The present invention relates to a method for preparing a polyolefin-polystyrene-based multiblock copolymer having a uniform structure and showing excellent physical properties through continuous type coordination polymerization and batch type anionic polymerization.

The disclosure provides an active cationic polymerization initiator composition for synthesizing a ternary diblock copolymer, a diisopropenylbenzene copolymer and a terpene polymer. The disclosure further provides a flame-retardant resin composition, which includes: (a) a hydrocarbon resin; and (b) a reactive flame-retardant, and may optionally include a modified polyphenylene ether. A flame-retardant resin cured product formed from the flame-retardant resin composition may have high heat resistance, low dielectric constant, low dissipation factor, flame retardancy and/or film-forming properties, and is suitable for uses in fabrication of a semiconductor packaging material, a substrate and the like for the high-speed and high-frequency field.