in which d 3 r 4 h and c 0 in a particular embodiment the compositions m of the invention contain polymers a in which in at least 70 of all the silane end groups preferably in at least 90 of all the silane end groups b 3 r 1 h and a 0 and polymers b in which in at least 70 of all the silane end groups more preferably in at least 90 of all the silane end groups d 1 r 4 h and c 1 in a further particular embodiment the compositions m of the invention contain polymers a in which in at least 70 of all the silane end groups preferably in at least 90 of all the silane end groups b 3 r 1 h and a 0 and polymers b in which in at least 70 of all the silane end groups preferably in at least 90 of all the silane end groups d 3 r 4 h and c 0 the compounds a used in accordance with the invention are commercial products or can be prepared by standard chemical methods examples of commercially available compounds a are the geniosil u00ae products of the stp e 10 stp e 15 stp e 30 or stp e 35 types from.