PARTICLE-SIZE AND MONOMER PARTITIONING IN MICROEMULSION POLYMERIZATION - 2 - ONLINE SMALL-ANGLE NEUTRON-SCATTERING STUDIES

Polymerization of n-hexyl methacrylate (C(6)MA) in aqueous microemulsi ons made with mixed dodecyltrimethylammonium bromide (DTAB) and didode cyldimethylammonium bromide (DDAB) surfactants yields very small (simi lar to 30 nm) latex particles of high molecular weight polymer. The re sults of an online small-angle neutron scattering (SANS) experiment ha ve verified some of the assumptions of a simple but accurate kinetic m odel that has been recently proposed for aqueous microemulsion polymer ization. The SANS results also support the predictions of an analytica l model that describes the evolution of the chain length and particle size distribution throughout the polymerization. During the microemuls ion polymerization of C(6)MA, the monomer does not significantly swell the polymer particles. A model of the reacting particle as a polymer core surrounded by a monomer-rich shell is consistent with both the ki netic and SANS data if the monomer concentration in the shell is equal to that in the core of the swollen micelles.