Cellulose separated from corncob was used as a new cellulose resource to produce esterified cellulose nanofiber (E-CNF) with hexanoyl chloride through one-step mechanochemical esterification by ball milling. The result showed that corncob cellulose was easily disintegrated and esterified to achevie a high DS, and then, thin nanofiber was compared to the common pulp cellulose resource. The DS of E-CNF was as high as 0.95, and the diameter was about 1.5–2.8 nm. Then, E-CNF was formed to nanopaper by vacuum filtration showing high optical transparency up to 89% at 550 nm. The transparent nanopaper had a Young’s modulus of 5.5 GPa and tensile strength of 110–125 MPa. Due to the introduction of alkyl chain, the wetting property of the nanopaper was changed from hydrophilicity to hydrophobicty. So, it may still work well in a humid environment.Keywords: Cellulose nanofiber (CNF); Corncob cellulose; Hydrophobic; Nanopaper; Transparent;

•A conformal series of castor oil based hyperbranched Alkyd/Fe3O4@SiO2 nanocomposites was developed as a coating material.•Structure-property relationship was studied by incorporating different nanofiller concentrations in the alkyd matrix.•Shape and size control of nano-Fe3O4@SiO2 is crucial to achieve well-dispersed nanospheres with good filler properties.•Well-dispersed nanoparticles (especially 0.5%) in alkyd matrix exerted improved mechanical and anticorrosive properties.Engineering innovative nanomaterials with low volatile organic content (VOC) has awarded great interest to control air pollutant emissions. We designed a highly branched alkyd matrix suitable for surface coating from castor oil via polyesterification. A simple A2 + B3 (di- and tri-functional monomers) methodology was used to prepare the hyperbranched polyester from natural multifunctional monomers. Magnetite-coated silica (Fe3O4@SiO2) particles with 60–70 nm average diameter were prepared by in situ method that binds magnetite nanoparticles to silica nanospheres. The magnetite size and attaching efficiency were controlled by the concentration of chemicals and reflux duration. The nanocomposite coating was prepared by solution casting. The structure-property relationship was studied for different concentrations of nanofiller in the alkyd matrix. The surface and anticorrosive properties were studied via contact angle and salt spray tests. Mechanical performance and thermal stability were assessed by various methods. The highest improvement was achieved with nanofiller insertion up to 0.5% Fe3O4@SiO2 nanospheres.Download high-res image (318KB)Download full-size image

ABSTRACTThe process of electrospinning can be affected by various parameters, leading to as-prepared nanofibers with different morphology and properties. In order to explore the impact of DC(+) high-voltage position on the resultant nanofibers, two setups with DC(+) high-voltage individually tethered to the needle (S-1) and the collecting plate (S-2) were fabricated. Nanofibers produced by both setups under the same conditions were examined to distinguish their differences in morphology and electrostatic properties. It was found that the nanofibers with positive surface potential produced by the S-1 setup have a larger surface coverage and porosity, smaller average diameter, and wider distribution of diameters. Furthermore, the differences between both setups in the trajectory of flying jets and the distribution of electric field intensity were studied. The results showed that the volume charge density (VCD) of the flying jets plays a crucial role in determining the morphology and electrostatic properties of the resultant nanofibers. The relationship between the position of DC(+) high-voltage and the VCD of flying jets was then discussed, which could develop a better understanding of the process of electrospinning and deliver more accurate control over the production of various functional nanofibers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44687.

The solventless mechanical treatment of native cellulose in a polytetrafluoroethylene (PTFE) vessel was found to cause friction transfer of PTFE to comminuted cellulose particles, resulting in their nanocoating. Cellulose particles after milling were irregular-shaped platelets, with typical sizes of 2–10 μm wide and 0.1–0.4 μm thick (28 h milled). Add-on of PTFE onto cellulose was assessed by weight gain of powder or weight loss of the pot. The PTFE-coated particles were highly hydrophobic and completely repelled from water, with a water contact angle of 110–121°. SEM-EDS analysis showed nearly continuous coverage of cellulose particles by PTFE layers of approx. 10 nm thick, which agreed well with peak-width analysis of X-ray diffraction. This finding may open a new class of solid-phase processing for nanocoating of particles.

Monodisperse gold nanoparticles (Au NPs) with sizes between 2.3 and 23.1 nm were synthesized with the assistance of a natural wood material as a reductant/dispersant. The average diameter of the Au NPs could be controlled by varying the concentration of the Au precursor, and the size distribution could be improved by the addition of NaOH. The different growing processes of Au NPs with and without NaOH were comprehensively studied. The obtained wood-supported Au NPs showed high catalytic activity for the reduction of p-nitrophenol as a model reaction. Moreover, Au NPs with smaller sizes exhibited higher catalytic activity and the catalyst could be easily recovered via centrifugation for reuse.

The extensional flow behaviors of cellulose/NaOH/urea/H2O solution were investigated by using capillary breakup extensional rheometry (CaBER). The effects of temperature, storage time and cellulose concentrations on both the storage modulus G′ and the loss modulus G″ were also analyzed. For 2 wt% cellulose solution, the G′, G″ and filament lifetime remained unchanged after long storage time. While, for 4 wt% cellulose solution, physical gels could form at either higher temperature or for longer storage time, and the filament lifetime, the relaxation time (λe) and the initial extensional viscosity (ηe0) first increased and then decreased with increase of the storage time. The transition points of the filament lifetime shifted to lower storage time with the increase of the temperature. The ηe0 is proportional to λe. The results presented suggest that the extensional properties of the cellulose/NaOH/urea/H2O solution first increase and then decrease during the gelation process, and the spinning time, which decreases linearly with the increase in the storage temperature, must be controlled below the time that ηe0 starts to decrease.

•NMR relaxometry was used for characterization of the porous structure of cellulose.•The hierarchical porous structure of cellulose was not modified during sample preparation and measurement.•The distribution of the porous structure in cellulose samples was obtained by using the NMR relaxometry data.Hierarchical porous structures in cellulose materials are important for the dissolution, properties and applications of cellulose materials. Methods for characterizing the hierarchical porous structures in cellulose materials without changing its original state are still limited. In this work, we introduced nuclear magnetic resonance (NMR) relaxometry for characterizing the hierarchical porous structures in cotton fibers without modifying their structure during sample preparation. By this method, the changes of the porous structures in cotton samples were characterized. It was found that soaking cellulose in water and stewing cellulose in N,N-dimethylacetamide at high temperature could efficiently improve the accessibility of cellulose samples to the solvent molecules and expand the Amorphous Region in cellulose. The method provided in this work can be used for the evaluation of the hierarchical porous structures of cellulose materials without additional modified information, which is helpful to the utilization of cellulose in various fields.Soaking cellulose in water can efficiently improve the accessibility of cellulose materials to the solvent molecules by expanding the Amorphous Region and the Inter-Microfiber Spaces in cellulose materials.

The effects of chloride salts on the dissolution of cellobiose in aqueous solution were investigated using calorimetry and 1H NMR. The dissolution of cellobiose in salt solutions is a typical entropy-driven process. The activity of ZnCl2 and LiCl hydrated ions is enhanced as the hydration number decreases with increasing temperature. Zn2+ and Li+ hydrates can interact with the oxygen atoms at the O5 and O6 positions of cellobiose and associate with the Cl− anions, leading to the breakage of cellobiose hydrogen bonds. We found that the solubility of cellobiose in aqueous solutions is on the order of ZnCl2 > LiCl > NaCl > H2O > KCl > NH4Cl, which is consistent with the Hofmeister series. For the first time, we recognized the specific ionic effects of the Hofmeister series on the dissolution of cellobiose in salt aqueous solutions. This finding is helpful for understanding the dissolving mechanism of cellulose in aqueous solvents with salts and providing fundamental knowledge for finding and designing new cellulose solvents.

Polar aprotic solvents are considered to act as cosolvents with ionic liquids (ILs) for cellulose, strengthening the solvating ability of ILs by improving their cellulose solvating kinetics without influencing the solubility of cellulose in ILs. In this work, it was found that dimethylsulfoxide (DMSO) at low concentration improves the cellulose solvating ability of [AMIM][Cl], but weakens it at high concentration. To clarify the mechanism of these dual effects of DMSO on the cellulose solvating ability of [AMIM][Cl], the [AMIM][Cl]/DMSO system was investigated using excess infrared spectroscopy, nuclear magnetic resonance (NMR) T2 relaxometry, 1H NMR, 35Cl NMR, and dynamic light scattering. The results indicate that the tight association between the cation and anion in the [AMIM][Cl] network is loosened at low DMSO concentration. As a result, mass transport is accelerated due to the enhanced dynamics of [AMIM][Cl], promoting the cellulose solvating kinetics of [AMIM][Cl]. However, ion clusters of [AMIM][Cl] start to form when the molar fraction of DMSO (xDMSO) exceeds 0.5. The hydrogen bonds between cations and anions in the ion clusters become much stronger than in pure [AMIM][Cl], leading to decreased ability of [AMIM][Cl] to form hydrogen bonds with cellulose and thus decreased cellulose solubility in the [AMIM][Cl]/DMSO mixture.

The nanoscale structural changes of crystalline cellulose by mechanical milling was studied by high-resolution microscopy (AFM, SEM, TEM). We examined influence of environment [dry, water, silicone oil (PDMS)] on cellulose milling, finding their characteristic effects on microscopic morphology of the products. Dry milling of cellulose gave aggregated globular particles with fast decrystallization. Milling with water or PDMS caused partial dispersion of nanofibers. Milling with PDMS formed micro-platelets <1 µm thick with slight decrystallization. Remarkably, nanoscale particles isolated from PDMS-milled cellulose by sonication in ethanol contained cellulose nanosheets, typically 0.1–10 µm wide and 4.2 nm thick, apparently formed by monolayer association of elementary fibrils. TEM and electron diffraction revealed crystalline nature of nanosheets, with specific orientation of (110) plane or (200) plane perpendicular to the sheet plane. A possible mechanism of the nanosheets formation is proposed, in which the elementary fibrils are aligned parallel by mechanical impacts.

Keratin graft poly(N-(2-hydroxypropyl)methacrylamide) (K-g-PHPMA) copolymers were synthesized and characterized. On account of the thiol groups of keratin and the amphiphilicity of the graft copolymers, micelles with cleavable cross-links on a keratin core were fabricated in water. The K-g-PHPMA micelles can efficiently encapsulate doxorubicin (DOX) and can be used as a drug carrier. The DOX content in the micelles increases with the keratin content of the graft copolymers. The release of the encapsulated DOX in the micelles is sensitive to the physiological environment. Redox trigger glutathione (GSH), especially at the intracellular level, and trypsin can effectively trigger the release of the encapsulated DOX. In vitro cellular uptake experiments indicate that the DOX released from the DOX-loaded K-g-PHPMA micelles can be efficiently internalized into cells. Under higher GSH condition, the DOX shows a much faster release into the nucleus of the cells. The K-g-PHPMA copolymers have promising applications as drug carriers for enhanced intracellular drug delivery in cancer therapy.

Ball mill-assisted surface-fluorination of cellulose nanofiber was studied for two solvents with different polarity as dispersion/reaction medium. Milling cellulose in neat toluene gave irregular-shaped decrystallized cellulose particles; addition of pentafluorobenzoyl chloride (PFBC) to the system gave partially fluorinated cellulose as thin flakes with smooth surfaces, which maintained original crystallinity. Milling in neat dimethyl formamide (DMF) caused partial dispersion of nanofibers without decrystallization; milling in PFBC/DMF gave more enhanced dispersion of surface-fluorinated nanofibers. Both fluorinated materials were hydrophobic, with water contact angles of 103°–113°. Bulk degree of esterification was 0.20 for toluene and 0.57 for DMF systems. These results show characteristic influences of solvent species in reactive ball milling of cellulose in terms of fibrillation and surface esterification of nanofibers.

Cellobiose was used as a model compound for cellulose to study dissolution in aqueous systems with additives. The dissolution of cellobiose in alkali solutions is a typical exothermic enthalpy-driven process, confirming that lower temperature is beneficial for dissolution of cellulose in NaOH aqueous systems. OH− plays an important role in cellobiose dissolution by forming cellobiose–OH− hydrogen-bonded complexes. The ability to form hydrogen bonds between additives and cellobiose in aqueous solutions follows the order NaOH/urea/ZnO > NaOH/urea/NaAlO2 > NaOH/urea > NaOH. Direct interactions between OH−, amino groups of urea, Na+ hydrates, and cellobiose result in stable hydrogen-bonding complexes among cellobiose, OH−, Na+ hydrates, and urea. Addition of ZnO or NaAlO2 can promote the dissolution power of the solvent system for cellulose. This work clarifies the interactions and dissolution mechanisms of cellulose in aqueous solution systems with additives through hydrogen-bonding interactions.

Rheological properties of cellulose solutions in 1-ethyl-3-methylimidazolium chloride/dimethyl sulfoxide ([Emim]Cl/DMSO, 7/3, w/w) in a wide range of concentration and temperature were investigated. The viscosity of cellulose/[Emim]Cl/DMSO solution agrees well with the complex viscosity suggesting Cox–Merz law is valid for the solution. The viscosity contributed by cellulose (η0–ηs) and cellulose concentration (c) scales as (η0–ηs)~cn with n in the range of 2.00–1.57 and 4.52–3.79 in semidilute unentangled and semidilute entangled regimes, respectively, in the temperature of 25–100 °C. Intrinsic viscosity of the solutions remains constant at temperature below 60 °C and decreases linearly with the increase of temperature above 60 °C. The activation energy of cellulose/[Emim]Cl/DMSO solution increases with the increase in cellulose concentration. The chain dynamics of cellulose in [Emim]Cl/DMSO follows Zimm model and Rouse model in dilute regime (lower than 0.5 wt%) and semidilute unentangled regime (between 0.5 and 2 wt%), respectively.

Dextran graft poly((N-amidino)hexyl methacrylamide) (Dex-g-PAHMA) copolymers were synthesized by free radical polymerization in aqueous solution and characterized. Dex-g-PAHMA copolymers can self-assemble into micelles with the PAHMA rich core and dextran rich shell in aqueous media. The CO2 sensitivity of the micelles was investigated by dynamic light scattering (DLS), conductivity and zeta potential. The results confirmed that the Dex-g-PAHMA copolymer micelles have reversible CO2 sensitivity. The micelles can be used as doxorubicin (DOX) carriers and DOX molecules are mainly located in the core of the micelles. The MTT assay indicated that the Dex-g-PAHMA graft copolymers are non-toxic to cells in the copolymer concentration range of 5–1000 μg mL−1, whereas the relative cell viability is greatly reduced with the increase of copolymer concentration for DOX-loaded micelles. The DOX-loaded micelles can be endocytosed by MCF-7 cells and the DOX can release from micelles and diffuse into the cell nucleus. The Dex-g-PAHMA copolymers have promising applications as drug carriers for cancer therapy.

•Core-sheath electrospun nanofibers with naproxen and naproxen-loaded liposomes in the core were produced.•Naproxen-loaded hybrid and core-sheath nanofibers were also prepared for comparison.•Naproxen formed hydrogen bonds with the polymer molecules and dispersed homogenously in the polymer matrixes.•Hybrid and core-sheath nanofibers released the naproxen in 24 h.•Liposome-loaded core-sheath nanofibers showed a specific drug release behavior with a burst release within 8 h and then a sustained drug release as long as 12 days.Naproxen (NAP) loaded nanofibers of different structures have been successfully prepared by electrospinning. The structures of the nanofibers are NAP and cellulose acetate (CA) mixed nanofibers (NF-1), nanofibers with NAP/CA mixed core and CA sheath (NF-2), and NAP loaded liposomes and sodium hyaluronate (HA-Na) mixed core with CA sheath (NF-3). The structure and morphology of the nanofibers were characterized and the drug release behaviors were investigated. It was found that NAP can disperse in the HA-Na or CA matrix in molecular level without formation of NAP crystals and dimers. The drug release behaviors of NF-1 and NF-2 show a non-Fickian diffusion mechanism, while the NF-3 shows a specific drug release behavior with a burst release within 8 h followed by a sustained drug release for 12 days. The particular two-stage drug release behavior of NF-3 nanofibers offers the materials promising applications as wound dressing materials.

Understanding the interactions between solvent molecules and cellulose at a molecular level is still not fully achieved in cellulose/N,N-dimethylacetamide (DMAc)/LiCl system. In this paper, cellobiose was used as the model compound of cellulose to investigate the interactions in cellulose/DMAc/LiCl solution by using Fourier transform infrared spectroscopy (FTIR), 13C, 35Cl, and 7Li nuclear magnetic resonance (NMR) spectroscopy and conductivity measurements. It was found that when cellulose is dissolved in DMAc/LiCl cosolvent system, the hydroxyl protons of cellulose form strong hydrogen bonds with the Cl–, during which the intermolecular hydrogen bonding networks of cellulose is broken with simultaneous splitting of the Li+–Cl– ion pairs. Simultaneously, the Li+ cations are further solvated by free DMAc molecules, which accompany the hydrogen-bonded Cl– to meet electric balance. Thereafter, the cellulose chains are dispersed in molecular level in the solvent system to form homogeneous solution. This work clarifies the interactions in the cellulose/DMAc/LiCl solution at molecular level and the dissolution mechanism of cellulose in DMAc/LiCl, which is important for understanding the principle for selecting and designing new cellulose solvent systems.

•Small unilamellar vesicles (SUVs) in the diameter about 50 nm were prepared and stabilized by sodium hyaluranate (HA-Na) aqueous solution.•Liposome-loaded core–sheath HA-Na/PVP ultrathin fibers were produced by coaxial electrospinning.•SUVs dispersed in the core HA-Na matrix and were in the elliptical shape.•SUVs were stable within the core–sheath fibers and can be rehydrated in water.Ultrathin core–sheath fibers with small unilamellar vesicles (SUVs) in the core were prepared by coaxial electrospinning. SUVs/sodium hyaluranate (HA-Na)/water and polyvinylpyrrolidone (PVP)/ethanol solutions were used as core and sheath fluid in electrospinning, respectively. The ultrathin fibers were characterized by scanning and transmission electron microscopy (SEM and TEM) and laser scanning confocal microscopy (LSCM). The SUVs were successfully encapsulated in the core HA-Na matrix of the ultrathin fibers and are in the elliptic shape. The SUVs encapsulated in the core matrix of the ultrathin fibers have an excellent stability. The SUVs embedded in the ultrathin fibers are stable. When the ultrathin fibers were re-dissolved in water after one-month storage at room temperature, the rehydrated SUVs have the similar size and size distribution as the as-prepared SUVs. The liposome-loaded ultrathin fiber mats have the promising applications in wound healing materials.

Controlling the assembled structures of graphene has recently attracted enormous attention due to intriguing properties of the resultant structures. In this study, three-dimensional (3D) porous structures of reduced graphene oxide (RGO) with various ratios of RGO to cellulose have been fabricated by a scalable, but simple and efficient, approach that consists of ball milling assisted chemical reduction of GO, template shaping, coagulating, and lyophilization. The efficient mechanical shearing of ball milling and the hydrogen bond interactions between RGO and cellulose molecules contribute to the formation of a homogeneous RGO/cellulose hydrogel, improved thermal stability of the resultant composites, and enhanced crystallinity of the cellulose in the composites. The coagulation effect of cellulose maintains the RGO sheets in the 3D structures of cellulose; on the other hand, the RGO sheets facilitate the preservation of the 3D structures during freeze-drying, leading to the formation of 3D porous structures of RGO/cellulose composites. Benefiting from the continuous RGO network in the composites, the 3D porous structures of RGO(70)/cellulose(100) (GO:cellulose = 70:100 in weight) show an electrical conductivity of 15.28 S m−1. Moreover, the 3D porous structures show potential application in supercapacitors due to the fact that they provide high specific surface area and fast charge propagation.

•Thermal sensitive cellulose graft copolymer is synthesized via SET-LP.•The control of SET-LP graft copolymerization depends on solvent.•LCST of the graft copolymers in aqueous solution is adjusted to body temperature.•Thermal sensitivity is due to the change of hydrophilicity of HPC backbone via the graft of short PNIPAm chain.Hydroxyproyl cellulose graft poly(N-isopropylacryamide) (HPC-g-PNIPAm) copolymers were synthesized by single-electron transfer living radical polymerization (SET-LRP) in water and THF mixture solvent and characterized. The controllability and polymerization rate of SET-LRP can be adjusted by the water/THF ratio in the mixture solvent. The monomer conversion rate is relatively low in the solvent with low water content. The thermal responsive property of HPC-g-PNIPAm copolymers in aqueous solution depends on the length of the graft chains. The relatively short PNIPAm side chains (<150 repeat units) can effectively regulate the low critical solution temperature (LCST) of the HPC-g-PNIPAm copolymers in aqueous solution due to the hydrophilic properties of the short PNIPAm chains. This work provides an approach for the regulation of the LCST to body temperature region by graft copolymerization.

•Supported a new method to study the confined crystallization of POM.•Used two technologies to detect the crystallization of POM.•The FTIR could detect the conformation of POM chain well.•The confinements had strong effects on the crystallization behavior of POM.•The crystal structure could affect the degradation temperature of POM.Polyoxymethylene (POM)/cellulose acetate (CA) core–sheath ultrafine fibers were fabricated by coaxial electrospinning and used to study crystallization in a confined, long cylindrical space. Scanning electron microscopy and transmission electron microscopy revealed that the core–sheath structured ultrafine morphology was presented for the fibers with the average sheath diameter from 679 to 1495 nm and core diameter from 148 to 1000 nm which increased with increasing the concentration of the POM solution. The nonisothermal crystallization study indicated that the confinements sharply reduced the crystallinity and the crystallization temperature of the POM. The Avrami index derived from isothermal crystallization was also decreased with decreasing the dimension of the confined space. However, Wide angle X-ray diffraction showed the crystal size of the POM was decreased distinctly only when the dimension of the confinement was about 150 nm and increased with increasing the dimension of the confinement. It was suggested that both the mode of the crystal growth and the crystallinity will be affected by the cylindrical confinement during POM crystallization.Graphical abstract

One-dimensional confinements were fabricated by coaxial electrospinning and confined crystallization as well as crystal transition of poly(vinylidene fluoride) (PVDF) were studied. It was found that the PVDF can be confined in the nano-tube with the diameter from 50 nm to 350 nm, formed by polyacrylonitrile (PAN). Since the crystallization temperature of PVDF is higher than the glass transition temperature of PAN, the crystallization of PVDF took place in the soft PAN nano-tubes. The confinement weakened the ability of PVDF crystallization, resulting in the crystallinity (Xc) decreasing sharply in the confined condition and the crystallization temperature (Tc) shifted to very low temperature when the confinement diameter was smaller than 75 nm. The observation by FTIR indicated that there was transition in absorption for during cooling where the absorption abruptly rose up at certain temperature and ended immediate raise at a low temperature. The change of temperature range for transition was similar with the Tc checked by DSC, which was related to the crystallization. Also, it was observed that the crystalline structure in as-spun fibers was almost β-phase, and β-crystal transformed into α-crystal at different degrees in confined and un-confined PVDF. These results inferred the chain orientation in company with confinements affected the crystallization of PVDF.

A novel drug carrier with dual triggerable release properties based on keratin graft poly(ethylene glycol) (keratin-g-PEG) copolymers is reported. Keratin-g-PEG copolymers with different graft densities are synthesized through thiol–ene click chemistry. Taking advantage of the amphiphilicity and the thiol groups of the graft copolymer, nanoparticles stabilized with PEG chains and keratin as the core, bearing glutathione (GSH) cleavable cross-links, are fabricated in aqueous solutions. The keratin-g-PEG copolymer nanoparticles can serve as excellent carriers for doxorubicin hydrochloride salt (DOX·HCl) with a highest loading capacity of 18.1% (w/w). The release of the loaded DOX is sensitive to the concentration of GSH, especially at a GSH concentration of cellular level. Trypsin can further trigger the release of the loaded DOX in the nanoparticles. In vitro cellular uptake experiments indicate that DOX released from the DOX-loaded keratin-g-PEG nanoparticles can be internalized into the cells efficiently, and the loaded DOX shows a faster release into the nuclei of the cells under higher GSH concentrations. The carriers have promising applications as drug carriers for intracellular drug delivery for cancer therapy.

Poly(lactic acid)-based ternary blends consisting of poly(lactic acid) (PLA), cellulolytic enzyme lignin (CEL), and polyolefine grafting maleic anhydride (PGMA) were prepared by extrusion blending and the mechanical properties and the morphology of the ternary blends were investigated. It was found that the mechanical properties varied with various loading of the components in the blends. Compared to neat PLA, the tensile strength and the Young's modulus of the ternary blends were decreased, but the elongation at break and the impact strength were effectively improved. Scanning electron microscope observations revealed that the CEL plays a bridging role between PLA and PGMA, enhancing the miscibility between them and resulting in the improvement of ductility and toughness of the ternary blends. Considering the cost and performance, we obtained the optimal blend PLA/CEL/PGMA (80/20/20, w/w/w), of which the impact strength and the elongation at break were doubled as that of neat PLA, and the tensile strength remained moderate.

“Green”/bio-based blends of poly(lactic acid) (PLA) and cellulolytic enzyme lignin (CEL) were prepared by twin-screw extrusion blending. The mechanical and thermal properties and the morphology of the blends were investigated. It was found that the Young’s modulus of the PLA/CEL blends is significantly higher than that of the neat PLA and the Shore hardness is also somewhat improved. However, the tensile strength, the elongation at break, and the impact strength are slightly decreased. Thermogravimetric analysis (TGA) shows that the thermal stability of the PLA is not significantly affected by the incorporation of the CEL, even with 40 wt% CEL. The results of FT-IR and SEM reveal that the CEL and the PLA are miscible and there are efficient interactions at the interfaces between them. These findings show that the CEL is a kind of feasible filler for the PLA-based blends.

A new type of cellulose derivative was synthesized by means of conjugating cysteamine to hydroxypropyl cellulose (HPC) and the degree of thiol groups could be controlled by the feed ratio of the reactants. The thiolated HPC (HPC–SH) maintains the thermosensitivity of HPC and the thiol groups on the HPC chain can be oxidized to disulfide bonds. Cytotoxity tests performed on MG-63 cells proved that HPC–SH is not harmful to the cells. Nanogels can be fabricated by the self-association of HPC–HS in the solution at 45 °C and then oxidation of thiol groups to disulfide bonds occurs to stabilize the associated structure. The crosslinking degree of the nanogels could be controlled by the substitution degree of thiol groups (–SH) in the thiolated HPC. The hydrodynamic radius of the nanogels can be tuned by adjusting the degree of crosslinking and the concentration of the initial thiolated HPC solution in the self-association process. The hydrodynamic radius of the nanogels can be changed with the temperature and the dissociation process can happen by adding the reducing agent dithiothreitol (DTT). The dual-stimuli sensitive nanogels may have potential applications in controlled drug release, transfer switch device and sensors.

Dextran graft copolymers, including dextran graft poly(N-methacryloylglycylglycine) copolymers conjugated with polyethylene glycol and tyrosine (Dex-g-PMAGGCONHPEG3k-NHTyr), dextran graft poly(N-(2-hydroxypropyl) methacrylamide-co-N-methacryloylglycylglycine)-tyrosine conjugates (Dex-g-P(HPMA-co-MAGGCONHTyr)), and dextran graft poly(methacrylpolyethylene glycol-co-N-methacryloylglycylglycine)-tyrosine conjugates (Dex-g-P(MPEG-co-MAGGCONHTyr)) were synthesized for the purpose to improve the biodistribution and blood clearance time of ploy(N-methacryloylglycylglycine)-tyrosine conjugates (Dex-g-PMAGGCONHTyr). Dynamic light scattering (DLS) results indicated that no aggregation formed in 0.9% saline solution. The graft copolymers were labeled with 125I and the labeled copolymers are stable in 0.9% saline and 1% BSA of PBS solutions. Pharmacokinetics studies showed that 125I labeled graft copolymer Dex-g-P(HPMA-co-MAGGCONHTyr) had a longer blood clearance time than the others. Biodistribution images confirmed the preferable liver and spleen accumulation at 1 h after injection, and especially for blood tissue, the mean %ID/g value of the PHPMA-modified graft copolymer Dex-g-P(HPMA-co-MAGGCONHTyr) is 7 folds higher than that of Dex-g-PMAGGCONHTyr.

Dextran graft poly (N-methacryloylglycylglycine) copolymer–tyrosine conjugates (dextran-g-PMAGGCONHTyr) were synthesized and characterized. Dynamic light scattering (DLS) results indicated that the graft copolymers are soluble in pH 7.4 PBS and 0.9% saline solutions. The graft copolymers were labeled with 125I, and the labeling stability in 0.9% saline solution was investigated. Pharmacokinetics studies showed a rapid clearance of 125I-labeled graft copolymers from the blood pool. Biodistribution images confirmed the preferable liver and spleen accumulation within 1 h after injection and rapid clearance from all the organs over time. The graft copolymer with molecular weight of 9.8 kDa was eliminated from the kidney significantly faster than those with higher molecular weight. The effect of the numbers of −COOH groups on the graft copolymers on the biodistribution was also investigated. It was found that the graft copolymers with the average number of −COOH groups per glucopyranose unit (DS–COOH) of 0.57 and 0.18 are mainly distributed in liver and spleen at 1 h after injection, whereas the graft copolymer with DS–COOH of 0.07 is mainly accumulated in kidney.

The micellization and sustained drug release behavior of ethyl cellulose graft poly(poly(ethylene glycol) methyl ether methacrylate) (EC-g-PPEGMA) copolymers with well-defined structure were investigated by using pyrene as the fluorescent probe and model drug. It was found that the EC-g-PPEGMA copolymers have a low critical micelle concentration (CMC) at about 5 × 10−4 mg/mL. Drug loading experiments indicate that a low graft density of the copolymers corresponds to a higher drug loading efficiency and a higher loading capacity of drug in the micelles. The release rate of the loaded pyrene depends on both the length of the side chains and the loading capacity of pryene in the micelles. A shorter side chain of the copolymer and a higher ratio of the copolymer to the pyrene in the micelles correspond to a lower release rate. The self-assembly system shows a potential application in controlled drug delivery.

The conformational changes of syndiotactic polypropylene (sPP) during melting and isothermal crystallization processes were studied by infrared (IR) and two-dimensional (2D) correlation analysis. The band at 963 cm−1 is assigned to the contribution of the amorphous component, and the band at 978 cm−1 is assigned to a shorter helical conformational length than the bands at 867 and 812 cm−1, which are related to crystalline helical conformation. The difference spectra and 2D correlation spectra analysis of the crystallization process indicated that the changes in these regular bands occur in rapid sequence, which is not easily detected by conventional IR spectroscopy. It was found that the absorption intensity of the band at 963 cm−1 increases earlier than that of the band at 978 cm−1, as well as of the bands at 867 and 812 cm−1. The results suggest that the partial chains among the amorphous component change in conformation first, then the sPP chains adjust their local conformations to form short helical conformations and finally crystallization occurs.

Porous silica with hierarchical structures was prepared from ethyl-cyanoethyl cellulose/poly(3-(methacryloyloxy)propyl-trimethoxysilane) (E-CE)C/P(MPTOS) composites with fixed cholesteric liquid crystalline (LC) phase. The scanning and transmission electron microscopy (SEM and TEM) and N2 sorption measurements results indicate that the silica prepared from cholesteric LC composites is of hierarchical macro-, meso- and micro-porous structures, and the average pore size of the silica can be tailored by the content of the cholesteric LC phase in the (E-CE)C/P(MPTOS) composites. The resultant silicas have high specific surface area with the highest value of 837 m2/g at the pore volume of 0.83 cm3/g. This approach provides a new choice for the preparation of porous silica materials, especially from the templates that are not compatible with aqueous system.

A novel drug carrier with dual triggerable release properties based on keratin graft poly(ethylene glycol) (keratin-g-PEG) copolymers is reported. Keratin-g-PEG copolymers with different graft densities are synthesized through thiol–ene click chemistry. Taking advantage of the amphiphilicity and the thiol groups of the graft copolymer, nanoparticles stabilized with PEG chains and keratin as the core, bearing glutathione (GSH) cleavable cross-links, are fabricated in aqueous solutions. The keratin-g-PEG copolymer nanoparticles can serve as excellent carriers for doxorubicin hydrochloride salt (DOX·HCl) with a highest loading capacity of 18.1% (w/w). The release of the loaded DOX is sensitive to the concentration of GSH, especially at a GSH concentration of cellular level. Trypsin can further trigger the release of the loaded DOX in the nanoparticles. In vitro cellular uptake experiments indicate that DOX released from the DOX-loaded keratin-g-PEG nanoparticles can be internalized into the cells efficiently, and the loaded DOX shows a faster release into the nuclei of the cells under higher GSH concentrations. The carriers have promising applications as drug carriers for intracellular drug delivery for cancer therapy.