Abstract: A curable composition is disclosed and comprises the following components.(A) 100 parts by weight of a oxypropylene polymer having a polymer main chain containing a repeating unit represented by the following formula ##STR1## and having at least one group containing a silicon atom bonded to a hydroxyl group and/or a hydrolyzable group and capable of crosslinking by forming a siloxane bond, wherein Mw/Mn thereof is not more than 1.6 and the number average molecular weight is at least 6,000,(B) from 1 to 200 parts by weight of a filler having a BET specific surface area of not higher than 10 m.sup.2 /g, and(C) from 0.1 to 20 parts by weight of a curing catalyst, said composition containing substantially no plasticizer.

Abstract: A polyalkylene oxide having unsaturated end groups. The polymer has a distribution of molecular weight Mw/Mn of not more than 1.5, and a process for the same. The polymer is useful as rubber materials, and can provide cured rubber having an excellent elongation.

Abstract: Polypropylene oxide having unsaturated end groups is prepared by polymerizing alkylene oxide in the presence of a complex catalyst prepared by reacting an organoaluminum compound with a porphyrin compound and an active hydrogen-containing compound and converting at least one hydroxyl end groups into an unsaturated end group(s), the prepared polymer having a narrow distribution of molecular weight.