Assembly of polymer/lipid composite films on solids based on hairy rod LB-films

Abstract

The present work deals with the assembly of multilayers or rod-like polymers with hydrophobic side chains (called hairy rods) and their potential application as ultrathin polymer cushions for the build-up of self healing supported membranes on various solids (Si/SiO₂-wafer, gold covered substrates). Three types of hairy rods were studied: Isopentyl cellulose (IPC), phtalocyaniatopolysiloxane with mixed alkane side chains (PCPS) and trimethylsilane cellulose (TMCS). Detailed analysis of the thickness of supported multilayers as a function of the number of deposited monolayers with ellipsometry, near infrared surface plasmon resonance (NIR-SPR), a quartz crystal microbalance (QCM) and reflection interference contrast microscopy (RICM), show that the basic building blocks of hairy rod multilayers are bilayers with the hydrophobic surfaces of the monolayers facing each other. Continuous and stable firms of hairy rods can be deposited if the hydrophobicities of the solid surface and the monolayer are matched. It is demonstrated by lateral diffusion measurements (using photobleaching techniques) that continuous phospholipid bilayers can be deposited onto multilayers of rigid rods of TMCS after hydrophilization by cleavage of trimethylsilane side chains in HCl-vapour, while stable lipid monolayers can be deposited onto hydrophobic surfaces of rigid rod layers. NIR-SPR allows the observation of double band reflectivity curves at interfaces separating different surface layers and thus offers the possibility of differential detection of ligand binding at the interface of differently functionalized domains.