Bamboo fiber reinforced poly (acrylonitrile-styrene-acrylic)/chlorinated polyethylene via compabilization.

In the quest to enhance the performance of natural fiber-reinforced polymer composites, achieving optimal dispersion of fiber materials within a polymeric matrix has been identified as a key strategy. Traditional approaches, such as the surface modification of natural fibers, often necessitate the use of additional synthetic chemical processes, presenting a significant challenge. In this work, taking poly (acrylonitrile-styrene-acrylic) (ASA) and bamboo fiber (BF) as a model system, we attempt to use the elastomer-chlorinated polyethylene (CPE) as a compatibilizer to tailor the mechanical properties of ASA/CPE/BF ternary composites. It was found that increasing CPE content contributed to more remarkable reinforcing efficiency, where composite with 15 phr CPE exhibited a nearly four-fold increase in reinforcing efficiency of tensile strength (20 %) compared with that of composite system without CPE (4.1 %). Such improvement was ascribed to the compatibilizing effect exerted by CPE, which prevented the aggregation of BF within polymeric matrix. Surface properties suggested the stronger interface between CPE and BF compared to that between ASA and BF and thereby contributed to the compabilizing effect. Since no chemical process was involved, it is suggested that the introduction of elastomer to be a universal, green and sustainable approach to achieve the reinforcement.

Comparison and assessment of methods for cellulose crystallinity determination.

The degree of crystallinity in cellulose significantly affects the physical, mechanical, and chemical properties of cellulosic materials, their processing, and their final application. Measuring the crystalline structures of cellulose is a challenging task due to inadequate consistency among the variety of analytical techniques available and the lack of absolute crystalline and amorphous standards. Our article reviews the primary methods for estimating the crystallinity of cellulose, namely, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Raman and Fourier-transform infrared (FTIR) spectroscopy, sum-frequency generation vibrational spectroscopy (SFG), as well as differential scanning calorimetry (DSC), and evolving biochemical methods using cellulose binding molecules (CBMs). The techniques are compared to better interrogate not only the requirements of each method, but also their differences, synergies, and limitations. The article highlights fundamental principles to guide the general community to initiate studies of the crystallinity of cellulosic materials.

Facile Preparation and Characteristic Analysis of Sulfated Cellulose Nanofibril via the Pretreatment of Sulfamic Acid-Glycerol Based Deep Eutectic Solvents.

A deep eutectic solvent (DES) composed of sulfamic acid and glycerol allowed for the sustainable preparation of cellulose nanofibrils (CNF) with simultaneous sulfation. The reaction time and the levels of sulfamic acid demonstrated that fibers could be swelled and sulfated simultaneously by a sulfamic acid-glycerol-based DES and swelling also promoted sulfation with a high degree of substitution (0.12). The DES-pretreated fibers were further nanofibrillated by a grinder producing CNF with diameters from 10 nm to 25 nm. The crystallinity ranged from 53-62%, and CNF maintained the original crystal structure. DES pretreatment facilitated cellulose nano-fibrillation and reduced the energy consumption with a maximum reduction of 35%. The films prepared from polyvinyl alcohol (PVA) and CNF showed good UV resistance ability and mechanical properties. This facile and efficient method provided a more sustainable strategy for the swelling, functionalization and nano-fibrillation of cellulose, expanding its application to UV-blocking materials and related fields.

Structural reconstruction strategies for the design of cellulose nanomaterials and aligned wood cellulose-based functional materials - A review.

Cellulose is the world's most abundant natural polymer that displays highly desirable characteristics such as biodegradability and sustainability. Its derivatives and associated structured functional materials have potential in various fields such as surface engineering, energy and storage, water treatment, flexible electronics, construction, physical protection, and optical components. All of these applications demand nanocellulose-based micro/nano structural reconstruction for high performance. Recently, functional materials based on aligned nanocellulose in wood obtained through a top-down strategy have highlighted the importance of structure reconstruction strategies on functional designs. In this review, various cellulose or wood micro/nano materials designed by structure reconstruction were examined to highlight the importance of structure reconstruction strategies for various functionalities.

Enhancement of Lignin Extraction of Poplar by Treatment of Deep Eutectic Solvent with Low Halogen Content.

A novel choline-based deep eutectic solvent (DES) with low halogen content-namely choline lactate-lactic acid (CLL)-was synthesized by replacing the chloride anion with lactate anion in choline chloride-lactic acid (CCL). CLL and CCL treatments were conducted at 140 °C for 12 h with hydrogen bond acceptor/hydrogen bond donor =1/10, thereafter composition analysis and characterizations of the lignin extracted by DES treatment (DES lignin) and the solid residue were carried out. The proposed low halogen content DES presented an improved lignin extraction efficiency. The CLL treatment extracted 90.13% of initial lignin from poplar, while CCL extracted 86.02%. In addition, the CLL treatment also provided DES lignin with an improved purity (91.17%), lower molecular weight (Mw/Mn=1805/971 g/mol) and more concentrated distribution (polydispersity index=1.86). The efficient lignin extraction was mainly ascribed to the cleavage of ß-O-4 bonds in lignin macromolecule, especially in the guaiacyl units, thereby breaking them into smaller molecules, facilitating the lignin extraction. The replacement of chloride anion allowed CLL acting as a more efficient DES to interact with lignin macromolecules, thus providing lignin with higher uniformity and suitable molecular weight. The low halogen content DES system proposed in present work could benefit the fractionation of biomass, improve the valorization of lignin compounds and facilitate industrial process in the downstream.

Highly tunable bioadhesion and optics of 3D printable PNIPAm/cellulose nanofibrils hydrogels.

A hybrid poly(N-isopropylacrylamide) (PNIPAm)/cellulose nanofibrils (CNFs) hydrogel composite was fabricated by inverted stereolithography 3D printing to provide a new platform for regulating lower critical solution temperature (LCST) properties and thus tuning optical and bioadhesive properties. The phenomena of interest in the as-printed PNIPAm/CNF hydrogels may be attributed to the fiber-reinforced composite system between crosslinked PNIPAm and CNFs. The optical tunability was found to be correlated to the micro/nano structures of the PNIPAm/CNF hydrogel films. It was found that PNIPAm/CNF hydrogels exhibit switchable bioadhesivity to bacteria in response to CNF distribution in the hydrogels. After 2.0 wt% CNF was incorporated, it was found that a remarkable 8°C reduction of the LCST was achieved relative to PNIPAm hydrogel crosslinked by TEGDMA without CNF. The prepared PNIPAm/CNF hydrogels possessed highly reversible optical, bioadhesion, and thermal performance, making them suitable to be used as durable temperature-sensitive sensors and functional biomedical devices.

Stabilization of chitosan-based polyelectrolyte nanoparticle cargo delivery biomaterials by a multiple ionic cross-linking strategy.

PolyElectrolyte Nanoparticles (PENs) obtained by layer-by-layer self-assembly of polycations/polyanions suffer from a lack of colloidal stability in physiological conditions. We report a simple innovative approach for increasing their stability by multiple ionic cross-linkers. Herein, a chitosan-based core was stabilized by polyanions such as tripolyphosphate and dextran sulfate at pHs of 3 (aPENs) and 8 (bPENs) to improve the quality of electrostatic interactions in the core and manage self-assembly of polyethyleneimine shell onto the core. The physicochemical properties of the particles were characterized by DLS, SEM, TEM, FT-IR, and TGA. TEM micrographs showed visible core/shell structures of bPENs. From particle size and polydispersity indices, the bPENs stability was salt concentration-dependent. The release profiles of PENs using nicotinic acid demonstrated sustained release in a pH-independent manner with a good fit of Korsmeyer-Peppas model. These results suggest that multiple ionic cross-linkers can be an efficient approach to increase the colloidal stability of PENs.

Nanocellulose-based multilayer barrier coatings for gas, oil, and grease resistance.

Cellulose derivatives such as cellulose nanofibers (CNF) and cellulose nanocrystals (CNC) have enormous potential to reduce or replace petroleum and fluorochemicals for food and other packaging applications. CNFs have been studied for their excellent oxygen and gas barrier properties; however, their performance rapidly decreases in the presence of moisture and higher humidity. CNCs are less sensitive to moisture due to their highly crystalline nature; however, coatings and films made of CNCs are much more prone to fracture due to their high brittleness. Our work demonstrates a unique composite barrier coating system of CNF and CNC that synergistically enables oil and grease resistance (a kit rating of 11) comparable to fluorochemicals. It also demonstrates a significant increase in air resistance (∼by a factor of about 300), and a reduction in oxygen transmission rate (∼by a factor of about 260) compared to uncoated paper. The improvements in oil and gas barrier properties were evaluated with respect to the molecular, chemical, and structural properties of the developed coatings.

Characterization of Lignin Extracted from Willow by Deep Eutectic Solvent Treatments.

Purity, morphology, and structural characterization of synthesized deep eutectic solvent (DES)-lignins (D6h, D9h, D12h, D18h, D24h) extracted from willow (Salix matsudana cv. Zhuliu) after treatment with a 1:10 molar ratio of choline chloride and lactic acid at 120 °C for 6, 9, 12, 18, and 24 h were carried out. The purity of DES-lignin was ~95.4%. The proportion of hydrogen (H) in DES-lignin samples increased from 4.22% to 6.90% with lignin extraction time. The DES-lignin samples had low number/weight average molecular weights (1348.1/1806.7 to 920.2/1042.5 g/mol, from D6h to D24h) and low particle sizes (702⁻400 nm). Atomic force microscopy (AFM) analysis demonstrated that DES-lignin nanoparticles had smooth surfaces and diameters of 200⁻420 nm. Syringyl (S) units were dominant, and total phenolic hydroxyl content and total hydroxyl content reached their highest values of 2.05 and 3.42 mmol·g-1 in D12h and D6h, respectively. ß-Aryl ether (ß-O-4) linkages were eliminated during DES treatment.

Deep Eutectic Solvents (DESs) for the Isolation of Willow Lignin (Salix matsudana cv. Zhuliu).

Deep eutectic solvents (DESs) are a potentially high-value lignin extraction methodology. DESs prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBD)-lactic acid (Lac), glycerol, and urea-were evaluated for isolation of willow (Salix matsudana cv. Zhuliu) lignin. DESs types, mole ratio of ChCl to HBD, extraction temperature, and time on the fractionated DES-lignin yield demonstrated that the optimal DES-lignin yield (91.8 wt % based on the initial lignin in willow) with high purity of 94.5% can be reached at a ChCl-to-Lac molar ratio of 1:10, extraction temperature of 120 °C, and time of 12 h. Fourier transform infrared spectroscopy (FT-IR) , 13C-NMR, and 31P-NMR showed that willow lignin extracted by ChCl-Lac was mainly composed of syringyl and guaiacyl units. Serendipitously, a majority of the glucan in willow was preserved after ChCl-Lac treatment.

Ionic Liquid-Mediated Homogeneous Esterification of Cinnamic Anhydride to Xylans.

A new functional biopolymer was synthesized through an ionic liquid-mediated homogeneous grafting of cinnamic anhydride to xylans. The ionic liquid used was 1-allyl-3-methylimidazolium chloride (AMIMCl) ionic liquid. Xylans with degrees of substitution (DS) between 0.11 and 0.57 were accessible in a completely homogeneous system by changing catalysts (NaOH, KOH and LiOH), time, reaction temperature, and cinnamic anhydride/xylan molar ratio. The chemical structure and the thermal stability of the derivatives were characterized by Fourier transform infrared spectroscopy (FT-IR), 13C-NMR spectroscopy, and thermogravimetry. The thermal stability of the derivatives was reduced compared with the original xylan. Possible applications of the cinnamic anhydride-acylated xylan derivatives include wet-end papermaking, organic-inorganic composite films, and hydrogels.

Intrinsic parameters for the synthesis and tuned properties of amphiphilic chitosan drug delivery nanocarriers.

Chitosan (CS) is a material derived from chitin, the most abundant biopolymer on the planet. It has shown potential among a wide variety of biomedical applications especially within the context of self-assembling nanocarriers usable in biomedical applications such as drug delivery, macroscopic injectables, tissue-engineering scaffolds, and nano-imaging agents. To date, many reviews have been focused on the biomedical properties and applications of CS-based nanocarriers, but a review is lacking on the role and prospects of different factors such as formulation parameters and preparation conditions on the properties of amphiphilic chitosan nanocarriers (ACNs) that have shown critical value in advancing drug delivery.

Understanding shape and morphology of unusual tubular starch nanocrystals.

Starch nanocrystals (SNC) are aptly described as the insoluble degradation byproducts of starch granules that purportedly display morphologies that are platelet-like, round, square, and oval-like. In this work, we reported the preparation of SNC with unprecedented tubular structures through sulfuric acid hydrolysis of normal maize starch, subsequent exposure to ammonia and relaxation at 4°C. High-resolution transmission electron microscopy observation clearly proved that the SNCs possess tubular nanostructures with polygonal cross-section. After further reviewing the transformations of SNC by acid hydrolysis, ammonia treatment, and curing time at 4°C, a mechanism for T-SNC formation is suggested. It is conjectured that T-SNC gradually self-assembles by combination of smaller platelet-like/square nanocrystals likely loosely aggregated by starch molecular chains from residual amorphous regions. This work paves the way for the pursuit of new approaches for the preparation of starch-based nanomaterials possessing unique morphologies.

The role of heteropolysaccharides in developing oxidized cellulose nanofibrils.

A fundamental study was undertaken to determine the general role of heteropolysaccharides during the production of TEMPO-oxidized cellulose nanofibrils (TOCNs). Four major fiber resources, viz., fully bleached kraft pulps of softwood and hardwood varieties (pine, eucalyptus) and non-woods (bamboo, bagasse) were used because of their substantial morphological differences and relative abundance. The effect of heteropolysaccharides during TEMPO-mediated oxidation and high-pressure homogenization for TOCNs production was investigated under constant conditions. Most galactoglucomannans were removed during oxidation, whereas the majority of xylans were retained. The galactoglucomannans, however, non-beneficially consumed NaClO, the terminal TEMPO oxidant, while xylans adversely affected carboxylate group formation by limiting chemical accessibility to cellulose. However, lower xylans content led to more transparent and processable suspensions, while during mechanical processing, heteropolysaccharides supported nanofibrillation. The average length of the final TOCNs from eucalyptus, bamboo, bagasse, and pine were 290, 350, 360 and 370nm, respectively, with average widths of ∼4nm.

Unique Dual Functions for Carbon Dots in Emulsion Preparations: Costabilization and Fluorescence Probing.

Recently, carbon dots (CDs) have drawn much attention as evidenced by their incorporation into many branches of science and engineering. Herein, a further unique application is elucidated: CDs that are synthesized by the hydrothermal treatment of gelatin for a dual functionality as expressed in costabilization of particle-based emulsions and their concomitant role as fluorescent probes. CDs either with or without gelatin matrixes induce the aggregation of Laponite particles. The introduction of CDs thus enhanced the stability of Laponite-stabilized emulsions and promoted the formation of multiple emulsions and emulsions with fine and uniform droplets when the CD-to-Laponite mass ratio was less than 45% and exceeded 60%, respectively. However, CDs without gelatin matrixes show slightly higher efficiency than CDs within gelatin matrixes for the costabilization of emulsions. CDs also costabilized emulsions with Laponite to allow the distribution of Laponite particles to be traced and the emulsion profiled under UV.

Adsorption of cationized eucalyptus heteropolysaccharides onto chemical and mechanical pulp fibers.

Adsorption of native eucalyptus heteropolysaccharides onto bleached softwood and hardwood kraft pulps and bleached CTMP was explored in this work to potentially improve the mechanical properties of the final furnish. It was found that adsorption of native heteropolysaccharides onto softwood kraft pulp was slightly higher than hardwood; however, heteropolysaccharides with low arabinose content were preferentially adsorbed onto the hardwood fibers. Adsorption onto CTMP was the lowest, although the general phenomenon of native absorption was rather low under the applied conditions. A strategy to increase the absorption required cationizing the heteropolysaccharides with 2,3-epoxy propyltrimethylamonium chloride that in general significantly increased the overall phenomenon, again with the same general tendencies as observed for the native adsorption.

Polymerization topochemistry of cellulose nanocrystals: a function of surface dehydration control.

The activation (dehydration) of cellulose nanocrystals (CNCs) toward surface "brush" polymerization is accomplished either by freeze drying or solvent exchange. However, the question of which one of these protocols to choose over the other is generally open-ended. The current study attempts to shed light on this question by installing a standard polymer, polycaprolactone (PCL), onto the surface of both freeze-dried and solvent-exchanged CNCs by ring-opening polymerization (ROP) and examining the differences in polymerization and final product properties. The work is the first to demonstrate that the efficiency of surface polymerization and final product properties are in fact influenced by the protocols. The differences between the two sample PCL-grafted CNCs were investigated by X-ray photoelectron spectroscopy (XPS), elemental analysis, gel permeation chromatography (GPC), and contact-angle measurements. The freeze-dried samples had a significantly reduced PCL surface density. The crystallinity of the solvent-exchanged PCL-grafted CNCs (SECNC-g-PCL), however, was lower than that of either pure CNCs or freeze-dried PCL-grafted CNCs (FDCNC-g-PCL). It was determined that solvent exchange sufficiently modified the CNC surface to provide enhanced reactivity, an effect that was not as apparent for FDCNC-g-PCL. The solvent-exchanged CNCs tended to have more porous, nanotextured surfaces that were tended to be more responsive toward brush polymerization. In addition to the physical dissimilarities in surface morphology and surface accessibility contributing to topochemical differences between the two species, it was also found that the dispersibility, aggregation, and thermal stability were different.

Acid-generated soy protein hydrolysates and their interfacial behavior on model surfaces.

The present work attempts to provide data to warrant the consideration of soy proteins (SP) as potentially useful biomolecules for practical chemical and surface applications. Despite their sundry properties, SP use has been limited by their high molecular weight. In response to this limitation, we analyze acid hydrolysates of soy proteins (0.1 N HCl, 70 °C) for surface modification. Techniques typical in protein (SDS-PAGE) as well as colloidal (charge demand and electrophoretic mobility) analyses were used to follow the effects of molecular changes that occur upon hydrolysis. Adsorption experiments on hydrophobic (polypropylene) and mineral (aluminum oxide) surfaces were subsequently carried out to further interrogate the surface activity resultant from soy hydrolysis. It was found that during adsorption the hydrolysates tended to form less surface aggregates and adsorbed at faster rates compared with unmodified SP. Overall, the benefits derived from the application of SP hydrolysates are highlighted.

Synthesis, characterization, and evaluation of chitosan-complexed starch nanoparticles on the physical properties of recycled paper furnish.

The objectives of the current research were to synthesize and characterize chitosan-complexed starch nanoparticles and examine their effect on the physical performance of recycled pulp, specifically old corrugated containerboard (OCC). This new approach provides a uniquely renewable and useful approach to enhance mechanical properties of pulp while maintaining environmental compatibility, industrial compatibility, and paper qualities. The starch nanoparticles used for the research were prepared from cooked cornstarch gel with ethanol and reacted with diethylenetriamine pentaacetic acid (DTPA) in the presence of sodium hypophosphite. Thereupon, the DTPA-modified starch nanoparticles (SNs) were complexed with chitosan as part of a general chemical strategy to improve their incorporation into an OCC matrix and increase interfiber bonding. Spectral characterization of the SNs was done using TGA, DSC, FT-IR, and SEM to analyze their composition and structure. Approximately 2% chitosan-complexed starch nanoparticle derivatives by mass (SNX/C) of OCC-based slurry were thoroughly mixed before manufacturing a two-dimensional sheet for physical testing. The tensile and burst strength of the modified OCC pulp sheet increased 50 and 49%, respectively, albeit having a decreased tear strength compared to the control sample. However, when the OCC pulp sheet was coated with a 1% SNX/C by mass solution, the tensile and burst strength increased 120 and 70%, respectively, while also providing significantly increased gloss, decreased roughness, and tear strength. Because the mechanical properties are the most critical property facing the recyclability of OCCs, the tremendous gains afforded by the starch nanoparticle-DTPA-chitosan proposed give the system enormous potential applicability as a viable dry strength agent for paper substrates.

Water-wettable polypropylene fibers by facile surface treatment based on soy proteins.

Modification of the wetting behavior of hydrophobic surfaces is essential in a variety of materials, including textiles and membranes that require control of fluid interactions, adhesion, transport processes, sensing, etc. This investigation examines the enhancement of wettability of an important class of textile materials, viz., polypropylene (PP) fibers, by surface adsorption of different proteins from soybeans, including soy flour, isolate,glycinin, and ß-conglycinin. Detailed investigations of soy adsorption from aqueous solution (pH 7.4, 25 °C) on polypropylene thin films is carried out using quartz crystal microbalance (QCM) and surface plasmon resonance (SPR). A significant amount of protein adsorbs onto the PP surfaces primarily due to hydrophobic interactions. We establish that adsorption of a cationic surfactant, dioctadecyldimethylammonium bromide (DODA) onto PP surfaces prior to the protein deposition dramatically enhances its adsorption. The adsorption of proteins from native (PBS buffer, pH 7.4, 25 °C) and denatured conditions (PBS buffer, pH 7.4, 95 °C) onto DODA-treated PP leads to a high coverage of the proteins on the PP surface as confirmed by a significant improvement in water wettability. A shift in the contact angle from 128° to completely wettable surfaces (≈0°) is observed and confirmed by imaging experiments conducted with fluorescence tags. Furthermore, the results from wicking tests indicate that hydrophobic PP nonwovens absorb a significant amount of water after protein treatment, i.e., the PP-modified surfaces become completely hydrophilic.