Showing papers by "Yoshiyuki Okamoto published in 2008"

Copolymers of methyl methacrylate and fluoroalkyl methacrylates: Effects of fluoroalkyl groups on the thermal and optical properties of the copolymers

Abstract: Fluoroalkyl methacrylates, 2,2,2-trifluoroethyl methacrylate (1), hexafluoroisopropyl methacrylate (2), 1,1,1,3,3,3-hexafluoro-2-methyl-2-propyl methacrylate (3), and perfluoro t-butyl methacrylate (4) were synthesized. Homopolymers and copolymers of these fluoroalkyl methacrylates with methyl methacrylate (MMA) were prepared and characterized. With the exception of the copolymers of MMA and 2,2,2-trifluoroethyl methacrylate (1), the glass transition temperatures (Tgs) of the copolymers were found to deviate positively from the Gordon-Taylor equation. The positive deviation from the Gordon-Taylor equation could be accounted for by the dipole–dipole intrachain interaction between the methyl ester group and the fluoroalkyl ester group of the monomer units. These Tg values of the copolymers were found to fit with the Schneider equation. The fitting parameters in the Schneider equation were calculated, and R2 values, the coefficients of determination, were almost 1.0. The refractive indices of the copolymers, measured at 532, 633, and 839 nm wavelengths, were lower than that of PMMA and showed a linear relationship with monomer composition in the copolymers. 2 and MMA have a tendency to polymerize in an alternating uniform monomer composition, resulting in less light scattering. This result suggests that the copolymer prepared with an equal molar ratio of 2 and MMA may have useful properties with applications in optical devices. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4748–4755, 2008

Design and synthesis of graded index plastic optical fibers by copolymeric system

Abstract: Graded index plastic optical fibers (GI POF) based on the copolymer of 2,3,5,6-tetrafluorophenyl methacrylate (TFPMA) and methyl methacrylate (MMA) were prepared. The copolymers of 10 wt% and 20 wt% of TFPMA with MMA were prepared in bulk using di-tert-butyl peroxide as the radical initiator at 90–120°C for 48 hr. The glass transition temperatures (Tg) of the copolymers were 115 and 118°C, and the refractive indexes were 1.4912 and 1.4901 at 589 nm, respectively. The transmittances of the copolymers were a slightly higher than that of pure PMMA. Copolymer tubes (diameter 18 mm, length 600 mm) were prepared by the copolymerization of TFPMA (10 and 20 wt%) with MMA (90 and 80 wt%) as the cladding of the optical fiber. In order to prepare GI POF based on these copolymers, a high refractive index compound, diphenyl sulfide (DPS) , was added to the mixture of the monomers in the tube (as a core material) and then copolymerized by an interfacial gel polymerization technique. The material dispersion and optimum index exponent g were calculated and found to be very close to that of GI POF prepared from pure PMMA. The obtained copolymer preforms were drawn by heating at 220–250°C with controlling of drawing velocity. The resulting fiber diameter was 0.75 mm and the length was 50–150 m. The attenuation spectra of the fibers were measured and found to be similar to GI POF prepared using pure PMMA. The results indicate that the core material of GI POF can be prepared by a copolymer system in which the refractive indexes of homopolymers are very close to each other and the monomers yield a random copolymer. Copyright © 2008 John Wiley & Sons, Ltd.