Infrared Study on Molecular Orientation and Phase Transition in Langmuir−Blodgett Films of an Amphiphilic Microgel Copolymer with the Branching of Octadecyl Groups

Abstract

Molecular orientation, structure, and phase transition in Langmuir−Blodgett (LB) films of an amphiphilic polymer consisting of a flexible hydrophilic epichlorohydrin−ethylenediamine slightly cross-linking microgel and a number of hydrophobic stearic chains (ES-3) have been studied by infrared (IR) transmission and reflection−absorption (RA) spectroscopy. The infrared study indicates that the LB films of ES-3 possess crystalline, tightly packed methylene chains and extended interchain hydrogen bonds between the amide groups, which connect the alkyl chains with the microgel. A comparison of the band intensities between the transmission and RA spectra suggests that the hydrocarbon chains are highly oriented with a small tilt angle and that N−H and CO bonds of the amide groups and the interchain hydrogen bonds between the N−H and CO bonds are nearly parallel to the surface. It is indicated from infrared spectra of LB films of ES-3 prepared under different surface pressures that the alkyl chains are highly ord...