The influences of chemical structure of (meth)acrylate monomers, including the carbon atom number of alkyl ester groups and the a-methyl group, on the adhesion of polyacrylate sizes to all-polyester, pure cotton, and polyester/cotton blend fiber substrates are investigated by using an impregnated roving method for warp sizing. The adhesion is evaluated in terms of the bonding strength, breaking extension, and work of break of a slightly sized roving. The polyacrylate sizes are prepared through free radical copolymerization of (meth)acrylates with acrylic acid in ethanol. It was found that the adhesion is strongly affected by the structure of acrylate monomers. The adhesion enhances with increasing the carbon atom number of alkyl ester side chains of acrylates, whether or not it is an acrylate or a methacrylate. The a-methyl does not favor the adhesion to polyester fibers, but favor to polyester/cotton blend fibers. Moreover, the molar ratio of butyl acrylate to acrylic acid is also considered. Excessively lowering the amount of acrylate or acrylic acid damages the adhesion. A favorable molar ratio of butyl acrylate to acrylic acid is found to be about 60 : 40. (C) 2004 Wiley Periodicals, Inc.