α-hydro-ω-[[[(1,1-dimethylethyl)dioxy]carbonyl]oxy]-poly[oxy(methyl-1,2-ethanediyl)] ether with 2,2-bis(hydroxymethyl)-1,3-propanediol (4:1); reaction product of: α-hydro-ω-((chlorocarbonyl)oxy)-poly(oxy(methyl-1,2-ethanediyl)) ether with 2,2-bis(hydroxymethyl)-1,3-propanediol with potassium 1,1-dimethylethylperoxalate