Viscosity modifier polybutadiene polymers

A process comprising the steps of:

• forming through polymerization, a precursor polybutadiene block copolymer comprising at least one precursor crystallizable segment comprising 1,4-polybutadiene and at least one precursor low crystallinity segment of polybutadiene wherein butadiene is added to the polymer chain as 1,4 butadiene and 1,2 butadiene, the precursor block copolymer comprising at least 10 percent by weight precursor crystallizable segments, wherein polymerization comprises forming a segment comprising at least 70 mole percent butadiene added as 1,2-butadiene:
• forming a 1,4-polybutadiene segment;
• and forming a segment comprising at least 70 mole percent butadiene added as 1,2-butadiene;
• adding a coupling agent to form a precursor star block copolymer;
• and
• substantially hydrogenating the precursor polybutadiene star block copolymer to form a hydrogenated block copolymer, arms of which comprise at least 10 percent by weight of at least one crystallizable segment comprised of methylene units and having an average methylene content corresponding to a 1,4-polybutadiene content of at least about 20 mole percent, and at least one low crystallinity segment comprised of methylene units and substituted methylene units and having an average methylene content corresponding to a 1,4-polybutadiene content of less than about 20 mole percent.