Nanocellulose

The following sections are included:

• Dedication
• Foreword
• Preface
• About the Editors
• About the Contributors
• Acknowledgments
• Contents

Cellulose with at least one of its dimensions less than or equal to 100 nm is termed as nanocellulose. It is a unique and promising natural material extracted from native cellulose and produced by certain microbial cells and cell-free systems. Nanocellulose has received immense consideration in last couple of decades owing to its abundance, renewability, remarkable physical properties, special surface chemistry, and excellent biological features (biocompatibility, biodegradability, and non-toxicity). Taking advantage of the structure and properties of nanocellulose, the current science of biomaterials aims at developing new and formerly non-existing materials with novel and multifunctional properties, in an attempt to meet current requirements in different fields such as biomedicine, the environment, energy, pharmaceutics, agriculture, food, etc. This chapter provides an overview of different synthesis methods of nanocellulose: mechanical approaches by applying high-pressure, grinding, crushing, sonication, and milling; chemical synthesis involving alkaline, acidic, oxidation, and enzymatic treatment; as well as by using bacteria and cell-free systems. It further discusses different morphological forms of nanocellulose including cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs), bacterial nanocellulose (BNC), and cellulose produced by cell-free systems, in terms of their features such as chemical structure, macrostructural morphology, physico-mechanical properties, thermal and biological properties, rheology, optical behavior, and their interrelationships and applications.

In this study, the characteristics of cellulose nanofiber (CNF) from oil palm mesocarp fiber (OPMF) produced by two different nanofibrillation methods — high-pressure homogenization (HPH) and wet disk milling (WDM) — were compared for their morphological, crystallinity, and thermal stability analyses. Results showed that CNF produced from HPH and WDM had almost similar characteristics, with WDM being advantageous due to its ability to process cellulose at higher concentration without clogging. This may suggest the suitability of WDM for large-scale CNF production via mechanical processing route.

Cellulose is the most abundant renewable natural biopolymer on earth and exists in a wide variety of living species including plants, animals and some bacteria. The term “nanocellulose” generally refers to cellulosic materials having at least one dimension in the nanometer range. On the basis of their dimensions, functions, and preparation methods, nanocellulose can be categorized into different groups: cellulose nanocrystals (CNC), microfibrillated cellulose (MFC), cellulose nanofiber (CNF), bacterial cellulose (BC), etc. The qualities of large surface area, exceptional mechanical properties, surface versatility and biodegradability bring nanocellulose to the forefront as a functional or structural component with uses in a wide range of fields, e.g., composites, drug release, wearable devices. By carefully adjusting interactions with the surrounding medium, we may be able to engineer nanocellulose with unprecedented properties. As a result, the focus of present chapter is the surface modification of nanocellulose by surfactant coupling, co-dispersion, chemical modification and nano-deposition.

With the advancement of science and technology, people of the modern civilized era are becoming more dependent on advanced materials. One of the major gifts that chemistry has ever conferred to the human society is the so-called “polymer” or “polymeric materials”, without which the world have been in a totally different position. This chapter deals with recent developments in starch and nanocellulose-reinforced starch nanocomposites.

The cellulose-based hydrogels have received immense interest for various biomedical applications owing to their unique structural, physico-chemical, mechanical, and biological properties. This chapter provides an overview of different cellulose-dissolving systems, cellulose derivatives, cellulose nanostructures, and cellulose-producing microorganisms, with emphasis on the fabrication, properties, and biomedical applications of cellulose-based hydrogels. Further, it highlights the current developments of the latest synthesis methods and technologies, such as 3D and 4D printing, inspired from the naturally occurring biomaterials or soft/hard tissues with numerous excellent properties, to fabricate cellulose-based hydrogels with a highly ordered microstructure, to further improve their properties and applications.

As a virtuous material for biomaterial fabrication, nanocellulose has been extensively explored for biomedical applications, and specifically for the repair and regeneration of skin tissue, due to its unique physico-chemical properties particularly interesting for wound healing. Owing to its high hydrophilicity, collagen-like fibrous structure, biocompatibility, and mechanical stability, it satisfies the main requirements for wound dressing application, with a chemical structure allowing for further functionalization and composite formation for the development of improved and adaptable materials. Following a brief description of skin physiology and wound healing biology, the potential of this biopolymer for the repair of skin tissue is outlined throughout this chapter, emphasizing its advantages and beneficial properties for wound healing application. Modification modalities for endowing the material with novel properties are also discussed, before addressing the various nanocellulose-incorporating biomaterials that are being proposed for wound healing application.

The discovery of new drugs, poor patient compliance, limitations of the conventional dosage forms, and switching to more suitable routes of administration have led to the development of new dosage forms, which in turn demands innovation/discovery of pharmaceutical excipients. In addition to number of excipients, the addition of polymer(s) in drug formulation(s) is unavoidable, as this plays a vital role in the stability, solubility, release, and bioavailability of the drug. The selection of an excipient with ideal properties such as non-toxicity, stability, excess availability, biodegradability, biocompatibility, ease of processing, contaminant-free, and non-allergic response are the major concerns. These issues can be addressed by using cellulose, its derivatives, and different forms as drug delivery systems. To this end, nanocellulose (NC) has received great interest due to its outstanding mechanical, rheological, chemical, and optical properties. It serves as an eco-friendly and sustainable material with vast pharmaceutical applications and is obtained from numerous natural sources of cellulose. NC is hydrophilic in nature; however, the alteration of its surface properties may enhance its applications to meet the challenges of the future. The cellulose produced by microbes, also known as bacterial/microbial cellulose, is a biomaterial with fascinating properties including extremely high purity, high porosity, ultrafine fiber network, high water holding capacity, great tensile strength, and permeability to diffusion of liquids, gases, and small molecules. In the field of drug delivery, cellulose plays a pivotal role in dosage formulations in the form of filler, stabilizer, thickening agent, coating agent, in the preparation of transdermal patches, controlled drug delivery, protein delivery, and macromolecular pro-drug delivery. The current chapter gives an overview of the applications of nanocellulose in drug delivery based on the available literature. An explorative look to NFC applications in the pharmaceutical field and various approaches adopted in the field of drug delivery are also discussed. The approaches made for the safe, effective, and convenient delivery of drugs into body are discussed in detail. Based on current literature, it is suggested that further experimental work is required for the exploration of NFC applications in the stimuli-responsive delivery of drugs.

Presently the entire world, especially the third-world countries, are greatly suffering from food shortages while the available food is sometimes of low quality due to poor processing and lack of storage facilities. To increase the shelf life and improve the quality, the food products need to be appropriately processed, packaged, and protected to minimize the risk of contamination and spoilage. The use of sustainable, low-cost, and lightweight biobased materials could be potential candidates used for food packaging to ensure the transportation of food to other regions and preserve it for extended duration. The idea of introducing different technologies to food science is to increase the sustainability, shelf-life, and nutritional quality of food. Currently, the development of a new generation of products with improved properties for food packaging is of utmost importance. Nanocellulose, a versatile material possessing unique structural, physico-chemical, mechanical, thermal, and biological features, has been vastly explored in food industry for various application. This chapter describes the merits and challenges of nanocellulose in food science as well as its functionalization through surface modification and in situ addition of reinforcement materials to meet the demand of using it as food packaging material and dietary aid, food additive, and emulsion stabilizer. It also discusses the development of active food packaging materials by using biodegradable polymers and antimicrobial materials as an innovative and attractive approach in food science to inhibit the growth of microorganism and retain the quality, freshness, and safety of food.

The human environment is at high risk of contamination by the extensive use of non-degradable resources as well as exhaustion of naturally available resources. To combat the environmental and energy issues, recent developments in nanotechnology have open gateways for the sustainable development of eco-friendly, biodegradable, and renewable polymeric materials. Nanocellulose, possessing unique features such as fibrous structure, high mechanical strength, large surface area, low visual scattering, low-cost, renewability, non-toxicity, biocompatibility, and easy availability, serves as an ideal material for diverse environmental applications. In addition, its unique three-dimensional fibril arrangement allows the impregnation of variety of nanosize materials to enable the development of nanocomposites in the form of hydrogels, aerogels, and films, papers, or membranes. Such substrates serve as templates for inorganic nanoparticles and polymers, or a combination of both. Such unique features make nanocellulose-based materials more efficient, robust, stable, reliable, and environmentally-friendly, thus enabling it to find potential applications in the development of antimicrobial filters and devices for removal of heavy metals, in water treatment and wastewaters purification, in the development of pollutant sensors, as well as in potential applications in catalysis and renewable energy. This chapter provides a comprehensive picture of the recent developments in nanocellulose-based materials to address various issues associated with environment and renewable energy.

Nanocellulose, due to its sustainability, biodegradability, and high performance such as high tensile stiffness and low thermal expansion coefficient, can potentially replace the fossil fuel-based materials for different applications. Among them, paper and the board industry is the most promising field because of the massive product tonnage of paper. It can be used both as a dry and wet-end in the paper industry such as papermaking, paper coating, packaging, and for the production of hygienic and absorbent products. In this chapter, the first part of the chapter discusses the recent progress in the applications of nanocellulose as a dry- and wet-strength agent. The second part describes the use of nanocellulose in coating and barrier packaging. It needs to provide prospects of nanocellulose by reducing its production cost and post-processing, and explore novel application for paper-based products.

A paper with special properties that can be used for specialized applications is termed as “specialty paper”. The basic features of specialty paper include the specific performance, specialized application-based features, low quantity demand, small-scale production, low-cost input equipment, narrow application, and high value-added and technical threshold; it should demonstrate uniform structure and good appearance. It has been developed rapidly in the domestic paper market, which is putting a great impact on the domestic paper, design, and printing industry. The specialty paper could be classified according to performance and applications in different fields. This chapter provides a comprehensive overview of the concept, properties, and classification of specialty paper. It discusses the potential of nanocellulose, the smallest physical structural unit of cellulose possessing nanometer network structure and excellent properties, to be replaced with wood pulp in making the specialty paper. Nanocellulose can add more fillers and reduce the overall production cost of specialty paper, which can further impart stability and strength and improve the printing quality of specialty paper. It further summarizes various applications of nanocellulose-based specialty paper in developing energy storage and electronic devices as well as in nanomedicine and water cleaning.

The cellulose-based materials are transparent in nature as these allow the light to pass through them; however, if it is present in the form of fibers whose size is comparable to the wavelength of light, it can greatly scatter the light. This chapter discusses the light measurement of nanocellulose, and its optical behavior associated with dielectric materials. The optical properties of nanocellulose endow it a large space for optoelectronic design and applications, including in flexible electronics, solar cells, displays, and touch screens. The chapter further discusses the applications of nanocellulose-based materials in photoreduction, plasmonic, and ecological building and energy-saving systems. It also provides prospects for establishing advanced approaches for developing nanocellulose-based novel materials with varying dimensions and for novel applications.

The increasing environmental pollution and serious shortage of energy and resources have become big problems in human society in the recent years. Exploration of novel renewable and biodegradable materials based on biomass and construction of biomass-based energy-related applications have received more and more attention. Cellulose is the most abundant biomass on earth. Especially, nanocellulose possesses excellent mechanical, thermal, and optical properties. In this chapter, we review the recent advances in nanocellulose-based energy conversion materials, including piezoelectric materials, loudspeakers, antenna, phototransistors, organic light-emitting diodes (OLEDs), and touch screen.

The demand for bio-based flexible energy devices has increased rapidly in recent decades due to their unique advantages such as flexibility, light weight nature, shape diversity, etc. Nanocellulose has been established as a promising potential candidate for high-performance flexible energy storage device fabrication due to its exceptional physical, mechanical, and optical properties. In this chapter, we discuss about the recent advances in nanocellulose-based flexible energy storage devices for a wide range of applications. Various chemical and physical modification strategies on nanocellulose have also been discussed. The unique properties of nanocellulose enable multiscale structuring of functional composites, which can be tailored to develop new concepts of energy storage devices. This chapter is a comprehensive effort focusing the recent advances on nanocellulose-based flexible energy devices, including supercapacitors, sensors, batteries, and solar cells.

Nanocellulose is a renewable and biocompatible nanomaterial with a high strength, low density, and tunable surface chemistry. Since a lot of hydroxyl groups are present on the surface of the nanocellulose, this gives them various surface chemistries that can be tailor-made for specific application. This unique property makes them a promising candidate for various applications. Nanocellulose aerogels have gained considerable interest in the scientific community globally due to their renewability, good mechanical properties, low density, high porosity, natural biodegradability, and environmental friendliness. These fascinating properties makes them an attractive material in environmental and engineering applications. This chapter reviews recent attempts to apply nanocellulose aerogels as efficient materials for thermal insulation, flame retardancy, EMI shielding, oil absorption etc.

Over the past couple of decades, the microbial cells-produced cellulose, termed as bacterial cellulose (BC) or bacterial nanocellulose (BNC), has received immense consideration for its applications in different fields. The unique morphological features, surface chemistry, mechanical strength, and inertness make BC an ideal biomaterial. BC, both alone and in the form of composites with other materials ranging from natural and synthetic polymers, nanomaterials, and clay materials, have found applications in different fields. This chapter provides an overview of applications of BC in the biomedical field, including as wound dressings, antimicrobials, drug delivery system, blood vessels, optics, and bone and cartilage implants. It further discusses its applications in food industry as packaging material as well as a dietary food, food additive, and stabilizer. The non-toxic, hydrophilic, high liquid absorbing capacity, and biocompatible nature enable BC to find applications in cosmetics industry.

The following section is included:

• Index