Cold flow-reduced polymers having good processing characteristics have, at the ends of the polymer chains, a silane-containing carboxyl group of the formula (I) where R1 and R2 are the same or different and are each an H, alkyl, alkoxy, cycloalkyl, cycloalkoxy, aryl, aryloxy, alkaryl, alkaryloxy, aralkyl or aralkoxy; R3 and R4 are the same or different and are each an H, alkyl, cycloalkyl, aryl, alkaryl or aralkyl radical; A is a divalent organic radical.