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Ring-opening copolymerization thermodynamics and kinetics of ?-valerolactone/?-caprolactone.

ABSTRACT: The general misconception that ?-lactones are not thermodynamically polymerizable has limited the development of all ?-lactone-based copolymers. A few studies have reported copolymerization of these five-membered cyclic esters with more reactive monomers, yet a systematic investigation of kinetics and thermodynamics is still lacking. To explore the feasibility of the reaction, we combined equilibrium and non-isothermal syntheses for the copolymerization of ?-valerolactone with ?-caprolactone, initiated with methoxy polyethyleneglycol and catalyzed by Tin(II) 2-ethylhexanoate. Here, we present the polymerization kinetic and thermodynamic parameters for different monomer ratios in the reaction feed. We observed the dependency of enthalpy and entropy of polymerization upon monomer ratio changes, and estimated a linear increase in the activation energy by increasing the ?-valerolactone fraction in the starting monomer mixture. Our data demonstrate that ?-valerolactone can copolymerize with ?-caprolactone, but only under specific conditions. The reaction parameters determined in this study will enable preparation of additional ?-valerolactone-based copolymers and development of a family of degradable materials with improved properties in respect to commonly used polyesters.

SUBMITTER: Gagliardi M

PROVIDER: S-EPMC6013151 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Ring-opening copolymerization thermodynamics and kinetics of γ-valerolactone/ϵ-caprolactone.

Gagliardi Mariacristina M Bifone Angelo A

PloS one 20180621 6

The general misconception that γ-lactones are not thermodynamically polymerizable has limited the development of all γ-lactone-based copolymers. A few studies have reported copolymerization of these five-membered cyclic esters with more reactive monomers, yet a systematic investigation of kinetics and thermodynamics is still lacking. To explore the feasibility of the reaction, we combined equilibrium and non-isothermal syntheses for the copolymerization of γ-valerolactone with ϵ-caprolactone, in ...[more]

PMID: 29927986

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Project description:Thermoplastic elastomers benefit from high elasticity and straightforward (re)processability; they are widely used across a multitude of sectors. Currently, the majority derive from oil, do not degrade or undergo chemical recycling. Here a new series of ABA triblock polyesters are synthesized and show high-performances as degradable thermoplastic elastomers; their composition is poly(cyclohexene-alt-phthalate)-b-poly(ε-decalactone)-b-poly(cyclohexene-alt-phthalate) {PE-PDL-PE}. The synthesis is accomplished using a zinc(ii)/magnesium(ii) catalyst, in a one-pot procedure where ε-decalactone ring-opening polymerization yielding dihydroxyl telechelic poly(ε-decalatone) (PDL, soft-block) occurs first and, then, addition of phthalic anhydride/cyclohexene oxide ring-opening copolymerization delivers semi-aromatic polyester (PE, hard-block) end-blocks. The block compositions are straightforward to control, from the initial monomer stoichiometry, and conversions are high (85-98%). Two series of polyesters are prepared: (1) TBPE-1 to TBPE-5 feature an equivalent hard-block volume fraction (f hard = 0.4) and variable molar masses 40-100 kg mol-1; (2) TBPE-5 to TBPE-9 feature equivalent molar masses (∼100 kg mol-1) and variable hard-block volume fractions (0.12 < f hard < 0.4). Polymers are characterized using spectroscopies, size-exclusion chromatography (SEC), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). They are amorphous, with two glass transition temperatures (∼-51 °C for PDL; +138 °C for PE), and block phase separation is confirmed using small angle X-ray scattering (SAXS). Tensile mechanical performances reveal thermoplastic elastomers (f hard < 0.4 and N > 1300) with linear stress-strain relationships, high ultimate tensile strengths (σ b = 1-5 MPa), very high elongations at break (ε b = 1000-1900%) and excellent elastic recoveries (98%). There is a wide operating temperature range (-51 to +138 °C), an operable processing temperature range (+100 to +200 °C) and excellent thermal stability (T d,5% ∼ 300 °C). The polymers are stable in aqueous environments, at room temperature, but are hydrolyzed upon gentle heating (60 °C) and treatment with an organic acid (para-toluene sulfonic acid) or a common lipase (Novozyme® 51032). The new block polyesters show significant potential as sustainable thermoplastic elastomers with better properties than well-known styrenic block copolymers or polylactide-derived elastomers. The straightforward synthesis allows for other commercially available and/or bio-derived lactones, epoxides and anhydrides to be developed in the future.

Dataset Information

Ring-opening copolymerization thermodynamics and kinetics of ?-valerolactone/?-caprolactone.

Publications

Ring-opening copolymerization thermodynamics and kinetics of γ-valerolactone/ϵ-caprolactone.

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