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The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution. Pretreating biomass by biological, chemical, mechanical, or physical means can render plant feedstocks more facile for processing and thus lower energy requirements to produce CNFs. CNFs from nonconventional fibrillation methods have been investigated for various applications, including films, composites, aerogels, and Pickering emulsifiers. Continued research is needed to develop protocols to standardize the characterization (e.g., degree of fibrillation) of the lignocellulosic fibrillation processes and resulting CNF products to make them more attractive to the industry for specific product applications.

In nature, cellulose nanofibers form hierarchical structures across multiple length scales to achieve high-performance properties and different functionalities. Cellulose nanofibers, which are separated from plants or synthesized biologically, are being extensively investigated and processed into different materials owing to their good properties. The alignment of cellulose nanofibers is reported to significantly influence the performance of cellulose nanofiber-based materials. The alignment of cellulose nanofibers can bridge the nanoscale and macroscale, bringing enhanced nanoscale properties to high-performance macroscale materials. However, compared with extensive reviews on the alignment of cellulose nanocrystals, reviews focusing on cellulose nanofibers are seldom reported, possibly because of the challenge of aligning cellulose nanofibers. In this review, the alignment of cellulose nanofibers, including cellulose nanofibrils and bacterial cellulose, is extensively discussed from different aspects of the driving force, evaluation, strategies, properties, and applications. Future perspectives on challenges and opportunities in cellulose nanofiber alignment are also briefly highlighted.

We report biomass-derived, shape-memory materials prepared via simple reactions, including “grafting from” ATRP and TAD click chemistry. Although the biomass, including plant oils and cellulose nanocrystals, has heterogeneous chemical structures in nature, these materials exhibit excellent multiple shape-memory properties toward temperature, water, and organic solvents, which are comparable to petroleum counterparts. The work presented herein provides burgeoning opportunities to design the next-generation, low-cost, biomass-prevalent, green materials for niche applications.

Amphiphilic molecules, including macromolecules and small surfactants, inherently self-assemble into a wide variety of nanostructures in selective solvents. However, the sequential structure for sy...

A variety of biobased polymers have been derived from diverse natural resources. However, the mechanical properties of some of these polymers are inferior due to low chain entanglement. We report a...

Polymer coatings have been heavily utilized in many industrial and civil applications where a protective thermoset material with enhanced properties such as chemical and physical resistance, thermal stability, and tailorable mechanical properties is desired. Plant oils are a class of promising biomass toward sustainable polymers, but have yet to be fully harnessed in tailorable thermoset coatings due to the challenging functionalization and extensive crosslinking processes required to achieve desirable thermomechanical properties. In this work, we demonstrated that soybean methacrylate (SBMA) from high oleic soybean oil (HOSO) can be utilized to produce bio-based acrylic thermoset copolymers through an industrially viable semi-batch emulsion polymerization process with various commonly used co-monomers such as methyl methacrylate, styrene, and butyl acrylate. A wide range of monomer feed ratios with SBMA from 0 to 50 wt% was easily achieved with minimal modifications allowing for good tunability of thermal and mechanical properties in the prepared latexes. More importantly, a simple and effective auto-oxidative crosslinking of the latex films provided extreme mechanical enhancements making these thermosets good candidates in ultra-strong, ultra-tough, and high Tg coating applications.

Interest in converting waste into renewable energy has increased recently due to concerns about sustainability and climate change. This solid waste is mainly derived from municipal solid waste (MSW), biomass residue, plastic waste, and their mixtures. Gasification is one commonly applied technology that can convert solid waste into usable gases, including H2, CO, CH4, and CO2. Single- and multi-staged reactors have been utilized for solid waste gasification. Comparison in reactor dimensions, operating factors (e.g., gasification agent, temperature, and feed composition), performance (e.g., syngas yield and selectivity), advantages, and disadvantages are discussed and summarized. Additionally, discussion will include economic and advanced catalysts which have been developed for use in solid waste gasification. The multi-staged reactor can not only be applied for gasification, but also for pyrolysis and torrefaction.

Biomass-based polymers show promise for the mitigation of environmental issues associated with petroleum-derived commodity polymers; however, due to poor entanglement, many of these polymers typically lack mechanical strength and toughness. Herein, we report a facile approach to utilizing metal–ligand coordination to create physical crosslinking, and thus chain entanglements for plant oil-derived polymers. A series of soybean oil-derived copolymers containing a pendant acid group can be easily synthesized using free radical polymerization. The resulting chain architecture can be controlled through supramolecular interactions to produce bioplastics with enhanced thermomechanical properties. The metal–ligand coordination in this work can be varied by changing the metal lability and the density of metal–ligand bonds, allowing for further control of properties. The final bioplastics remain reprocessable and feature good thermoplastic and stimuli-responsive properties.

Natural fibers have been widely used for reinforcing polymers attributed to their sustainable nature, excellent stiffness to weight ratio, biodegradability, and low cost compared with synthetic fibers like carbon or glass fibers. Thermoplastic composites offer an advantage of recyclability after their service life, but challenges and opportunities remain in the recycling of natural fiber reinforced polymer composites (NFRPCs). This article summarized the effects of reprocessing/recycling on the material properties of NFRPCs. The material properties considered include mechanical performance, thermal properties, hygroscopic behavior, viscoelasticity, degradation, and durability. NFRPCs can generally be recycled approximately 4–6 times until their thermomechanical properties change. After recycling 7 times, the tensile strength of NFRPCs can decrease by 17%, and the tensile modulus can decrease by 28%. The mitigation approaches to overcome degradation of material properties of NFRPCs such as adding functional additives and virgin plastics are also discussed. The main challenges in these approaches such as degradation and incompatibility are discussed, and an effort is made to provide a rationale for reprocessing/recyclability assessment. Future applications of NFRPCs such as additive manufacturing and automotive part use are discussed.

Shape-memory epoxy resins were synthesized using plant oils and cellulose nanocrystals (CNCs). Epoxidized soybean homopolymers (PESBMA) were grafted from CNCs using surface-initiated atom transfer radical polymerization (SI-ATRP). The polymer grafted CNCs were combined with P(ESBMA-co-SBMA) copolymer and cured using anhydride to prepare epoxy resins. Controlling weight fractions of CNCs and ratios of epoxide to anhydride provided tunability over mechanical and thermal properties. The grafted polymer nanocomposites were also compared to simple blends to confirm better properties of the grafted system. Thermo- and chemo-responsive shape memory properties were obtained for these materials.

Thermal insulation materials are crucial to improve the energy performance of buildings and industrial applications. We report an approach to create hermetically vacuum-sealed silica-based hollow microspheres that can lower the thermal conductivity of closed-cell insulation materials. The wall structure of these hollow microspheres includes a reticulated network of pores or channels that extend through the thickness of the wall. When a thin layer of glass material is applied to the wall exterior, followed by a vacuum-assisted thermal treatment process, the coated microsphere surfaces display a highly dense conformal coverage and near-complete elimination of surface porosity. The sealing efficiency of these microspheres is verified by trapping argon within their cavities as well as through evacuating their hollow cores. Notably, incorporating the evacuated microspheres into a polymer matrix resulted in ∼27% enhancement in its thermal insulation performance and no notable loss of performance was observed following three months of exposure to ambient conditions. Thus, we believe that the present study offers a commercially viable strategy that opens the door to applications of such inorganic hollow particles in areas ranging from vacuum-based thermal insulation systems to catalysis, separation technologies, and medical fields.

We report an atom-efficient approach to the preparation of sustainable polyesters and their corresponding thermosetting resins (RESINs) from renewable plant oils. Specifically, a diol monomer, oleic acid diethanol amide (OADEA), was derived from high oleic soybean oil (HOSBO) via a powerful amidation reaction. A series of OADEA-derived polyesters were prepared by condensation polymerization of this diol monomer with four different diacids. These polyesters were then epoxidized and cured using anhydrides with the aid of organocatalytic amines, yielding HOSBO-derived RESINs. Both thermal and mechanical properties of RESINs were dictated by the main-chain structures. The curing formulations and conditions were tested extensively to obtain the optimal mechanical properties of thermosetting resins, ranging from plastic to elastomeric properties. Both polyesters and RESINs were fully degradable under basic conditions.

Sustainable functional materials derived from renewable biomass provide momentum for the communities of polymer science. We report a supramolecular approach to the preparation of strong biobased polymer nanocomposites with stimuli-responsive behaviors using soybean oil (SO) and cellulose nanocrystals (CNCs). SO-derived polymers were modified with hydroxyl −OH and carboxyl −COOH groups via thiol–ene click chemistry, facilitating hydrogen-bonding interactions with CNCs to improve the overall compatibility in the nanocomposites. These nanocomposites exhibited high tensile strength and maintained high storage modulus up to 200 °C. Moreover, these nanocomposites showed a fast and reversible mechanical response to water, an external stimulus to tune intermolecular hydrogen bonding.

Advanced templating techniques have enabled delicate control of both nano- and microscale structures and have helped thrust functional materials into the forefront of society. Cellulose nanomaterials are derived from natural polymers and show promise as a templating source for advanced materials. Use of cellulose nanomaterials in templating combines nanoscale property control with sustainability, an attribute often lacking in other templating techniques. Use of cellulose nanofibers for templating has shown great promise in recent years, but previous reviews on cellulose nanomaterial templating techniques have not provided extensive analysis of cellulose nanofiber templating. Cellulose nanofibers display several unique properties, including mechanical strength, porosity, high water retention, high surface functionality, and an entangled fibrous network, all of which can dictate distinctive aspects in the final templated materials. Many applications exploit the unique aspects of templating with cellulose nanofibers that help control the final properties of the material, including, but not limited to, applications in catalysis, batteries, supercapacitors, electrodes, building materials, biomaterials, and membranes. A detailed analysis on the use of cellulose nanofibers templating is provided, addressing specifically how careful selection of templating mechanisms and methodologies, combined toward goal applications, can be used to directly benefit chosen applications in advanced functional materials.

Sustainable bioelastomers with high elastic recovery, high resilience and mendability are conceptualized with low chain-entanglement polymers that are predominantly originated from renewable biomass. Polymers with plant oil-derived fatty groups at the side chain were installed with furan, which allowed Diels-Alder addition to introduce dynamic covalent crosslinking. These elastomers are mendable via retro Diels-Alder. Reprocessing of these polymers led to the formation of elastomers with preservation of excellent resilience and elastic recovery.

Epoxy polymers (EPs) derived from soybean oil with varied chemical structures are synthesized. These polymers are then cured with anhydrides to yield soybean-oil-derived epoxy thermosets. The curing kinetic, thermal, and mechanical properties are well characterized. Due to the high epoxide functionality per epoxy polymer chain, these thermosets exhibit tensile strength over an order of magnitude higher than a control formulation with epoxidized soybean oil. More importantly, thermosetting materials ranging from soft elastomers to tough thermosets can be obtained simply by using different EPs and/or by controlling feed ratios of EPs to anhydrides.