Langmuir-Blodgett patterning of phospholipid microstripes: effect of the second component.

We systematically describe the striped pattern formation of the mixed monolayers of 1,2-di(2,4-octadecadienoyl)-sn-glycero-3-phosphocholine (DOEPC) and l-alpha-dipalmitoylphosphatidylcholine (DPPC) from the liquid expanded (LE) phase onto a mica surface by Langmuir-Blodgett (LB) transfer. The addition of the second component, DOEPC, strongly affects the formation of DPPC stripe patterns. When the molar ratio of DPPC and DOEPC is 1:0.1, the horizontal stripes dominate, while in the case of pure DPPC monolayer, there are three kinds of patterns: horizontal stripes, grids, and vertical stripes. The width and periodicity of stripes formed from the mixed monolayers are ca. 4-5 times smaller than those formed from pure DPPC patterns at the same transfer conditions, while the widths of channels are similar. A phase shift of substrate-mediated microphase separation in the two-component system during LB transfer is considered to be the mechanism for the influence of the second component on the formation of DPPC stripe patterns.