Polymers PCL

Poly(e-caprolactone) (PCL) is synthesized by anionic, cationic or coordination polymerization of e-caprolactone. Degradable block copolymers with polyethylene glycol, diglycolide, substituted caprolactones and /-valerolactone can also be synthesized. Like the lactide polymers, PCL and its copolymers degrade both in vitro and in vivo by bulk hydrolysis, with the degradation rate affected by the size and shape of the device and additives. 

A biodegradable composite material for tissue repair has been described, formulated from water soluble glass fibers impregnated with a biodegradable polymer, PCL (65). Such a biodegradable composite is particularly useful for the repair of nerve or bone tissue, especially the bones of the skull. 

Recently some biosynthetic composites have appeared, such as PCL/ periosteum composites for osteochondral defect repair. In vivo studies on cylindrical defects created in 10 rabbits showed that PCL-based biocomposites promote excellent subchondral bone regeneration. Research is currently focused on the synthesis of PCL composites, to combine the versatility of caprolactone together with the mechanical properties of other polymers. As poly(e-caprolactone) is another FDA-approved polymer, PCL-PLA copolymers are primary items of investigation. 

Blends with styrene-acrylonitrile copolymer (SAN) 7 represent an important series of systems in which a crystallisable polymer, PCL, is blended with an amorphous (co)polymer. The overall system, with its inherent variations, is complex and provides a good example of situations which can arise generally. These blends have been the subject of a major series of studies which raise many issues which must have a relevance to blends of PCL with other polymers but which have not been addressed in studies of other systems. 

Poly(e-caprolactone) is an aliphatic polyester produced from petroleum products. PCL is compatible with human tissues and an excellent additive for starch polymers. PCL is used by Novamont with the Mater-Bi biodegradable plastic. PCL can be used for adhesives, compatibiliz-ers, plasticizers, and films for the packaging and for the biomedical industries. 

Figure 9.11 Comparison of size for nanoparticles prepared from different initial menthol to polymer mass ratio (menthol dissolved in acetone together with polymer) PCL (M = 14,000) has constant initial concentration, 6 mg/mL. A, MR = 1 , MR = 2 , MR = 3 , MR = 4. Measured after synthesis and quench (quench volumetric ratio = 1) in CIJM-dl.

Suitable polymers PCL, PEO, PLA Mofokeng, J P Luyt, A S, Thermo-chim Acta, 613, 41-53, 2015. 

The good agreement between degradation data found for the same polymer (PCL -1) in film and tube form, representing more than a tenfold change in surface to volume ratio, indicates again a uniform degradation of the bulk of the sample. 

FIGURE 16 Representative melting and glass transition temperatures of bio and fossil based polymers (PCL-Str - Polycaprolactone/Starch blends, PC - Polycaprolactone, mcPHA - medium chain Polyhydroxyalkanoates, Ali-coPES - Aliphatic (co)Polyesters, PUBAf -Polyhydroxy Butyrate/valerate, and PEA - Polyester Amides). 

Supercritical carbon dioxide (SCCO2) was employed for the first time to prepare polyesters via ROP of lactones. Lipase-catalyzed ROP of e-CL proceeded to give a polymer (PCL) with molecular weight higher than 10". Copolymerization of e-CL with DDL afforded a random copolyester. The enzymatic polycondensation between divinyl adipate and 1,4-butane diol also took place to produce the corresponding polyester [73]. Later, a similar study on ROP of e-CL in SCCO2 followed [74]. 

---