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Stimuli-responsive emulsion stabilized by amphiphilic block copolymers for drug delivery systems

Laboratoire Sciences et Ingénierie de la Matière Molle, (SIMM)

Adresse:ESPCI, 10 Rue Vauquelin 75005 Paris

Directeur du laboratoire : Christian Frétigny

Responsables du stage : Patrick Perrin et Nadège Pantoustier

Contact : Patrick Perrin - 01 40 79 46 42/ Nadège Pantoustier - 01 40 79 44 17

   

Projet scientifique :
Emulsions (out-of-equilibrium mixtures of oil and water stabilized by surfactants) are a very important subject in applied science due fact that they bring together two incompatible liquids. In particular, there is a special need for designing stimulable emulsions where an oil-in-water phase (O/W) can be switched into a water-in-oil phase (W/O) by external stimulus. Multiple emulsions (like W/O/W phase) are more complicated to stabilize on the long run and this has limited their practical importance. However their potential is important either in drug delivery or in cosmetics and food industry. In our laboratory, we have designed a class of new amphiphilic copolymers which are able to stabilize such emulsions. These copolymers are made of a poly(styrene) block (PS) and of a statistical block of PS and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA) by controlled radical polymerization. At low pH and low temperatures, such copolymers stabilize O/W phases while at higher pH and temperatures W/O phases are found if the copolymer is enough hydrophobic. This change of phases is dynamical since, when prepared at pH around 6, a rise in the temperature induces a transition from an O/W to a W/O phase [1] while decreasing the temperature reverses the transition. More recently, we have explored in greater detail the pattern of phases for O/W emulsions and discovered that very stable multiple emulsions are also stabilized by such copolymers. This is very intriguing phenomenon since usually two kinds of surfactants are needed for the formation of stable multiple emulsions. The pH range where such multiple emulsions appear is highly dependent on the polymer architecture. We thus propose to extend our knowledge in studying the effect of the molar mass of the copolymers on the encapsulation potential of the multiple emulsions. Varying this parameter is very challenging and may give a much better fondamental understanding of the making of multiple emulsions for encapsulation applications, in particular in cosmetics or pharmaceutical industries.


Techniques utilisées : Synthesis of block copolymers by atom transfer radical polymerization (ATRP), Size Exclusion Chromatography (SEC), Differential scanning calorimetry (DSC), emulsification process, Scanning electronic microscopy (SEM), optical microscopy

Expected results : Synthesis and characterization of styrene and (2-dimethylamino)ethyl methacrylate based copolymers ; Diagrams of emulsion type as a function of pH, ionic strength, temperature and copolymer molar mass.
Références :
- L. Besnard et al. Advanced Materials, 25(20), 2844-2848 (2013) ; Soft Matter, 10, 7073-7087 (2014)
- M. Protat et al. Langmuir, 32, 10912-10919 (2016)

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