Poly(epsilon-caprolactone) (PCL) is known to biodegrade under composting or water sewage plant conditions. However, as compared with poly(alpha-hydroxy acids) derived from lactic and glycolic acids, PCL is much more resistant to chemical hydrolysis and is achiral, a feature that limits very much the possibility of property modulation through the configurational structure of polymer chains. For the sake of enlarging the family of PCL-type polymers, a novel method is proposed which is based on the anionic activation of PCL chain by the removal of a proton from the methylene group in alpha-position of the ester carbonyl present in the main chain, using a nonnucleophilic base such as lithium diisopropyl amide (LDA). This activation leads to a polycarbanion onto which various electrophile groups can be attached. The feasibility of the process was first shown on poly(methyl acrylate), (PMA), whose polyacrylic main chain is resistant to strong bases. The PMA polycarbanion was modified by various electrophiles, namely benzaldehyde, naphthoyl chloride, benzyl chloroformate, and iodomethane. In a second stage, the same reactions were performed successfully on PCL. The degree of substitution depended on the experimental conditions. PCL underwent main chain degradation during the formation of the polycarbanion whereas the reaction with the electrophiles did not cause any further main chain cleavages. The degradation of PCL chains can be limited enough to give access to novel functional PCL polymers.

Poly(lactic acid) polymers (PLA) are presently the most attractive compounds in the field of artificial degradable and biodegradable polymers. In order to enlarge the family, and thus the range of accessible properties, stereocopolymers and copolymers with various co-monomers have been synthesized. However, very few are functionalized, i.e. include functional groups attached to the main chains or as part of the side chains. In the search for degradable PLA-type polymers bearing functional groups to serve as intermediates for further chemical modifications, we are exploring two different routes. The first one is copolymerization with a protected hydroxyl-bearing lactide-type monomer, namely 3-(1,2,3,4-tetraoxobutyldiisopropylidene)dioxane-2,5-dione. The second route consists of the formation of a carbanionic site in the alpha-position to intrachain carbonyl functions by using lithium N,N-diisopropylamide followed by the coupling of electrophiles. Recent advances in this search are presented using several examples. In particular, it is shown that OH-functionalized PLA-type macromolecules can be made fluorescent by chemical coupling. It is also shown that substituents can be attached to PLA-type macromolecules in solution or to the surface of PLA-based devices selectively.

Aliphatic polyesters derived from lactic and glycolic acids (PLAGA) are the most attractive degradable polymers with respect to biomedical and environmental applications. Poly(∊-caprolactone), PCL, is a hydrophobic highly crystalline aliphatic polyester that is more resistant to hydrolytic degradation than PLA. It is not biodegradable in animal body but is rapidly degraded by outdoor microorganisms. In order to increase the rate of hydrolysis of the material, carboxyl-bearing PCL copolymers (PCLCOOH) were synthesized by anionic activation with LDA and reaction of CO2 on the polycarbanion. Variations in crystallinity, thermal properties and hydrophilicity caused by the presence of the pendent carboxyl groups were investigated. The degradation behavior of PCLCOOH was assessed by the evaluation of water uptake, mass loss, molecular masses and ESEM microphotographs. A dramatic increase in the hydrolytic degradation rate was observed compared with pure PCL, thus PCLCOOH can now be considered as a hydrolytically degradable polymer.

The resistance of synthetic polymers to the action of living systems is becoming more and more problematic in certain domains in which they are used for a limited period of time before becoming waste. It is exemplified in surgery, pharmacology, agriculture and in the environment too. In these domains, time‐resistant polymeric wastes are less and less acceptable. From this viewpoint, sutures, bone fracture fixation devices, mulch films and packagings are comparable. Basically they should be eliminated after use. Post‐use biorecycling is regarded as a possible solution to some of the problems raised by the management of these polymeric wastes, regardless of the domain of application. This contribution aims to present simple and versatile methods with a potential to investigate the fate, and especially the bioassimilation, of the degradation by‐products of degradable or bio‐degradable polymers in complex living media such as the human body, a compost or the outdoor environment. Two versatile methods are presented that have been developed to radio‐label degradable and biodegradable artificial aliphatic polyesters by substituting some protons by tritium atoms. It is also shown that weighing a population of starved earthworms, allowed to be in contact with degradable or biodegradable polymer, is a worthwhile method to demonstrate that degradation by‐products are bioassimilated.© 2002 Society of Chemical Industry

Bromoacetylated α-hydroxy-ω methoxy-poly (ethyleneglycol) (Mn = 2000 g mol−1) was allowed to react with a poly(∊ caprolactone) (Mn = 53,700, Mw/Mn =(1.50) that was first activatedby removing some of the proton atoms borne by the carbon atoms locatedin -position of carbonyl groups using lithium N-N-diisopropylamide as basic reagent in tetrahydrofurane at 78°C under argon flow. The reaction resulted in the grafting of methoxy poly(ethylene glycol) segments to some of the poly("-caprolactone) chains. The resulting polymeric compounds were characterized by various analytical techniques including NMR, SEC, DSC, X-ray diffraction and contact angle. Various characteristics of the recovered compounds, namely degree of substitution, degree of crystallinity, glass transition and melting temperatures, hydrophilicity, were evaluated. It was concluded that grafting was effective but sometimes not all poly("-caprolactone) chains were modified, depending on experimental conditions. Moreover, 150 nm nanoparticles were obtained without any additional surfactant for a 0.74% substitution degree copolymer.