| abstract |
Provided are a polyfunctional vinyl aromatic copolymer having reactivity and solubility which enable use thereof in manufacturing of a copolymer rubber, and a copolymer rubber material that is provided with each of workability, strength, and uniformity and that is obtained from the polyfunctional vinyl aromatic copolymer. A polyfunctional vinyl aromatic copolymer containing 0.5 mol% to 40 mol% of structural units (a) derived from a divinyl aromatic compound and containing 60 mol% to 99.5 mol% of structural units (b) derived from a monovinyl aromatic compound, said polyfunctional vinyl aromatic copolymer being characterized in that at least a portion of the structural units (a) are crosslinked structural units (a2) represented by formula (2) and vinyl-group-containing structural units (a1) represented by formula (1) (R1 in the formulas each independently representing a C6-30 aromatic hydrocarbon group), the mole fraction of the crosslinked structural units (a2) with respect to the structural units (a) is in the range of 0.05-0.50, the mole fraction of the vinyl-group-containing structural units (a1) with respect to the total of the structural units (a) and (b) is in the range of 0.001-0.35, the number-average molecular weight Mn of the polyfunctional vinyl aromatic copolymer is 1,000-50,000, and the molecular weight distribution (Mw/Mn) represented by the ratio of the weight-average molecular weight Mw and the number-average molecular weight Mn is no greater than 8.0. |