Polyurethane-block-polystyrene prepared by polymerization in miniemulsion

Waterborne polyurethane-block-polystyrene latexes were prepared by miniemulsion polymerization in a single batch. A direct miniemulsion of the monomers mixture containing styrene, IPDI, 2,4-diethyl-1,5-pentanediol and a diol-functionalized azoinitiator was prepared in water. The polyaddition reaction of the PU was then performed in a first step at room temperature, with the help of the catalysts mixture DBTDL/ DMDA, yielding a PU macroazoinitiator. In a second step, the miniemulsion was heated to 72 degrees C to start the radical polymerization of styrene from the macroazoinitiator chains. The polymers obtained from the miniemulsion were fractionated and each fraction was analyzed by GPC, DSC and H-1 NMR spectroscopy. It was shown that 45% of a (linear) copolymer consisting of a PU and PS was obtained, which is a good compatibilizer for PU/PS polymer blends. TEM from the polymer particles in miniemulsion revealed a homogeneous structure inside the particles.