Hydrophobically associating polyacrylamide (HAPAM) was prepared for the first time by inverse microemulsion polymerization.Its rheological properties were determined by using a Brookfield viscometer and compared with those of HAPAM prepared traditionally by micelle polymerization.Results showed that the apparent viscosity of the former kind of HAPAM increased with increasing co-polymer concentration and co-monomer content

even if when the co-polymer concentration was low.As for the latter kind of HAPAM

when the content of co-monomer increased to 1%

the apparent viscosity decreased os as to be lower than that of the copolymer of which the co-monomer content was 0.5%.In comparison

the former HAPAM won an advantage over the latter on salt resistance and shear stability.These results were interpreted in terms of hydrophobical associations in aqueous solutions which played an important role in rheological properties:in the macromolecular chain of the former HAPAM

hydrophobical co-monomers distributed randomly

but not in block.As a result

it was the intermoleculat association instead of the intramolecular association predominated

which made the apparent viscosity increase remarkably and improved the salt resistance and shear stability.