# Polyoxetane
**Polyoxetane** is a polyether whose backbone consists of repeating trimethylene oxide units, –CH₂–CH₂–CH₂–O–, produced by the ring-opening polymerization of oxetane, the four-membered cyclic ether also known as trimethylene oxide, oxacyclobutane, or 1,3-epoxypropane.[1](https://onlinelibrary.wiley.com/doi/abs/10.1002/0471440264.pst520) • [2](https://www.sciencedirect.com/science/article/pii/S0167273813004499) Substituted oxetane monomers give polyoxetanes with pendant functional groups, a feature that underlies the two largest areas of application: energetic binders for solid propellants and solid polymer electrolytes for lithium batteries.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/) • [2](https://www.sciencedirect.com/science/article/pii/S0167273813004499)
| Key fact | Detail |
|---|---|
| Backbone | Poly(trimethylene oxide), –(CH₂CH₂CH₂O)–, from ring-opening polymerization of oxetane monomers[2](https://www.sciencedirect.com/science/article/pii/S0167273813004499) |
| Ring strain | Oxetane ring strain is 106 kJ·mol⁻¹, between epoxides (112 kJ·mol⁻¹) and tetrahydrofuran (25 kJ·mol⁻¹)[4](https://doi.org/10.1021/acs.chemrev.6b00274) |
| First polymer | Poly[3,3-bis(chloromethyl)oxetane] (PBCMO), polymerized in 1954 and commercialized in the 1950s as Penton by Hercules[5](https://openscience.ub.uni-mainz.de/bitstreams/9e7d395d-c1e9-48cb-906d-7c92d714ab95/download) |
| Dominant mechanism | Cationic ring-opening polymerization; oxetanes are more basic than epoxides (pK_b 3.60 vs 7.55) and so are preferentially polymerized by cationic routes[6](https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cctc.202401032) |
| Energetic binders | Poly(BAMO) and poly(AMMO) have glass transition temperatures of −41 °C and −42 °C, compared with −70 °C for hydroxyl-terminated polybutadiene[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/) |
| Energy content | Poly(BAMO) has Δ_fH⁰ = 2.16 kJ·g⁻¹, the highest of the listed energetic azide polymers, but is crystalline and solid, so only copolymers serve as binders[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC7070646/) |
| Battery electrolytes | Nitrile-functional polyoxetane films with lithium salts reach conductivity over 0.1 mS·cm⁻¹[2](https://www.sciencedirect.com/science/article/pii/S0167273813004499) |
## Structure and polymerization
The oxetane monomer is a four-membered ring containing one oxygen atom, with an inherent ring strain of 106 kJ·mol⁻¹; the ring adopts an essentially planar structure with a puckering angle of only 8.7° at 140 K.[4](https://doi.org/10.1021/acs.chemrev.6b00274) Opening this strained ring releases energy and forms the polyether chain. The heat of polymerization of oxetane is 1.4 kJ·g⁻¹, about half that of ethylene oxide at 2.9 kJ·g⁻¹, a consequence of the lower ring strain.[8](https://doi.org/10.1021/acs.chemrev.2c00686)
**Cationic ring-opening polymerization (CROP)** is the standard route. Oxetanes are much more basic than epoxides, with pK_b values of 3.60 versus 7.55, so they are preferentially polymerized under cationic conditions.[6](https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cctc.202401032) Proton donors such as strong protic acids (H₂SO₄) or aprotic Lewis acids initiate the polymerization of energetic monomers such as BAMO and AMMO; a triisobutylaluminium–water (TIBA–water) catalyst system has also been used, in which the water:Al(C₄H₉)₃ ratio determines the composition of the reaction products.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/) Living cationic polymerization in nonpolymerizable solvents such as dioxane or tetrahydropyran has given well-defined poly(oxetane)s with number-average molecular weights up to 150,000 g/mol and polydispersity below 1.3.[9](https://kinampark.com/PL/files/Aldivar-Guerra%202013%2C%20Handbook%20of%20Polymer%20Synthesis%2C%20Characterization%2C%20and%20Processing.pdf)
Anionic routes also exist. In 1996, Takeuchi and Aida reported a controlled coordinate anionic polymerization of oxetane using a quaternary ammonium halide with an organoaluminum diphenolate in the presence of a bulky Lewis acid, and later work produced well-defined poly(oxetane)s of M_n up to 10 kg·mol⁻¹ at room temperature via a monomer-activated strategy using Oct₄NBr as initiator with a large excess of iBu₃Al.[6](https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cctc.202401032) Anionic ring-opening polymerization with monomer activation has also been used to make amphiphilic block copolymers of poly(ethylene oxide) and polyoxetane.[10](https://pubs.rsc.org/en/content/articlehtml/2018/py/c8py00307f)
## History
The first oxetane polymers were established in 1954 by the polymerization of 3,3-bis(chloromethyl)oxetane (BCMO), followed by unsubstituted and other substituted oxetanes.[5](https://openscience.ub.uni-mainz.de/bitstreams/9e7d395d-c1e9-48cb-906d-7c92d714ab95/download) Poly[3,3-bis(chloromethyl)oxetane] (PBCMO) was commercialized in the 1950s by Hercules Inc. under the trade name Penton, a chlorinated polyether with excellent resistance to corrosive chemicals and organic solvents, used as a coating material for tanks, reaction vessels, and pipelines.[5](https://openscience.ub.uni-mainz.de/bitstreams/9e7d395d-c1e9-48cb-906d-7c92d714ab95/download) • [11](https://patents.google.com/patent/US3277022A/en) Polymers based on the unsubstituted oxetane exhibit poor physical properties and were never relevant for industrial applications, whereas PBCMO found use and is now also a precursor for preparing the energetic binder poly(BAMO) by post-polymerization substitution.[5](https://openscience.ub.uni-mainz.de/bitstreams/9e7d395d-c1e9-48cb-906d-7c92d714ab95/download)
## Energetic binders
The largest current research effort concerns energetic polyoxetanes, in which energetic groups such as azido, difluoroamino, and nitrato groups are attached to the oxetane monomer before polymerization.[12](https://www.sciencedirect.com/science/article/pii/S0014305723003440) The oxetane ring is a saturated quaternary cycloether monomer that can carry dual energetic groups into the polymer skeleton, giving both higher energy and flexibility; compared with three-membered epoxides, the four-membered oxetane allows easier control of molecular mass and functionality, better flexibility after ring opening, and grafting of two different energetic groups on one monomer.[12](https://www.sciencedirect.com/science/article/pii/S0014305723003440)
The principal monomers are 3,3-bis(azidomethyl)oxetane (BAMO) and 3-azidomethyl-3-methyloxetane (AMMO). Azide groups are energetically favorable because they readily decompose, releasing significant amounts of energy and molecular nitrogen.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/) The polyoxetane backbone is relatively flexible, but substituents change its rigidity: replacing the methyl group of AMMO with an azidomethyl group (giving BAMO) significantly alters the rigidity of the resulting polymer.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/)
The homopolymer poly(BAMO) has the highest energy output of the listed energetic azide polymers, Δ_fH⁰ = 2.16 kJ·g⁻¹, but its symmetric structure makes it a crystalline solid with a melting point of approximately 70 °C, so it cannot be used directly as a binder in conventional curing processes conducted at 60 °C.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC7070646/) • [13](https://onlinelibrary.wiley.com/doi/10.1002/pol.20230241) Modification strategies therefore center on copolymerization, chain extension, and hyperbranched architectures.[14](https://onlinelibrary.wiley.com/doi/full/10.1002/prep.70163) BAMO–AMMO copolymers synthesized at molar ratios of 80:20, 50:50, and 20:80 show glass transition temperatures of −36, −43, and −51 °C respectively, and the 80:20 copolymer was reported as having the most favorable properties among the three for use as a high-energy material.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/) The copolymer p(BAMO-AMMO) has a formation enthalpy of up to 3.44 kJ·g⁻¹, attractive for energetic thermoplastic elastomers in extruded propellants and explosives, although its low-temperature properties are not optimal.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC7070646/)
Other energetic polyoxetanes include poly(NIMMO), used in high-energy propellant formulations for low-vulnerability ammunition; an initial poly(NIMMO)/HMX composite propellant showed a significant impulse of 1230 kJ/kg along with low sensitivity to initiating stimuli.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/) A recurring criticism of the field is that many reported investigations are fragmentary, describing synthesis and fundamental properties without follow-up mechanical or energetic performance data in specific propellant formulations, and only a scarce handful of reports compare polyoxetane energetic binders against reference materials such as well-defined HTPB.[3](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/)
## Solid polymer electrolytes
Polyoxetanes with nitrile-functional side chains serve as matrices for solid polymer electrolytes in lithium batteries. Polymers such as PCEO and PCOA are prepared by ring-opening polymerization of functional oxetane monomers and are based on the poly(trimethylene oxide) backbone with nitrile-bearing side groups.[2](https://www.sciencedirect.com/science/article/pii/S0167273813004499) Coordination of Li⁺ ions with the polar nitrile groups tethered to the main chain plays a crucial role in enhancing lithium-ion transport in poly(3-(2-cyanoethoxymethyl)-3-ethyloxetane) (PCEO).[15](https://pubs.rsc.org/en/content/articlehtml/2017/ra/c7ra07636c) PCOA-based electrolyte films offer conductivity over 0.1 mS·cm⁻¹ through enhanced dissolution of lithium salts by solvation of lithium ions with the cyanoethoxymethyl groups in each side chain.[2](https://www.sciencedirect.com/science/article/pii/S0167273813004499) In test cells of the form Li | P(CYAMEO)-based electrolyte | LiCoO₂, electrolytes containing LiN(CF₃SO₂)₂ showed better discharge performance than those with other lithium salts.[16](https://www.jstage.jst.go.jp/article/electrochemistry/78/5/78_5_387/_article/-char/en)
## Other uses and processing behavior
Oxetane monomers are used in coatings and UV-curable systems because [cationic ring-opening polymerization](https://www.edgepedia.org/cationic-ring-opening-polymerization) is insensitive to oxygen and suffers significantly less from polymerization shrinkage than free-radical polymerization of comparable liquid-crystal monomers.[17](https://pubs.rsc.org/en/content/articlehtml/2020/sm/d0sm00489h) In frontal polymerization, oxetanes generate slower, colder fronts than epoxy analogs because of their lower ring strain; under UV-activated cationic conditions the monomer DOX gave a maximum temperature of about 160 °C and a front velocity of 14 cm·min⁻¹, yet temperature time-evolutions within the reaction zone still reached 135 °C·s⁻¹.[8](https://doi.org/10.1021/acs.chemrev.2c00686) Bis(oxetane)s polyadded with 1,3,5-benzenetricarboxylic acid using tetraphenylphosphonium chloride as catalyst at 140 °C yield hyperbranched poly(ester)s with many pendant primary hydroxy groups in 21–84% yields.[18](https://www.nature.com/articles/pj200620)
## References
1. [Oxetane Polymers, Dreyfuss, Major Reference Works, Wiley](https://onlinelibrary.wiley.com/doi/abs/10.1002/0471440264.pst520)
2. [Ionic conductive properties of solid polymer electrolyte based on poly(oxetane) with branched side chains of terminal nitrile groups, ScienceDirect](https://www.sciencedirect.com/science/article/pii/S0167273813004499)
3. [Energetic Polyoxetanes as High-Performance Binders for Energetic Composites: A Critical Review, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC9656426/)
4. [Bull et al., Oxetanes: Recent Advances in Synthesis, Reactivity, and Medicinal Chemistry, Chemical Reviews 2016](https://doi.org/10.1021/acs.chemrev.6b00274)
5. [Synthesis of Reactive Energetic Oxetane Derivatives and Polymers thereof, University of Mainz dissertation](https://openscience.ub.uni-mainz.de/bitstreams/9e7d395d-c1e9-48cb-906d-7c92d714ab95/download)
6. [Illy et al., Simple/Commercially Available Lewis Acid in Anionic Ring-Opening Polymerization, ChemCatChem 2025](https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cctc.202401032)
7. [Reactive & Efficient: Organic Azides as Cross-Linkers in Material Sciences, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC7070646/)
8. [Frontal Polymerizations: From Chemical Perspectives to Macroscopic Properties and Applications, Chemical Reviews](https://doi.org/10.1021/acs.chemrev.2c00686)
9. [Cationic Ring-Opening Polymerization, Handbook of Polymer Synthesis, Characterization, and Processing](https://kinampark.com/PL/files/Aldivar-Guerra%202013%2C%20Handbook%20of%20Polymer%20Synthesis%2C%20Characterization%2C%20and%20Processing.pdf)
10. [Anionic polymerization of activated oxetane and its copolymerization with ethylene oxide, Polymer Chemistry (RSC)](https://pubs.rsc.org/en/content/articlehtml/2018/py/c8py00307f)
11. [US3277022A, Adherent poly-3,3-bis(chloromethyl)-oxetane, Google Patents](https://patents.google.com/patent/US3277022A/en)
12. [Wen et al., Progress in synthesis and properties of oxetane-based energetic polymers, European Polymer Journal 2023](https://www.sciencedirect.com/science/article/pii/S0014305723003440)
13. [Touidjine et al., Review on energetic copolymer binders for propulsion applications, Journal of Polymer Science 2023](https://onlinelibrary.wiley.com/doi/10.1002/pol.20230241)
14. [Zhang et al., BAMO-Based Energetic Binders: Opportunities, Challenges, and Pathways Toward Industrial Application in Solid Propellants, Propellants, Explosives, Pyrotechnics](https://onlinelibrary.wiley.com/doi/full/10.1002/prep.70163)
15. [Steric effect on Li+ coordination and transport properties in polyoxetane-based polymer electrolytes bearing nitrile groups, RSC Advances](https://pubs.rsc.org/en/content/articlehtml/2017/ra/c7ra07636c)
16. [Shintani & Tsutsumi, Poly(oxetane)-based Electrolytes with Nitrile Groups for All Solid-state Rechargeable Lithium Batteries, Electrochemistry](https://www.jstage.jst.go.jp/article/electrochemistry/78/5/78_5_387/_article/-char/en)
17. [Epoxide and oxetane based liquid crystals for advanced functional materials, Soft Matter (RSC)](https://pubs.rsc.org/en/content/articlehtml/2020/sm/d0sm00489h)
18. [Synthesis of Hyperbranched Poly(ester)s with Pendant Hydroxy Groups by the Polyaddition of Bis(oxetane)s, Polymer Journal](https://www.nature.com/articles/pj200620)
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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Alcohols, ethers, and organooxygen groups › Ethers › Cyclic ethers and epoxides › Oxetanes*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license