As a novel material of low loss and high thermal stability, a graded index plastic optical fiber (GI POF) comprised of a copolymer of methyl a-chloro acrylate (MCA) and 2,2,2-trichloroethyl methacrylate (TCEMA) was prepared and the thermal, mechanical, and optical characteristics were investigated. Although each homopolymer had low loss and desirable high thermal stability, they had crucial disadvantages for the fiber fabrication process. To draw a MCA polymer (PMCA) fiber, it has to be heated above 270 degrees C. However, the polymer started to decompose at a lower temperature and produced numerous bubbles. In contrast, TCEMA polymer (PTCEMA) is too brittle to roll up during heat drawing. In this study, we succeeded to improve the strong viscoelasticity and the low decomposition temperature of PMCA and the brittleness of PTCEMA by copolymerizing MCA and TCEMA. In addition, the glass transition temperatures (T-g) of the copolymers were in the range of 133-147 degrees C and the transmittances of the copolymers were much higher than that of PMMA which has been commonly used as a base material of POF A suitable GI POF was obtained using the MCA and TCEMA copolymer. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym. Chem 47: 3352-3361, 2009