Spectroscopic Ellipsometry and Fluorescence Study of Thermochromism in an Ultrathin Poly(diacetylene) Film: Reversibility and Transition Kinetics

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We have investigated the thermochromic transition of an ultrathin poly(diacetylene) film. The Langmuir film is composed of three layers of polymerized 10,12-pentacosadiynoic acid [CH{sub 3}(CH{sub 2}){sub 11}C{triple_bond}CC{triple_bond}C(CH{sub 2}){sub 8}COOH] (poly-PCDA) organized into crystalline domains on a silicon substrate. Spectroscopic ellipsometry and fluorescence intensity measurements are obtained with in-situ temperature control. Poly-PCDA films exhibit a reversible thermal transition between the initial blue form and an intermediate ''purple'' form that exists only at elevated temperature (between 303-333 K), followed by an irreversible transition to the red form after annealing above 320 K. We propose that the purple form is thermally distorted blue ... continued below

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29 p.

Creation Information

Carpick, R. W.; Mayer, Thomas M.; Saski, Darryl Y. & Burns, Alan R. January 18, 2000.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

We have investigated the thermochromic transition of an ultrathin poly(diacetylene) film. The Langmuir film is composed of three layers of polymerized 10,12-pentacosadiynoic acid [CH{sub 3}(CH{sub 2}){sub 11}C{triple_bond}CC{triple_bond}C(CH{sub 2}){sub 8}COOH] (poly-PCDA) organized into crystalline domains on a silicon substrate. Spectroscopic ellipsometry and fluorescence intensity measurements are obtained with in-situ temperature control. Poly-PCDA films exhibit a reversible thermal transition between the initial blue form and an intermediate ''purple'' form that exists only at elevated temperature (between 303-333 K), followed by an irreversible transition to the red form after annealing above 320 K. We propose that the purple form is thermally distorted blue poly-PCDA, and may represent a transitional configuration in the irreversible conversion to red. This hypothesis is supported by the appearance of unique features in the absorption spectra for each form as derived from the ellipsometry measurements. Significant fluorescence emission occurs only with the red form, and is reduced at elevated temperatures while the absorption remains unchanged. Reduced emission is likely related to thermal fluctuations of the hydrocarbon side chains. Time-resolved fluorescence measurements of the irreversible transition have been performed. Using a first-order kinetic analysis of these measurements we deduce an energy barrier of 17.6 {+-} 1.1 kcal mol{sup -1} between the blue and red forms.

Physical Description

29 p.

Notes

OSTI as DE00750313

Medium: P; Size: 29 pages

Source

  • Journal Name: Langmuir; Other Information: Submitted to Langmuir

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  • Report No.: SAND2000-0158J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 750313
  • Archival Resource Key: ark:/67531/metadc706086

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  • January 18, 2000

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  • Sept. 12, 2015, 6:31 a.m.

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  • April 10, 2017, 7:09 p.m.

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Carpick, R. W.; Mayer, Thomas M.; Saski, Darryl Y. & Burns, Alan R. Spectroscopic Ellipsometry and Fluorescence Study of Thermochromism in an Ultrathin Poly(diacetylene) Film: Reversibility and Transition Kinetics, article, January 18, 2000; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc706086/: accessed September 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.