Structure and light switching of organic films with an amphiphilic polymer

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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 microgels 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 microgels. 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 OO bonds are nearly parallel to the surface. The phase transitions have been observed in the narrow temperature ranges near 65, 105, and 140 ーC for multi-layer LB … More films of ES-3. The three temperatures are very close to those for the phase transitions of bulk materials of ES-3, but the transitions occur more sharply for the LB films. Of note is that the transition temperatures of the LB films are markedly different from those of the self-assembling (SA) films previously reported. This may be due to structural differences in the alkyl chains between the two kinds offilms ; the SA films have partial interdigitation of the alkyl tails while the LB films do not have it.A kind of amphiphilic polymer, ES- 1, was transferred onto solid substrates as so-called "reversed duckweed" polymeric LB films. The molecular orientation, structure and phase transition behavior of the films were studied by infrared (IR) transmission and reflection-absorption (RA) spectroscopy. The IR studies have revealed that the alkyl chains are nearly perpendicular to the film surface and assume highly ordered conformation. The first monolayer has different orientation and arrangement from other layers in the ES-1 LB films deposited on Au-evaporated glass slides because of the interaction between the hydrophobic gold surface and hydrophilic head group of ES-1. Temperature-dependent IR measurements of an ES-1 LB film on an Au-evaporated glass slide have shown that the order-disorder phase transition of the film takes place at about 60-C after pretransitional structural modifications. The packing density of alkyl chains decreases gradually with temperature after the order-disorder transition in the LB film. The alkyl chains in an ES-1 casting film on a CaF2 plate are nearly perpendicular to the film surface. However, the alkyl chains of an ES-1 casting film on an Au-evaporated glass slide are tilted considerably. The IR study on the phase transition behavior has revealed that the two casting films on the different substrates give rise to the order-disorder transition at about 75 ーC after undergoing pretransitional structural changes. The alkyl chains in the casting film of ES-1 on the Au-evaporated glass slide show a phenomenon of reorientation ; they change from a more tilted orientation to a more perpendicular orientation before the order-disorder transition takes place, and become tilted again above the transition temperature. Less