# Polyglycolide

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{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 464209860
| Name = Polyglycolide
| ImageFile = PGA.png

| ImageName = Polyglycolide
| IUPACName = Poly[oxy(1-oxo-1,2-ethanediyl)]
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 26124-68-5
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = H1IL6F7KB8
| SMILES = *C(=O)CO*
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = none
  }}
|Section2={{Chembox Properties
| Formula = (C<sub>2</sub>H<sub>2</sub>O<sub>2</sub>)<sub>n</sub>
| MolarMass = (58.04)n
| Density = 1.530 g/cm<sup>3</sup> at 25 °C
| MeltingPtC = 225 to 230
| MeltingPt_notes = 
| BoilingPt = Decomposes
  }}
}}

'''Polyglycolide''' or '''poly(glycolic acid)''' ('''PGA'''), also spelled as '''polyglycolic acid''', is a [biodegradable](/source/biodegradable), [thermoplastic](/source/thermoplastic) [polymer](/source/polymer) and the simplest linear, [aliphatic](/source/aliphatic) [polyester](/source/polyester). It can be prepared starting from [glycolic acid](/source/glycolic_acid) by means of [polycondensation](/source/Condensation_reaction) or [ring-opening polymerization](/source/ring-opening_polymerization). PGA has been known since 1954 as a tough [fiber](/source/fiber)-forming polymer.  Owing to its [hydrolytic](/source/hydrolysis) instability, however, its use was slow to develop.<ref name="Gilding">{{cite journal | last = Gilding | first = D. K. |author2=A. M. Reed | title = Biodegradable polymers for use in surgery - polyglycolic/poly (lactic acid) homo- and copolymers: 1 | journal = Polymer | volume = 20 | pages = 1459–1464 | date = December 1979 | doi = 10.1016/0032-3861(79)90009-0 | issue = 12 }}</ref> Polyglycolide and its [copolymer](/source/copolymer)s ([poly(lactic-''co''-glycolic acid)](/source/PLGA) with [lactic acid](/source/lactic_acid), poly(glycolide-''co''-caprolactone) with [ε-caprolactone](/source/caprolactone) and poly (glycolide-''co''-trimethylene carbonate) with [trimethylene carbonate](/source/trimethylene_carbonate)) are widely used as a material for the synthesis of absorbable [suture](/source/surgical_suture)s and are being evaluated in the [biomedical](/source/Biomedical_engineering) field.<ref name="middleton">{{cite journal | last = Middleton | first = J. | author2 = A. Tipton | title = Synthetic biodegradable polymers as medical devices | journal = Medical Plastics and Biomaterials Magazine | date = March 1998 | url = http://www.devicelink.com/mpb/archive/98/03/002.html | accessdate = 2006-07-04 | archive-url = https://web.archive.org/web/20070312013555/http://www.devicelink.com/mpb/archive/98/03/002.html | archive-date = 2007-03-12 | url-status = dead }}</ref>

==Physical properties==
Polyglycolide has a [glass transition temperature](/source/glass_transition_temperature) between 35 and 40&nbsp;°C and a [melting point](/source/melting_point) in the range of 225 to 230&nbsp;°C. PGA also exhibits an elevated degree of [crystallinity](/source/crystallinity), around 45–55%, thus resulting in insolubility in [water](/source/water_(molecule)).<ref name="middleton"/> The high [molecular weight](/source/molecular_weight) form is insoluble in common [organic solvent](/source/organic_solvent)s ([acetone](/source/acetone), [dichloromethane](/source/dichloromethane), etc.), whereas low molecular weight [oligomer](/source/oligomer)s are more soluble. Polyglycolide is soluble in highly [fluorinated](/source/fluorine) solvents like [hexafluoroisopropanol](/source/hexafluoro-2-propanol) (HFIP) and [hexafluoroacetone sesquihydrate](/source/hexafluoroacetone), that can be used to prepare solutions of the high MW polymer for [melt spinning](/source/melt_spinning) and film preparation.{{cn|date=June 2025}} Fibers of PGA exhibit high strength and [modulus](/source/Young's_modulus) (7 [GPa](/source/Pascal_(unit))) and are particularly stiff.<ref name="middleton"/>

==Synthesis==
Polyglycolide can be obtained through several processes starting with different materials:

* polycondensation of [glycolic acid](/source/glycolic_acid)
* ring-opening polymerization of [glycolide](/source/glycolide)
* [solid-state](/source/solid-state_chemistry) polycondensation of halogenoacetates

Polycondensation of glycolic acid is the simplest process available to prepare PGA, but it is not the most efficient because it yields a low molecular weight product.{{cn|date=June 2025}}

The most common synthesis of high molecular weight form of the polymer is ring-opening polymerization of glycolide, the bislactone cyclic dimer of glycolic acid. Glycolide can be prepared by thermal [cracking](/source/Cracking_(chemistry)), collecting the diester by means of distillation. Ring-opening polymerization of glycolide can be [catalyzed](/source/catalysis) using diverse [catalyst](/source/catalyst)s, including [antimony](/source/antimony) compounds, such as [antimony trioxide](/source/antimony_trioxide) or antimony trihalides, [zinc](/source/zinc) compounds (zinc lactate) and [tin](/source/tin) compounds like [stannous octoate](/source/stannous_octoate) (tin(II) 2-ethylhexanoate) or tin alkoxides. Stannous octoate is the most commonly used initiator, since it is approved by the [FDA](/source/Food_and_Drug_Administration) as a food stabilizer. Usage of other catalysts has been disclosed as well, among these are [aluminium isopropoxide](/source/aluminium_isopropoxide), [calcium](/source/calcium) [acetylacetonate](/source/acetylacetonate), and several [lanthanide](/source/lanthanide) alkoxides (e.g. [yttrium isopropoxide](/source/yttrium_isopropoxide)).<ref name="Bero">{{cite journal | last = Bero | first = Maciej |author2=Piotr Dobrzynski |author3=Janusz Kasperczyk  | title = Application of Calcium Acetylacetonate to the Polymerization of Glycolide and Copolymerization of Glycolide with ε-Caprolactone and L-Lactide | journal = Macromolecules | volume = 32 | issue = 14 | pages = 4735–4737 | publisher = ACS | date = 18 June 1999 | doi = 10.1021/ma981969z | bibcode = 1999MaMol..32.4735D }}</ref><ref name="Stridsberg">{{cite book | last = Stridsberg | first = Kajsa M. |author2=Maria Ryner |author3=Ann-Christine Albertsson | title = Controlled Ring-Opening Polymerization: Polymers with designed Macromolecular Architecture | volume = 157 | pages = 41–65 | publisher = [Springer](/source/Springer_Science%2BBusiness_Media) | year = 2002 | doi = 10.1007/3-540-45734-8_2 | series = Advances in Polymer Science | isbn = 978-3-540-42249-5 }}</ref>

frame|center|Ring-opening polymerization of glycolide to polyglycolide

Another procedure consists in the thermally induced solid-state polycondensation of halogenoacetates with general formula
X-&mdash;CH<sub>2</sub>COO<sup>−</sup>M<sup>+</sup> (where M is a monovalent metal like [sodium](/source/sodium) and X is a [halogen](/source/halogen) like [chlorine](/source/chlorine)), resulting in the production of polyglycolide and small [crystal](/source/crystal)s of a [salt](/source/salt_(chemistry)). Polycondensation is carried out by heating an halogenoacetate, like [sodium chloroacetate](/source/sodium_chloroacetate), at a temperature between 160 and 180&nbsp;°C, continuously passing nitrogen through the reaction vessel. During the reaction polyglycolide is formed along with [sodium chloride](/source/sodium_chloride) which precipitates within the polymeric matrix; the salt can be conveniently removed by washing the product of the reaction with water.<ref name="apple">{{cite journal | last1 = Epple | first1 = Matthias | title = A detailed characterization of polyglycolide prepared by solid-state polycondensation reaction | journal = Macromolecular Chemistry and Physics | volume = 200 | issue = 10 | pages = 2221–2229 | publisher = Wiley | year = 1999 | doi = 10.1002/(SICI)1521-3935(19991001)200:10<2221::AID-MACP2221>3.0.CO;2-Q | last2 = Epple | first2 = Matthias }}</ref>

PGA can also be obtained by [carbonylation](/source/carbonylation) (reaction with [carbon monoxide](/source/carbon_monoxide)) of formaldehyde or the related compounds like [paraformaldehyde](/source/paraformaldehyde) or [trioxane](/source/trioxane).{{cn|date=June 2025}}

==Degradation==
The hydrolytic degradation appears to take place in two steps during which the polymer is converted back to its monomer glycolic acid: first water diffuses into the amorphous (non-crystalline) regions of the polymer matrix, cleaving the ester bonds; the second step starts after the amorphous regions have been eroded, leaving the crystalline portion of the polymer susceptible to hydrolytic attack. Upon collapse of the crystalline regions the polymer chain dissolves.

When exposed to physiological conditions, polyglycolide is degraded by random hydrolysis, and apparently it is also broken down by certain [enzyme](/source/enzyme)s, especially those with [esterase](/source/esterase) activity. The degradation product, [glycolic acid](/source/glycolic_acid), is nontoxic, but like [ethylene glycol](/source/ethylene_glycol), it is metabolized to [oxalic acid](/source/oxalic_acid), which could make it dangerous. A part of the glycolic acid is also excreted by [urine](/source/urine).<ref name="gunatillake">{{cite journal | last = Gunatillake | first = Pathiraja A. | author2 = Raju Adhikari | title = Biodegradable Synthetic Polymers for tissue engineering | journal = European Cells and Materials | volume = 5 | pages = 1–16 | year = 2003 | doi = 10.22203/eCM.v005a01 | url = http://www.ecmjournal.org/journal/papers/vol005/pdf/v005a01.pdf | accessdate = 2015-02-08 | pmid = 14562275 | doi-access = free | archive-date = 2017-07-13 | archive-url = https://web.archive.org/web/20170713100711/http://www.ecmjournal.org/journal/papers/vol005/pdf/v005a01.pdf | url-status = live }}</ref>

Studies undergone using polyglycolide-made sutures have shown that the material loses half of its strength after two weeks and 100% after four weeks. The polymer is completely resorbed by the organism in a time frame of four to six months.<ref name="middleton"/> Degradation is faster [in vivo](/source/in_vivo) than [in vitro](/source/in_vitro), this phenomenon thought to be due to cellular enzymatic activity.<ref name="Nita">{{cite journal |author=Niță |first=Tiberiu |author-link= |date=Mar 2011 |title=Concepts in biological analysis of resorbable materials in oro-maxillofacial surgery |url=http://www.revistaomf.ro/(23) |journal=Revista de chirurgie oro-maxilo-facială și implantologie |language=ro |volume=2 |issue=1 |pages=33–38 |issn=2069-3850 |id=23 |accessdate=2012-06-06}}{{Dead link|date=May 2020|bot=InternetArchiveBot|fix-attempted=yes}}(webpage has a translation button)</ref>

==Uses==
250px|right|thumb|Sutures made from polyglycolic acid. These sutures are adsorbable and are degraded by the body over time.

While known since 1954, PGA had found little use because of its sensitivity to [hydrolysis](/source/hydrolysis) when compared with other synthetic polymers. However, in 1962 this polymer was used to develop the first synthetic absorbable suture which was marketed under the [tradename](/source/tradename) of Dexon<ref name="Gilding"/> by the [Davis & Geck](/source/Davis_%26_Geck) subsidiary of the American Cyanamid Corporation. After its coating with polycaprolactone and calcium stearate it is being sold under the brand name of Assucryl.

PGA suture is classified as a synthetic, absorbable, braided multifilament. It is coated with N-[laurin](/source/laurin) and L-[lysine](/source/lysine), which render the thread extremely smooth, soft and safe for [knot](/source/knot)ting. It is also coated with [magnesium stearate](/source/magnesium_stearate) and finally sterilized with [ethylene oxide](/source/ethylene_oxide) gas. It is naturally degraded in the body by [hydrolysis](/source/hydrolysis) and is absorbed as water-soluble monomers, completed between 60 and 90 days. Elderly, [anemic](/source/anemia) and [malnourished](/source/malnutrition) patients may absorb the suture more quickly. Its color is either [violet](/source/Violet_(color)) or undyed and it is sold in sizes USP 6-0 (1 metric) to USP 2 (5 metric). It has the advantages of high initial tensile strength, smooth passage through tissue, easy handling, excellent knotting ability, and secure knot tying. It is commonly used for [subcutaneous](/source/Subcutaneous_tissue) sutures, intracutaneous closures, abdominal and thoracic surgeries.

The traditional role of PGA as a biodegradable suture material has led to its evaluation in other biomedical fields. Implantable medical devices have been produced with PGA, including [anastomosis](/source/anastomosis) rings, pins, rods, plates and screws.<ref name="middleton"/> It has also been explored for [tissue engineering](/source/tissue_engineering) or controlled drug delivery. Tissue engineering scaffolds made with polyglycolide have been produced following different approaches, but generally most of these are obtained through [textile](/source/textile) technologies in the form of [non-woven felts](/source/Nonwovens).

The [Kureha Chemical Industries](/source/Kureha_Chemical_Industries) has commercialized high molecular weight polyglycolide for food packaging applications under the tradename of Kuredux.<ref>[http://www.kureha.com/product-groups/pga.htm Kuredux® Polyglycolic Acid (PGA) Resin] {{Webarchive|url=https://web.archive.org/web/20201209142533/http://www.kureha.com/product-groups/pga.htm |date=2020-12-09 }} ''www.kureha.com'', accessed 4 December 2021</ref> Production is at Belle, West Virginia, with an intended capacity of 4000 annual metric tons.<ref>{{Cite web |url=http://www.chemicals-technology.com/projects/kurehacorporationpol/ |title= Kureha Corporation Polyglycolic Acid Plant |access-date=2011-03-06 |archive-date=2020-12-09 |archive-url=https://web.archive.org/web/20201209113045/https://www.chemicals-technology.com/projects/kurehacorporationpol/ |url-status=dead }}</ref> Its attributes as a barrier material result from its high degree of crystallization, the basis for a tortuous path mechanism for low permeability.  It is anticipated that the high molecular weight version will have use as an interlayer between layers of [polyethylene terephthalate](/source/polyethylene_terephthalate) to provide improved barrier protection for perishable foods, including carbonated beverages and foods that lose freshness on prolonged exposure to air.  Thinner plastic bottles which still retain desirable barrier properties may also be enabled by this polyglycolide interlayer technology. A low molecular weight version (approximately 600 amu) is available from [The Chemours Company](/source/The_Chemours_Company) (formerly part of [DuPont](/source/DuPont_(1802%E2%80%932017))) and is purported to be useful in oil and gas applications.<ref>{{Cite web |url=http://www2.dupont.com/Oil_and_Gas/en_CA/assets/downloads/DuPont_Polyglycolic_Acid_Sheet.pdf |title=DuPont_Polyglycolic_Acid_Sheet.pdf |access-date=2011-02-18 |archive-date=2011-05-11 |archive-url=https://web.archive.org/web/20110511035542/http://www2.dupont.com/Oil_and_Gas/en_CA/assets/downloads/DuPont_Polyglycolic_Acid_Sheet.pdf |url-status=dead }}</ref>

==References==
{{Reflist}}

<!---Place all category tags here-->

Category:Biodegradable plastics
Category:Biomaterials
Category:Polyesters
Category:Surgical suture material
Category:Thermoplastics

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Adapted from the Wikipedia article [Polyglycolide](https://en.wikipedia.org/wiki/Polyglycolide) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Polyglycolide?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.