Surface Phase Behavior of Poly(tert-butyl methacrylate)−Fatty Acid Glyceride Binary Mixtures as Monolayers at the Air−Water Interface

Abstract

Mixtures of poly(tert-butyl methacrylate) (PtBMA) and the lipids monoolein, diolein, and triolein spread as monolayers at the air−water interface have been used as models to examine the surface phase behavior of lipid−polymer mixtures as a function of lipid structure, polymer molecular weight (17K to 3400K), and mixture composition. A measure of miscibility and polymer−lipid interactions was obtained through analysis of surface pressure−area isotherms and by direct observation with fluorescence microscopy. At all molecular weights of PtBMA, for the polymer alone and in mixtures, identical surface pressure−area isotherms were obtained when area was expressed on a per monomer basis, indicating that all monomer segments were located at the interface and equally accessible to the lipid molecules. Through thermodynamic analysis, it was found that monoolein, with two hydroxyl groups, formed nonideal miscible mixed monolayers with PtBMA under what appear to be good solvent conditions. Diolein, with one hydroxyl group, behaved very much as a ϑ solvent, forming nearly ideal homogeneous monolayers, while a lack of affinity between triolein and PtBMA due to poor hydrogen bonding led to surface phase separation at higher surface pressures, consistent with poor solvent conditions.

Spectroscopic characterizations of non-amphiphilic 2-(4-biphenylyl)-6-phenyl benzoxazole molecules at the air–water interface and in Langmuir–Blodgett films

“…2 two component systems was established by analyzing the p-A isotherm of the pure components as well as the binary mixtures [37]. The excess areas of mixing A E which provides a measure of nonideality, were calculated as a function of surface pressure, mixture of composition and the molecular weight using the additivity rule [38][39][40] …”

“…It is important to note that in bulk binary miscible mixtures if two liquids are ideally miscible, it usually means that they are physically and chemically similar, so that the intermolecular forces of these two components are identical and the presence of the solute does not affect the solvent molecules. However, complete immiscibility means strong attractive interactions among like molecules and almost no interaction between the unlike molecules [37]. The existence of strong attractive interaction among PBBO molecules may lead to the formation of clusters and aggregates.…”

Monolayer Characteristics of Chitosan Assembled in Langmuir Films Mixed With Arachidic Acid

“…On the other hand the AA monolayer film shows no hysteresis [figure not shown] with overlapping compression -expansion isotherm. This is expected for long chain fatty acids, as they form stable monolayer films 36 . On the other hand, at the higher mole fraction in the mixed film the number of CHS moiety increases.…”

“…Such liquid expanded phases were also reported for several other molecules in Langmuir monolayer and explained due to the occurrence of certain reorientation of the constituent molecule in the monolayer [34][35] . In order to have more information about the AA-CHS mixed monolayer, we have studied the mixing behaviour using additivity and surface phase rule [36][37] . It relevant to mention in this context that the thermodynamic nature of the mixing of various two component systems can be established by analyzing the pressure versus area per molecule isotherm of the pure components as well as the binary mixtures 36 .…”

“…In order to have more information about the AA-CHS mixed monolayer, we have studied the mixing behaviour using additivity and surface phase rule [36][37] . It relevant to mention in this context that the thermodynamic nature of the mixing of various two component systems can be established by analyzing the pressure versus area per molecule isotherm of the pure components as well as the binary mixtures 36 . The excess areas of mixing A E which provides a measure of non-ideality can be calculated as a function of surface pressure, mixture of composition and the molecular area using the additivity rule 37 figure 1, a noticeable deviation from the additivity rule is observed, which is an indication of interaction among the constituent molecules of the binary mixture in the mixed monolayer.…”