Polycaprolactone (PCL) is a biodegradable polyester with a low

melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depen ...

of around 60 °C and a

glass transition temperature The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rub ...

of about −60 °C. The most common use of polycaprolactone is in the production of speciality

polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...

s. Polycaprolactones impart good resistance to water, oil, solvent and chlorine to the

produced. This polymer is often used as an additive for resins to improve their processing characteristics and their end use properties (e.g.,

impact resistance In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.starch to lower its cost and increase

biodegradability Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...

or it can be added as a polymeric

plasticizer A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. Plasticiz ...

to polyvinyl chloride (PVC). Polycaprolactone is also used for splinting, modeling, and as a feedstock for prototyping systems such as

fused filament fabrication Fused filament fabrication (FFF), also known as fused deposition modeling (with the trademarked acronym FDM), or called ''filament freeform fabrication'', is a 3D printing process that uses a continuous filament of a thermoplastic material. Filam ...

3D printer 3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer co ...

Synthesis

PCL is prepared by

ring opening polymerization In polymer chemistry, ring-opening polymerization (ROP) is a form of chain-growth polymerization, in which the terminus of a polymer chain attacks cyclic monomers to form a longer polymer (see figure). The reactive center can be radical, anion ...

of ε-caprolactone using a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

such as stannous octoate. A wide range of catalysts can be used for the ring opening polymerization of caprolactone. Polycaprolactone synthesis

Biomedical applications

PCL is degraded by

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...

of its

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

linkages in physiological conditions (such as in the human body) and has therefore received a great deal of attention for use as an implantable

biomaterial A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose, either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one. As a science, biomateria ...

. In particular it is especially interesting for the preparation of long term implantable devices, owing to its degradation which is even slower than that of

polylactide Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula or , formally obtained by condensation of lactic acid with loss of water (hence its name). It can also be prepared by rin ...

. PCL has been widely used in long-term implants and controlled drug release applications. However, when it comes to tissue engineering, PCL suffers from some shortcomings such as slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of calcium phosphate-based ceramics and bioactive glasses into PCL has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity that are suitable for bone tissue engineering. PCL has been approved by the

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

(FDA) in specific applications used in the human body as (for example) a

drug delivery Drug delivery refers to approaches, formulations, manufacturing techniques, storage systems, and technologies involved in transporting a pharmaceutical compound to its target site to achieve a desired therapeutic effect. Principles related to dr ...

device, suture, or

adhesion barrier An adhesion barrier is a medical implant that can be used to reduce abnormal internal scarring (adhesions) following surgery by separating the internal tissues and organs while they heal. Surgeons have realized that proper surgical technique is c ...

. PCL is used in the rapidly growing field of human esthetics following the recent introduction of a PCL-based microsphere

dermal filler Injectable filler (injectable cosmetic filler, injectable facial filler) is a soft tissue filler injected into the skin at different depths to help fill in facial wrinkles, provide facial volume, and augment facial features: restoring a smoother ap ...

belonging to the collagen stimulator class (Ellansé). Through the stimulation of collagen production, PCL-based products are able to correct facial ageing signs such as volume loss and contour laxity, providing an immediate and long-lasting natural effect. It is being investigated as a scaffold for tissue repair by

tissue engineering Tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biolog ...

, GBR membrane. It has been used as the hydrophobic block of

amphiphilic An amphiphile (from the Greek αμφις amphis, both, and φιλíα philia, love, friendship), or amphipath, is a chemical compound possessing both hydrophilic (''water-loving'', polar) and lipophilic (''fat-loving'') properties. Such a compo ...

synthetic block

copolymers In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...

used to form the vesicle membrane of

polymersome In biotechnology, polymersomesDischer B M; Won Y Y; Ege D S; Lee J C; Bates F S; Discher D E; Hammer D A ''Science'' (1999), ''284''(5417), 1143-6. are a class of artificial vesicles, tiny hollow spheres that enclose a solution. Polymersomes are ma ...

s. A variety of drugs have been encapsulated within PCL beads for controlled release and

targeted drug delivery Targeted drug delivery, sometimes called smart drug delivery, is a method of delivering medication to a patient in a manner that increases the concentration of the medication in some parts of the body relative to others. This means of delivery is la ...

. In dentistry (as the composite named Resilon), it is used as a component of "night guards" (dental splints) and in

root canal A root canal is the naturally occurring anatomic space within the root of a tooth. It consists of the pulp chamber (within the coronal part of the tooth), the main canal(s), and more intricate anatomical branches that may connect the root ...

filling. It performs like

gutta-percha Gutta-percha is a tree of the genus ''Palaquium'' in the family Sapotaceae. The name also refers to the rigid, naturally biologically inert, resilient, electrically nonconductive, thermoplastic latex derived from the tree, particularly from ...

, has similar handling properties, and for re-treatment purposes may be softened with heat, or dissolved with solvents like chloroform. Similar to gutta-percha, there are master cones in all ISO sizes and accessory cones in different sizes and taper available. The major difference between the polycaprolactone-based root canal filling material (Resilon and Real Seal) and gutta-percha is that the PCL-based material is biodegradable, whereas gutta-percha is not. There is a lack of consensus in the expert dental community as to whether a biodegradable root canal filling material, such as Resilon or Real Seal is desirable.

Hobbyist and prototyping

PCL also has many applications in the hobbyist market where it is known as Re-Form, Polydoh, Plastimake, NiftyFix, Protoplastic, InstaMorph, Polymorph, Shapelock, ReMoldables, Plastdude or TechTack. It has physical properties of a very tough, nylon-like plastic that softens to a putty-like consistency at only 60 °C, easily achieved by immersing in hot water. PCL's specific heat and conductivity are low enough that it is not hard to handle by hand at this temperature. This makes it ideal for small-scale modeling, part fabrication, repair of plastic objects, and rapid prototyping where heat resistance is not needed. Though softened PCL readily sticks to many other plastics when at higher temperature, if the surface is cooled, the stickiness can be minimized while still leaving the mass pliable.

Biodegradation

Bacillota The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have gram-positive cell wall structure. The renaming of phyla such as Firmicutes in 2021 remains controversial among microbiologists, many of whom continue to use the earl ...

and Pseudomonadota can degrade PCL. ''

Penicillium ''Penicillium'' () is a genus of ascomycetous fungi that is part of the mycobiome of many species and is of major importance in the natural environment, in food spoilage, and in food and drug production. Some members of the genus produce pe ...

'' sp. strain 26-1 can degrade high density PCL; though not as quickly as thermotolerant ''

Aspergillus ' () is a genus consisting of several hundred mold species found in various climates worldwide. ''Aspergillus'' was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Mic ...

'' sp. strain ST-01. Species of '' Clostridium'' can degrade PCL under

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

conditions.

Synthesis

Biomedical applications

Hobbyist and prototyping

Biodegradation

See also

References

Further reading