Injection-foamable styrenic monomer-diolefin copolymer, a method for the preparation thereof and use thereof

A method for preparing a copolymer having micro-blocks of polystyrenic monomer and micro-blocks of polydiolefin monomer, comprising:

• 1) adding at least one solvent and at least one activator to a polymerization reactor, and heating the contents to a temperature ranging from 50 to 110° C.;
• 2) adding at least one initiator to the reactor, and allowing the reaction to continue for a period of time ranging from 0 to 30 minutes;
• 3) preparing a mixture comprising a styrenic monomer and a first amount of a diolefin monomer, and adding the mixture to the reactor over a period of time ranging from 5 to 180 minutes continuously, wherein the rate at which the monomers are consumed in the polymerization is comparable to or greater than the rate at which the mixture is added, and further wherein the reaction temperature during the addition differs from the initiating temperature by no more than 50° C.;
• 4) optionally adding a second amount of the diolefin monomer to the reactor, and allowing the reaction to continue for a period of time ranging from 5 to 30 minutes;
• 5) adding at least one coupling agent to the reactor, and allowing the reaction to continue for a period of time ranging from 5 to 60 minutes;
• and
• 6) recovering the copolymer,
• wherein no microstructure modifier is used in the method and in the resulting copolymer, at least 50 mol % of polymerized styrenic monomers and at least 50 mol % of polymerized diolefin monomers are present in molecule chains of the copolymer as micro-blocks.