title: Phase transitions in polymer monolayers: Application of the Clapeyron equation to PEO in PPO-PEO Langmuir films.
abstract: In this paper we investigate the application of the two-dimensional Clapeyron law to polymer monolayers. This is a largely unexplored area of research. The main problems are (1) establishing if equilibrium is reached and (2) if so, identifying and defining phases as functions of the temperature. Once this is validated, the Clapeyron law allows us to obtain the entropy and enthalpy differences between two coexisting phases. In turn, this information can be used to obtain insight into the conformational properties of the films and changes therein. This approach has a wide potential for obtaining additional information on polymer adsorption at interfaces and the structure of their monolayer films. The 2D Clapeyron law was applied emphasizing polyethylene oxide (PEO) in polypropylene oxide (PPO)-PEO block copolymers, based on new well-defined data for their Langmuir films. Values for enthalpy per monomer of 0.12 and 0.23 kT were obtained for the phase transition of two different PEO chains (Neo of 2295 and 409, respectively). This enthalpy was estimated to correspond to 1.2±0.4 kT per EO monomer present in train conformation at the air/water interface.
authors.affiliation: Food Research and Development Centre, 3600 Casavant Blvd West, Saint-Hyacinthe, QC J2S 8E3, Canada.
authors.forename: Louise
authors.initials: L
authors.lastname: Deschênes
authors.affiliation: Laboratory for Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, Netherlands.
authors.forename: Johannes
authors.initials: J
authors.lastname: Lyklema
authors.affiliation: Food Research and Development Centre, 3600 Casavant Blvd West, Saint-Hyacinthe, QC J2S 8E3, Canada.
authors.forename: Claude
authors.initials: C
authors.lastname: Danis
authors.affiliation: Food Research and Development Centre, 3600 Casavant Blvd West, Saint-Hyacinthe, QC J2S 8E3, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Saint-Germain
keywords: Clapeyron; Monolayers; PEO; PPO; Phase transition