Bacterial Copolyesters Research Articles

Modulated crystallization behavior of bacterial copolyester poly(3-hydroxybutyrate-co-3-hydroxyhexanoate): Effect of a linear multiple amides derivative as a nucleator

A multiple amides-based linear organic compound (TMC-300) was synthesized and as an efficient nucleator was incorporated into PHBH to fabricate PHBH/TMC-300 composite to investigate effect of TMC-300 on crystallization behavior of PHBH in-depth. Nucleation capacity of TMC-300 on the PHBH is significantly higher than those of two conventional inorganic nucleators. TMC-300 exhibits dual effects on crystallization behavior of PHBH in terms of its weight fraction (fTMC-300). Low fTMC-300 increased substantially crystallization rate, crystallinity and crystal density, and decreased greatly crystallization time of PHBH, but relative higher fTMC-300 hindered slightly crystallization process. Hydrogen bond interaction exists between PHBH and TMC-300 and facilitates excellent dispersion of TMC-300 in PHBH matrix. In-situ FTIR measurement suggests that hydrogen interaction hindered reorganization of ester bond in crystallization process of PHBH. Mechanisms on nucleation of PHBH and effect of TMC-300 on crystallization behavior of PHBH, are proposed and discussed.

Effect of the Addition of Nano-Clay on the Physical Property and the Melt-Spinnability of Bacterial Polyester

Synthetic mica organically treated with alkylamines was added to poly (3-hydroxybutyrate-co-3hydroxyhexanoate) (PHBH), one of the bacterial co-polyesters. Mica dispersing in PHBH acted as a crosslinking point of PHBH chains and increased the melt viscosity of PHBH significantly. The melt spinnability of PHBH was greatly improved by the addition of mica and the crystallization of PHBH in the spinline was highly promoted. WAXD spectra showed that the as-spun fibers of PHBH/MICA contain both highly oriented α-and β-forms of PHBH crystal. Further the SAXS revealed that the mica dispersing in the PHBH fiber oriented with its surface parallel to the fiber axis. The crystalline orientation of PHBH, orientation of mica, and the formation of β-form all improve the mechanical property of PHBH fibers.

Crystallization kinetics of bacterial poly(3‐hydroxylbutyrate) copolyesters with cyanuric acid as a nucleating agent

AbstractEffects of cyanuric acid (CA) on nonisothermal and isothermal crystallization, melting behavior, and spherulitic morphology of bacterial copolyesters of poly(3‐hydroxybutyrate), i.e., poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) (PHBH), have been investigated. CA has excellent acceleration effectiveness on the melt crystallization of bacterial PHB, PHBV, and PHBH, better than the nucleating agents reported in the literatures, such as boron nitride, uracil, and orotic acid. PHBV and PHBH do not crystallize upon cooling from the melt at 10°C/min, while they are able to complete crystallization under the same conditions with an addition of 1% CA, with a presence of sharp crystallization exotherm at 75–95°C. Isothermal crystallization kinetics of neat and CA‐containing PHBV and PHBH were analyzed by Avrami model. Crystallization half‐times (t1/2) of PHBV and PHBH decrease dramatically with an addition of CA. The melting behavior of isothermally melt‐crystallized PHBV and PHBH is almost not influenced by CA. Spherulitic numbers of PHBV and PHBH increase and the spherulite sizes reduce with an incorporation of CA. Nucleation densities of PHBV and PHBH increase by 3–4 orders of magnitude with a presence of 1% CA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis, characterizations, and biocompatibility of block poly(ester‐urethane)s based on biodegradable poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3/4HB) and poly(ε‐caprolactone)

A type of block poly(ester-urethane)s (abbreviated as PUBC) based on bacterial copolyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) and biodegradable poly(ε-caprolactone) (PCL) was synthesized by melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent, with different 3HB, 4HB and PCL contents and segment lengths. Stannous octanoate (Sn(Oct)(2)) was used as catalyst. The chemical structure, molecular weight and thermal property were characterized by (1)H NMR, FTIR GPC, DSC and TGA. DSC analysis revealed that the PUBC polyurethanes exhibit amorphous to semi-crystalline (20.9% crystallinity degree) with T(g) range from -39.7 to -21.5 °C. The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). The obtained PUBCs are hydrophobic (water contact angle 73.7-90.2°). Platelet adhesion study and plasma recalcification time revealed that the block polyurethanes possess hemastasis ability. CCK-8 assay illuminated that the no cytotoxic polyurethanes maintain rat aortic smooth muscle cells (RaSMCs) good viability. It was found that the 4HB content in the materials is an important factor to affect the sustainable cell viability.

Modeling the kinetics of water transport and hydroexpansion in a lignocellulose-reinforced bacterial copolyester

The governing kinetic behavior of water transport in a biopolymeric composite material derived from poly(β-hydroxybutyrate)-co-poly(β-hydroxyvalerate) and lignocellulosic wood flour were investigated along with the influence of temperature, wood flour content, and chemical modification (silane, maleic anhydride) on polymer and composite diffusivity. The water absorption process in both untreated and treated composites was found to follow the kinetics of Fickian diffusion theory. Diffusion coefficients for neat polymer and composite samples were experimentally determined, and the thermodynamics of diffusive water transport were observed to exhibit Arrhenius rate-law behavior. A model for predicting equilibrium moisture content in wood-polymer composites is presented and substantiated by obtained results and cited experimental data. Isodiffusion plots are presented to evaluate the effectiveness of chemical modifications, which were found to reduce the rates of water uptake. Both in- and out-of-plane dimensional changes were monitored during the absorption process, permitting the determination of moisture-dependent hydroexpansion coefficients.

Amorphous amphiphilic P(3HV-co-4HB)-b-mPEG block copolymer synthesized from bacterial copolyester via melt transesterification: Nanoparticle preparation, cisplatin-loading for cancer therapy and in vitro evaluation

Cisplatin is a chemotherapeutic agent used against a variety of tumors. We determined the efficacy and bioavailability of cisplatin in the form of cisplatin-loaded self-assembled amphiphilic copolymer nanoparticles (NPs). Non-crystallizing bacterial copolyester was employed as hydrophobic segment to increase drug loading efficiency. Novel amorphous amphiphilic block copolymer P(3HV-co-4HB)-b-mPEG was synthesized from bacterial copolyester poly(3-hydroxyvalerate-co-4-hydroxybutyrate) coupled via transesterification reaction using bis(2-ethylhexanoate) tin catalyst to monomethoxypoly(ethylene glycol). The product was characterized, and core–shell particles with nanometer size range were prepared by emulsification–solvent evaporation method. Transmission electron microscopy (TEM) examination revealed that the NPs took the shape of spheres with inner concealed core of hydrophobic P(3HV-co-4HB) polymer and the outer shell formed by hydrophilic mPEG segment. The in vitro release profile of cisplatin from the core hydrophobic domain showed a sustained release of the drug. TEM and confocal microscopy examination revealed clearly the internalization of cisplatin-loaded NPs into the tumor cells. MTT assay, flow cytometry, western blot and confocal microscopy revealed a suppression effect by the NPs on tumor cell growth, and enhancement of apoptotic process of the tumor cells compared to free drug treated cells. The amorphous polymeric NPs could be effective vehicles for the sustained delivery of toxic anticancer drugs.

Elaboration and Characterization of Nano-Biocomposites Based on Plasticized Poly(Hydroxybutyrate-Co-Hydroxyvalerate) with Organo-Modified Montmorillonite

Nano-biocomposites based on a biodegradable bacterial copolyester, poly(hydroxybutyrate-co-hydroxyvalerate), have been elaborated with an organo-modified montmorillonite (OMMT) clay as nanofiller, and acetyl tributyl citrate as plasticizer. The corresponding (nano)structures, thermal and mechanical properties, permeability, and biodegradability have been determined. Polyhydroxyalkanoates are very thermal sensitive then to follow the degradation the corresponding matrices have been analyzed by size exclusion chromatography. The results indicate that the addition of the plasticizer decreases the thermo-mechanical degradation, during the extrusion. These nano-biocomposites show an intercalated/exfoliated structure with good mechanical and barrier properties, and an appropriated biodegradation kinetic. Intending to understand the changes in the thermal properties, the nano-biocomposites were characterized by thermal gravimetric analysis and differential scanning calorimetry. The presence of the OMMT clay did not influence significantly the transition temperatures. However, the filler not only acted as a nucleating agent which enhanced the crystallization, but also as a thermal barrier, improving the thermal stability of the biopolymer. The results indicated that the addition of the plasticizer reduces the glass transition temperature and the crystalline melting temperature. The plasticizer acts as a processing aid and increases the processing temperature range (lower melting temperature).

Cyclodextrin-Modified Polyesters from Lactones and from Bacteria: An Approach to New Drug Carrier Systems

Copper(I)-catalyzed cycloaddition of synthetic and bacterial copolyesters bearing pendant alkyne group with mono-(6-azido-6-desoxy)-β-cyclodextrin was carried out to synthesize β-CD-functionalized copolyester. The synthetic “clickable” copolyesters were obtained by the ring-opening copolymerization of the propargyl-modified lactones and e-caprolactone. The bacterial copolyesters containing an alkyne group were biosynthesized from a mixture of 10-undecynoic acid and hexanoic acid by the Gram-negative bacteria Pseudomonas oleovorans. The modified products of the “click” reaction were characterized by FT-IR, 1H NMR spectroscopy, and DSC. Furthermore, the host guest capability of covalently attached β-cyclodextrin moieties was proved by dynamic light scattering measurements.

Rapid crystallization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer accelerated by cyclodextrin-complex as nucleating agent

The nucleation effect of inclusion complex (IC) between poly(3-hydroxybutyrate) (PHB) and alpha-cyclodextrin (α-CD) on the rapid crystallization of a series of bacterial copolyesters poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with 3HH molar fraction ranging from 7 to 18 mol% was investigated by differential scanning calorimetry (DSC) and a polarized optical microscopy (POM). The results were compared with the effectiveness of PHB particles as a nucleation agent. Both the PHB-IC and the PHB particles enhance the nucleation and crystallization of PHBH, whereas the PHB-IC particles show much more effective nucleation ability than the PHB particles for the crystallization of PHBH. With introduction of PHB-IC, PHBH with 18% 3HH unit can finish crystallization during cooling process from the melt at 10 °C/min, and its crystallinity is greatly increased. The crystallization half-time (t1/2) of PHBH with 7–18% 3HH units decreases significantly in the presence of PHB-IC. The PHB crystals in the PHB-IC are suggested to favorably nucleate PHBH crystallization with the same crystalline lattice.

Effect of Aging on the Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

The effect of aging on the mechanical properties was investigated for a series of bacterial copolyester poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)] with 3HH molar fraction ranging from 5 to 18 mol %. The mechanism behind the aging phenomenon was studied by using gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS) in parallel to the tensile testing. It was found that the high initial crystallinity and the narrower amorphous region in the P(3HB-co-3HH) films are the key factors that cause the secondary crystallization in the aging process to embrittle the films of copolymers with 3HH fraction lower than 10 mol %. For the copolymers with 3HH fractions higher than 10 mol %, because of the intrinsically lower crystallinity and thicker amorphous region, the secondary crystallization cannot affect the mechanical properties significantly.

Bio-composite of bacterial poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) reinforced with vegetable fibers

Composites of a bacterial copolyester poly(3-hydroxybutyrate- co-3-hydroxyhexanoate), P(3HB- co-3HH), with flax fibers were investigated. A satisfactory reinforcing effect was observed in composites prepared by compression molding and using long fiber mats (long fiber composites, LFC). On the other hand, composites obtained by batch mixing fibers with molten polymer resulted in poor mechanical properties, owing to drastic fiber shortening during processing (short fiber composites, SFC). In order to improve fiber–matrix adhesion in SFC, fibers chemically modified at the surface (by acetylation or by short-chain-PEG grafting) were also used. The best results were obtained with surface acetylated fibers. In the flax fiber composites the crystallization rate of P(3HB- co-3HH) remarkably increased compared with that of the plain polyester. The fibers displayed a nucleating effect on P(3HB- co-3HH) crystallization, whose magnitude depended on fiber surface chemistry. This feature was confirmed by the appearance of transcrystallinity in isothermal crystallisation experiments run in a hot stage of a polarized optical microscope.

Thermal and dynamic mechanical properties of binary blends of bacterial copolyester poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) with poly(2-hydroxyethylmethacrylate) (PHEMA)

Thermal and dynamic mechanical properties of binary blends of bacterial copolyester poly(hydroxybutyrate-co-hydroxyvalerate) (PHBHV) with poly(2-hydroxyethylmethacrylate) (PHEMA)

Cocrystallization and Phase Segregation in Blends of Two Bacterial Polyesters

AbstractBy fractional precipitaion of bacterial copolyesters, it has been strongly suggested that the bacterial PHA copolymer normally has broad and/or multimodal chemical composition distribution (CCD). In this paper, we try to review the works on the blends of two bacterial polyesters in order to accumulate knowledge on the relation between CCD and various properties required for the practical application of bacterial copolymers. Phase structures of the blends of poly(3‐hydroxybutyrate) [PHB] and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [PHB‐HV] and crystallization kinetics of the blends of PHB‐HV and poly(3‐hydroxybutyrate‐co‐3‐hydroxypropionate) [PHB‐HP] are described.

Infrared Spectroscopy and X‐Ray Diffraction Studies on the Structure and Thermal Behavior of Biodegradable Polyhydroxyalkanoates

AbstractThe structure and thermal behavior of new types of bacterial copolyester, poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate); P(HB‐co‐HHx) (HHx=2.5, 3.4, and 12 mol %) have been explored by means of wide‐angle x‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and infrared (IR) spectroscopy. The WAXD pattern of P(HB‐co‐HHx) (HHx=12 mol %) copolymer measured at room temperature has revealed that it has an orthorhombic system (α=β=γ=90°) with a=5.76Å, b=13.20Å, c=5.96Å (fiber repeat), which is identical to that of poly(3‐hydroxybutyrate) (PHB). It has been found from the temperature‐dependent variations of the WAXD pattern that only the a lattice parameter shows the thermal expansion, while the b lattice parameter changes little with temperature in the crystalline P(HB‐co‐HHx) (HHx=12 mol %). This observation suggests that there are inter and intramolecular interactions between C=O groups and alkyl groups along the a axis and that interactions are broken little by little with temperature. IR spectra were measured for the four kinds of polymers over a temperature range from 30°C to high temperatures (200°C; PHB, 180°C; P(HB‐co‐HHx) (HHx=2.5 mol %), 180°C; P(HB‐co‐HHx) (HHx=3.4 mol %), 150°C; P(HB‐co‐HHx) (HHx=12 mol %)). Temperature‐dependent IR spectral variations were analyzed for the CH, C=O, and C‐O‐C stretching band regions, and bands characteristic of crystalline and amorphous parts were identified in each region. It has been found from the IR study that the strength of interaction between the C=O group and the CH3 (or CH2) group is similar among the four polymers and that the population of C=O groups that are not involved in the interaction becomes higher with the increase in HHx. Both WAXD and IR studies have revealed that the crystallinity of P(HB‐co‐HHx) (HHx=12 mol %) decreases gradually starting from relatively low temperature (about 60°C) while that of PHB remains high up to 170°C.

Infrared and Raman spectroscopy and quantum chemistry calculation studies of C–H⋯O hydrogen bondings and thermal behavior of biodegradable polyhydroxyalkanoate

This review paper reports infrared (IR) and Raman spectroscopy and quantum chemistry calculation studies of C–H⋯O hydrogen bondings and thermal behavior of biodegradable polyhydroxyalkanoates. IR and Raman spectra were measured for poly(3-hydroxybutyrate) (PHB) and a new type of bacterial copolyester, poly(3-hydroxybutyrate- co−3-hydroxyhexanoate), P(HB- co-HHx) (HHx=12 mol%) over a temperature range of 20 °C to higher temperatures (PHB, 200 °C; HHx=12 mol%, 140 °C) to explore their structure and thermal behavior. One of bands due to the CH 3 asymmetric stretching modes appears near 3010 cm −1 in the IR and Raman spectra of PHB and P(HB- co-HHx) at 20 °C. These frequencies of IR and Raman CH 3 asymmetric stretching bands are much higher than usual. These anomalous frequencies of the CH 3 asymmetric stretching bands together with the X-ray crystallographic structure of PHB have suggested that there is an inter- or intra-molecular C–H⋯O hydrogen bond between the C O group in one helical structure and the CH 3 group in the other helical structure in PHB and P(HB- co-HHx). The quantum chemical calculation of model compounds of PHB also has suggested the existence of C–H⋯O hydrogen bonds in PHB and P(HB- co-HHx). It is very likely that a chain of C–H⋯O hydrogen bond pairs link two parallel helical structures in the crystalline parts. The temperature-dependent IR and Raman spectral variations have revealed that the crystallinity of P(HB- co-HHx) (HHx=12 mol%) decreases gradually from a fairly low temperature (about 60 °C), while the crystallinity of PHB remains almost unchanged until just below its melting temperature. It has also been found from the IR and Raman studies that for both PHB and P(HB- co-HHx) the weakening of the C–H⋯O hydrogen bonds starts from just above room temperature, but the deformation of helical structures occurs after the weakening of the C–H⋯O hydrogen bonds advances to some extent.

Infrared Spectroscopy Studies of CH···O Hydrogen Bondings and Thermal Behavior of Biodegradable Poly(hydroxyalkanoate)

Infrared (IR) spectra of new types of bacterial copolyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), P(HB-co-HHx) (HHx = 2.5, 3.4, and 12 mol %), and poly(3-hydroxybutyrate) (PHB) were measu...

Thermal Behavior and Molecular Interaction of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Studied by Wide-Angle X-ray Diffraction

The thermal behavior and molecular interaction of a new type of bacterial copolyester, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), P(HB-co-HHx) (HHx = 12 mol %), was investigated by using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The WAXD measurements were carried out over a temperature range from 25 to 110 °C in the scattering angle range of 2θ = 5−13°. The WAXD pattern at room temperature shows that the P(HB-co-HHx) copolymer has an orthorhombic system (α = β = γ = 90°) with a = 5.76 A, b = 13.20 A, and c = 5.96 A (fiber repeat), which is identical to the crystal system of poly(3-hydroxybutyrate) (PHB) homopolymer. However, temperature-dependent variations in the lattice parameters, a and b, of P(HB-co-HHx) are quite different from those of PHB. Only the a lattice parameter increases with temperature, while the b lattice parameter changes very little in the case of crystalline P(HB-co-HHx). It seems that the intermolecular and intramolecular interactions between...

Cocrystallization and Phase Segregation in Crystalline/Crystalline Polymer Blends of Bacterial Copolyesters

Cocrystallization and phase segregation in blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [PHBV] and poly(3-hydroxybutyrate-co-3-hydroxypropionate) [PHBP] at 80−100 °C were analyzed through the in situ observation of crystallization by FTIR microscopy and the measurement of melting curve by DSC. To trace the crystallization process of the blend components separately by a FTIR microscope, deuterated PHBV (D-PHBV) is blended with normal PHBP. The C−D and CO stretching bands of the IR spectra are used to trace the crystallization of D-PHBV and the whole blend, respectively. Five pairs of PHBV and PHBP were selected so as to make variations in the spherulite growth rates (G) of components and their difference. Three of them are the pairs of which PHBV has a higher G than PHBP. They show four types of crystalline phase structures with various extent of phase segregation: complete cocrystallization, cocrystallization forming PHBV-rich cocrystals, phase segregation forming PHBV-rich cocrystals and PHBP ...

Comonomer-unit compositions, physical properties and biodegradability of bacterial copolyhydroxyalkanoates.

The comonomer-unit compositions and their distribution of as-produced bacterial copolyesters, including poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxy-butyrate-co-3-hydroxypropionate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) are described in this paper. Each copolyester sample can be comonomer-unit compositionally fractionated into several fractions, indicating that the original copolymers are mixtures of copolymers with different comonomer-unit compositions. The effects of comonomer-unit compositional distribution on thermal properties, crystallization, biodegradability and solid-state phase behavior are investigated using comonomer compositionally fractionated copolymers.

Infrared spectroscopic analysis of a series of blends of poly(lactic acid) and poly(3-hydroxybutyrate- co-3-hydroxyhexanoate), a bacterial copolyester

Infrared (IR) spectra were collected on a series of blends of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate- co-3-hydroxyhexanoate) (P(3HB- co-3HHx) (3HHx=13.4 mol%)) using a single-bounce temperature-controlled attenuated-total-reflection (ATR) accessory with a diamond internal reflection element (IRE). Different approaches were used to analyze the raw spectral data, including peak positions, widths and intensities, principal components, and 2D correlation spectra. Differences in the interactions between the functional groups of the components become apparent as a function of temperature and composition. This study provides insights into the submolecular-level interactions and miscibility of this polymer blend system. In particular for the 40/60 PLA/P(3HB- co-3HHx) blend, two types of crystalline P(3HB- co-3HHx) CO bands were observed. The band representing a more-ordered local CO environment had a peak absorbance at a lower wavenumber than the second, less-ordered CO species. The 2D IR correlation analysis also revealed that the more-ordered material disappeared first upon heating of the sample and the amorphous P(3HB- co-3HHx) CO band formed before the less-ordered P(3HB- co-3HHx) CO band disappeared. This observation is likely the result of the less-ordered crystalline form being replenished by thermally induced disordering of the more-ordered crystalline form. Thus, the less-order crystalline material may be viewed as an intermediate form during the melting process. In the 80/20 PLA/P(3HB- co-3HHx) blend, it was observed that the lower wavenumber peak in the PLA CO doublet preferentially interacts with amorphous P(3HB- co-3HHx). When 10–20% P(3HB- co-3HHx) is added to PLA, the crystallinity of P(3HB- co-3HHx) is restricted, probably due to domain size restriction and inherent low nucleation density. These IR results suggest that P(3HB- co-3HHx) has the potential to increase the toughness of PLA dramatically, thereby enlarging the design space of sustainable materials achievable by blending.