| abstract |
A star polymer having viscosity index enhancing properties and acceptable shear stability is provided. The present invention provides the following compositions: (a) Star polymers comprising: (i) polyvalent (meth) acrylic acid monomers, oligomers or polymers thereof, or polyvalent A core portion comprising divinyl non-acrylic acid monomers, oligomers or polymers thereof; and (ii) at least two arms of polymerized (meth) acrylic acid alkyl ester; and (b) an oil of lubricating viscosity, the core The moiety further comprises a functional group of formula (I) —CH 2 —C (R 1 ) (C (═O) A) —Y—, wherein R 1 contains hydrogen, 1 to 5 carbon atoms. A is nitrogen or oxygen; Y is one or more atoms or groups of atoms that can be transferred by a radical mechanism under polymerization conditions, halogen, —O—N = Group and -S-C (= ) - it is a free radical leaving group selected from the group. [Selection figure] None |