BC Nanofibers Research Articles

Tailoring the Wettability of Bacterial Cellulose Magnetobots via the Assembly of In Situ Synthesized and Surfactant-Coated Magnetic Nanoparticles.

This study showcases the possibility of tailoring the wettability of magnetic bacterial cellulose (m-BC) composites by the combined effect of in situ synthesized magnetic nanoparticles (MNPs) distribution and simultaneous oleic acid (OA) coating within the BC matrix. This combined effect of MNPs and OA resulted in m-BC composites exhibiting solvent-dependent and time-dependent surface-wetting behavior, which was not observed in either individual cases of BC that have been modified with OA or BC that has MNPs adsorbed on its fibers. This tailored wettability in m-BCs was achieved via varying the concentrations of iron precursors, which governed the arrangement and morphology of MNPs (uniformly or clustered) on the BC membrane, although the same fraction of MNPs was observed in both the m-BCs. Finally, we have achieved delayed water absorption in m-BC_x (synthesized in a comparatively lower precursor concentration) and no absorption of water in m-BC_4x (synthesized in a 4-times-higher precursor concentration). The m-BC_4x composite maintained its hydrophobic characteristics in diverse environments, ranging from highly acidic conditions (pH 1.2) to physiological environments at pH 4, 5.5, and 7.4. The MNP agglomerates on the BC nanofibers in the m-BC_4x composite were found to be instrumental in attaining a stable cyclic absorption performance with structural integrity. Additionally, the magnetic-inducing heat generation efficiency of the m-BCs can be extended for evaporating low-boiling-point solvents. The present study expands the frontiers of BC-based magnetic composites by emphasizing the assembly of surfactant-coated magnetic nanostructures in their responsiveness to polar/nonpolar liquids with stable performance even in complex scenarios.

Highly interweaved carbonaceous interlayer synchronously decorated by foreign atoms and metals for adsorbing and catalyzing polysulfides in lithium-sulfur batteries

A highly interweaved carbonized bacterial cellulose (CBC) decorated by heteroatoms and metallic nanoparticles was fabricated through initial coating of a metallic coordination polymer onto BC nanofibers followed by carbonization. The carbonaceous CBC networks not only efficiently transfer electrons but also entrap the soluble polysulfides by physical interception. Moreover, the polar ingredients of foreign atoms and metals on CBC networks enable a favorable chemisorption toward polysulfides, and meanwhile the embedded metallic nanoparticles promote the conversion kinetics via electrocatalysis. Theoretical simulation and experimental investigation co-confirm that the decorated Ni species greatly enhance the adsorption capability towards polysulfides, as well as reduce the energy barrier of the rate-determining step via electrocatalysis. As a consequence, the lithium-sulfur batteries equipped with the optimal Ni-NCBC interlayer exhibited relatively high specific capacity (1245 mAh g−1 at 0.2 A g−1), superior rate capability (820 mAh g−1 at 4.0 A g−1), and stable cycling performance (73.2 % capacity retention after 1000 cycles). This work proposes a facile strategy to synchronously incorporate heteroatoms and metallic decorations into highly conductive nanofibrous networks for alleviating the shuttling effects of polysulfides effectively.

Enhanced interfacial interactions and enriched active sites in self-assembly amino-functionalized bacterial cellulose/MXene composite for wastewater treatment

With rapid industrialization and economic growth, the serious environmental pollution caused by heavy metals and dyes is a pressing issue to be solved. The efficient construction of enriched active sites and porous structures is the key to obtain water purification material for pollution removal. In this study, an efficient electrostatic self-assembly strategy to achieve amino-functionalized bacterial cellulose/Ti3C2Tx MXene (ABC/MX) composite with a 3D cross-linked porous structure has been proposed. Experimental characterization and theoretical calculations reveal that the successful incorporation of amino groups not only enhances the interfacial interactions between BC nanofibers and Ti3C2Tx nanosheets, but also increases the active sites available for adsorption. The results highlight that the ABC/MX composite exhibits exceptional removal efficiency, with maximum adsorption capacities of 200.7 mg/g for Cr(VI) and 1103.7 mg/g for Congo red (CR). In particular, it reveals that the multifaceted adsorption processes of Cr(VI) and CR involve electrostatic interactions, reduction reactions, chelation, and hydrogen bonding effects. These findings highlight a versatile strategy for synthesizing BC-based adsorbents with remarkable adsorption properties and are suitable for practical wastewater treatment applications.

Metal/bacteria cellulose nanofiber bilayer membranes for high-performance hydrovoltaic electric power generation

Hydrovoltaic devices that produce electricity from water represent a promising solution for green energy harvesting. Hydrovoltaic power generators based on various emerging nanostructured materials have shown great potential in water-enabled electricity generation. However, the development of high-performance and practical hydrovoltaic devices remains limited because of low electric power generation, high cost of precursor materials, and complicated fabrication processes. In this study, we developed a novel metal-coated bacteria cellulose nanofiber bilayer membrane (MBCBM) for high-performance hydrovoltaic power-generation devices. The top side of the MBCBM has metal-bacteria cellulose (BC) nanofibers that serve as a conducting electrode for fast charge carrier collection, whereas the bottom side has BC nanofibers that serve as hydrovoltaic materials for high efficient energy generation. A Schottky barrier was incorporated into the hydrovoltaic device, which enhanced the electric power output. Experiments revealed that the optimized single-MBCBM based hydrovoltaic device generated a maximum voltage of 0.935 V, current of 7.51 mA, and power output of 6.07 mW with a 50 μl electrolyte solution. The hybrid membrane and device design concept is expected to effectively utilize practical sustainable and clean energy sources for Internet of Things (IoT) devices and self-powered wearable devices in next-generation electronics.

Biomass-Based Anion Exchange Membranes Using Poly (Ionic Liquid) Filled Bacterial Cellulose with Superior Ionic Conductivity and Significantly Improved Strength

ABSTRACT How to simultaneously improve the ionic conductivity and mechanical properties is a key problem facing currently used anion-exchange membranes (AEMs). Here, novel AEMs were prepared using quaternized bacterial cellulose (QBC) as a dual-functional substrate and then filled with a polymeric ionic liquid (poly(vinylbenzyl) trimethylammonium chloride, PVD) with high ion-exchange capacity through in situ polymerization and crosslinking. The dense quaternary ammonium groups grafted on the surface of BC nanofibers greatly increased the ionic conductivity, while the special three-dimensional network structure of BC significantly enhanced the tensile strength and chemical stability of the obtained PVD filled quaternized BC (QBC/PVD) membranes. The ionic conductivity of QBC/PVD membrane reached as high as 111 mS cm−1 at 80°C, which was 109% higher than that of the pure BC/PVD membrane (only 53 mS cm−1). Moreover, the QBC/PVD membrane exhibited extremely high dry strength of 72.3 MPa and satisfactory wet strength and flexibility, this membrane can hang a container containing 500 g of water when at fully hydrated state. The alkaline direct methanol fuel cell equipped with QBC/PVD output a peak power density of 64 mW cm−2, showing its great application potential as an AEM.

Nanoporous Magnetic Carbon Nanofiber Aerogels with Embedded α-Fe/γ-Fe Core–Shell Nanoparticles for Oil Sorption and Recovery

Biomass-based carbon aerogels have received a lot of attention as oil sorbents or oil/water separators due to their effectiveness, low cost, and vast availability of natural resources as their precursors. Magnetically functionalizing the carbon aerogel improves its reusability by magnetic recovery after oil sorption. This work fabricated magnetic carbon nanofibers (MCF) aerogels from the pyrolysis of magnetic bacterial cellulose (MBC) aerogels. The effect of the pyrolysis temperature on the phase transformation and functionalities of the MCF aerogel was investigated. The combined characterization techniques concluded that the MBC aerogel consists of the BC nanofiber matrix decorated with nonmagnetic FeC4H2O4 and magnetic Fe3O4 nanoparticles, which transformed into amorphous carbon nanofibers anchored with the α-Fe/Fe3O4 core–shell structured nanoparticles after pyrolysis at 700 °C. Increasing the pyrolysis temperature to 800–900 °C led to the formation of purer amorphous carbon nanofibers, whereas the nanoparticles turned into the α-Fe/γ-Fe core–shell structure. At 1000 °C, the amorphous carbon structure is better developed and coated on the α-Fe/γ-Fe core–shell nanoparticles. The interpretation explains the results from the magnetic measurement very well and fits perfectly on the Fe–C phase diagram. Furthermore, the MCF aerogels show excellent properties as an efficient oil sorbent, such as large surface area, low density, and hydrophobic properties. Among the samples, the MCF aerogel pyrolyzed at 700 °C (MCF700) exhibits the most desirable properties while requiring the lowest pyrolysis temperature. It could adsorb various oils and organic solvents with high sorption capacity and could be recycled several times. With its magnetic attraction ability, the MCF700 could be magnetically manipulated toward oil, and it could be retrieved after use without direct human contact. These synergistic functionalities make it practically helpful for oil-spill remedies over a large-scale area.

Enhanced mechanical properties and biocompatibility on BC/HAp composite through calcium gluconate fortified bacterial

Bacterial cellulose/hydroxyapatite (BC/HAp) composite is an outstanding candidate for bone tissue engineering. The conventional biomimetic mineralization method takes a long time with unsatisfactory mechanical properties and biocompatibility. Herein, we modified the BC by changing the carbon source to calcium gluconate during the biosynthesis process of BC by bacteria, providing nucleation sites for further mineralization in simulated body fluid. Results show spherical porous HAp in the size of 100–200 nm was fully filled in the three-dimensional network structure of BC nanofibers uniformly within five days of mineralization. Molecular dynamics simulation shows that the aggregation of cellulose units in aqueous solution can enhance the adsorption of calcium ions. By this means, we significantly improved the mechanical properties and biocompatibility of the BC/HAp composite, as well as simplified the preparation process, compared to conventional method, which, therefore, suggests, it could be further studied for biomedical applications such as bone tissue engineering.

Robust Silica-Bacterial Cellulose Composite Aerogel Fibers for Thermal Insulation Textile

Aerogels are nanoporous materials with excellent properties, especially super thermal insulation. However, owing to their serious high brittleness, the macroscopic forms of aerogels are not sufficiently rich for the application in some fields, such as thermal insulation clothing fabric. Recently, freeze spinning and wet spinning have been attempted for the synthesis of aerogel fibers. In this study, robust fibrous silica-bacterial cellulose (BC) composite aerogels with high performance were synthesized in a novel way. Silica sol was diffused into a fiber-like matrix, which was obtained by cutting the BC hydrogel and followed by secondary shaping to form a composite wet gel fiber with a nanoscale interpenetrating network structure. The tensile strength of the resulting aerogel fibers reached up to 5.4 MPa because the quantity of BC nanofibers in the unit volume of the matrix was improved significantly by the secondary shaping process. In addition, the composite aerogel fibers had a high specific area (up to 606.9 m2/g), low density (less than 0.164 g/cm3), and outstanding hydrophobicity. Most notably, they exhibited excellent thermal insulation performance in high-temperature (210 °C) or low-temperature (−72 °C) environments. Moreover, the thermal stability of CAFs (decomposition temperature was about 330 °C) was higher than that of natural polymer fiber. A novel method was proposed herein to prepare aerogel fibers with excellent performance to meet the requirements of wearable applications.

Fabrication of Robust, Shape Recoverable, Macroporous Bacterial Cellulose Scaffolds for Cartilage Tissue Engineering.

Recently, the fabricating of three-dimensional (3D) macroporous bacterial cellulose (MP-BC) scaffolds with mechanically disintegrated BC fragments has attracted considerable attention. However, the successful implementation of these materials depends mainly on their mechanical stability and robustness. Here, a non-toxic crosslinker, 1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS), is employed to induce crosslinking reactions between BC fragments. In addition to their large pore sizes, the EDC/NHS-crosslinked MP-BC scaffolds exhibit excellent compression properties and shape recovery ability, owing to the EDC/NHS-induced crosslinking on the BC nanofibers. The results of in vitro studies reveal that the biocompatibility of MP-BC scaffolds is better than that of pristine BC scaffolds because the former provided more space for cell proliferation. The results of in vivo studies show that the neocartilage tissue with native cartilage appearance and abundant cartilage-specific extracellular matrix deposition is successfully regenerated in nude mice. The findings reveal the immense application potential of mechanically robust BC scaffolds with controllable pore sizes and shape-recoverable properties in tissue engineering.

Continuous and integrated PEDOT@Bacterial cellulose/CNT hybrid helical fiber with “reinforced cement-sand” structure for self-stretchable solid supercapacitor

As the demand for wearable electronic devices persistent to booming, the stretchability of supercapacitors is essential. However, it is still challenging in preparing fiber-based stretchable supercapacitors with the self-stretchable structure instead of relying on an elastic matrix. Here, we constructed a self-stretchable poly(3,4-ethylenedioxythiophene)(PEDOT)@bacterial cellulose(BC)/Carbon nanotube (CNT) hybrid helical fiber with “reinforced cement-sand” structure through wet-spinning and coiling processes by using dissolved BC as bonded matrix, undissolved BC nanofibers and CNT as supporters, PEDOT as reinforcements materials. This structure avoids the disadvantage of relying on the elastic matrix or auxiliary materials to provide elasticity. More importantly, the helical fiber can exhibit the ultimate stretch of 1175%, and the cyclic tests demonstrate the remarkable cycle stability after 100 times of 100% cyclic stretching. Meanwhile, the self-stretchable PEDOT@BC1/CNT2 hybrid helical fiber electrodes show a gravimetric specific capacitance as high as 175.1F/g, which can remain stable under different bending degrees and tensile strains. The energy density and power density of the solid supercapacitor can reach 4.0 Wh/kg and 120.1 W/kg, respectively. This work provides a new strategy of stretchable supercapacitors independent of elastic materials, which will show wide application prospects in wearable electronic products.

Oppositely charged aligned bacterial cellulose biofilm with nanofluidic channels for osmotic energy harvesting

The reverse electrodialysis (RED) is one of the most promising approaches for osmotic energy harvesting. Recently, the RED devices based on nanofluidic channels are considered as the high-performance osmotic energy generators. However, the high cost and the difficult processing of these materials used in RED devices restrict their development in the field. Here, we first report the osmotic energy harvesting device based on negatively and positively charged aligned bacterial cellulose (N-ABC, and P-ABC) membranes. The high surfaced charge density and narrow nanochannel can promote the ion selectivity and transmissibility. By controlling the mixing of artificial sea water (0.5 M) and river water (0.01 M), an output power density of 0.23 W m−2 can be obtained, which is the highest value of the nanocellulose based materials. By connecting 18 units of BC-RED device, the output voltage can reach up to 2.34 V, which can directly power the LED. This research paves the way for application of BC membranes as ion-exchange membranes in RED devices for the osmotic energy harvesting and opens up a new way to use the nanochannels in BC nanofibers.

Biomimetic phosphorylcholine-modified bacterial cellulose membranes with cell fouling resistance

Novel biomimetic zwitterionic phosphorylcholine (PC) modified bacterial cellulose (PCBC) membranes were prepared based on the Pudovik reaction of oxidized BC nanofiber clusters and then solution casting technology. Their chemical structure, morphology, hydrophilicity, mechanical and biocompatible properties were characterized and compared with non-modified BC membranes. The composition and morphology analysis of PCBC membranes confirmed the existence of zwitterionic PC groups on the membrane surfaces, and their nano-fibrous structure was kept. Compared with BC membranes, PCBC membranes exhibited better hydrophilicity, similar tensile strength, but decreased rupture strain. And PCBC membranes were non-hemolytic and non-cytotoxic like BC membranes. The anti-biofouling performance investigation revealed that PCBC membranes with zwitterionic surface showed significantly reduced protein adsorption for bovine serum albumin, as well as inhibited cell attachment for both L929 cells and macrophage RAW 264.7. The results strongly suggested that PCBC membranes with excellent cell fouling resistance are expected to be a promising anti-adhesion biomaterial.

Biotemplate synthesis of polypyrrole@bacterial cellulose/MXene nanocomposites with synergistically enhanced electrochemical performance

Polypyrrole (PPy) has received extensive attention in supercapacitor electrodes due to its promising electrochemical activity, while the poor cycling stability and densely packed structure limited its electrochemical performance. Herein, we demonstrate the fabrication of flexible and freestanding PPy@bacterial cellulose (BC)/MXene composite film with significantly enhanced electrochemical performance. PPy nanoparticles were uniformly deposited on BC nanofibers via in situ polymerization, and assembled with highly conductive MXene (Ti3C2Tx) nanoflakes through strong interfacial interactions. BC as a biological template can effectively disperse PPy nanoparticles. The intercalation of PPy@BC nanofibers into Ti3C2Tx layers constructs hierarchically packed nanofibrous structure, which provides extensive accessible electrochemical active sites. Freestanding PPy@BC/Ti3C2Tx (PBM) electrode exhibits superior specific capacitance (gravimetric and areal capacitance of up to 550 F g−1 and 879 mF cm−2, respectively) and excellent capacitance retention of 83.5% after 10,000 cycles. In addition, the symmetric supercapacitor assembled by PBM papers present a high energy density of 33.1 W h kg−1 (power density of 243 W kg−1) and excellent capacitance retention. The elaborately designed nanostructure and PPy-Ti3C2Tx hybridization make great contribution to the enhanced electrochemical performance, which provide a feasible method for the fabrication of conductive polymer-based high-performance flexible supercapacitor electrodes.

Multifunctional adsorbent based on metal-organic framework modified bacterial cellulose/chitosan composite aerogel for high efficient removal of heavy metal ion and organic pollutant

A novel adsorbent based on zeolitic imidazolate framework-67 (ZIF-67, a sort of metal-organic framework) modified bacterial cellulose/chitosan (BC/CH) composite aerogel was prepared through a facile method combining physical mixture, in situ synthesis, and lyophilization. The water stability of CH aerogel was improved by incorporating BC nanofibers instead of using environmentally unfriendly chemical crosslinking agent. The loading rate of ZIF-67 was as high as 46.1% and the BET specific surface area of ZIF-67/BC/CH aerogel reached to 268.7 m2 g−1, which was much larger than that of BC/CH aerogel (8.4 m2 g−1). The as-prepared ZIF-67/BC/CH aerogel was employed to remove heavy metal ions and organic dye in aqueous solution. The adsorption capacities of the composite aerogel for Cu2+ and Cr6+ were 200.6 mg g−1 and 152.1 mg g−1, respectively. Moreover, the adsorption mechanism was investigated by X-ray photoelectron spectroscopy (XPS). Besides, the aerogel also showed almost 100% of removal rate toward active red X-3B through one time of adsorption. Consequently, the ZIF-67/BC/CH aerogel, as a novel and high efficient adsorbent, has a good application potential for wastewater treatment.

A simple method for controlling the bacterial cellulose nanofiber density in 3D scaffolds and its effect on the cell behavior

In this paper, we provide a simple method to control cellulose nanofiber density inside three-dimensional (3D) gelatin/bacterial cellulose (Gel/BC) scaffold. Different cellulose nanofiber densities inside 3D scaffold were achieved by changing the bacterial density during cellulose biosynthesis. By increasing bacterial densities, Gel/BC scaffolds exhibited higher BC nanofiber density (average distance between cellulose nanofiber and fiber area ratio). And higher BC nanofiber density improved mechanical properties of scaffold, while the average pore size of scaffold was constant. Nanofiber density has been shown to direct cell behavior on 2D substrates. It is important to study that whether the BC nanofiber density can modulate the cell behavior in 3D scaffold. It is the first time to evaluate the effect of BC nanofiber density on cell behavior in 3D scaffold. Results revealed that higher BC nanofiber density in scaffold could facilitate adipose-derived stem cells (ADSCs) proliferation. Interestingly, ADSCs seeded in scaffolds with higher BC nanofiber density showed more spherical and smaller size which meant the potential preservation of ADSCs phenotype. Our findings highlight the importance of BC nanofiber density on cell behavior and provide new guidelines for the construction of tissue engineered scaffold for tissue regeneration.

Characterization of CuO-bacterial cellulose nanohybrids fabricated by in-situ and ex-situ impregnation methods

The aim of this research was to fabricate CuO-bacterial cellulose (BC) nanohybrids by two in-situ synthesis methods including sonochemical and precipitation methods. The ex-situ synthesized nanohybrid was also prepared by immersing BC pellicles in commercial CuO dispersion. FT-IR analysis confirmed the formation of real nanohybrid by occurring new interactions between CuO-NPs and BC. XRD results approved no disruption effect of nanohybrid formation on the crystallinity index of BC nanofibers. FE-SEM results indicated the formation of small sized NPs attached to the inner space of BC network at in-situ synthesized nanohybrids. But agglomerated NPs precipitated on the surface of BC layer was observed for ex-situ synthesized sample. In spite of higher loading capacity of ex-situ method, the in-situ synthesized nanohybrids exhibited lower release rate of NPs into the water. The antibacterial activity of ex-situ synthesized nanohybrid against S.aureus and E.coli bacteria was more than both of in-situ synthesized samples.

Facile method to enhance output performance of bacterial cellulose nanofiber based triboelectric nanogenerator by controlling micro-nano structure and dielectric constant

The development of triboelectric nanogenerators (TENGs) can convert mechanical energy into electricity and bring new prospect for energy crisis. Improving tribo-charge surface density and contact area are two pivotal factors to enhance the output performance of TENG. However, improving the charge density and manipulating surface structure cannot be achieved simultaneously and complicated fabrication procedures may limit application of TENG. In this work, an environment friendly TENG based on bacteria cellulose film fabricated via facile vacuum filtration method was reported. In the presence of modifications, high dielectric particles BaTiO3 were introduced into BC nanofiber film to improve the dielectric constant as well as construct micro-nano structure at the same. With the combination of the enhancement of dielectric constant and surface structure of BC nanofibers layer, the open voltage of 181 V, the short current of 21 μA, and transfer charge of 76.6 nC was achieved at a frequency of 2 Hz and a peak force of 42 N with the optimized film consisting of 13.5 vol% BaTiO3 particles. Additionally, a peak power density of 4.8 W/m2 was achieved when connecting with the resistance in series. Moreover, the TENG showed excellent stability and can harvest the mechanical energy by human motion. This work gives a better understanding of the triboelectricity produced by the TENG from the point of materials and provides a feasible and effective way to enhance the output performance of TENG from the material itself as well as surface modification.

Molecularly imprinted composite bacterial cellulose nanofibers for antibiotic release

The aim of this work is to develop drug carrier system with high loading capacity and controlled drug release profile for antibiotic release. For this purpose, composite molecularly imprinted nanofibers were prepared via in-situ graft polymerization of methacrylic acid as a monomer, N,N’-methylene bisacrylamide as a crosslinker and gentamicin sulfate as a template molecule onto surface-modified bacterial cellulose nanofibers. Gentamicin imprinted microparticles were fabricated onto bacterial cellulose nanofibers resulting in the formation of composite BC nanofibers. Thus, the composite nanofibers incorporated with gentamicin imprinted microparticles were achieved to fabricated. The in-vitro drug release tests were performed to evaluate the release performance of the resultant composite nanofibers at 37 °C. Also, kinetic models were applied to the drug release data. It was determined that the drug release from the composite molecularly imprinted nanofibers fit well in the Korsmeyer-Peppas model.

Poly(3-hydroxybutyrate) Modified by Nanocellulose and Plasma Treatment for Packaging Applications.

In this work, a new eco-friendly method for the treatment of poly(3-hydroxybutyrate) (PHB) as a candidate for food packaging applications is proposed. Poly(3-hydroxybutyrate) was modified by bacterial cellulose nanofibers (BC) using a melt compounding technique and by plasma treatment or zinc oxide (ZnO) nanoparticle plasma coating for better properties and antibacterial activity. Plasma treatment preserved the thermal stability, crystallinity and melting behavior of PHB‒BC nanocomposites, regardless of the amount of BC nanofibers. However, a remarkable increase of stiffness and strength and an increase of the antibacterial activity were noted. After the plasma treatment, the storage modulus of PHB having 2 wt % BC increases by 19% at room temperature and by 43% at 100 °C. The tensile strength increases as well by 21%. In addition, plasma treatment also inhibits the growth of Staphylococcus aureus and Escherichia coli by 44% and 63%, respectively. The ZnO plasma coating led to important changes in the thermal and mechanical behavior of PHB‒BC nanocomposite as well as in the surface structure and morphology. Strong chemical bonding of the metal nanoparticles on PHB surface following ZnO plasma coating was highlighted by infrared spectroscopy. Moreover, the presence of a continuous layer of self-aggregated ZnO nanoparticles was demonstrated by scanning electron microscopy, ZnO plasma treatment completely inhibiting growth of Staphylococcus aureus. A plasma-treated PHB‒BC nanocomposite is proposed as a green solution for the food packaging industry.

Role of bacterial cellulose and poly (3-hydroxyhexanoate-co-3-hydroxyoctanoate) in poly (3-hydroxybutyrate) blends and composites

Biodegradable and biocompatible poly (3-hydroxybutyrate) (PHB) is considered a good candidate for biomedical applications provided that its inherent brittleness and thermal stability are corrected. In this work, poly (3-hydroxyhexanoate-co-3-hydroxyoctanoate) (PHHO) and bacterial cellulose nanofibers (BC) were used as “soft” and “stiff” modifiers to improve PHB properties. PHHO (5–20 wt%) increased the thermal stability of PHB and PHB-BC composites. On the other hand, BC increased the glass transition and the crystallization temperature of PHB in the blends. The surface morphology of PHB was differently changed by the addition of PHHO and BC: a microporous surface morphology with many well spread pores was produced by the addition of PHHO (20–50 wt%) and a smoother surface by the addition of BC. Still, the surface morphology of PHB/PHHO blends, with homogenously spread submicronic pores, was not changed by BC. Thermal, structural and morphological investigations showed that BC nanofibers are mainly located in PHHO rich phase and at interface. PHB nanocomposite with 20 wt% PHHO showed balanced stiffness-toughness properties and excellent thermal stability, with the onset thermal degradation temperature higher than 270 °C. These properties and its porous surface morphology besides the inherent biodegradability and biocompatibility promote this nanocomposite as a valuable material for tissue engineering. It is remarkable that these favorable properties were obtained by a simple, easily controlled method without additional processes or additives.