Studies of multiple-chain alkylaminomethyl p-cyanophenol derivatives for Langmuir-Blodgett films

Langmuir films and Langmuir-Blodgett deposition have been studied for 2,6-dioctadecyl-aminomethyl-4-cyanophenol (CPR₂R₂) and 2-dioctadecyl-aminomethyl-4-cyanophenol (CPR₂). Stable Langmuir films were obtainable for both compounds at high pH, but only for CPR₂R₂ at low pH. Molecular modelling and semiempirical MNDO calculations suggest that high pH favours stability by disrupting intramolecular hydrogen bonding. X-ray diffraction on Y-type Langmuir-Blodgett films deposited on hydrophobic glass substrates gives layer spacings of about 56 Å for both compounds, indicating that the alkyl chains orient perpendicular to the substrate. Modelling and MNDO calculations suggest that analogous compounds with a single octadecyl chain on nitrogen could be stable at both low and high pH.