Polycaprolactone

Polycaprolactone
Names
	IUPAC name (1,7)-Polyoxepan-2-one
	Systematic IUPAC name Poly(hexano-6-lactone)
	Other names 2-Oxepanone homopolymer; 6-Caprolactone polymer
Identifiers
CAS Number	24980-41-4;
Abbreviations	PCL
ChemSpider	none;
Properties
Chemical formula	(C6H10O2)n
Density	1.145 g/cm3
Melting point	60 °C (140 °F)
Thermal conductivity	0.05 W/(m K) @25°C
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Polycaprolactone (PCL) is a synthetic, semi-crystalline, biodegradable polyester with a melting point of about 60 °C and a glass transition temperature of about −60 °C.^[2]^[3] The most common use of polycaprolactone is in the production of speciality polyurethanes. Polycaprolactones impart good resistance to water, oil, solvent and chlorine to the polyurethane 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). Being compatible with a range of other materials, PCL can be mixed with starch to lower its cost and increase biodegradability or it can be added as a polymeric plasticizer to polyvinyl chloride (PVC).

Polycaprolactone is also used for splinting, modeling, and as a feedstock for prototyping systems such as fused filament fabrication 3D printers.

Synthesis

PCL is prepared by ring opening polymerization of ε-caprolactone using a catalyst such as stannous octoate. A wide range of catalysts can be used for the ring opening polymerization of caprolactone.^[4]

Biomedical applications

PCL is degraded by hydrolysis of its ester 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. 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.

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.^[5] PCL–Hydroxyapatite composite scaffolds for bone tissue engineering can mimic the composition and morphology of the bone mineral phase and can be 3D printed into intricate designs. ^[6]

PCL has been approved by the Food and Drug Administration (FDA) in specific applications used in the human body as (for example) a drug delivery device, suture, or adhesion barrier.^[7] PCL is used in the rapidly growing field of human esthetics following the recent introduction of a PCL-based microsphere dermal filler belonging to the collagen stimulator class (Ellansé).^[8]

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.^[8]^[9] It is being investigated as a scaffold for tissue repair by tissue engineering, GBR membrane. It has been used as the hydrophobic block of amphiphilic synthetic block copolymers used to form the vesicle membrane of polymersomes.

A variety of drugs have been encapsulated within PCL beads for controlled release and targeted drug delivery.^[10]

In dentistry (as the composite named Resilon), it is used as a component of "night guards" (dental splints) and in root canal filling. It performs like gutta-percha, 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,^[11] 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, TechTack, or Friendly Plastic. 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.^[12] 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 and Pseudomonadota can degrade PCL.^[13] Penicillium sp. strain 26-1 can degrade high density PCL; though not as quickly as thermotolerant Aspergillus sp. strain ST-01. Species of Clostridium can degrade PCL under anaerobic conditions.

References

^ Sharma, Adit; Kopylov, Alexey; Zadorozhnyy, Mikhail; Stepashkin, Andrei; Kudelkina, Vera; Wang, Jun-Qiang; Ketov, Sergey; Churyukanova, Margarita; Louzguine-Luzgin, Dmitri; Sarac, Baran; Eckert, Jürgen; Kaloshkin, Sergey; Zadorozhnyy, Vladislav; Kato, Hidemi (2020). "Mg-Based Metallic Glass-Polymer Composites: Investigation of Structure, Thermal Properties, and Biocompatibility". Metals. 10 (7): 867. doi:10.3390/met10070867.
^ Kumbar, Sangamesh; Laurencin, Cato T.; Deng, Meng (2014). Natural and synthetic biomedical polymers (1st ed.). Burlington, MA: Elsevier. ISBN 978-0-12-396983-5.
^ Narayan, Roger J. (2019), "Preface", Encyclopedia of Biomedical Engineering, Elsevier, pp. xxxv–xxxvi, doi:10.1016/b978-0-12-804829-0.05001-x, ISBN 978-0-12-805144-3, retrieved 2023-11-01
^ Labet M, Thielemans W (December 2009). "Synthesis of polycaprolactone: a review". Chemical Society Reviews. 38 (12): 3484–504. doi:10.1039/B820162P. PMID 20449064.
^ Hajiali F, Tajbakhsh S, Shojaei A (28 June 2017). "Fabrication and Properties of Polycaprolactone Composites Containing Calcium Phosphate-Based Ceramics and Bioactive Glasses in Bone Tissue Engineering: A Review". Polymer Reviews. 58 (1): 164–207. doi:10.1080/15583724.2017.1332640. S2CID 103102150.
^ Codrea, C.I.; Lincu, D.; Ene, V.L.; Nicoară, A.I.; Stan, M.S.; Ficai, D.; Ficai, A. Three-Dimensional-Printed Composite Scaffolds Containing Poly-ε-Caprolactone and Strontium-Doped Hydroxyapatite for Osteoporotic Bone Restoration. Polymers 2024, 16, 1511. https://doi.org/10.3390/polym16111511
^ Li, L.; LaBarbera, D. V. (2017-01-01), Chackalamannil, Samuel; Rotella, David; Ward, Simon E. (eds.), "2.16 - 3D High-Content Screening of Organoids for Drug Discovery", Comprehensive Medicinal Chemistry III, Oxford: Elsevier, pp. 388–415, doi:10.1016/b978-0-12-409547-2.12329-7, ISBN 978-0-12-803201-5, retrieved 2020-07-14
^ ^a ^b Moers-Carpi MM, Sherwood S (March 2013). "Polycaprolactone for the correction of nasolabial folds: a 24-month, prospective, randomized, controlled clinical trial". Dermatologic Surgery. 39 (3 Pt 1): 457–63. doi:10.1111/dsu.12054. PMC 3615178. PMID 23350617.
^ Kim JA, Van Abel D (April 2015). "Neocollagenesis in human tissue injected with a polycaprolactone-based dermal filler". Journal of Cosmetic and Laser Therapy. 17 (2): 99–101. doi:10.3109/14764172.2014.968586. PMID 25260139. S2CID 5799117.
^ Bhavsar MD, Amiji MM (2008). "Development of novel biodegradable polymeric nanoparticles-in-microsphere formulation for local plasmid DNA delivery in the gastrointestinal tract". AAPS PharmSciTech. 9 (1): 288–94. doi:10.1208/s12249-007-9021-9. PMC 2976886. PMID 18446494.
^ Hiraishi N, Yau JY, Loushine RJ, Armstrong SR, Weller RN, King NM, Pashley DH, Tay FR (August 2007). "Susceptibility of a polycaprolactone-based root canal-filling material to degradation. III. Turbidimetric evaluation of enzymatic hydrolysis". Journal of Endodontics. 33 (8): 952–6. doi:10.1016/j.joen.2007.05.004. PMID 17878081.
^ Supercilii C. "DIY Material Guide: Polymorph Plastic (a thermal plastic with low melting point)". Instructables. Autodesk. Retrieved 20 August 2015.
^ Tokiwa Y, Calabia BP, Ugwu CU, Aiba S (August 2009). "Biodegradability of plastics". International Journal of Molecular Sciences. 10 (9): 3722–42. doi:10.3390/ijms10093722. PMC 2769161. PMID 19865515.