Templating Hollow Polymeric Spheres from Catanionic Equilibrium Vesicles:  Synthesis and Characterization

Abstract

Hollow polymer spheres of styrene and divinyl benzene can be templated from catanionic equilibrium vesicles formed by cetyltrimethylammonium tosylate (CTAT) and sodium dodecylbenzenesulfonate (SDBS) or cetyltrimethylammonium bromide (CTAB) and sodium octyl sulfate (SOS). Characterization by many methods suggests the microstructure of the equilibrium vesicle template is left largely intact in the final polymer product. The particles have an average radius of ca. 60 nm and a membrane shell less than 10 nm thick. The cross-linked hollow polymer vesicles are robust and withstand complete drying and resuspension in water with no apparent change in microstructure. The polymer membrane surfaces can be functionalized by sulfonation or surfactant adsorption, and this functionalization prevents aggregation of the polymer particles when they are resuspended in water.

Preparation of block copolymer vesicles in solution

“…108 The polyelectrolytes were applied to the surfaces of the particles by layer-by-layer sequential adsorption and produced stable, hollow capsules ranging in size from approximately 1 to 11 m. Hollow polymer spheres ranging in size from several tens of nanometers up to hundreds of micrometers can be created by the crosslinking polymerization of hydrophobic monomers inside dimethyldioctadecylammonium chloride vesicles, followed by the removal of the surfactant matrix. 97 Similarly, McKelvey et al 101 created styrene and divinyl benzene hollow polymer spheres from cationic vesicles produced from a mixture of anionic and cationic surfactants. The approximately 60 nm vesicles, with a wall thickness of 3-9 nm, retained their original structure even after vacuum drying and resuspension in water.…”

Pharmaceutical applications for catanionic mixtures

“…Polymerization can be achieved either by having an amphiphile containing a polymerizable group (Hirano et al 1991;Chung & Chung 2002;Chung et al 2003bChung et al , 2004aLiu et al 2003), or by the addition of separate polymerizable monomers within the surfactant bilayer (Morgan et al 1997). The latter technique has mainly been used to produce hollow polymer spheres (McKelvey et al 2000;McKelvey & Kaler 2002), which will be presented below. Hirano et al (1991) studied the vesicle stability after polymerization of the ion pair amphiphile N, propyl]ammonium stearate, the structure of which is displayed in Figure 7.…”

“…The method developed by Morgan et al (1997) has been used for the synthesis of hollow polymer spheres (McKelvey et al 2000;McKelvey & Kaler 2002). Particles with an average radius of 60 nm and a shell thickness of 10 nm were made using styrene and divinyl benzene in the system CTAT/SDBS and CTAB/SOS (McKelvey et al 2000).…”

Nanofabrication in polymer matrices

“…While such spherical surfactant vesicles could and have been used for the polymerization of hollow polymer spheres by incorporating a polymerizable group into the surfactant itself, Kaler and co-workers [138] succeeded to devise a templating process involving standard monomers such as styrene (with divinyl benzene as crosslinker), swelling the organic bilayer of vesicles formed by standard surfactants, with subsequent polymerization to form hollow polymer spheres. The surfactant combinations used for forming the vesicles were cetyltrimethylammonium tosylate (CTAT) with sodium dodecylbenzenesulfonate (SDBS), and cetyltrimethylammonium bromide (CTAB) with sodium octyl sulfate (SOS), respectively.…”

“…The hollow spheres were found to be quite robust against treatments like drying and resuspending in water. Various surface modification strategies were discussed in order to stabilize the aqueous suspensions of these hollow polystyrene spheres [138].…”