NLOQO HomeIssue Contents

“Smart” Polysiloxane Monolayers and Self-organized Ultrathin Films
Yuli K. Godovsky, Sergei I. Belousov, Natalya N. Makarova, Gerald Brezesinski, Helmuth Mohwald, Torben R. Jensen and Kristian Kjaer

The surface pressure induced transitions of Langmuir monolayers to multilayers of 2D-nematic-like cyclolinear polyorganosiloxanes at the air/water interface is observed and characterized by film balance measurements, Brewster angle microscopy (BAM), surface sensitive synchrotron X-ray diffraction (GIXD) and reflectivity (XR) with a liquid surface diffractometer and scanning force microscopy (SFM) after deposition onto solid surfaces. Surface pressure (p) versus surface area (A) isotherm data for these polymers show several steps and plateaus and this had been assumed to indicate the formation of multilayers with distinct layer thickness consisting of 1, 2, 3, etc. (up to seven) layers. For the Langmuir monolayers (LM’s) and multilayers the observed single GIXD peak allowed to estimate: i) the inter-chain distance in planes, ii) the extent of the lateral positional correlation between parallel chains, iii) the thickness of the multilayers and separate monolayers. The results obtained with XR reveal that the multilayers have a very uniform layer thickness and that there is a significant degree of structural order in the packing of these polymers in the multilayers in a direction perpendicular to the polymer axis, i.e. two-dimensional structural order (in and out of plane). SFM performed on the Langmuir monolayers and bi-layers transferred to solid supports showed relatively homogeneous covering. Some possible application of the multi-layers is discussed.

Full Text (IP)