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We report here the synthesis and polymerization of a novel disubstituted valerolactone, β-acetoxy-δ-methylvalerolactone, derived from the renewable feedstock triacetic acid lactone (TAL). The bulk polymerization proceeds to 45% equilibrium monomer conversion at room temperature using diphenyl phosphate as the organic catalyst. The resultant amorphous material displays a glass transition temperature of 25 °C. The ring opening polymerization (ROP) behavior of the disubstituted valerolactone was examined, and the enthalpy () and entropy *() of polymerization were calculated to be −25 ± 2 kJ mol −1 and −81 ± 5 mol −1 K −1 , respectively. The polymerization kinetics were also measured and compared to those of other substituted valerolactones reported in the literature. This report is the first to demonstrate the successful ROP of a disubstituted valerolactone as well as the first to establish the ROP of a derivative of TAL.
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Cascade Ring Strain Release Polymerization of Cyclohexene Oxide and Derivatives Using a Mono(μ-Alkoxo)bis(alkylaluminum) Initiator
Cyclohexene oxide (CHO) is a useful building block for the synthesis of novel materials and is a model substrate for polymerization catalyst development. The driving force for CHO polymerization is derived from its bicyclic structure, which combines the release of the enthalpy from epoxide ring-opening (ca. −15 kcal/mol) and a twist-chair-to-chair conformation shift in the cyclohexane ring (ca. −5 kcal/mol) upon enchainment. The lack of regio-defined functional handles attached to the CHO monomer limits the ability to both pre- and post-functionalize the resultant materials and establish structure–property relationships, which reduces the versatility of currently accessible materials. We report the synthesis of two series of CHO derivatives with butyl, allyl, and halogen substituents in the α and β positions relative to the epoxide ring. Adding substituents to the CHO ring was found to affect polymerization kinetics, with 4-substituted (β) CHO being more reactive than 3-substituted (α) CHO analogs when initiated with a mono(μ-alkoxo)bis(alkylaluminum) pre-catalyst. Polymer thermal properties depended on substituent location and identity. Halogenated CHO rings were most reactive and produced the highest glass transition temperatures in the resultant polymers (up to 105 °C). Density functional theory revealed a possible mechanistic explanation consistent with the observed differences in polymerization rate for the 3- and 4-substituted CHOs derived from a combination of steric and thermodynamic considerations.
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- Award ID(s):
- 2004167
- PAR ID:
- 10467563
- Publisher / Repository:
- Macromolecules
- Date Published:
- Journal Name:
- Macromolecules
- Volume:
- 56
- Issue:
- 13
- ISSN:
- 0024-9297
- Page Range / eLocation ID:
- 4884 to 4894
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.macromol.3c00473
