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Title: Structure of poly([gamma]-benzyl-L-glutamate) monolayers at the gas[endash]water interface: A Brewster angle microscopy and x-ray scattering study

Abstract

This paper reports Brewster angle microscopy (BAM), x-ray specular reflectivity (XR), grazing incidence diffraction (GID) and off-specular diffuse scattering (XOSDS) measurements of Langmuir monolayers formed on water by both mono- and polydisperse samples of [alpha]-helical poly([gamma]-benzyl L-glutamate) (PBLG) as a function of area/monomer [ital A]. The microscopic behavior does not exhibit any discernible effects due to differing dispersity. At low surface densities (A[gt][approximately]21 hthinsp;[Angstrom][sup 2]/monomer, surface pressure [Pi]=0), BAM images reveal partial surface coverage by solidlike monolayer islands. GID measurements show an interhelix peak corresponding to a local parallel alignment of rodlike PBLG molecules, indicating their tendency to aggregate laterally without external pressure. Compression to A[lt]21 hthinsp;[Angstrom][sup 2]/monomer first leads to full and uniform surface coverage by the monolayer, followed by a steep rise in [Pi] that is accompanied by a decrease in the interhelix distance. Further compression results in a plateau of constant [Pi] in the [Pi]-A isotherm ([approximately]11.5[lt]A[lt][approximately]18.5 hthinsp;[Angstrom][sup 2]/monomer, [Pi][approximately]9 hthinsp;dyn/cm), which has previously been attributed to a first-order monolayer[endash]bilayer transition. The interfacial electron density profiles determined by the XR measurements on both sides of the coexistence plateau provide direct evidence for this transition. On the basis of x-ray scattering results, the film on the high-density sidemore » of the plateau is shown to consist of a newly formed incomplete and incommensurate second layer that sits on top of and has lower average density than a homogeneous first layer. GID measurements indicate that the second layer can be characterized by larger interhelix [ital d]-spacing than the first layer, while XOSDS measurements on the bilayer suggest that the second layer is microscopically inhomogeneous. For both mono- and bilayers, the analysis of observed GID peak widths indicates that the extent of lateral positional correlations between parallel PBLG rods ranges from a few to no more than [approximately]15 interhelix distances, implying short-range order. [copyright] [ital 1999 American Institute of Physics.]« less

Authors:
; ;  [1]; ; ;  [2]
  1. Department of Physics and Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)
  2. Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003 (United States)
Publication Date:
OSTI Identifier:
6060281
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 111:21; Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; INTERFACES; LIQUID CRYSTALS; MICROSCOPY; OPTICAL MICROSCOPY; POLYPEPTIDES; STRUCTURE FACTORS; THIN FILMS; X-RAY DIFFRACTION; COHERENT SCATTERING; CRYSTALS; DIFFRACTION; FILMS; FLUIDS; LIQUIDS; ORGANIC COMPOUNDS; PEPTIDES; PROTEINS; SCATTERING; 400201* - Chemical & Physicochemical Properties; 665000 - Physics of Condensed Matter- (1992-)

Citation Formats

Fukuto, M, Heilmann, R K, Pershan, P S, Yu, S M, Griffiths, J A, and Tirrell, D A. Structure of poly([gamma]-benzyl-L-glutamate) monolayers at the gas[endash]water interface: A Brewster angle microscopy and x-ray scattering study. United States: N. p., 1999. Web. doi:10.1063/1.480312.
Fukuto, M, Heilmann, R K, Pershan, P S, Yu, S M, Griffiths, J A, & Tirrell, D A. Structure of poly([gamma]-benzyl-L-glutamate) monolayers at the gas[endash]water interface: A Brewster angle microscopy and x-ray scattering study. United States. doi:10.1063/1.480312.
Fukuto, M, Heilmann, R K, Pershan, P S, Yu, S M, Griffiths, J A, and Tirrell, D A. Wed . "Structure of poly([gamma]-benzyl-L-glutamate) monolayers at the gas[endash]water interface: A Brewster angle microscopy and x-ray scattering study". United States. doi:10.1063/1.480312.
@article{osti_6060281,
title = {Structure of poly([gamma]-benzyl-L-glutamate) monolayers at the gas[endash]water interface: A Brewster angle microscopy and x-ray scattering study},
author = {Fukuto, M and Heilmann, R K and Pershan, P S and Yu, S M and Griffiths, J A and Tirrell, D A},
abstractNote = {This paper reports Brewster angle microscopy (BAM), x-ray specular reflectivity (XR), grazing incidence diffraction (GID) and off-specular diffuse scattering (XOSDS) measurements of Langmuir monolayers formed on water by both mono- and polydisperse samples of [alpha]-helical poly([gamma]-benzyl L-glutamate) (PBLG) as a function of area/monomer [ital A]. The microscopic behavior does not exhibit any discernible effects due to differing dispersity. At low surface densities (A[gt][approximately]21 hthinsp;[Angstrom][sup 2]/monomer, surface pressure [Pi]=0), BAM images reveal partial surface coverage by solidlike monolayer islands. GID measurements show an interhelix peak corresponding to a local parallel alignment of rodlike PBLG molecules, indicating their tendency to aggregate laterally without external pressure. Compression to A[lt]21 hthinsp;[Angstrom][sup 2]/monomer first leads to full and uniform surface coverage by the monolayer, followed by a steep rise in [Pi] that is accompanied by a decrease in the interhelix distance. Further compression results in a plateau of constant [Pi] in the [Pi]-A isotherm ([approximately]11.5[lt]A[lt][approximately]18.5 hthinsp;[Angstrom][sup 2]/monomer, [Pi][approximately]9 hthinsp;dyn/cm), which has previously been attributed to a first-order monolayer[endash]bilayer transition. The interfacial electron density profiles determined by the XR measurements on both sides of the coexistence plateau provide direct evidence for this transition. On the basis of x-ray scattering results, the film on the high-density side of the plateau is shown to consist of a newly formed incomplete and incommensurate second layer that sits on top of and has lower average density than a homogeneous first layer. GID measurements indicate that the second layer can be characterized by larger interhelix [ital d]-spacing than the first layer, while XOSDS measurements on the bilayer suggest that the second layer is microscopically inhomogeneous. For both mono- and bilayers, the analysis of observed GID peak widths indicates that the extent of lateral positional correlations between parallel PBLG rods ranges from a few to no more than [approximately]15 interhelix distances, implying short-range order. [copyright] [ital 1999 American Institute of Physics.]},
doi = {10.1063/1.480312},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = ,
volume = 111:21,
place = {United States},
year = {1999},
month = {12}
}