The invention relates to compositions containing compounds of the structure (I): (R.sub.1).sub.a (R.sub.2).sub.b SiX.sub.c (I) wherein R.sub.1 is a neophyl, neohexyl or (CH.sub.3).sub.3 SiCH.sub.2 --group; R.sub.2 is a methyl group; X is a halo group or a saturated, unsaturated, branched, unbranched or cyclic alkoxy group of 1-18 carbon atoms; a is 1 or 2, b is an integer from 0 to 2, and c is an integer from 1 to 3.