Emulsion polymerization of hydrophobic monomers like stearyl acrylate withcyclodextrin as a phase transfer agent

In emulsion polymerization also water insoluble hydrophobic monomers like s tearyl acrylate can be used if cyclodextrin is added as a phase transfer ag ent. The characterization of the corresponding emulsion polymers by thermal analysis with DSC, by molecular weight determination with SEC and by measu ring particle size distribution, particle density distribution (i.e. chemic al composition and heterogeneity) and free cyclodextrin molecules in the aq ueous phase with the analytical ultracentrifuge provides first indications for the following mechanism: An especially high transfer resistance exists for longer alkyl chains containing molecules at the interface between the m onomer droplet and the water phase resulting in a concentration decrease in the polymerizing particle. Therefore, it is assumed that cyclodextrin and its ability to form a water soluble complex with hydrophobic molecules redu ce the kinetic barrier and makes it easier for the stearyl acrylate to leav e the monomer droplet. After arriving at the surface of the growing particl e, the stearyl acrylate is released from the complex and able to enter it. Now the free cyclodextrin can start its transport function again. Only 5 wt .-% of cyclodextrin is necessary to polymerize almost 100% of stearyl acryl ate.