To replace petroleum-derived polymers with cellulose fibres, it is desirable to have the option of melt processing. However, upon heating, cellulose degradation typically starts before the material reaches its softening temperature. Alternatives to plastics should also, ideally, be recyclable via existing recycling streams. Here, we address the problem of melt processing cellulose as fibres while preserving recyclability. Native cellulose fibres were partially modified to dialcohol cellulose to impart thermoplastic characteristics. We demonstrate melt processing of these modified fibres with only water as plasticiser. Processability was investigated at selected processing temperatures and initial moisture content by monitoring the axial force of the extruder screws as a rheological indicator. The effects on molecular structure, fibre morphology and material properties were characterised by NMR spectroscopy, microscopy, tensile testing, fibre morphology analysis and X-ray diffraction. When comparing the melt-processed extrudate with handsheets, the already exceptional ductility was further increased. Moderate losses in tensile strength and stiffness were observed and are attributable to a loss of crystallinity and fibre shortening. This is the first report of strong and durable extrudates using cellulosic fibres as the only feedstock. Finally, the potential for recycling the processed material with unmodified fibres by paper recycling procedures was demonstrated.

There are many bioelectronic applications where the additive manufacturing of conductive polymers may be of use. This method is cheap, versatile and allows fine control over the design of wearable electronic devices. Nanocellulose has been widely used as a rheology modifier in bio-based inks that are used to print electrical components and devices. However, the preparation of nanocellulose is energy and time consuming. In this work an easy-to-prepare, 3D-printable, conductive bio-ink; based on modified cellulose fibers and poly(3,4-ethylene dioxythiophene) poly(styrene sulfonate) (PEDOT:PSS), is presented. The ink shows excellent printability, the printed samples are wet stable and show excellent electrical and electrochemical performance. The printed structures have a conductivity of 30 S/cm, high tensile strains (>40%), and specific capacitances of 211 F/g; even though the PEDOT:PSS only accounts for 40 wt% of the total ink composition. Scanning electron microscopy (SEM), wide-angle X-ray scattering (WAXS), and Raman spectroscopy data show that the modified cellulose fibers induce conformational changes and phase separation in PEDOT:PSS. It is also demonstrated that wearable supercapacitors and biopotential-monitoring devices can be prepared using this ink.

If cellulosic materials are to replace materials derived from non-renewable resources, it is necessary to overcome intrinsic limitations such as fragility, permeability to gases, susceptibility to water vapour and poor three-dimensional shaping. Novel properties or the enhancement of existing properties are required to expand the applications of cellulosic materials and will create new market opportunities. Here we have overcome the well-known restrictions that impede melt-processing of high cellulose content composites. Cellulose fibres, partially derivatised to dialcohol cellulose, have been used to manufacture three-dimensional high-density materials by conventional melt processing techniques, with or without the addition of a thermoplastic polymer. This work demonstrates the use of melt processable chemically modified cellulose fibres in the preparation of a new generation of highly sustainable materials with tuneable properties that can be tailored for specific applications requiring complex three-dimensional parts.

In the quest to develop sustainable and environmentally friendly materials, cellulose is a promising alternative to synthetic polymers. However, native cellulose, in contrast to many synthetic polymers, cannot be melt-processed with traditional techniques because, upon heating, it degrades before it melts. One way to improve the thermoplasticity of cellulose, in the form of cellulose fibers, is through chemical modification, for example, to dialcohol cellulose fibers. To better understand the importance of molecular interactions during melt processing of such modified fibers, we undertook a molecular dynamics study of dialcohol cellulose nanocrystals with different degrees of modification. We investigated the structure of the nanocrystals as well as their interactions with a neighboring nanocrystal during mechanical shearing, Our simulations showed that the stress, interfacial stiffness, hydrogen-bond network, and cellulose conformations during shearing are highly dependent on the degree of modification, water layers between the crystals, and temperature. The melt processing of dialcohol cellulose with different degrees of modification and/or water content in the samples was investigated experimentally by fiber extrusion with water used as a plasticizer. The melt processing was easier when increasing the degree of modification and/or water content in the samples, which was in agreement with the conclusions derived from the molecular modeling. The measured friction between the two crystals after the modification of native cellulose to dialcohol cellulose, in some cases, halved (compared to native cellulose) and is also reduced with increasing temperature. Our results demonstrate that molecular modeling of modified nanocellulose fibers can provide fundamental information on the structure-property relationships of these materials and thus is valuable for the development of new cellulose-based biomaterials.

Cellulose-based hydrogels are promising sustainable materials for a variety of applications, including tissue engineering, water treatment, and drug delivery. However, the tailoring of diverse properties by efficient green chemistry methods is an ongoing challenge. Here, composite hydrogels of consistent spheroidal structure, incorporating TEMPO-oxidized cellulose nanofibrils and nanofibrous chiral Cu(II) aspartate coordination polymer, are presented. The hydrogels are prepared by a single-step procedure in aqueous media at ambient temperature and pressure, adhering to the principles of green chemistry. With a view to adapting this method for a variety of alternative coordination polymers (to tailor functional properties), the following critical factors for formation of robust composite hydrogel spheroids are identified: rheological properties of the primary matrix used for spheroidal hydrogel formation and coordination polymer self-assembly rate.

Coordination polymers, including metal-organic frameworks, are a diverse class of materials with myriad properties and potential applications. However, a number of drawbacks have hindered the scaling up of such materials towards commercial applications. These include health and safety risks, environmental hazards, poor cost efficiency and sustainability shortfalls. In contrast to the systematic progress of organic green chemistry, which has contributed to improvements in the sustainability of chemical processing, the development of green chemistry in the context of coordination polymers has been fragmented and sporadic. This review describes advances in the use of green components: benign sustainable ligands and non-hazardous earth abundant metals. Additionally, solvent considerations, synthesis strategies for improved sustainability and the performance of coordination polymers relative to alternative competing materials are discussed.