Ring-opening Polymerization Of Β-butyrolactone Research Articles

Star-shaped Poly(hydroxybutyrate)s from bio-based polyol cores via zinc catalyzed ring-opening polymerization of β-Butyrolactone

The ring-opening polymerization (ROP) of cyclic esters using multifunctional initiators is an efficient methodology that allows the preparation of polyesters with well-defined architectures. Here a series of star-shaped poly(β-hydroxybutyrates) (PHBs) has been synthesized by ROP of β-butyrolactone (BBL) with an amido-oxazolinate zinc catalyst. The star-shaped structure is constructed via a core-first approach, in which several bio-based multifunctional alcohols serve as the initiator for ROP. Specifically, three-, four-, and multi-armed star polymers are obtained and characterized by various techniques including NMR, GPC, TGA, and DSC, and the incorporation of the core structure in the star-shaped PHBs has been confirmed. The thermal properties can be modified by changing the arm number and arm length of PHBs, and the thermal stability decreases as the number of arms increases when they have the same arm lengths. The wetting behavior determined from AFM studies demonstrates a minimum in the macroscopic contact angle as a function of the number of arms of a star-shaped PHB.

Cyclic and Linear Polyhydroxylbutyrates from Ring-Opening Polymerization of β-Butyrolactone with Amido-Oxazolinate Zinc Catalysts

A series of amido-oxazolinate zinc complexes have been employed for the ring-opening polymerization of rac-β-butyrolactone (BBL). Experimental results show that these complexes efficiently catalyze...

Electrospun Pectin-Polyhydroxybutyrate Nanofibers for Retinal Tissue Engineering.

Natural polysaccharide pectin has for the first time been grafted with polyhydroxybutyrate (PHB) via ring-opening polymerization of β-butyrolactone. This copolymer, pectin-polyhydroxybutyrate (pec-PHB), was blended with PHB in various proportions and electrospun to produce nanofibers that exhibited uniform and bead-free nanostructures, suggesting the miscibility of PHB and pec-PHB. These nanofiber blends exhibited reduced fiber diameters from 499 to 336–426 nm and water contact angles from 123.8 to 88.2° on incorporation of pec-PHB. They also displayed 39–335% enhancement of elongation at break relative to pristine PHB nanofibers. pec-PHB nanofibers were found to be noncytotoxic and biocompatible. Human retinal pigmented epithelium (ARPE-19) cells were seeded onto pristine PHB and pec-PHB nanofibers as scaffold and showed good proliferation. Higher proportions of pec-PHB (pec-PHB10 and pec-PHB20) yielded higher densities of cells with similar characteristics to normal RPE cells. We propose, therefore, that nanofibers of pec-PHB have significant potential as retinal tissue engineering scaffold materials.

Enzymatic degradation of synthetic poly(3-hydroxybutyrates) as a tool for combinatorial microstructure determination

Microstructure of synthetic poly(3-hydroxybutyrate) (PHB) prepared by catalytic ring opening polymerization of β-butyrolactone determines the merit of the polymer for applications. Depending on the catalyst used, synthetic PHB can possess a complex microstructure, elucidation of which is not always straightforward. One of such PHBs is analyzed in this work using fractionation of the polymer, differential scanning calorimetry, X-ray powder diffraction, 1H and 13C NMR spectroscopy and, particularly, enzymatic hydrolysis. Only by correlation of the data obtained from different analytic methods, the detailed structural elucidation of the synthesized polymer becomes possible. That is, the bulk polymer features isotactic and syndiotactic enrichment at the same time. Based on the results of the analyses, a multi-stereoblock microstructure of the studied synthetic PHB is ruled out, suggesting a negligible rate of chain transfer/shuttling/transesterification reactions compared to polymerization rate under the applied conditions. An enantiomorphic site control of stereoregularity both for isotactic and for syndiotactic enchainment is found.

Versatile 2-Methoxyethylaminobis(phenolate)yttrium Catalysts: Catalytic Precision Polymerization of Polar Monomers via Rare Earth Metal-Mediated Group Transfer Polymerization

The present study is one of the first examples for rare earth metal-mediated group transfer polymerization (REM-GTP) with non-metallocene catalyst systems. 2-Methoxyethylaminobis(phenolate)yttrium trimethylsilylmethyl complexes were synthesized and showed moderate to high activities in the rare earth metal-mediated group transfer polymerizations of 2-vinylpyridine, 2-isopropenyl-2-oxazoline, diethyl vinylphosphonate, diisopropyl vinylphosphonate, and N,N-dimethylacrylamide as well as in the ring-opening polymerization of β-butyrolactone. Reaction orders in catalyst and monomer were determined for the REM-GTP of 2-vinylpyridine. The mechanistic studies revealed that the catalyst systems follow a living monometallic group transfer polymerization mechanism allowing a precise molecular-weight control of the homopolymers and the block copolymers with very narrow molecular weight distributions. Temperature-dependent reaction kinetics were conducted and allowed conclusions about the influence of the bulky substituents around the metal center on the polymerization activity. Additional polymerization experiments concerning the combination of REM-GTP and ROP to obtain block copolymers were performed.

Polymerization of cyclic esters using N-heterocyclic carbene carboxylate catalysts

The ring-opening polymerization of β-butyrolactone and lactide in solvent-free conditions and using NHC carboxylates as a (pre)catalyst is described. This class of catalysts enables the synthesis of aliphatic polyesters. These organocatalysts, which are easily synthesized, are remarkably robust, thus allowing the use of a bench-top reaction setup. In addition, NHC carboxylates are highly active in bulk conditions without the use of additives. Also, we have demonstrated for the first time that decarboxylation of NHC carboxylates depends on the nature of solvents under polymerization conditions.

Polyester hydrolytic and synthetic activity catalyzed by the medium-chain-length poly(3-hydroxyalkanoate) depolymerase from Streptomyces venezuelae SO1

The extracellular medium-chain-length polyhydroxyalkanote (MCL-PHA) depolymerase from an isolate identified as Streptomyces venezuelae SO1 was purified to electrophoretic homogeneity and characterized. The molecular mass and pI of the purified enzyme were approximately 27kDa and 5.9, respectively. The depolymerase showed its maximum activity in the alkaline pH range and 50°C and retained more than 70% of its initial activity after 8h at 40°C. The MCL-PHA depolymerase hydrolyzes various p-nitrophenyl-alkanoates and polycaprolactone but not polylactide, poly-3-hydroxybutyrate, and polyethylene succinate. The enzymatic activity was markedly enhanced by the presence of low concentrations of detergents and organic solvents, being inhibited by dithiothreitol and EDTA. The potential of using the enzyme to produce (R)-3-hydroxyoctanoate in aqueous media or to catalyze ester-forming reactions in anhydrous media was investigated. In this sense, the MCL-PHA depolymerase catalyzes the hydrolysis of poly-3-hydroxyoctanoate to monomeric units and the ring-opening polymerization of β-butyrolactone and lactides, while ε-caprolactone and pentadecalactone were hardly polymerized.

Homo- and Hetero-bimetallic Flexibly Linked Dinuclear Salphen Complexes Homo- and Hetero-bimetallic Flexibly Linked Dinuclear Salphen Complexes

Abstract A modification of the previously developed synthetic approach towards dinuclear flexibly linked salphen complexes is successfully utilized for the preparation of heterodinuclear salphen dimers. A dinuclear salphen species with Pd(II) and Cr(III) centers bears a stronger structural resemblance to the related bis-Cr(III) compound than the corresponding mononuclear Cr(III) salphen complex. Therefore, it was considered as a more useful model for the comparison with the homobinuclear Cr(III) complex regarding the catalytic activity in the ring-opening polymerization of β-butyrolactone, for which a bimetallic catalytic mechanism seems to operate. The polymerization results again have shown a higher activity of the homobinuclear Cr(III) complex.

Synthesis and evaluation of effectiveness of a controlled release preparation 2,4-d: a reduction of risk of pollution and exposure of workers

1 H-NMR, ESI-MS characterization of oligomers, assessment of the herbicide effectiveness. Abstract: A novel herbicidal controlled release formulation composed of (2,4-dichlorophenoxy) acetic acid (2,4-D) chemically bonded to biodegradable (R,S)-3-hydroxybutyric acid oligomers was investigated. The synthesis of (R,S)-3-hydroxy butyric acid oligomers was carried out via the ring opening polymerization of β-butyrolactone initiated by 2,4-dichlorophenoxy acetic potassium salt in the presence of complexing agents. The formed oligomers were characterized by size exclusion chromatography, proton magnetic resonance and electrospray mass spectrometry in order to fi nd out their molar mass distribution and molecular structures. An assessment of biological effectiveness of the obtained herbicidal formulation was carried out in the greenhouse vs. Sinapis alba var. Nakielska. A promotion of the controlled release formulation with decreased water solubility and with low vapor pressure of the active ingredient, instead of traditional formulations of 2,4-dichlorophenoxy acetic acid may help to ensure a greater safety for workers and reduce the risk of dissemination of the active ingredient in the soil profi le.

Electrospray tandem mass spectrometry of poly(3-hydroxybutanoic acid) end groups analysis and fragmentation mechanism

The electrospray ionization tandem mass spectrometry technique applied for the first time to aliphatic polyester analysis, allowed fast and reliable identification of the various macromolecules of poly(3-hydroxybutanoic acid) (PHB), synthesized via ring-opening polymerization of β-butyrolactone. It was demonstrated that the biomimetic polymers studied contain various end groups, depending on the anionic initiator employed, and show close similarity to the natural PHB produced by enzymes in living cells of prokaryotic and eukaryotic organisms. © 1998 John Wiley & Sons, Ltd.

Ring-Opening Polymerization of β-Butyrolactone by Thermophilic Lipases

Ring-Opening Polymerization of β-Butyrolactone by Thermophilic Lipases

The molecular structure of (R,S)-[Al6But6(μ3-O)4{μ3-O2CCH2C(H)(Me)O}2]: evidence for the latent Lewis acid catalyzed polymerization of (R,S)-β-butyrolactone

The reaction of [ButAl(µ3-O)]6 with 2 equiv. of (R,S)-β-butyrolactone resulted in the formation of the alumoxane, (R,S)-[Al6But6(µ3-O)4{µ3-O2CCH2C(H)(Me)O}2], with a molecular structure consisting of two ring-opened lactone moieties inserted into, and bridging, the edge of the Al6O6 alumoxane. The role of this alumoxane in the latent Lewis acid catalyzed ring-opening polymerization of β-butyrolactone is discussed.

Synthesis of a block copolymer of poly(3-hydroxybutyrate) and poly(ethylene glycol) and its application to biodegradable polymer blends

A block copolymer {P[(R,S)-HB-b-EG]} of atactic poly[(R,S)-3-hydroxybutyrate] {P[(R,S)-HB]} and poly(ethylene glycol) (PEG) was prepared by the ring-opening polymerization of β-butyrolactone in the presence of a macroinitiator (PEG/ZnEt2/H2O) which had been produced by the reaction of α,ω-dihydroxy PEG ( $$\overline M $$ n=3000) with ZnEt2/H2O (1/0.6) catalyst. The block copolymer ( $$\overline M $$ n=10,500, $$\overline M $$ w/ $$\overline M $$ n=1.2) was an A-B-A triblock copolymer comprising atactic P[(R,S)-HB] (A) and PEG (B) segments. The miscibility, physical properties, and biodegradability of binary blends of microbial poly[(R)-3-hydroxybutyrate] {P[(R)-HB]} with the block copolymer P[(R,S)-HB-b-EG] has been studied. The glass-transition temperature (T g) data showed that the P[(R)-HB]/P[(R,S)-HB-b-EG] blend was miscible in the amorphous state. The P[(R)-HB] film became flexible and tough by means of blending with P[(R,S)-HB-b-EG] block copolymer. The enzymatic degradation of blend films was carried out at 37°C and pH 7.4 in a 0.1M phosphate solution of an extracellular PHB depolymerase fromAlcaligenes faecalis. The enzymatic degradation took place solely on the surface of the blend films.