Comb graft polymers and their use in functional fluids

Abstract

There are disclosed novel comb graft polymers and copolymers comprising a backbone of a linear polymer of p-methylstyrene (p-MS) and grafted branches of a linear addition polymer of at least one anionically polymerizable compound. The polymers may be produced by metallating the p-MS polymer with an organo alkali metal metallating agent, e.g., an alkyllithium, at active hydrogen sites along the polymer chain and graft polymerizing the anionically polymerizable compound at the metallated sites to form the grafted branches. Certain of the foregoing comb graft polymers and copolymers, e.g., wherein the backbone is a homopolymer of p-MS or a copolymer of p-MS and a ring-substituted alkylstyrene such as p-tert-butylstyrene (t-BS) and the branches are a polymer of t-BS, are useful as additives to functional fluids, particularly hydrocarbon lubricating oils, for the purpose of thickening and improving their viscosity index.