ented by the general formula (4): (R.sup.2--).sub.3-aSiX.sub.a--R.sup.3W (4) (wherein R.sup.2, R.sup.3, X and a are as defined above, and W is an active-hydrogen-containing group selected from among hydroxyl, carboxyl, mercapto and (primary orsecondary) amino groups.) (.delta.) The method comprising introducing an olefinic group into an oxyalkylene polymer containing a functional group allowing in