The present invention provides aqueous chemical mechanical planarization (CMP) polishing compositions that comprise a mixture of (a) one or more alkoxylated diamines having a number average molecular weight (Mn) of from 1,000 to 20,000, or, preferably, from 1000-15000 and having four (poly)alkoxy ether groups each containing from 5 to 100 alkoxy repeat units; (b) from 0.01 to 2 wt. % or, preferably, from 0.1 to 1.5 wt. %, as solids, based on the total weight of the compositions, of one or more aqueous dispersions of elongated, bent or nodular colloidal silica particles, preferably, having a secondary particle size as determined by dynamic light scattering (DLS) of from 20 to 60 nm; and (c) ammonia or an amine base, wherein the compositions have a pH ranging from 9 to 11. The compositions are substantially free of metals, such as alkali or alkaline earth metals that can damage substrates in polishing.