Initiator-fragment incorporation radical polymerization of ethylene glycol dimethacrylate in the presence of 1,1-diphenylethylene: synthesis and characterization of soluble hyperbranched polymer nanoparticles

The polymerization of ethylene glycol dimethacrylate (EGDMA) as crosslinker was carried out at 70 and 80 degreesC in benzene using dimethyl 2,2'-azobisisobutyrate (MAIB) as initiator at concentrations as high as 0.50-0.70 mol l(-1) in the presence of 1,1-diphenylethylene (DPE), where the concentrations of EGDMA and DPE were 0.50-0.70 and 0.25-0.50 mol l(-1), respectively. The polymerization proceeded homogeneously, without gelation, to give soluble polymers. The yield and molecular weight of the resulting polymers increased with time. The homogeneous polymerization system involved ESR-observable DPE-derived radicals of considerably high concentration (3.6-5.3 x 10(-5) mol l(-1)). The methoxycarbonylpropyl groups as MAIB-fragments were incorporated as a main constituent (35-50 mol%) into the polymers (initiator-fragment incorporation radical polymerization). The polymers also contained DPE units (15 mol%) and EGDMA units with double bonds (10-25 mol%) and without double bonds (20 mol%). Results from gel permeation chromatography (GPC)-multiangle laser light scattering (MALLS), transmission electron microscopy (TEM) and viscometric measurements revealed that the individual polymer molecules were formed as hyperbranched nanoparticles. (C) 2004 Society of Chemical Industry.