Synthesis of highly isotactic poly[(<i>R</i>)‐3‐hydroxybutyrate] by ring‐opening polymerization of (<i>R,R,R</i>)‐4,8,12‐trimethyl‐1,5,9‐trioxacyclododeca‐2,6,10‐trione

Melchiors, Martin; Keul, Helmut; Höcker, Hartwig

doi:10.1002/marc.1994.030150608

Cited by 12 publications

(10 citation statements)

References 15 publications

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“…Ring-Opening Polymerization of TBL: Experimental Results. As reported earlier, the ring-opening polymerization of TBL to PHB‘ can be achieved in the melt with tin- or titanium-based catalysts (eq 11, Table ) . The best results with respect to conversion and polymer yield are obtained with Bu 2 Sn(OMe) 2 as a catalyst at 120 °C.…”

Section: Resultsmentioning

confidence: 60%

Depolymerization of Poly[(R)-3-hydroxybutyrate] to Cyclic Oligomers and Polymerization of the Cyclic Trimer: An Example of Thermodynamic Recycling

Melchiors¹,

Keul²,

Höcker³

1996

Macromolecules

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Biotechnologically produced poly[(R)-3-hydroxybutyrate] (PHB) was subjected to catalytic depolymerization in the melt and in solution. In the melt depolymerization yields crotonic acid beside linear oligomers according to an ester pyrolysis reaction independent of the catalyst used. In solution cyclic oligomers were obtained via back-biting reactions. Efficient catalysts for this reaction are dibutyltin dimethoxide and p-toluenesulfonic acid. The thermodynamic parameters of the depolymerization of PHB to yield (R,R,R)-4,8,12-trimethyl-1,5,9-trioxacyclododeca-2,6,10-trione (TBL) were determined from calorimetric measurements by Lebedev et al. as a function of temperature at standard pressure (p = 101.325 kPa) and are at T = 400 K: ΔH°depol = −43 kJ·mol-1, ΔS°depol = 66 J·K-1 mol-1, and ΔG°depol = −70 kJ·mol-1. The experimental results are in full agreement with these values. Polymerization of TBL in the melt with dibutyltin dimethoxide as initiator results in poly[(R)-3-hydroxybutyrate] (PHB‘) of low molecular weight (M n = 5 × 103), the spectroscopic characteristics are identical with those of the biotechnologically produced material. The thermodynamic parameters of the polymerization were determined from calorimetric measurements by Lebedev et al. as a function of temperature; they are at standard pressure (p = 101.325 kPa) and a polymerization temperature of T = 400 K: ΔH°pol = 12 kJ·mol-1, ΔS°pol = −32 J·K-1·mol-1, and ΔG°pol = 25 kJ·mol-1. These results contradict the polymerization experiment. The factors which may contribute to a decrease of ΔG°pol are discussed.

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Section: Resultsmentioning

confidence: 60%

Depolymerization of Poly[(R)-3-hydroxybutyrate] to Cyclic Oligomers and Polymerization of the Cyclic Trimer: An Example of Thermodynamic Recycling

Melchiors¹,

Keul²,

Höcker³

1996

Macromolecules

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“…Importantly, the Zn–O(ligand) unit is closer to the adjacent PHB carbonyl group compared to PCL (refer to SI for details), which presumably facilitates ligand reactivity. Elimination reactions that form crotonate or carboxy PHB end groups can be catalyzed by [(BDI)Zn(O i Pr)], Al(O i Pr) 3 , and tin-based catalysts. − While the MALDI-ToF analysis showed no evidence of crotonate or carboxy end groups, trace resonances of the crotonate groups were observed by 1 H NMR spectroscopy (5.81 and 7.00 ppm), suggesting that LZn 2 OBn may promote elimination reactions (refer to SI for further details). These findings agree with the M n values determined by 1 H NMR spectroscopy (Table S4), which were approximately half the calculated M n values.…”

Section: Results and Discussionmentioning

confidence: 99%

In Situ Versus Isolated Zinc Catalysts in the Selective Synthesis of Homo and Multi-block Polyesters

et al. 2020

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The in situ generation of metal-alkoxide complexes is a common initiation method in cyclic ester ring-opening polymerisation. Yet this method is often a "black box", where the species so generated are assumed to be the same as the isolated complex. We now demonstrate that an isolated Zn-benzoxide catalyst gives a remarkable reactivity enhancement in lactide ROP, with kobs values 10 times higher than the in situ generated analogue. The dinuclear zinc catalyst, built using the Trost ProPhenol ligand, offers these excellent activities and good control over homopolymerisation of multiple cyclic esters (rac-lactide, ε-caprolactone and rac-βbutyrolactone). The stability of this isolated catalyst also controls chain exchange and back-biting, allowing for one-pot synthesis of multi-block polyesters without loss of activity, selectivity and control. To the best of our knowledge, this is the first catalyst reported for the selective preparation of block terpolymers of ε-CL, rac-LA and rac-β-BL.

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“…The TBL obtained by ring-closing depolymerization of P3HB can be polymerized in the melt with dibutyltin dimethoxide as initiator, resulting in poly[(R)-3HB] of low molecular weight (M n = $5 kg/mol, Ð = 1.3-1.7). 57,58 However, both the TBL yield from the depolymerization of poly[(R)-3HB] and the M n of the resulting poly[(R)-3HB] from the repolymerization of TBL in this P3HB chemical recycling scheme are too low to be practically useful.…”

Section: Chemical Recycling Of P3hb Via a Cyclic Trimermentioning

confidence: 99%

Toward Infinitely Recyclable Plastics Derived from Renewable Cyclic Esters

Tang

Chen

2019

Chem

291

180

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Plastics, used in countless consumer products that our daily lives depend on, have become indispensable materials essential for modern life and the global economy. At the same time, currently unsustainable practices in the production and disposal of plastics continue to deplete our finite natural resources and create severe worldwide environmental consequences. In the search for feasible solutions to these issues, significant recent advances have been made in developing chemically recyclable plastics, which allow for recovery of the buildingblock chemicals via depolymerization, for repolymerization to virgin-quality plastics, or for creative repurposing into value-added materials. Among such recyclable plastics, polyesters derived from renewable cyclic esters possess real potential to meet these challenges. Hence, this review highlights the plastics derived from common four-, five-, six-, seven-, and eight-membered cyclic esters by covering synthetic strategies, material properties, and, particularly, chemical recyclability. Such studies have culminated a recent discovery of infinitely recyclable plastics with properties of common plastics.

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Synthesis of highly isotactic poly[(R)‐3‐hydroxybutyrate] by ring‐opening polymerization of (R,R,R)‐4,8,12‐trimethyl‐1,5,9‐trioxacyclododeca‐2,6,10‐trione

Cited by 12 publications

References 15 publications

Depolymerization of Poly[(R)-3-hydroxybutyrate] to Cyclic Oligomers and Polymerization of the Cyclic Trimer: An Example of Thermodynamic Recycling

Depolymerization of Poly[(R)-3-hydroxybutyrate] to Cyclic Oligomers and Polymerization of the Cyclic Trimer: An Example of Thermodynamic Recycling

In Situ Versus Isolated Zinc Catalysts in the Selective Synthesis of Homo and Multi-block Polyesters

Toward Infinitely Recyclable Plastics Derived from Renewable Cyclic Esters

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