MOLECULAR SELF-ASSEMBLY AT A PREFORMED LANGMUIR-BLODGETT TEMPLATE

The use of a Langmuir-Blodgett monolayer as a template for subsequent self-assembly of organic molecules from solution has been investigated . The template is formed by transferring a monolayer of octadecylphosp honic acid to a hydrophobic substrate and then binding Zr4+ ions to th e surface from solution. The asymmetric methylene (v(a)(CH2)) band of the template layer appears at 2918 cm-1 and possesses a full width at half-maximum of 20 cm-1 indicating that an all-trans close-packed temp late is formed. X-ray photoelectron spectroscopy (XPS) analysis of the template layer shows a 1:1 ratio of Zr:P. Octadecylphosphonic acid, 1 ,10-decanediyldiphosphonic acid (DDPA) and quaterthiophenediphosphonic acid (QDP) have been self-assembled to the template and characterized by attenuated total reflection-Fourier transform IR, XPS and UV-visib le techniques. Octadecylphosphonic acid self-assembles to the zirconiu m template and produces a well-ordered close-packed film as followed b y IR analysis. Multilayers of DDPA have been assembled to the template layer; however, the increase in the integrated area of the v(a)(CH2) band is not linear with the number of DDPA layers assembled. A rigid d iphosphonic acid molecule such as QDP has also been assembled one laye r at a time to the template. A plot of UV-visible absorbance vs. the n umber of layers of QDP shows a linear increase in absorbance after eac h QDP deposition step.