A novel aryl trifluorovinyl ether monomer, 1,1,1-tris(4-trifluorovinyloxyphenyl)-2,2,2-trifluoroethane (5), was prepared via a multistep reaction sequence adapted from previously reported procedures. Monomer 5 polymerizes by free-radical mediated thermal cyclodimerization to produce a crosslinked perfluorocyclobutyl (PFCB) polymer. Substituting CH3 for CF3 did not affect the polymerization kinetics as measured by differential scanning calorimetry. Surprisingly, the refractive index of poly5 (1.4931 at 1550 nm) is slightly higher than that measured for poly6 (1.4876 at 1550 nm) despite the significant increase in fluorine content. Compared to the CH3-containing monomer 6, fluorinated analogue 5 exhibits increased thermal and thermal oxidative stability and thus we expected lower optical loss for long-term high performance applications. Copolymerization with existing aryl trifluorovinyl ether monomers should allow access to new PFCB network copolymers with a tailored performance. (C) 2004 Wiley Periodicals, Inc.