novel silicone / polylactone graft copolymers , well suited as polymer composition additives , especially those destined for biomedical applications , have the average general formula : ## str1 ## in which p is an integer or decimal ranging from 1 . 5 to 6 , q is an integer or decimal ranging from 0 to 20 , a is a divalent hydrocarbon having from 2 to 20 carbon atoms , n is an integer ranging from 3 to 12 , m is an integer ranging from 2 to 25 , the radicals r &# 39 ;, which may be identical or different , are each hydrogen or c 1 - c 4 alkyl , and r is a hydrocarbon having up to 24 carbon atoms .