Monolayer and Brewster angle microscopy studies of poly(methyl methacrylate)-monopalmitin mixed systems at the air-water interface.
Mixed monolayers of poly(methyl metacrylate) (PMMA) and monopalmitin (Mp) were used for the study of their interactions. A thorough analysis of surface pressure (pi)-area (A) isotherms with the Langmuir monolayer technique, complemented with Brewster angle microscopy (BAM) images was performed. Mixed films show two phase transitions at a surface pressure of 14.5 mN/m and at 20-21 mN/m, respectively. Moreover, mixed monolayers show two well-defined collapses: one, corresponding to the lipid (at surface pressures of 50-51 mN/m) and the another one, ascribed to the PMMA, at surface pressure values of 57-58 mN/m. When the mean molecular areas of the mixed films (A(1,2)) were plotted versus film composition (X(1) or X(2)), positive deviations from the ideal behavior were observed at surface pressures below 15 mN/m, which were mainly attributed to a change in the conformation of the PMMA molecules at the surface. However, at higher surface pressures, the areas per monomer unit of the mixed monolayers obey the additivity rule, attributed to the fact that the film components form an immiscible system in these conditions.
Miñones Conde
Mercedes
M
Department of Optometry, School of Optics and Optometry, University of Santiago de Compostela, Campus Sur., 15706-Santiago de Compostela, Spain.
Trillo
J M
JM
Conde
Olga
O
Miñones
Jose
J
D000388:Air; D005989:Glycerides / Q000737:chemistry*; D008853:Microscopy; D010316:Particle Size; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry*
D005989:Glycerides; D014867:Water; D019904:Polymethyl Methacrylate; C027735:palmitoyl glycerol