# Polybutadiene

**Polybutadiene** is a synthetic rubber made by polymerizing 1,3-butadiene (C\(_{4}\)H\(_{6}\), monomer molecular weight 54.0904), a conjugated diene that can enter the chain in three distinct configurations: cis-1,4, trans-1,4, and 1,2-vinyl. The relative amounts of these units, the polymer's microstructure, control whether the product is a soft, resilient elastomer or a hard, crystalline plastic, and butadiene rubber (BR) is the second most produced rubber worldwide.<sup>[1](https://meridian.allenpress.com/rct/article/94/3/393/465710/BUTADIENE-RUBBER-SYNTHESIS-MICROSTRUCTURE-AND-ROLE)</sup><sup> • </sup><sup>[2](https://webbook.nist.gov/cgi/formula?ID=C40022035&Mask=4)</sup><sup> • </sup><sup>[3](https://www.sciencedirect.com/topics/chemical-engineering/polybutadiene)</sup>

| Key fact | Detail |
|---|---|
| Monomer | 1,3-Butadiene, C\(_{4}\)H\(_{6}\), molecular weight 54.0904; cis-1,4-polybutadiene CAS Registry Number 40022-03-5<sup>[2](https://webbook.nist.gov/cgi/formula?ID=C40022035&Mask=4)</sup> |
| Microstructures | cis-1,4, trans-1,4, and 1,2-vinyl addition; the mode of addition determines mechanical properties<sup>[3](https://www.sciencedirect.com/topics/chemical-engineering/polybutadiene)</sup><sup> • </sup><sup>[4](https://courses.ems.psu.edu/matse202/book/export/html/701)</sup> |
| Thermal data | Glass transition −102 °C (cis) and −83 °C (trans); equilibrium melting point 12 °C (cis) and 164 °C (trans)<sup>[5](https://www.sciencedirect.com/science/article/pii/S0032386108010227)</sup> |
| Catalysts | Ziegler–Natta systems based on titanium, cobalt, or nickel, and lanthanide (neodymium) systems, the most stereospecific for cis-1,4 polymerization<sup>[6](https://www.sciencedirect.com/science/article/pii/S0014305704001892)</sup><sup> • </sup><sup>[7](https://revistapolimeros.org.br/article/doi/10.1590/S0104-14282005000400015)</sup> |
| Commercial cis content | High-cis grades typically 93–96% cis; specific gravity about 0.90<sup>[8](https://www.eneos-materials.com/english/products/g_rubber/br/)</sup><sup> • </sup><sup>[9](https://csm.umicore.com/en/metal-carboxylates-organics/applications/rubbers-elastomers)</sup> |
| Main uses | Tire treads and sidewalls, belts, hoses, footwear, golf ball cores, and plastic modification of HIPS and ABS<sup>[8](https://www.eneos-materials.com/english/products/g_rubber/br/)</sup><sup> • </sup><sup>[10](https://www.titleist.com/learning-lab/how-its-made/golf-ball-core)</sup><sup> • </sup><sup>[11](https://www.synthosgroup.com/en/automotive-2/lithium-butadiene-rubber/)</sup> |
| History | First successful Ziegler–Natta polymerization of a conjugated diene (TiCl\(_{4}\) or TiCl\(_{3}\) with aluminum alkyls) in 1954<sup>[1](https://meridian.allenpress.com/rct/article/94/3/393/465710/BUTADIENE-RUBBER-SYNTHESIS-MICROSTRUCTURE-AND-ROLE)</sup> |

## Microstructure

[The 1](https://www.edgepedia.org/the-1),3-butadiene molecule contains two double bonds joined by a single bond, so an active chain end can add to it in several ways. Addition at one double bond gives 1,2-polybutadiene, which carries a pendant vinyl group on an asymmetric carbon and can be isotactic, syndiotactic, or atactic. Conjugative addition through carbons 1 and 4 keeps a double bond in the backbone and yields either the cis or the trans geometric isomer.<sup>[4](https://courses.ems.psu.edu/matse202/book/export/html/701)</sup><sup> • </sup><sup>[12](https://goldbook.iupac.org/terms/view/15252)</sup>

**Why the isomers differ.** The trans units form a regular zig-zag backbone that packs well, so trans-rich polybutadiene is crystalline, stiff, and hard, with an equilibrium melting point of 164 °C. The cis configuration folds the chain and suppresses crystallization, giving a flexible elastomer with a glass transition of −102 °C and an equilibrium melting point of only 12 °C.<sup>[5](https://www.sciencedirect.com/science/article/pii/S0032386108010227)</sup><sup> • </sup><sup>[4](https://courses.ems.psu.edu/matse202/book/export/html/701)</sup> Vinyl-rich polymers show no evidence of crystals and have a much higher glass transition, near 0 °C, which makes them unsuitable for most elastomer uses.<sup>[13](https://www.researchgate.net/publication/249776190_Structure_and_Properties_of_Model_Polybutadienes_-_Effect_of_Microstructure_on_the_Dynamic_Mechanical_Properties_of_Rubber)</sup><sup> • </sup><sup>[14](https://sirsyedcollege.ac.in/crm/public/uploads/download_image/BCuxT69IMJi4rfs0JHVhbVjvafNQL2.pdf)</sup> Marked changes in physical properties appear only when a relatively pure configuration is approached: polybutadiene of 95% cis content displays very low heat generation and high resilience, equaling natural rubber in these properties, together with excellent abrasion resistance.<sup>[15](https://cir.nii.ac.jp/crid/1361981468973093120?lang=en)</sup>

Microstructure is measured in the plant and laboratory by infrared, NMR, and [Raman spectroscopy](https://www.edgepedia.org/raman-spectroscopy). The carbon–carbon double-bond stretching of the three unit types gives strong, distinct Raman bands at about 1639 cm<sup>−1</sup> (1,2-vinyl), 1645–1650 cm<sup>−1</sup> (1,4-cis), and 1664–1669 cm<sup>−1</sup> (1,4-trans), and because Raman intensity is proportional to concentration the composition can be quantified to within ±1% reproducibility, in minutes rather than the up to 12 hours a <sup>13</sup>C NMR analysis can require.<sup>[16](https://www.us.endress.com/en/endress-hauser-group/Case-studies-application-notes/microstructural-analysis-polybutadienes)</sup>

## Catalysts and production

Industry produces high cis-polybutadiene through solution polymerization with [Ziegler–Natta catalyst](https://www.edgepedia.org/ziegler-natta-catalyst) systems built on titanium, cobalt, or nickel—and, in more recent years, on lanthanides, of which neodymium-based catalysts stand out for their high activity and [stereospecificity](https://www.edgepedia.org/stereospecificity).<sup>[6](https://www.sciencedirect.com/science/article/pii/S0014305704001892)</sup> The catalyst choice is the major factor influencing the reaction and the microstructure of the resulting polymer.<sup>[1](https://meridian.allenpress.com/rct/article/94/3/393/465710/BUTADIENE-RUBBER-SYNTHESIS-MICROSTRUCTURE-AND-ROLE)</sup> Cobalt systems are highly cis-selective; a commercial cobalt neodecanoate catalyst precursor enables production of polybutadiene rubber with a cis content of 96%.<sup>[9](https://csm.umicore.com/en/metal-carboxylates-organics/applications/rubbers-elastomers)</sup> In Australia, all production of stereoregular high-cis polybutadiene has been achieved with an aluminum alkyl halide–cobalt salt catalyst.<sup>[17](https://www.tandfonline.com/doi/abs/10.1080/00222338208056471)</sup>

**Neodymium systems.** The lanthanide-based technology is the most recent of the commercial routes and was the most employed in the decade before 2004. A neodymium Ziegler–Natta system contains three components: a neodymium compound (the catalyst, usually a carboxylate salt such as the neodecanoate or versatate), an alkylaluminium compound (the cocatalyst), and a halogen compound (the halogenating agent). The nature and concentration of these components, and the polymerization conditions, set the microstructure, molecular weight, and reaction activity.<sup>[18](https://www.researchgate.net/publication/26391883_Polimerizacao_14-cis_de_butadieno_com_sistemas_cataliticos_Ziegler-Natta_a_base_de_neodimio)</sup>

The neodymium route differs operationally from the nickel, cobalt, and titanium technologies. It is the only one that uses specifically aliphatic solvents, and it can run over a wide temperature range without loss of stereospecificity.<sup>[6](https://www.sciencedirect.com/science/article/pii/S0014305704001892)</sup> [Neodymium](https://www.edgepedia.org/neodymium) plants operate adiabatically and reach near-total monomer conversion, superior to the other technologies, which allows the monomer-recovery step to be eliminated and reduces investment and operating costs.<sup>[18](https://www.researchgate.net/publication/26391883_Polimerizacao_14-cis_de_butadieno_com_sistemas_cataliticos_Ziegler-Natta_a_base_de_neodimio)</sup> Catalyst activity varies across the lanthanide series: the propagation rate constant in one comparison was 140 L/(mol·min) for neodymium against 10 for lanthanum, and most active lanthanides give about 95–97% cis units, with neodymium at 97.3%.<sup>[18](https://www.researchgate.net/publication/26391883_Polimerizacao_14-cis_de_butadieno_com_sistemas_cataliticos_Ziegler-Natta_a_base_de_neodimio)</sup>

**Low-cis and vinyl routes.** [Anionic polymerization](https://www.edgepedia.org/anionic-polymerization) with lithium catalysts in hydrocarbon media produces a low-cis rubber with roughly equal cis and trans content and a lesser vinyl fraction; commercial lithium grades contain about 38% cis units.<sup>[11](https://www.synthosgroup.com/en/automotive-2/lithium-butadiene-rubber/)</sup> A separate product, syndiotactic 1,2-polybutadiene, is a thermoplastic with more than 90% 1,2-bonds, average molecular weight around 100,000–200,000, and crystallinity of 15–35%, sold for medical tubing, film, and footwear soles.<sup>[19](https://www.eneos-materials.com/english/products/tpe/rb/)</sup>

## Properties and applications

High-cis BR combines excellent abrasion resistance, high resilience, low heat buildup, low rolling resistance, and good resistance to dynamic stress, and it retains its resilience at low temperatures.<sup>[8](https://www.eneos-materials.com/english/products/g_rubber/br/)</sup><sup> • </sup><sup>[20](https://www.zeon-solutions.com/en/products/sbr-br/)</sup><sup> • </sup><sup>[21](https://www.sabic.com/en/products/polymers/elastomer-products)</sup> These properties make it one of the most used elastomers in the tire industry, in treads and sidewalls, and in belts, hoses, footwear, and rubberized fabric.<sup>[7](https://revistapolimeros.org.br/article/doi/10.1590/S0104-14282005000400015)</sup><sup> • </sup><sup>[8](https://www.eneos-materials.com/english/products/g_rubber/br/)</sup>

**Tires and fuel economy.** High-cis BR is a principal elastomer in the low rolling resistance tire, whose reduced rolling resistance releases less heat and yields a fuel saving of about 5%, with a correspondingly smaller release of toxic substances to the atmosphere.<sup>[18](https://www.researchgate.net/publication/26391883_Polimerizacao_14-cis_de_butadieno_com_sistemas_cataliticos_Ziegler-Natta_a_base_de_neodimio)</sup> For wet-grip performance in treads, BR is commonly blended with styrene-butadiene rubber.<sup>[22](https://essay.utwente.nl/fileshare/file/96281/Rezelman_MA_ET.pdf)</sup>

**Golf balls.** The core of a golf ball is made primarily of polybutadiene, chosen because it is resilient and recovers quickly when stressed by impact with a club, returning a large amount of energy.<sup>[10](https://www.titleist.com/learning-lab/how-its-made/golf-ball-core)</sup> Low-vinyl, high-cis neodymium grades are considered ideal for golf ball cores because of their high resilience.<sup>[8](https://www.eneos-materials.com/english/products/g_rubber/br/)</sup>

**Plastic modification.** Low-cis lithium polybutadiene is used mainly to modify plastics, improving the impact strength and processability of high-impact polystyrene (HIPS) and acrylonitrile-butadiene-styrene (ABS), where its solubility and compatibility with styrenic polymers, light color, and transparency are valued.<sup>[11](https://www.synthosgroup.com/en/automotive-2/lithium-butadiene-rubber/)</sup>

## References

1. [Butadiene Rubber: Synthesis, Microstructure, and Role of Catalysts, Rubber Chemistry and Technology 94 (3), 393–409 (2021)](https://meridian.allenpress.com/rct/article/94/3/393/465710/BUTADIENE-RUBBER-SYNTHESIS-MICROSTRUCTURE-AND-ROLE)
2. [cis-1,4-Polybutadiene, NIST Chemistry WebBook, SRD 69](https://webbook.nist.gov/cgi/formula?ID=C40022035&Mask=4)
3. [Polybutadiene, ScienceDirect Topics overview](https://www.sciencedirect.com/topics/chemical-engineering/polybutadiene)
4. [Modes of Addition for Conjugated Monomers, MATSE 202, Penn State](https://courses.ems.psu.edu/matse202/book/export/html/701)
5. [The melting process and the rigid amorphous fraction of cis-1,4-polybutadiene, Polymer (2008)](https://www.sciencedirect.com/science/article/pii/S0032386108010227)
6. [Synthesis and characterization of high cis-polybutadiene: influence of monomer concentration and reaction temperature, European Polymer Journal (2004)](https://www.sciencedirect.com/science/article/pii/S0014305704001892)
7. [Nunes, Coutinho, Mello (2005). Principais Aspectos da Polimerização do 1,3-Butadieno, Polímeros: Ciência e Tecnologia 15 (4), 296–305](https://revistapolimeros.org.br/article/doi/10.1590/S0104-14282005000400015)
8. [Polybutadiene Rubber / BR, ENEOS Materials](https://www.eneos-materials.com/english/products/g_rubber/br/)
9. [Catalysts & Crosslinking Agents for Rubbers, Umicore](https://csm.umicore.com/en/metal-carboxylates-organics/applications/rubbers-elastomers)
10. [What is the Core of a Golf Ball Made of?, Titleist Learning Lab](https://www.titleist.com/learning-lab/how-its-made/golf-ball-core)
11. [Lithium Butadiene Rubber (SYNTECA LiBR), Synthos](https://www.synthosgroup.com/en/automotive-2/lithium-butadiene-rubber/)
12. [Polydiene, IUPAC Compendium of Chemical Terminology (Gold Book)](https://goldbook.iupac.org/terms/view/15252)
13. [Structure and Properties of Model Polybutadienes: Effect of Microstructure on the Dynamic Mechanical Properties of Rubber](https://www.researchgate.net/publication/249776190_Structure_and_Properties_of_Model_Polybutadienes_-_Effect_of_Microstructure_on_the_Dynamic_Mechanical_Properties_of_Rubber)
14. [Polybutadiene microstructure and thermal properties, Sir Syed College course material](https://sirsyedcollege.ac.in/crm/public/uploads/download_image/BCuxT69IMJi4rfs0JHVhbVjvafNQL2.pdf)
15. [Polybutadienes of Controlled Cis, Trans and Vinyl Structures, CiNii Research](https://cir.nii.ac.jp/crid/1361981468973093120?lang=en)
16. [Microstructural analysis of polybutadienes, Endress+Hauser application note](https://www.us.endress.com/en/endress-hauser-group/Case-studies-application-notes/microstructural-analysis-polybutadienes)
17. [Polymerization of Butadiene Using Ziegler-Natta Catalysts—Recent Developments, Journal of Macromolecular Science Part A 17 (1)](https://www.tandfonline.com/doi/abs/10.1080/00222338208056471)
18. [Mello, Coutinho, Soares et al. (2004). Polimerização 1,4-cis de butadieno com sistemas catalíticos Ziegler-Natta à base de neodímio, Química Nova 27 (2), 277–286](https://www.researchgate.net/publication/26391883_Polimerizacao_14-cis_de_butadieno_com_sistemas_cataliticos_Ziegler-Natta_a_base_de_neodimio)
19. [Syndiotactic 1,2-Polybutadiene / RB, ENEOS Materials](https://www.eneos-materials.com/english/products/tpe/rb/)
20. [SBR / BR (Polybutadiene Rubber), Zeon Corporation](https://www.zeon-solutions.com/en/products/sbr-br/)
21. [SABIC Polybutadiene Rubber (BR), SABIC Elastomer Products](https://www.sabic.com/en/products/polymers/elastomer-products)
22. [Compounding and characterization of tire tread compounds using functionalized rubber, University of Twente thesis](https://essay.utwente.nl/fileshare/file/96281/Rezelman_MA_ET.pdf)

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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Organic reactions, structure and reference › Organic polymer classes › Polyethers and polyolefins › Polydienes and metathesis-derived polymers*

*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*

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