The invention provides active energy ray curable compositions which exhibit good curability with active energy rays and which have a low viscosity to attain excellent application properties when applied as materials such as adhesives or coatings onto substrates and can give highly flexible cured products upon irradiation with active energy rays. An active energy ray curable composition includes a (meth)acrylic triblock copolymer (A) including a (meth)acrylic polymer block(s) (aA) having an active energy ray curable group containing a partial structure represented by the following general formula (1), and a (meth)acrylic polymer block(s) (bA) having no active energy ray curable groups, and a (meth)acrylic diblock copolymer (B) including a (meth)acrylic polymer block (aB) having an active energy ray curable group containing a partial structure represented by the following general formula (1), and a (meth)acrylic polymer block (bB) having no active energy ray curable groups, the composition having a ratio of Mn (bB)/Mn (bA) in the range of 0.2 to 2.0 wherein Mn (bB) is the number average molecular weight of the (meth)acrylic polymer block (bB) present in the (meth)acrylic diblock copolymer (B), and Mn (bA) is the number average molecular weight of the (meth)acrylic polymer block (bA) present in the (meth)acrylic triblock copolymer (A).

##STR00001## (In the formula, R.sup.1 is a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.)

The present invention provides pressure-sensitive adhesive compositions which have excellent adhesion force, cohesion force, tack and holding power, and pressure-sensitive adhesive products including the pressure-sensitive adhesive compositions. The pressure-sensitive adhesive composition includes (i) 100 parts by mass of an acrylic block copolymer (I) including at least one polymer block (A) containing methacrylate ester units and at least one polymer block (B) containing acrylate ester units, the acrylic block copolymer (I) having a weight average molecular weight of 30,000 to 300,000, the acrylate ester units in the polymer block (B) including not less than 80 mass % of units from an acrylate ester (1) represented by the general formula (1):

CH.sub.2═CH—COOR.sup.2

(wherein R.sup.2 is an organic group having 7 to 12 carbon atoms); (ii) 1 to 300 parts by mass of a tackifier resin; and (iii) 1 to 200 parts by mass of at least one plasticizer selected from process oils, and organic acid esters and oligomers thereof.

The present invention provides pressure-sensitive adhesive compositions which have excellent adhesion force, cohesion force, tack and holding power, and pressure-sensitive adhesive products including the pressure-sensitive adhesive compositions. The pressure-sensitive adhesive composition includes (i) 100 parts by mass of an acrylic block copolymer (I) including at least one polymer block (A) containing methacrylate ester units and at least one polymer block (B) containing acrylate ester units, the acrylic block copolymer (I) having a weight average molecular weight of 30,000 to 300,000, the acrylate ester units in the polymer block (B) including not less than 80 mass % of units from an acrylate ester (1) represented by the general formula (1):

CH.sub.2═CH—COOR.sup.2

(wherein R.sup.2 is an organic group having 7 to 12 carbon atoms); (ii) 1 to 300 parts by mass of a tackifier resin; and (iii) 1 to 200 parts by mass of at least one plasticizer selected from process oils, and organic acid esters and oligomers thereof.

Provided is a method of purifying a monomer composition that contains a polycyclic aromatic vinyl compound including at least two monocycles selected from the group consisting of aromatic hydrocarbon monocycles and aromatic heteromonocycles. The purification method includes an impurity removal step of removing at least sulfur from the monomer composition.

Provided is a method of purifying a monomer composition that contains a polycyclic aromatic vinyl compound including at least two monocycles selected from the group consisting of aromatic hydrocarbon monocycles and aromatic heteromonocycles. The purification method includes an impurity removal step of removing at least sulfur from the monomer composition.

Provided are a block copolymer having a narrow molecular weight distribution such that the copolymer can be used in a DSA technique, a block copolymer intermediate thereof, and methods for producing the same. A block copolymer intermediate represented by the general formula (1) or (2) is used:

##STR00001##

wherein, in the general formulae (1) and (2), each of R.sup.1 and R.sup.3 independently represents a polymerization initiator residue, each of R.sup.2 and R.sup.4 independently represents an aromatic group or an alkyl group, Y.sup.1 represents a polymer block of (a)an (meth)acrylic acid ester, Y.sup.2 represents a polymer block of styrene or a derivative thereof, L represents an alkylene group having 1 to 6 carbon atoms, X represents a halogen atom, and each of m and n independently represents an integer of 1 to 5.

A polyolefin-polystyrene multi-block copolymer and a method of producing the same is disclosed herein. In some embodiments, the polyolefin-polystyrene multi-block copolymer has a first complex viscosity of 40,000 Pa.Math.s to 350,000 Pa.Math.s at a temperature of 160° C. and a first frequency of 0.5 rad/s, and has a second complex viscosity of 900 Pa.Math.s to 3,500 Pa.Math.s at a temperature of 160° C. and a second frequency of 125 rad/s. The polyolefin-polystyrene multi-block copolymer has a structure in which polystyrene chains are attached to both ends of a polyolefin chain.

A polyolefin-polystyrene multi-block copolymer and a method of producing the same is disclosed herein. In some embodiments, the polyolefin-polystyrene multi-block copolymer has a first complex viscosity of 40,000 Pa.Math.s to 350,000 Pa.Math.s at a temperature of 160° C. and a first frequency of 0.5 rad/s, and has a second complex viscosity of 900 Pa.Math.s to 3,500 Pa.Math.s at a temperature of 160° C. and a second frequency of 125 rad/s. The polyolefin-polystyrene multi-block copolymer has a structure in which polystyrene chains are attached to both ends of a polyolefin chain.

A composition for pattern formation includes a first polymer, a second polymer and a solvent. The first polymer includes: a first block including a first structural unit derived from a substituted or unsubstituted styrene; and a second block including a second structural unit other than the first structural unit. The second polymer includes: the first structural unit; and a group bonding to at least one end of a main chain thereof and including a polar group. The polar group is preferably a hydroxy group or a carboxyl group. A number average molecular weight of the second polymer is preferably no greater than 6,000. A mass ratio of the second polymer to the first polymer is preferably no less than 0.15 and no greater than 0.4. The solvent preferably comprises a compound comprising a hydroxyl group and an alkyl ester group.

A composition for pattern formation includes a first polymer, a second polymer and a solvent. The first polymer includes: a first block including a first structural unit derived from a substituted or unsubstituted styrene; and a second block including a second structural unit other than the first structural unit. The second polymer includes: the first structural unit; and a group bonding to at least one end of a main chain thereof and including a polar group. The polar group is preferably a hydroxy group or a carboxyl group. A number average molecular weight of the second polymer is preferably no greater than 6,000. A mass ratio of the second polymer to the first polymer is preferably no less than 0.15 and no greater than 0.4. The solvent preferably comprises a compound comprising a hydroxyl group and an alkyl ester group.