Interfacial properties of a PEG2000-PLA50 diblock copolymer at the air/water interface

In this paper, we compared the interfacial behaviors of spread films of pol y(ethylene glycol) (PEG2000), poly(D,L-lactide) (PLA50), and a mixture of P EG2000 and PLA50, to understand the properties of a PEG2000-PLA50 diblock c opolymer at the air/water interface. This was achieved (i) by analyzing the surface pressure-surface area curves obtained on a Langmuir trough and (ii ) by modeling the dilatational properties of the films according to a modif ied Maxwell model. The properties of the films composed of a mixture of PEG 2000 and PLA50 showed the influence of PEG2000 before the nucleation transi tion of PLA50. Then, increasing the lateral compression of the mixed monola yer led to the expulsion of PEG2000 segments with presumably their irrevers ible desorption into the bulk. In the case of the copolymer, the covalently bound PEG2000 segments were segregated at low surface coverage forming a s table film with the PEG corona oriented toward the water phase. This situat ion was conserved until high surface coverage (10-15 mN/m). Afterward, comp ression led to the penetration of PEG2000 into the tridimensional layer ori ented toward the air/phase. These results allow better understanding and mo dulation of the composition and the hydrophilic character of interfaces for med during emulsion processes and thus improvement of the control of the su rface properties of drug delivery systems.