Synthesis of [H-3]-labelled poly(epsilon-caprolactone)

Tritiated poly(epsilon-caprolactone), where part of the methylene-type prot ons close to the ester carbonyl groups are replaced by tritium, was synthes ized. The substitution was based on the elimination of some of the hydrogen atoms by a poorly nucleophilic strong base, namely lithium diisopropylamid e (LDA). This first step led to the formation of carbanionic sites on the m ain chain of the polymer. The second step consisted of an attack on the car banion by tritiated water (HTO) which resulted in H-1-->H-3 exchange along the polymer chains. The specific activity of the final compound was 5.63 MB q/g (152 mu Ci/g) equivalent to 2% substitution reaction. The radiolysis ra tio of the tritiated polymer was rather low (0.35% per month). The method i s very versatile and paves the road to deuterated and tritiated poly(epsilo n-caprolactone)s.