Synthesis and characterization of crosslinked uniform polymeric microspheres containing a polyimide prepolymer by a new emulsification process

A highly crosslinked poly(styrene–divinyl benzene–trimethyolpropane trimethacrylate) microsphere containing a polyimide prepolymer (PIP) was prepared by a new emulsification method, Shirasu porous glass (SPG) membrane emulsification, and a subsequent radical suspension polymerization. That is, a mixture of styrene, divinyl benzene, trimethyol propane trimethacrylate (TMPTMA), and PIP containing an initiator was permeated through the uniform pores of the SPG membrane into a continuous phase containing a stabilizer to form uniform droplets. Then, the suspension polymerization was carried out at 65 °C for 24 h. The trifunctional crosslinker TMPTMA was added to enhance the destructive strength of the microsphere, and PIP was incorporated into the microsphere to provide an adhesion force by a known self‐curing reaction at 220 °C. The effects of the feed amounts of TMPTMA and PIP on the monomer conversion, size distribution, and destructive strength of the microsphere were investigated. The monomer conversion increased with an increase in TMPTMA. The particle size distribution became narrower as the TMPTMA feed amount increased, but it became broader with an increase in PIP. The destructive strength increased with increases in TMPTMA and PIP. After a heat treatment at 220 °C, the destructive strength decreased because of the heat degradation of the polymer. The addition of TMPTMA suppressed the heat degradation, and PIP could undergo self‐curing at 220 °C. The obtained highly crosslinked uniform microsphere containing PIP has potential applications in liquid‐crystal displays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2588–2598, 2003 A highly crosslinked poly(styrene–divinyl benzene–trimethyolpropane trimethacrylate) microsphere containing a polyimide prepolymer (PIP) was prepared by a new emulsification method, Shirasu porous glass membrane emulsification, and a subsequent radical suspension polymerization. A trifunctional crosslinker, trimethyol propane trimethacrylate (TMPTMA), was added to enhance the destructive strength of the microsphere, and PIP was incorporated into the microsphere to provide an adhesion force by a known self‐curing reaction at 220 °C. A particle with a narrow size distribution of around 12% was obtained. The destructive strength increased with increases in the feed amounts of TMPTMA and PIP. The obtained highly crosslinked uniform microsphere containing PIP has potential applications in liquid‐crystal displays.