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Three vinyl-functionalized phosphine oxide photoinitiating monomers have been synthesized:  4-vinylbenzoyldiphenylphosphine oxide (VBPO), 2,6-dimethyl-4-vinylbenzoyldiphenylphosphine oxide (DMVBPO), and 2,4,6-trimethylbenzoylphenyl-4-vinylphenylphosphine oxide (TMBVPO). VBPO was copolymerized with vinylpyrrolidone or vinyl acetate (PPI-1a) and dimethylacrylamide (PPI-1b). DMVBPO and TMBVPO were both copolymerized with dimethylacrylamide (PPI-2 and PPI-3, respectively). The choice of vinylphosphine oxide and comonomer(s) had a significant influence on the properties of the resulting PPI. PPI-1a was not stable in solution in 2-hydroxyethyl methacrylate (HEMA), whereas the VBPO-dimethylacrylamide (DMA) copolymer (PPI-1b) was stable in HEMA but not stable in aqueous solutions. PPI-2 was both soluble and stable in water up to 22 months. PPI-1a was as effective as trimethylbenzoyldiphenylphosphine oxide (TPO, BASF Lucirin). PPI-2 was more effective in the polymerization of HEMA/water mixtures than PPI-3. PPI-2 and PPI-3 acted as self-cross-linking species, resulting in the formation of hydrogels; PPI 3 was more effective in this. PPI-2 was very effective in forming hydrogels based on poly(ethylene glycol) diacrylate.

The possibilities to develop an injectable hydrogel lens were investigated. Aqueous solutions of reactive polymers in combination with a water-soluble blue light photoinitiator were transformed into hydrogels by irradiation with blue light. Poly(ethylene glycol) diacrylates (PEGDA) with low molecular weights and an acrylate modified copolymer of N-vinylpyrrolidone and vinyl alcohol with a high molecular weight were used as reactive polymers. A copolymer of (4-vinyl-2,6-dimethylbenzoyl)diphenylphosphine oxide and dimethylacrylamide was used as a water-soluble blue light photoinitiator. PEGDA showed high reactivity and the hydrogels were more transparent than the natural lens. The mass loss and the additional swelling of the hydrogel were 1.0 and 4.0%, respectively. The refractive index of these hydrogels was 1.40, lower than that of natural lens. The viscosity of the solutions before cross-linking was too low for injection into the capsular bag. Hydrogels based upon the copolymer had a transmission comparable to a 25-year-old natural lens. The materials showed no mass loss and the additional swelling after curing was less than 1%. The refractive index was comparable to that of the natural lens (1.42). The viscosity of the polymer solutions was sufficient for injection into the capsular bag without leakage.