Molecular orientation and structure in ultrathin films of amphiphilic microgel copolymer with the branching of octadecyl groups studied by infrared spectroscopy

Abstract

Molecular orientation and structure in five-monolayer Langmuir-Blodgett (LB) films of an amphiphilic polymer consisting of a flexible hydrophilic epichlorohydrinethylene diamine cross-linking microgels and a number of hydrophobic chains have been studied by infrared (IR) transmission and reflection-absorption (RA) spectroscopy. The downward shifts of the NH and C=O stretching bands show that the amide groups are involved in medium hydrogen bonds. A comparison of the band intensities between the transmission and RA spectra indicates that the hydrocarbon chains are nearly perpendicular to the substrate surface while the C-N bond of the amide group is nearly parallel to the surface. The vibrational frequencies of the two CH₂ stretching bands suggest that the LB films have highly ordered alkyl chains.