Thermodynamics of Confined Perfluoropolyether Films on Amorphous Carbon Surfaces Determined from the Time-Dependent Evaporation Kinetics

Autor:	R. J. Waltman, G. W. Tyndall
Rok vydání:	2000
Předmět:	Reaction rate constant Materials science Amorphous carbon Kinetics Materials Chemistry Evaporation Perfluoropolyether Thermodynamics Molar mass distribution Physical and Theoretical Chemistry Desorption kinetics Surfaces Coatings and Films
Zdroj:	The Journal of Physical Chemistry B. 104:7085-7095
ISSN:	1520-5207 1520-6106
Popis:	The thermodynamics of ultrathin (≤10 A) perfluoropolyether (PFPE) films in contact with amorphous carbon surfaces (CHx and CNx) are derived from the time-dependent kinetics of film evaporation. Two nonfunctionalized PFPE structures were studied: a polydisperse (Mw/Mn = 1.4) Fomblin Z with an average molecular weight of 4000 g mol-1 and a fractionated (Mw/Mn = 1.05) Demnum sample of average molecular weight 2200 g mol-1. Data is also presented for the evaporation of a fractionated (Mw/Mn = 1.08) sample of the hydroxyl-terminated Fomblin Zdol (Mw = 2100 g mol-1). Evaporation of the nonfunctionalized PFPEs from amorphous carbon follows nonclassical, first-order desorption kinetics having a rate constant that varies inversely with time. Evaporation of the functionalized Fomblin Zdol is also nonclassical; however, the time dependence of the rate constant deviates substantially from that characteristic of the nonfunctionalized PFPEs. These evaporation kinetics result from the increase in the surface free energ...
Databáze:	OpenAIRE
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