Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)‐based biocomposites reinforced with kenaf fibers

Biodegradable thermoplastic‐based composites reinforced with kenaf fibers were prepared and characterized. Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), produced by bacterial fermentation, was selected as polymeric matrix. To improve PHBV/fibers adhesion, low amount of a proper compatibilizing agent, obtained by grafting maleic anhydride onto PHBV, was added during matrix/fibers melt mixing (reactive blending). When compared with uncompatibilized composites, the presence of the compatibilizer induces a stronger interfacial adhesion and a more pronounced improvement of the mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Layer double hydroxides for enhanced poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) crystallization

Enabling the widespread utilization of poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] (PHBV) is strongly associated with enhancing its crystallization kinetics. In this article, we utilize a highly surface active (one reactive group per nanometer square) anion exchanged layered‐double hydroxide (LDH) functionalized by stearic acid to probe the crystallization kinetics of PHBV. Our prior work has shown that the addition of LDH decreases the cold crystallization and induces a melt recrystallization peak in PHBV. Since the melt‐recrystallization temperature shifted to higher temperature and its corresponding enthalpy increased with increasing LDH loading, this article is focused on understanding the effect of LDH on kinetics and energetics of PHBV crystallization. Both Avrami and Lauritzen–Hoffman modeling are utilized to develop a comprehensive understanding of thermal history effects through differential scanning calorimetry and polarized optical microscopy measurements. Five concentrations by weight of LDH are used: 1, 3, 5, and 7%. The results show that the addition of LDH promoted both primary and secondary nucleation at low concentrations but additional LDH resulted in primary nucleation alone. The crystallization rate and activation energy show a significant increase, which is accompanied by a decrease in the nucleation constant, the surface energy and the work of chain folding for PHBV crystallization. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2013     

Photografting polymerization of polyacrylamide on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) films. II. Wettability and crystallization behaviors of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)‐graft‐polyacrylamide films

The wettability and crystallization behaviors of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)‐graft‐polyacrylamide (PAM) films were studied. X‐ray photoelectron spectroscopy analyses illustrated that about 62 atom % of the total polar functionalities on the grafted film with 17% grafting percentage (GP) was amide groups. Wide‐angle X‐ray diffraction results suggest that grafted PAM induced defects in PHBV crystals and influenced their crystal structure. Differential scanning calorimetry (DSC) spectra showed the two melting regions, 60–90 and 145–170°C, of the imperfect PHBV crystals of the grafted films. Grafted PAM could suppress the recrystallization of PHBV, which was consistent with the polarizing optical microscopy results, in which the maximum PHBV spherulite diameter decreased from 350 μm for the PHBV film to 50 μm for the film with 53% GP. In addition, DSC studies revealed that the crystallinity of the grafted films decreased with increasing GP, which facilitated the diffusion of water into the films. The water contact angle of grafted films decreased and the water‐swelling percentage increased as GP went up. These results demonstrate the potential of PHBV‐g‐PAM for wettable surface constructs in tissue engineering applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Miscibility and crystallization behavior of biodegradable poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/phenolic blends

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 T_gs 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     

Drug release from electrospun fibers of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) grafted with poly(N‐vinylpyrrolidone)

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     

Effect of graft modification with poly(N‐vinylpyrrolidone) on thermal and mechanical properties of poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

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 (T_m) 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 (T_c) decreased with increasing graft yield (graft%) of samples. Analysis of isothermal crystallization kinetics showed that both the surface free energy (σ_e) 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     

Miscibility of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) with high molecular weight poly(lactic acid) blends determined by thermal analysis

An important strategy used in the polymer industry in recent years is blending two bio‐based polymers to attain desirable properties similar to traditional thermoplastics, thus increasing the application potential for bio‐based and bio‐degradable polymers. Miscibility of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) with poly(L ‐lactic acid) (PLA) were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Three different grades of commercially available PLAs and one type of PHBV were blended in different ratios of 50/50, 60/40, 70/30, and 80/20 (PHBV/PLA) using a micro‐compounder at 175°C. The DSC and TGA analysis showed the blends were immiscible due to different stereo configuration of PLA polymer and two distinct melting temperatures. However, some compatibility between PHBV and PLA polymers was observed due to decreases in PLA's glass transition temperatures. Additionally, the blends do not show clear separation by SEM analysis, as observed in the thermal analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Thermal analysis of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) irradiated under vacuum

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 (T_o) and the temperature of maximum weight‐loss rate (T_p) of control and irradiated PHBV were in line with the heating rate (°C min^?1). T_o and T_P 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 (T_m) 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     

Miscibility,crystallization kinetics,and mechanical properties of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)(PHBV)/poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)(P3/4HB) blends

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)(PHBV)/poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3/4HB) blend films were prepared by solvent‐cast method. The nonisothermal crystallization results showed that PHBV and P3/4HB are miscible due to a single glass transition temperature (T_g), which is dependent on blend composition. The isothermal crystallization results demonstrate that the crystallization rate of PHBV becomes slower after adding amorphous P3/4HB with 19.2 mol% 4HB, which could be proved through depression of equilibrium melt point ($T_m^o$ ) from 183.7°C to 177.6°C. For pure PHBV and PHBV/P3/4HB (80/20) blend, the maximum crystallization rate appeared at 88°C and 84°C, respectively. FTIR analysis showed that PHBV/P3/4HB blend films would maintain the helical structure, similar to pure PHBV. Meanwhile, with increasing P3/4HB content, the inter‐ and intra‐interactions of PHBV and P3/4HB decrease gradually. Besides, a lower elastic modulus and a higher elongation at break were obtained, which show that the addition of P3/4HB would make the brittle PHBV to ductile materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermogravimetric analysis of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

The thermal degradation of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐HV)] was studied using thermogravimetry (TG). In the thermal degradation of PHB, the temperature at the onset of weight loss (T_o) was derived by T_o = 0.97B + 259, where B represents the heating rate (°C/min). The temperature at which the weight loss rate was maximum (T_p) was T_p = 1.07B + 273, and the final temperature (T_f) at which degradation was completed was T_f = 1.10B + 280. The percentage of the weight loss at temperature T_p (C_p) was 69 ± 1% whereas the percentage of the weight loss at temperature T_f (C_f) was 96 ± 1%. In the thermal degradation of P(HB‐HV) (7:3), T_o = 0.98B + 262, T_p = 1.00B + 278, and T_f = 1.12B + 285. The values of C_p and C_f were 62 ± 7 and 93 ± 1%, respectively. The derivative thermogravimetric (DTG) curves of PHB confirmed only one weight loss step change because the polymer mainly consisted of the HB monomer only. The DTG curves of P(HB‐HV), however, suggested multiple weight loss step changes; this was probably due to the different evaporation rates of the two monomers. The incorporation of 10 and 30 mol % of the HV component into the polyester increased the various thermal temperatures (T_o, T_p, andT_f) by 7–12°C (measured at B = 20°C/min). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2237–2244, 2001     

The morphology and thermal properties of multi‐walled carbon nanotube and poly(hydroxybutyrate‐co‐hydroxyvalerate) composite

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     

Effects of the energy dissipation rate and surface erosion on the biodegradation of poly(hydroxybutyrate‐co‐hydroxyvalerate) and its blends with synthetic polymers in an aquatic medium

The anaerobic biodegradation of polymers by soil microorganisms was investigated in shaking flask cultures at different rotation speeds or energy dissipation rates. The polymers included poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV), poly(?‐caprolactone) (PCL), polystyrene (PS), two binary PHBV/PCL blends (80/20 and 25/75 w/w), and a triple PHBV/PCL/PS blend (76/5/19 w/w/w). The specific degradation rate of PHBV found from the specimen's residual mass fraction with time was constant after a lag phase and was significantly affected by the agitation strength (<0.5 day^?1 at 60 rpm or lower and >15 day^?1 at 120 rpm or greater). Tiny polymer fragments were formed on the specimen surface and observed with scanning electron microscopy during degradation. The detachment of those fragments under high hydraulic shear stress caused surface erosion and renewal, resulting in the high degradation rate. The hydraulic shear stress (0.6 Pa) at an energy dissipation rate of 0.5 W/kg was a threshold level, above which the external force did not increase the degradation rate very much. PHBV degradation in the binary blends with compatible PCL was retarded, depending on the blend composition. Blending PHBV with noncompatible PS did not affect PHBV degradation, and the overall degradation rate of the triple blend was faster than the rate of PHBV alone because of the surface erosion of both PHBV and nondegradable PS fragments from the specimens. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1036–1045, 2002     

Effect of nucleating agents on the crystallization of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)

The effect of nucleating agents on the crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) was studied. A differential scanning calorimeter was used to monitor the energy of the crystallization process from the melt and melting behavior. During the crystallization process from the melt, nucleating agent led to an increase in crystallization temperature (T_c) of PHBV compared with that for plain PHBV (without nucleating agent). The melting temperature of PHBV changed little with addition of nucleating agent. However, the areas of two melting peaks changed considerably with added nucleating agent. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of nucleating agent caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation and growth of the PHB crystals. The equilibrium melting temperature of PHBV was determined as 187°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. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2145–2152, 2002     

Water transport properties in poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) biopolymers

Water sorption and diffusion have been investigated in poly(3‐hydroxybutyrate) (PHB) and three poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) copolymers [P(HB‐HV)] by means of a Cahn electromicrobalance. Permeability of these samples have been determined using a gravimetric permeation cell. Two experimental setups were used for the gravimetric sorption measurements, under dynamic and static conditions, respectively. The differences observed in the results obtained using these techniques are discussed. The sorption measurements have evidenced the tendency of water molecules to form aggregates or clusters in the polymer. In addition, the static sorption method revealed the potential of PHB and P(HB‐HV) to undergo molecular relaxations, eventually leading to a partial desorption of the previously sorbed water after an induction period. The clustering effect was adequately described by the polycondensation model. On the other hand, the interpretation of the diffusivity in terms of mobility coefficients has revealed a competition between a plasticization effect and clustering. As a whole, water transport properties in PHB and its copolymers can be considered to be very close in magnitude to those of common thermoplastics such as PVC and PET. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 455–468, 1999     

Reactive compatibilization and performance evaluation of miscanthus biofiber reinforced poly(hydroxybutyrate‐co‐hydroxyvalerate) biocomposites

Dicumyl peroxide (DCP) initiated reactive compatibilization of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV)/miscanthus fibers (70/30 wt %) based biocomposite was prepared in a twin screw extruder followed by injection molding. In the presence of DCP, both the flexural and the tensile strength of the PHBV/miscanthus composites were appreciably higher compared with PHBV/miscanthus composite without DCP as well as neat PHBV. The maximum tensile strength (29 MPa) and flexural strength (51 MPa) were observed in the PHBV/miscanthus composite with 0.7 phr DCP. The enhanced flexural and tensile strength of the PHBV/miscanthus/DCP composites are attributed to the improved interfacial adhesion by free radical initiator. Unlike flexural and tensile strength, the modulus of the PHBV/miscanthus/DCP composites was found to slightly lower than the PHBV/miscanthus composite. The modulus difference in the PHBV/miscanthus composite with and without DCP has good agreement with the observed crystallinity. However, the flexural and tensile modulus of all the prepared biocomposites was at least two fold higher than the neat PHBV. The storage modulus value of the PHBV/miscanthus and PHBV/miscanthus/DCP biocomposites follows similar trend like tensile and flexural modulus. The melting temperature and crystallization temperature of PHBV/DCP and PHBV/miscanthus/DCP samples were considerably lower compared with the neat PHBV and PHBV/miscanthus composites. The surface morphology revealed that the PHBV/miscanthus/DCP composites have good interface with less fiber pull‐outs compared with the corresponding counterpart without DCP. This suggests that the compatibility between the matrix and the fibers is enhanced after the addition of peroxide initiator. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44860.     

Quercetin and curcumin in nanofibers of polycaprolactone and poly(hydroxybutyrate‐co‐hydroxyvalerate): Assessment of in vitro antioxidant activity

Polymeric nanofibers are materials that can be used as scaffolds in tissue engineering. Quercetin and curcumin are antioxidants because of scavenge free radicals and chelate metal ions properties, protecting tissues of lipid peroxidation. The objective of this study was to develop a scaffold with potential antioxidant activity that was produced from nanofibers consisting of polycaprolactone (PCL) and a blend of PCL/poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHB‐HV) with the addition of quercetin or curcumin as the bioactive compound. Curcumin and quercetin were integrated into the solution at a concentration of 3%. The electrospun nanofibers were characterized using calorimetry and thermogravimetric analysis, and the addition of bioactive compounds did not alter the thermal properties of the biomaterial. The antioxidant activity of scaffolds with the active compounds was evaluated by hydrate 2,2‐diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS) methods. The scaffolds with PCL and PCL/PHB‐HV blend with quercetin exhibited higher antioxidant activity than curcumin with both methods. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43712.     

Miscibility and crystallization kinetics of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/ poly(methyl methacrylate) blends

The miscibility and crystallization kinetics of the blends of random poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐co‐HV)] copolymer and poly(methyl methacrylate) (PMMA) were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB‐co‐HV)/PMMA blends were miscible in the melt. Thus the single glass‐transition temperature (T_g) of the blends within the whole composition range suggests that P(HB‐co‐HV) and PMMA were totally miscible for the miscible blends. The equilibrium melting point (T°_m) of P(HB‐co‐HV) in the P(HB‐co‐HV)/PMMA blends decreased with increasing PMMA. The T°_m depression supports the miscibility of the blends. With respect to the results of crystallization kinetics, it was found that both the spherulitic growth rate and the overall crystallization rate decreased with the addition of PMMA. The kinetics retardation was attributed to the decrease in P(HB‐co‐HV) molecular mobility and dilution of P(HB‐co‐HV) concentration resulting from the addition of PMMA, which has a higher T_g. According to secondary nucleation theory, the kinetics of spherulitic crystallization of P(HB‐co‐HV) in the blends was analyzed in the studied temperature range. The crystallizations of P(HB‐co‐HV) in P(HB‐co‐HV)/PMMA blends were assigned to n = 4, regime III growth process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3595–3603, 2004     

Miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/poly(vinyl acetate) blends

The miscibility and crystallization behavior of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (P(HB‐co‐HV))/poly(vinyl acetate) (PVAc) blends have been investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that P(HB‐co‐HV)/PVAc blends were miscible in the melt over the whole compositions. Thus the blend exhibited a single glass transition temperature (T_g), which increased with increasing PVAc composition. The spherulitic morphologies of P(HB‐co‐HV)/PVAc blends indicated that the PVAc was predominantly segregated into P(HB‐co‐HV) interlamellar or interfibrillar regions during P(HB‐co‐HV) crystallization because of the volume‐filled spherulites. As to the crystallization kinetics study, it was found that the overall crystallization and crystal growth rates decreased with the addition of PVAc. The kinetics retardation was primarily attributed to the reduction of chain mobility and dilution of P(HB‐co‐HV) upon mixing with higher T_g PVAc. The overall crystallization rate was predominantly governed by the spherulitic growth rate and promoted by the samples treated with the quenched state because of the higher nucleation density. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 980–988, 2006     

Bone cell viability on collagen immobilized poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) membrane: Effect of surface chemistry

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