Netherlands