Block copolymer having mixed molecular weight endblocks

Claim 1

A pressure sensitive adhesive composition comprising: (a) 100 parts by weight of a polymodal asymmetric elastomeric block copolymer; (b) about 25 to 400 parts by weight of a tackifying resin; (c) 0 to about 50 parts by weight of a crosslinking agent; and (d) 0 to about 200 parts by weight of a plasticizer; wherein said polymodal asymmetric elastomeric block copolymer has the formula O n Y and comprises from about 4 to about 40 percent by weight of a polymerized monovinyl aromatic compound and from about 96 to about 60 percent by weight of polymerized conjugated diene, wherein: O represents an individual arm of the block copolymer and has the formula S-B; n represents the number of arms O in the block copolymer and is a whole number of at least 3; and Y is the residue of a multifunctional coupling agent; and further wherein: (a) S is a nonelastomeric polymer segment endblock of a polymerized monovinyl aromatic homopolymer, there being at least two different molecular weight endblocks in the copolymer, a higher molecular weight endblock and a lower molecular weight endblock, wherein: (i) the number average molecular weight of the higher molecular weight endblock (Mn) H is in the range of from about 5,000 to about 50,000; (ii) the number average molecular weight of the lower molecular weight endblock (Mn) L is in the range of from about 1,000 to about 10,000; and (iii) the ratio (Mn) H /(Mn) L is at least 1.25; and (b) B is an elastomeric polymer segment midblock which connects each arm to the residue of a multifunctional coupling agent (Y) and comprises a polymerized conjugated diene or combination of conjugated dienes.