Formation of polymeric microspheres using electron beam radiation

Polymeric particulates are currently being produced by a variety of different techniques. This new approach illustrates the formation of cross‐linked polymeric microspheres by incorporating trimethylolpropane propoxylate triacrylate (a radiation‐sensitive monomer) into a polyaphron system and exposing it to electron beam radiation. Polyaphrons are essentially a collection of droplets encapsulated in a very thin aqueous film dispersed in a aqueous matrix. This film gives extreme stability to the system, which allows for extremely high dispersed‐phase concentrations. The formation of polyaphrons requires the presence of a surfactant in both the dispersed (monomer) and continuous (aqueous) phases. The effects of monomer‐phase concentration, monomer‐ and acqueous‐phase surfactant concentration, aqueous‐phase surfactant type, and preparation temperature were studied to gain an understanding of the conditions that promote the formation of polymeric microspheres with a narrow size distribution. Polymeric microspheres ranging from 2 to 40 microns in diameter were formed with monomer concentrations as high as 67 vol % without any aphron bridging occurring or need for agitation to keep the monomer‐phase dispersed in the aqueous matrix. In addition, the ability to reduce the wettability of the microspheres is demonstrated through incorporation of a polymerizable fluorinated acrylate in the dispersed phase.