Curable, foamable composition containing alkoxysilane polyethers of the formula having more than one alkoxysilyl function per chain end reactive towards epoxide groups where a is an integer from 1 to 3, b is an integer from 0 to 2, and the sum of a and b is 3, c is an integer from 0 to 22, d is an integer from greater than 1 to 1000, e is an integer from 0 to 10 000, f is an integer from 0 to 1000, g is an integer from 0 to 1000, h, i and j are integers from 0 to 500, and with the proviso that the fragments having the indices d to j are freely permutable with one another, i.e. are interchangeable in the sequence within the polyether chain, n is an integer between 2 and 8; and R represents one or more identical or different radicals selected from linear or branched, saturated, singly or multiply unsaturated alkyl radicals having 1 to 20 carbon atoms or haloalkyl groups having 1 to 20 carbon atoms, R 1 represents a saturated or unsaturated, unbranched or branched radical or a polyether radical of the type of an alkoxy, arylalkoxy or alkylarylalkoxy group, in which the carbon chain may be interrupted by oxygen atoms, or R 1 is a singly or multiply fused aromatic group to which a phenolic OH group is directly attached, R 2 or R 3, and also R 5 or R 6, is or else independently of one another are each H or a saturated or unsaturated, monovalent or polyvalent hydrocarbon radical, the radicals R 5 or R 6 being a monovalent hydrocarbon radical and it being possible for the hydrocarbon radical to be bridged cycloaliphatically via the fragment Y; Y may be absent, or else may be a methylene bridge having 1 or 2 methylene units; if Y is absent, then R 2 or R 3 independently of one another are each a linear or branched radical having 1 to 20 carbon atoms; R 2 -R 3 may be a -CH 2 CH 2 CH 2 CH 2 - group, Y thus being a -(CH 2 CH 2 -)- group and the hydrocarbon radicals R 2 and R 3 may in turn be further substituted and carry functional groups such as halogens, hydroxyl groups or glycidyloxypropyl groups, R 4 is a linear or branched alkyl radical of 1 to 24 carbon atoms or an aromatic or cycloaliphatic radical which if appropriate may, in turn, carry alkyl groups, R 7 and R 8 are independently of one another either hydrogen or alkyl, alkoxy, aryl or aralkyl groups which are copolymerized by ring-opening polymerization to give crosslinkable polyether esters containing alkoxysilane groups, R 9, R 10, R 11 and R 12 are independently of one another either hydrogen, alkyl, alkenyl, alkoxy, aryl or aralkyl groups, it being possible for the hydrocarbon radical to be bridged cycloaliphatically or aromatically via the fragment Z, Z being either a divalent alkylene radical or alkenylene radical and one or more blowing agents. a is an integer from 1 to 3, b is an integer from 0 to 2, and the sum of a and b is 3, c is an integer from 0 to 22, d is an integer from greater than 1 to 1000, e is an integer from 0 to 10 000, f is an integer from 0 to 1000, g is an integer from 0 to 1000, h, i and j are integers from 0 to 500, and with the proviso that the fragments having the indices d to j are freely permutable with one another, i.e. are interchangeable in the sequence within the polyether chain, n is an integer between 2 and 8; and R represents one or more identical or different radicals selected from linear or branched, saturated, singly or multiply unsaturated alkyl radicals having 1 to 20 carbon atoms or haloalkyl groups having 1 to 20 carbon atoms, R 1 represents a saturated or unsaturated, unbranched or branched radical or a polyether radical of the type of an alkoxy, arylalkoxy or alkylarylalkoxy group, in which the carbon chain may be interrupted by oxygen atoms, or R 1 is a singly or multiply fused aromatic group to which a phenolic OH group is directly attached, R 2 or R 3, and also R 5 or R 6, is or else independently of one another are each H or a saturated or unsaturated, monovalent or polyvalent hydrocarbon radical, the radicals R 5 or R 6 being a monovalent hydrocarbon radical and it being possible for the hydrocarbon radical to be bridged cycloaliphatically via the fragment Y; Y may be absent, or else may be a methylene bridge having 1 or 2 methylene units; if Y is absent, then R 2 or R 3 independently of one another are each a linear or branched radical having 1 to 20 carbon atoms; R 2 -R 3 may be a -CH 2 CH 2 CH 2 CH 2 - group, Y thus being a -(CH 2 CH 2 -)- group and the hydrocarbon radicals R 2 and R 3 may in turn be further substituted and carry functional groups such as halogens, hydroxyl groups or glycidyloxypropyl groups, R 4 is a linear or branched alkyl radical of 1 to 24 carbon atoms or an aromatic or cycloaliphatic radical which if appropriate may, in turn, carry alkyl groups, R 7 and R 8 are independently of one another either hydrogen or alkyl, alkoxy, aryl or aralkyl groups which are copolymerized by ring-opening polymerization to give crosslinkable polyether esters containing alkoxysilane groups, R 9, R 10, R 11 and R 12 are independently of one another either hydrogen, alkyl, alkenyl, alkoxy, aryl or aralkyl groups, it being possible for the hydrocarbon radical to be bridged cycloaliphatically or aromatically via the fragment Z, Z being either a divalent alkylene radical or alkenylene radical and one or more blowing agents.