Copolymerization Behaviour and Structure of Styrene and Polymerizable Surfactants in Three-Component Cationic Microemulsion

Michael Dreja^$, Wim Pyckhout-Hintzen^#, and Bernd Tieke^$*

^$Institut für Physikalische Chemie, Universität zu Köln, Luxemburger Strasse 116, D-50939 Köln, Germany, and ^#Institut für Festkörperforschung, Forschungszentrum Jülich (KFA), Postfach 1913, D-52425 Jülich, Germany

Received July 31, 1997

Revised Manuscript Received October 31, 1997

Abstract:

The copolymerization and structural properties of the ternary o/w-microemulsions formed from water, styrene and (11-(acryloyloxy)undecyl)trimethylammonium bromide or (2-(methacryloyloxy)ethyl)dodecyldimethylammonium bromide as cationic polymerizable surfactants are investigated. The two surfactants contain the polymerizable group either at the hydrophobic tail (T-type) or at the hydrophilic head group (H-type) and form micellar structures in aqueous solution. Upon addition of styrene, transparent, globular o/w-microemulsions are formed without any addition of a cosurfactant. The microemulsions can be polymerized upon gamma-irradiation at room temperature. Copolymers with completely different morphology are obtained. With styrene and the T-type surfactant, very small nanolatex particles are formed similar to microemulsion polymerization of styrene and nonpolymerizable surfactants. In contrast, copolymerization of styrene and the H-type surfactant monomer results in transparent nanogels with high water content. The structure of the micelles and o/w-microemulsions before and after polymerization was studied using small-angle neutron scattering (SANS), while the copolymer structure was analyzed using NMR and IR spectroscopy. SANS experiments show that in the water/H-type surfactant/styrene system the overall structure of the parent microemulsion is largely preserved whereas in the T-type system distinct changes are observed. Structure models are presented which take into account the different properties of the resulting polymer materials at both a macroscopic and a microscopic length scale.