Tethered Chains in Poor Solvent Conditions: An Experimental Study Involving Langmuir Diblock Copolymer Monolayers

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We have employed Langmuir monolayer of highly asymmetric polydimethylsiloxane- polystyrene (PDMS-PS) diblock copolymers on dioctyl phthalate (DOP) at temperatures ranging from 22 "C to -35 `C as a model system for tethered chains in poor solvent conditions. The thicknesses of the tethered PS layers extending into the DOP subphase, measured by neutron reflection, decrease with decreasing temperature (T) over this entire r~ge. However, the v~iation with T becomes weak below -20 "C. At the ]owest T, the layer thicknesses are contracted 55 % -75 `% of their values at the theta condition (T8 = 22 "C), but are still quite ... continued below

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Kent, M.S.; Lee, L.T.; Majewski, J.; Satija, S. & Smith, G.S. October 13, 1998.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Laboratories, Albuquerque, NM, and Livermore, CA
    Place of Publication: Albuquerque, New Mexico

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We have employed Langmuir monolayer of highly asymmetric polydimethylsiloxane- polystyrene (PDMS-PS) diblock copolymers on dioctyl phthalate (DOP) at temperatures ranging from 22 "C to -35 `C as a model system for tethered chains in poor solvent conditions. The thicknesses of the tethered PS layers extending into the DOP subphase, measured by neutron reflection, decrease with decreasing temperature (T) over this entire r~ge. However, the v~iation with T becomes weak below -20 "C. At the ]owest T, the layer thicknesses are contracted 55 % -75 `% of their values at the theta condition (T8 = 22 "C), but are still quite swollen compared to the fully collapsed, nonsolvent limit. The contraction of the layer with decreasing T is determined as a function of surface density and molecular weight. These data are compared to universal scaling forms. The PS segments are depleted from the air surface over the entire T range, the thickness of the depletion layer increasing slightly with decreasing T. The free energy of the surface layer is probed by surface tension measurements. Negative surface pressures are observed at low coverages for both PDMS-PS and PDMS monolayer, indicating metastability toward lateral phase separation. Evidence for a trruisition from a dispersed phase to a condensed phase with decreasing T was observed in the reflectivity at very low PDMS-PS coverage.

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  • Journal Name: Journal of Chemical Physics

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  • Other: DE00001091
  • Report No.: SAND98-2300J
  • Grant Number: AC04-94AL85000
  • DOI: 10.1063/1.475952 | External Link
  • Office of Scientific & Technical Information Report Number: 1091
  • Archival Resource Key: ark:/67531/metadc621607

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  • October 13, 1998

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  • June 16, 2015, 7:43 a.m.

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  • Dec. 2, 2016, 3:21 p.m.

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Kent, M.S.; Lee, L.T.; Majewski, J.; Satija, S. & Smith, G.S. Tethered Chains in Poor Solvent Conditions: An Experimental Study Involving Langmuir Diblock Copolymer Monolayers, article, October 13, 1998; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc621607/: accessed December 12, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.