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1.
Photografting polymerization of polyacrylamide (PAM) onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) films using benzophenone as photoinitiator was studied. The morphology and structure of the grafted PHBV film were characterized by Fourier transformed infrared spectroscopy (FTIR) with attenuated total reflectance (ATR) and scanning electron microscope (SEM) with energy dispersive X‐ray spectrometer (EDX). The grafting percentage and grafting efficiency of the grafted PHBV film went up with the increase of acrylamide concentration and irradiation time. It was observed that photografting polymerization of PAM was not only limited to the film surface, but also in situ occurred inside the film to form the pore microstructure. Sheep bone marrow stromal cell studies showed that MSCs cells attachment efficiency on the grafted PHBV films increased and cells grew well. These results demonstrated the potentiality of PAM‐photografting PHBV in medical applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 4088–4095, 2007  相似文献   

2.
This study examines the isothermal treatment of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) powders and films. The PHB and PHBV crystallinities were determined using X‐ray diffractometry, and shown to increase with temperature (130–150°C) and then decreased from 55% to 45% at 180°C. The crystal morphology of crystal planes (101) and (111) became sharp at a high temperature. The weight average molecular weight (Mw) of PHB decreased from 1,028,000 to 41,800 g/mol when heated at 180°C for 30 min. The molecular weight of PHB decreased more rapidly than that of PHBV with time. No peak signal was observed in gel permeation chromatography after heating at 150°C because the solubility of PHB changed with crystallinity. The thermal behaviors of PHB and PHBV were analyzed by differential scanning calorimetry and thermogravimetric analysis. The roughness, contact angle, and surface morphology of PHB and PHBV films were also measured to determine the surface properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3659–3667, 2013  相似文献   

3.
Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. The effect of graft modification with PVP on the thermal and mechanical properties of PHBV was investigated. The thermal stability of grafted PHBV was remarkably improved while the melting temperature (Tm) was almost not affected by graft modification. The isothermal crystallization behavior of samples was observed by polarized optical microscopy and the results showed that the spherulitic radial growth rates (G) of grafted PHBV at the same crystallization temperature (Tc) decreased with increasing graft yield (graft%) of samples. Analysis of isothermal crystallization kinetics showed that both the surface free energy (σe) and the work of chain‐folding per molecular fold (q) of grafted PHBV increased with increasing graft%, implying that the chains of grafted PHBV are less flexible than ungrafted PHBV. This conclusion was in agreement with the mechanical testing results. The Young's modulus of grafted PHBV increased while the elongation decreased with increasing graft%. The hydrophilicity of polymer films was also investigated by the water contact angle measurement and the results revealed that the hydrophilicity of grafted PHBV was enhanced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

4.
Formation of porous films from poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) using the breath figures (BF) method was investigated by evaporating solutions in chloroform in humid air and examining film structure using optical and scanning electron microscopy (SEM). BF films were successfully fabricated from PHB (Mw = 486,000 g/mol) and displayed hexagonal arrays of pores, which varied in diameter (D = 7–2 μm) with solution concentrations (0.5–2.00%). SEM of fractured films also showed subsurface closed nano‐pores (D = 500–700 nm). BF films cast from PHBV (5% HV) formed arrays with smaller pores and apparent surface defects. Differential scanning calorimetry showed that porous PHB and PHBV films produced using the BF method were more crystalline than nonporous solvent cast films of PHB and PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers  相似文献   

5.
Poly(N‐vinylpyrrolidone) (PVP) groups were grafted onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) backbone to modify the properties of PHBV and synthesize a new novel biocompatible graft copolymer. Based on these graft copolymers, electrospun fiber mats and commonly cast films were explored as drug delivery vehicles using tetracycline hydrochloride as a model drug. Toward that end, the fibers were electrospun and the films were cast from chloroform solutions containing a small amount of methanol to solubilize the drug. The Brookfield viscosities of the solution were determined to achieve the optimal electrospinning conditions. The vitro release of the tetracycline hydrochloride from these new drug delivery systems was followed by UV–vis spectroscopy. To probe into the factors affected on the release behavior of these drug delivery systems, their water absorbing abilities in phosphate buffer solution were investigated, together with their surface hydrophilicity, porosity and crystallization properties were characterized by water contact angles, capillary flow porometer, DSC, and WAXD, respectively. The morphological changes of these drug delivery vehicles before and after release were also observed with SEM. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

6.
The preparation and properties of nanocomposites, consisting of a poly(3‐Hydroxybutyrate‐co‐3‐hydroxyvalerate) and an organophilic clay are described. The effect of organophilic clay on the crystallization behavior of (PHBV) was studied. A differential scanning calorimeter (DSC) was used to monitor the energy of the crystallization process from the melt. During the crystallization process from the melt, the organophilic clay led to an increase in crystallization temperature (Tc) of PHBV compared with that for plain PHBV. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of organophilic clay caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation, and growth of the PHBV crystals and the increase caused by a small quantity of clay is move effective than that large one. The equilibrium melting temperature of PHBV was determined as 186°C. Analysis of kinetic data according to nucleation theories showed that the increase in crystallization rate of PHBV in the composite is due to the decrease in surface energy of the extremity surface. The mechanical test shows that the tensile strength of hybrid increased to 35.6 MPa, which is about 32% higher than that of the original PHBV with the incorporation of 3 wt % clay, and the tensile modulus was also increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 655–661, 2004  相似文献   

7.
Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/phenolic blends are new miscible crystalline/amorphous polymer blends prepared via solution casting method in this work, as evidenced by the single composition dependent glass transition temperature. The measured Tgs can be well fitted by the Kwei equation with a q value of 13.6 for the PHBV/phenolic blends, indicating that the interaction between the two components is strong. The negative polymer–polymer interaction parameter, obtained from the melting depression of PHBV using the Nishi‐Wang equation, indicating the thermal miscibility of PHBV and phenolic. The spherulitic morphology and crystal structure of PHBV/phenolic blends were studied with polar optical microscopy and wide angle X‐ray diffraction compared with those of neat PHBV. It is found that the growth rates of PHBV in the blends are lower than that in neat PHBV at a given crystallization temperature, and the crystal structure of PHBV is not modified by the presence of phenolic in the PHBV/phenolic blends, but the crystallinity decrease with the increasing of phenolic. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

8.
In this work, nanocomposites of poly(hydroxybutyrate‐co‐hydroxyvalerate) PHBV and multiwalled carbon nanotubes (MWNT) were prepared by melt blending. Mechanical, thermal, morphological, and electrical properties of the prepared PHBV/MWNT nanocomposites were investigated. Differential scanning calorimetry (DSC) and X‐ray diffraction (XRD) results showed MWNT effectively enhanced the crystallization and nucleation of PHBV. Dynamic thermo‐mechanical and static uniaxial mechanical tensile and compressive properties were increased by the addition of MWNT. MWNT observed in the nanocomposites using transmission electron microscopy (TEM) showed dimensions similar to separated nanotubes inferring a good dispersion. The presence of nanotubes in close vicinity with each other formed an interconnecting network that led to the formation of electrically conductive nanocomposites. The electrical resistance of the nanocomposites was reduced with the addition of MWNT. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers  相似文献   

9.
The effect of surface chemistry on proliferation and morphology of bone cells cultured on surface modified poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) (PHBV) and untreated PHBV was evaluated. The surface of cast PHBV film was physically and chemically immobilized with collagen. For preparing chemically immobilized collagen surface, PHBV film was ozone treated followed by grafting of PMAA chains and the immobilization of collagen. The surface roughness and hydrophilicity of PHBV film were determined by atomic force microscopy (AFM) and contact angle measurements, respectively. It was found that the duration of ozone exposure and monomer concentration used for grafting PMMA chains influenced the amount of collagen immobilized. The cell proliferation on PHBV surfaces with chemically and physically immobilized collagen was compared with untreated PHBV using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay. The bone cell activity on chemically and physically immobilized collagen PHBV films was found to be 246 and 107% for UMR‐106 and 68 and 9% for MC3T3 cell lines, respectively. Although the results are very preliminary, the chemically grafted collagen on PHBV surface provided a favorable matrix for cell proliferation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2445–2453, 2004  相似文献   

10.
Porous poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) (PHBV) film was prepared by solute leaching of salt/PHBV cast film. The surface chemistry of the PHBV membrane was modified by performing graft polymerization of methacrylic acid (MAA) on ozone treated porous PHBV film, followed by immobilization of type I collagen. The surface characteristics of the modified and nonmodified porous films were measured by water contact angle. The rat osteosarcoma cell line UMR‐106 osteoblast like cells were used as model cells to evaluate the cell viability on surfaces. The initial cell attachment, growth pattern, and proliferation as measured by MTT assay were used to evaluate the bone cell viability on the modified and nonmodified films. Among the PHBV films studied, the nonmodified porous PHBV and the porous PHBV film type I collagen dip coated showed no significant difference in cell attachment and proliferation, while the porous PHBV membrane that was collagen immobilized after MAA grafting showed considerable activity of osteoblast like cells. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1916–1921, 2005  相似文献   

11.
Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was irradiated by 60Co γ‐rays (doses of 50, 100 and 200 kGy) under vacuum. The thermal analysis of control and irradiated PHBV, under vacuum was carried out by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The tensile properties of control and irradiated PHBV were examined by using an Instron tensile testing machine. In the thermal degradation of control and irradiated PHBV, a one‐step weight loss was observed. The derivative thermogravimetric curves of control and irradiated PHBV confirmed only one weight‐loss step change. The onset degradation temperature (To) and the temperature of maximum weight‐loss rate (Tp) of control and irradiated PHBV were in line with the heating rate (°C min?1). To and TP of PHBV decreased with increasing radiation dose at the same heating rate. The DSC results showed that 60Co γ‐radiation significantly affected the thermal properties of PHBV. With increasing radiation dose, the melting temperature (Tm) of PHBV shifted to a lower value, due to the decrease in crystal size. The tensile strength and fracture strain of the irradiated PHBV decreased, hence indicating an increased brittleness. Copyright © 2004 Society of Chemical Industry  相似文献   

12.
Biopolymers are gaining increasing interest because of decline of mineral oil reserves, increasing waste problem, and increasing consciousness of society for environmental problems. However, competitiveness of biopolymers compared with conventional plastics is still limited due to partly insufficient properties and high prices. This study investigates the influence of blending of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) with poly(butylene adipate‐co‐terephthalate) (PBAT) as well as the influence of addition of functionalized montmorillonite (OMMT) to the blends on morphology and thermal behavior. Dispersion state and morphology of the nanocomposites are studied by X‐ray diffraction as well as scanning electron microscopy. Thermal stability is studied by thermogravimetric analysis and crystallization behavior is studied by differential scanning calorimetry and polarized optical microscopy. With respect to the morphology for the blends it can be seen that the immiscible biopolymers PHBV and PBAT are distributed in interlocking zones. There is a good dispersion and homogeneous distribution of OMMT within the biopolymer blends. The addition of 50% or more PBAT to PHBV as well as the insertion of OMMT enhances thermal stability of PHBV. In the blends, the addition of PBAT retards crystallization of PHBV. The OMMT acts as nucleating agent leading in total to more but less perfect crystals in the blends, and the crystallization slows further due to constraint in the movement of polymer chains. These results contribute to the understanding of the structure–properties relationship of bionanocomposite materials for packaging applications. POLYM. COMPOS., 36:2051–2058, 2015. © 2014 Society of Plastics Engineer  相似文献   

13.
The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were investigated. According to the X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 30B exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV–12% HBP–2% Cloisite 30B nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride‐alt‐1‐octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 30B, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan‐δ curve, specific toughness, and strain‐at‐break of the PHBV–HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV–HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV–HBP–nanoclay‐based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers  相似文献   

14.
Electrospinning is a method for the preparation of nanosized polymer fibers. Here, electrospinning is used to prepare a blend of a polyester, poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), and a globular protein, bovine serum albumin (BSA). The electrospun blend film is compared with a solution‐cast blend film and with single‐component electrospun films made of PHBV and BSA. In the electrospun blend films, BSA manifests itself as flat ribbons and a fine network formed from fibers less than 50 nm in diameter. The dissolution rate of BSA from the electrospun blended film is lower than from the solution‐cast one. The films are characterized using scanning electron microscopy, differential scanning calorimetry, and contact‐angle measurements. The obtained PHBV+BSA blend films have several emergent properties: a slow BSA dissolution rate, a fine BSA network, and unusual thermal behavior. Thus, the PHBV+BSA blend films introduce a new class of polymer–protein blends. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45090.  相似文献   

15.
Nanocomposites based on poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and multi‐walled carbon nanotubes (MWNTs) were prepared by solution processing. Ultrasonic energy was used to uniformly disperse MWNTs in solutions and to incorporate them into composites. Microscopic observation reveals that polymer‐coated MWNTs dispersed homogenously in the PHBV matrix. The thermal properties and the crystallization behavior of the composites were characterized by thermogravimetric analysis, differential scanning calorimetry and wide‐angle X‐ray diffraction, the nucleant effect of MWNTs on the crystallization of PHBV was confirmed, and carbon nanotubes were found to enhanced the thermal stability of PHBV in nitrogen. Copyright © 2004 Society of Chemical Industry  相似文献   

16.
The crystallization and melting behavior of poly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate) (PHBV) and a 30/70 (w/w) PHBV/poly(propylene carbonate) (PPC) blend was investigated with differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). The transesterification reaction between PHBV and PPC was detected in the melt‐blending process. The interaction between the two macromolecules was confirmed by means of FTIR analysis. During the crystallization process from the melt, the crystallization temperature of the PHBV/PPC blend decreased about 8°C, the melting temperature was depressed by 4°C, and the degree of crystallinity of PHBV in the blend decreased about 9.4%; this was calculated through a comparison of the DSC heating traces for the blend and pure PHBV. These results indicated that imperfect crystals of PHBV formed, crystallization was inhibited, and the crystallization ability of PHBV was weakened in the blend. The equilibrium melting temperatures of PHBV and the 30/70 PHBV/PPC blend isothermally crystallized were 187.1 and 179°C, respectively. The isothermal crystallization kinetics were also studied. The fold surface free energy of the developing crystals of PHBV isothermally crystallized from the melt decreased; however, a depression in the relative degree of crystallization, a reduction of the linear growth rate of the spherulites, and decreases in the equilibrium melting temperature and crystallization capability of PHBV were detected with the addition of PPC. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2514–2521, 2004  相似文献   

17.
Blends of synthetic poly(propylene carbonate) (PPC) with a natural bacterial copolymer of 3‐hydroxybutyrate with 3‐hydroxyvalerate (PHBV) containing 8 mol % 3‐hydroxyvalerate units were prepared with a simple casting procedure. PPC was thermally stabilized by end‐capping before use. The miscibility, morphology, and crystallization behavior of the blends were investigated by differential scanning calorimetry, polarized optical microscopy, wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS). PHBV/PPC blends showed weak miscibility in the melt, but the miscibility was very low. The effect of PPC on the crystallization of PHBV was evident. The addition of PPC decreased the rate of spherulite growth of PHBV, and with increasing PPC content in the PHBV/PPC blends, the PHBV spherulites became more and more open. However, the crystalline structure of PHBV did not change with increasing PPC in the PHBV/PPC blends, as shown from WAXD analysis. The long period obtained from SAXS showed a small increase with the addition of PPC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 4054–4060, 2003  相似文献   

18.
Poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) is a natural polyester known for its biocompatibility and biodegradability. The hydrolysis of PHBV nanoparticles (90–150 nm) and microparticles (33–58 µm) was investigated. Particles were formulated from preformed polymer(s) by miniemulsification/solvent evaporation technique to obtain nanoparticles or by emulsification/solvent evaporation technique to obtain microparticles. The morphology of the nanoparticles was studied by Field Emission Gun‐Scanning Electron Microscopy (FEG‐SEM). The kinetics of PHBV degradation was followed by gel permeation chromatography. After storage of PHBV nanoparticles for 25 days at 37 °C, the Mn and Mw of PHBV was reduced up to 85 and 80%, respectively. PHBV nanoparticles stored at 4 °C presented a much lower molecular weight reduction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

19.
The crystallization behavior of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) induced by two kinds of nucleating agents, boron nitride (BN) and talc, was investigated by differential scanning calorimetry, polarized optical microscopy and X‐ray diffraction. Both BN and talc have good nucleating ability in the crystallization of PHB and PHBV. From these results, combined with molecular weight measurement by gel permeation chromatography, the mechanism of nucleation by BN and talc in the crystallization of PHB and PHBV has been proposed. BN acts as a nucleating agent itself and initiates nucleation in the crystallization of PHB and PHBV. Talc acts in a different way. It reacts as a chemical reagent with the molten chains of PHB/PHBV, while the reaction product acts as the true nucleating agent, which lowers the crystallization barriers of PHB and PHBV. 1H NMR spectroscopy provides evidence for the reaction between PHB and talc and supports the proposed nucleation mechanism. Copyright © 2005 Society of Chemical Industry  相似文献   

20.
Orthopedic implant failure due to bacterial infection has been a concern in bone tissue engineering. Here, we have formulated a composite made of biodegradable polymer, i.e., poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and silver chloride. Ag+ ions released from the AgCl/PHBV film can promote an aseptic environment by promoting inhibition of bacterial growth while maintaining bone cell growth, depending on AgCl loading. The objective of this study is to formulate AgCl/PHBV film(s) of varying composition so as to evaluate the dependence of AgCl loading in the film on antimicrobial activity and cytotoxicity. The release kinetics of silver ions from AgCl/PHBV film in aqueous and Dulbecco's Modified Eagle Medium showed similarity in the initial burst of ions during the first day of desorption followed by a gradual release of ions over extended time period. The antibacterial efficacy of AgCl/PHBV film against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa was evaluated by microbiological assay, while cytotoxicity of the film toward MC3T3‐E1 cells was determined by MTT assay. For all compositions studied, a clear zone of inhibition around AgCl/PHBV film was noticed on a modified Kirby‐Bauer disk diffusion assay. We established that MC3T3‐E1 cell attachment on AgCl/PHBV film is strongly related to loading of AgCl in the film. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45162.  相似文献   

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