Novel dissymmetric fumarate monomers (1a-c) having both an alkoxyethyl group such as 2-methoxyethyl (a), 2-(2-methoxyethoxy)ethyl (b), and 2-(2-(2-methoxyethoxy)ethoxy)ethyl (c) and a bulky 3-[tris(trimethylsiloxy)silyl]propyl group were synthesized successfully, and their radical homopolymerizations and copolymerizations with styrene (St) were investigated. Monomer reactivities of the 1a-c in homopolymerizations were enhanced with an increase in the length of alkoxyethyl chains. The enhancement in the reactivity was explained with the suppression of the termination reaction, resulting from the increased steric hindrance induced by an increase in the size of alkoxyethyl chains. Copolymerizations of the 1a-c with St were carried out in bulk in the presence of AIBN at 60 degrees C, and their copolymerizations proceeded in a highly alternating tendency regardless of alkoxyethyl chain lengths. The Q, e values of the la-c were obtained as 0.48, +1.55 for the 1a, 0.66, +1.16 for the 1b, and 0.60, +1.16 for the 1c, respectively, from the terminal model reactivity ratios, and the la-c were found to be conjugative, electron-accepting monomers. Membranes containing the la unit, prepared by the copolymerization of la with N-vinylpyrrolidone (NVP) and terpolymerization of 1a, NVP, and 2-hydroxyethyl methacrylate, have higher oxygen permeability than those containing no la unit, and also they have much better transparency compared with the membranes containing 3-[tris(trimethylsilyloxy)silyl]propyl methacrylate unit. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 420-433, 2009