Several new classes of triarylsulfonium salts have been discovered which possess enhanced efficiency as photoinitiators of cationic polymerization. One of these compounds was identified among the components of the Friedel Crafts reaction of benzene with sulfur monochloride and chlorine. Specific new syntheses were developed and are described for the synthesis of these compounds in high yields. The development of several new thermal initiator systems for cationic polymerization based on dialkyl-4-hydroxyphenylsulfonium and dialkylphenacylsulfonium salts is also discussed. KEY WORDS Photoinitiated Cationic Polymerization I Triarylsulfonium Salts I Diphenyl-4-thiophenoxyphenylsulfonium Salts I Thermally Initiated Cationic Polymerization I Dialkyl-4-hydroxyphenylsulfonium Salts I Dialkylphenacylsulfonium Salts I

Aims: To evaluate in vivo fibroplasia and biological stability of porous polymers intended for use in the Seoul-type keratoprosthesis (S-KPro). Methods: Four porous polymers (polypropylene, two kinds of polyethylene terephthalate (PE70 and PE50), and polyurethane) were investigated. Discs of polymers were inserted into the corneal stroma of rabbits for a 2 and 5 month period. Corneal oedema and neovascularisation were evaluated. The fibroplasia and collagen deposition were examined under light and transmission electron microscopy. S-KPros, whose skirt was made of four types of polymer, were implanted into the rabbits' eyes. The retention time and complications were evaluated. Results: Neovascularisation and corneal oedema were found in all of the disc inserted eyes, but the corneal oedema subsided within 2 months in most of the eyes. The mean number of fibroblasts increased significantly in polypropylene and PE50 disc inserted eyes compared with polyurethane disc inserted eyes. Plentiful collagen deposition was also found in both polypropylene and PE50 disc inserted eyes. Mean retention time in the polypropylene SK-Pro implanted eyes was longer than that of the other eyes (20.7 weeks). The PE70 skirt induced corneal melting around the prosthesis. Conclusion: Polypropylene encourages fibroblast ingrowth and shows good biological stability when used as a skirt material in S-KPro.T he most common problem associated with keratoprosthesis (KPro) implantation results from an inadequate integration between the peripheral edge of the device and the residual rim of the host cornea. From the time that Barber first examined cellular ingrowth into the carbon fibre Teflon composite Propoplast in interlamellar pockets, 1 many different materials intended for use in a KPro have been evaluated as to their biocompatibility, especially with respect to fibroplasia. 2-5The Seoul-type keratoprosthesis (S-KPro) which is composed of a PMMA cylinder and a porous polymer skirt is being developed in our laboratory.6 A major characteristic of the S-KPro is a double fixed design, which includes the anchoring sutures of a skirt to the cornea and ab internal scleral fixation of the haptics, which synergistically improves the mechanical biostability (Fig 1). Therefore, the skirt, which is anchored to the cornea, does not need to serve as a strong support. An adequate coaptation with the surrounding cornea is emphasised in our model rather than a role as a support. We are currently attempting to find a material that enhances fibroblast migration even though it may have low tensile strength. Initially, polyurethane was used for the S-KPro skirt, because the fabrication of its pore size is easily controlled to allow fibroblast invasion.7 However, the polyurethane skirt was found to degenerate in a keratoprosthetic human eye after a long period. Therefore, we tried to find another porous material, which is biologically stable and allows more fibroblast invasion than polyurethane. Our goal was to compare the biological response, especially the fi...