Linear polypropylene ether glycols of high molecular weight are made by reacting a linear polypropylene ether glycol of lower molecular weight first with an alkaline agent such as sodium hydroxide or other suitable base to form an alcoholate, and then coupling the alcoholate with a suitable difunctional coupling agent, such as the benzene-sulfonic acid diester of ethylene glycol or with some other suitable arylsulfonic acid diester of a C.sub.2 to C.sub.6 alcohol, thereby obtaining a 100 percent linear polypropylene ether glycol of a desirably higher molecular weight. Materials so produced find use in an aqueous medium as defoaming agents, thickeners, or emulsifiers, and use as protective colloids to improve the low-temperature stability of polyurethane and other latices.