ISSN:
0887-6266
Keywords:
interface structure
;
spectroscopy
;
phase transition
;
polymer solution properties
;
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The structures, in particular the amount of conformational order in terms of the trans/gauche ratio of the methylene units, associated with monolayer films at the air-water interface, of a phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, a vinyl comblike polymer, poly(octadecyl acrylate) and a hairy-rod co-polyglutamate with long alkyl side chains, all have been studied by external reflectance Fourier transform infrared spectroscopy. The structures of these monolayers were monitored as a function of molecular area/surface pressure and subphase temperature using a microcomputer-controlled Langmuir trough interfaced to an infrared spectrometer. The unique features of this combination of techniques permit the direct evaluation of the molecular dynamics associated with the formation and collapse of spread monolayer films at the air-liquid interface, as well as the description of the adsorption kinetics of amphiphile molecules at an air-solution interface. The conformation sensitive methylene stretching vibrations of the hydrocarbon side chains proved to be extremely sensitive indicators of conformational change during slow dynamic compression of the Langmuir films changing from expanded to more condensed monolayer states up to their collapse region. The three systems exhibit significantly different spectroscopic features that can be directly associated with differences in the intermolecular packing. The effect of temperature (from +8 to +27°C) on the molecular order for compressed monolayers of poly(octadecyl acrylate) was also studied. The frequencies of the methylene stretching bands for the liquid crystalline co-polyglutamate showed that at high compression, the long flexible hydrocarbon side chains were mostly in an all-trans configuration. At low compression, the side chains became disordered and contained a large fraction of gauche configurations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2843-2855, 1997
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
