Semi-batch synthesis of colloidal spheres with fluorinated cores and varying grafts of poly(ethylene glycol).

Fluorinated spheres with grafted poly(ethylene glycol) (PEG) have been synthesized using a semi-batch emulsion polymerization in which the initiator is fed slowly to the reaction. In this way, PEG-grafted colloidal spheres can be fabricated with varying PEG chain length, different cores and varying degrees of crosslinking. The resulting batches have been characterized using disc centrifuge photosedimentometry and small-angle X-ray scattering. The size distribution is shown to be a sensitive function of the molar ratio of the reactive PEG macromonomer to fluorinated monomer, and with some optimization latices of very low polydispersity can be obtained with this simple synthesis method. For short PEG grafts too high a molar ratio results in a build up of smaller size particles and a broadening of the size distribution, whereas for longer grafts the mean particle size increases with decreasing molar ratio.