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A new method of preparing gradient refractive-index (GRIN) rods by using the swollen-gel polymerization technique is discussed. The polymerization of methyl methacrylate with benzyl methacrylate (BzMA) was carried out in a poly(methyl methacrylate) tube. The diffusion of the higher-refractive-index monomer BzMA in the swollen gel led to the formation of a GRIN distribution. After complete polymerization, a good symmetric and bubble-free GRIN rod was fabricated. An image with no distortion can be observed through the GRIN rods prepared by swollen-gel polymerization.

SUMMARY: The swollen-gel copolymerization of methyl methacrylate (MMA) with benzyl methacrylate (BzMA) was carried out in a poly(methyl methacrylate) tube in the presence of dicumyl peroxide (DCPO). The diffusion of the higher-refractive-index monomer BzMA into the swollen gel leads to the formation of a refractive index gradient (GRIN). After complete polymerization, a symmetric and bubble-free GRIN optical rod was obtained. It was found that high initiator concentrations cause a great shrinkage during polymerization and lead to the formation of bubbles. A long swelling process (t A 24 h) will cause the deformation of the cylindrical shape of the PMMA tube. The influence of initiator concentration, swelling temperature, swelling time, and polymerization temperature on the optical characteristics of the GRIN rods was investigated. An image with no distortion is observed through the GRIN rods prepared in this investigation. Resolution of 50 lm parallel lines transmitted through the GRIN rod was also examined.

A new method for preparing gradient refractive index (GRIN) rods by using the swollen-gel polymerization technique was elaborated. The polymerization of MMA (methyl methacrylate) with BSA (benzyl salicylate) was carried out in the presence of BPO (benzoyl peroxide) in a PMMA (poly(methy1 methacrylate)) tube. The three-dimensional refractive index profile of plastic rods was estimated. The dependence of optical properties of the GRIN rod on swelling time, swelling temperature, polymerization temperature and MMA/BSA feed ratio were investigated. Image transmission without distortion is observed through the GRIN rods fabricated in this investigation.

A new method for preparing light‐focusing plastic rod with gradient refractive index (GRIN) profile was fabricated by using the swollen‐gel polymerization technique. Monomer pair systems of methyl methacrylate (MMA) with reactive benzyl methacrylate and unreactive bromonaphthalene, benzyl phenyl acetate, benzyl salicylate, triphenyl phosphate, and dibromobenzene were investigated. It was found that refractive index difference and numeric aperture (NA) values of MMA with an unreactive agent are larger than those of a reactive agent system, and a high NA value of 0.336 in a system of MMA/BN = 2/1 was obtained. A distortion‐free image can be observed through GRIN rods fabricated by using the swollen‐gel polymerization method. Optical characteristics of the GRIN rod were also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 849–854, 1997