From molecular flexibility to shape, curvature and thermotropic transitions in pure surfaces |
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Authors: | B Bassetti CA Mantica P Jona |
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Institution: | (1) Università degli Studi di Milano, Dipartimento di Fisica, Via Celoria 16, 20123 Milano, Italia, IT;(2) Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20123 Milano, Italia, IT |
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Abstract: | A material surface of pure constituents with a flexible molecular chain (amphiphilics) is considered; thermodynamic behaviour
is studied in the chain length-temperature plane. The Hamiltonian of the system is modelled as the sum of a formation term
which refers to the polymer nature of the chain, and of a fluctuation term with a specific elastic form. For closed systems
the model exhibits phases with uniform curvature and conformational order/disorder or, alternatively, modulated phases; a
critical chain length is found for the existence of modulated phases; the dependence of transition temperature on energy parameters
is determined. A critical region is found for open systems, where conformational disorder drives spontaneous generation of
curvature; this lies above a characteristic chain length and around the shape transition temperature.
Received: 13 November 1996 / Revised: 9 May 1997 / Received in final form: 4
November 1997 / Accepted: 10 November 1997 |
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Keywords: | PACS 64 60 -i General studies of phase transitions- 68 35 Rh Phase transitions and critical phenomena- 87 22 -q Physics of cellular and physiological processes |
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