Polyfunctional vinyl aromatic copolymer, process for producing the same, and resin composition

A production method for a soluble polyfunctional vinyl aromatic copolymer, comprising allowing the following compounds to react through a cation copolymerization with each other:

• a divinyl aromatic compound (a);
• a monovinyl aromatic compound (b);
• and
• an aromatic ether compound (c),
• wherein:
• 5 to 95 mol % of the divinyl aromatic compound (a) and 95 to 5 mol % of the monovinyl aromatic compound (b) are used with respect to 100 mol % of a total of the divinyl aromatic compound (a) and the monovinyl aromatic compound (b);
• 0.5 to 500 mol of the aromatic ether compound (c) represented by the following formula (7):
• where:
• R2 represents a hydrocarbon group having 1 to 18 carbon atoms and optionally including an oxygen atom or a sulfur atom;
• and R3 represents hydrogen or a methyl group
• with respect to 100 mol of all monomers, and one or more kinds of catalysts selected from the group consisting of a Lewis acid catalyst, an inorganic strong acid, and an organic sulfonic acid are further used;
• polymerization raw materials including the compounds and the catalysts are dissolved in a solvent having a dielectric constant of 2.0 to 15.0 to form a uniform solvent;
• and
• the compounds are polymerized at a temperature of 20 to 120° C. in the uniform solvent to provide a copolymer having, at an end, a end group represented by the following formula (1):
• where:
• R2 represents a hydrocarbon group having 1 to 18 carbon atoms and optionally including an oxygen atom or a sulfur atom;
• and R3 represents hydrogen or a methyl group at a ratio of 1.0 (group/molecule) or more and being soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform.