Atactic polypropylene comb block polyolefins useful as modifiers in polyolefins and hydrocarbons

A process for preparing comb-block polyolefins comprising:

• contacting, at a temperature within a range from 20 to 70° C., propylene with a first metallocene precursor and an activator to form vinyl-terminated atactic polypropylene having a weight average molecular weight of at least 8000 g/mole and a crystallinity of less than 20%;
• contacting in a subsequent step, at a temperature within a range from 40 to 150° C., the vinyl-terminated atactic polypropylene with ethylene, propylene, or both, a second metallocene precursor, and an activator to form a comb-block polyolefin;
• and
• forming in said subsequent step a linear low molecular weight component (LLMW) comprising ethylene or ethylene/propylene copolymers and having a number average molecular weight within a range from 7,000 to 50,000 g/mole,
• wherein the comb-length of the comb-block polyolefin is greater than the entanglement molecular weight of atactic polypropylene.