Natural Polymers

10 Key excerpts on "Natural Polymers"

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  eBook - ePub

  Green Polymeric Nanocomposites

  • Satya Eswari Jujjavarapu, Krishna Mohan Poluri(Authors)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  These biodegradable polymers are broadly classified into two different classes, that is, Natural Polymers and synthetic polymers, based on their origin. Natural Polymers are acquired from natural sources; synthetic polymers are the polymer substances produced through numerous chemical synthesis processes. The best example of a natural polymer is starch; it is produced by green plants as an energy reserve, stored in plant cells for future requirements (van Beilen & Poirier, 2008). It is a highly biodegradable, low-cost and abundantly available natural polysaccharide (plant-based natural polymer), broadly distributed in the form of minute granules as the chief standby polymer/carbohydrate in the trunks, roots, grains and fruits of all types of leafy plants (Mukherjee, Lerma‐Reyes, Thompson, & Schrick, 2019). Furthermore, it is produced from atmospheric carbon dioxide and water in the presence of chlorophyll and sunlight by a process called photosynthesis. Due to its readily biodegradable nature, biocompatibility, low cost and renewability, this plant-based natural polymer has gained much attention in recent years.

  4.2Natural Polymers

  A polymer is a large macromolecule formed when monomer units are repeatedly linked together by chemical bonds. These compounds are produced by polymerization and they occur both in natural form as well as in synthetic form. Natural Polymers are more in demand because they are biodegradable, with a few exceptions, and also biocompatible, nontoxic and, moreover, readily available. In addition, they are capable of chemical modification (Hon, 2017; Teodorescu, Bercea, & Morariu, 2018). Based on their source of origin, polymers are classified into two types, i.e., either polysaccharide or protein-derived, coming from plant or animal sources, respectively.

  Polymers produced by living organisms have been utilized by humans for a very long time, as they are biodegradable in nature and do not cause harm. On the other hand, polymers produced by chemicals have adverse effects on the atmosphere as well as on human health. Biopolymers and their composites occupy a unique position in the new world of biomaterials. Various applications of these composites in the fields of food technology, medicine and the pharmaceuticals are increasing day by day, which is leading to advances in biomaterial technology (Liu, Xie, Li, Zhou, & Chen, 2015; Kunduru, Basu, & Domb, 2016; Ivanova, Bazaka, & Crawford, 2014). Natural Polymers and their types are illustrated in Figure 4.1

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  Chemistry

  Principles and Reactions

  • William Masterton, Cecile Hurley(Authors)
  • 2020(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  576 ▼ 23 Organic Polymers, Natural and Synthetic I n previous chapters we have discussed the chemical and physical properties of many kinds of substances. For the most part, these materials were made up of either small molecules or simple ions. In this chapter, we will be concerned with an important class of compounds containing large molecules. We call these compounds polymers . A large number of small molecular units, called monomers , combined together chemically make up a polymer. A typical polymer molecule contains a chain of mono-mers several thousand units long. The monomer units that comprise a given polymer may be the same or different. We start with synthetic organic polymers. ▲ Since about 1930, a variety of syn-thetic polymers have been made available by the chemical industry. The monomer units are joined together either by addition (Section 23-1) or by condensation (Section 23-2). They are used to make cups, plates, fabrics, automobile tires, and even artificial hearts. The remainder of this chapter deals with Natural Polymers. These are large mol-ecules, produced by plants and animals, that carry out the many life-sustaining pro-cesses in a living cell. The cell membranes of plants and the woody structure of trees are composed in large part of cellulose, a polymeric carbohydrate. We will look at the structures of a variety of different carbohydrates in Section 23-3. Another class of Natural Polymers are the proteins. Section 23-4 deals with these polymeric materials, which make up our tissues, bone, blood, and even hair. Industrial chemists work more with polymers than with any other class of materials. Dale Chihuly, Chihuly Bridge of Glass, Crystal Towers detail, 2002, Tacoma, Washington. Photo by Scott M. Leen The glasslike sculpture is made of a polymer, which allows it to stand up to the outdoor weather. The repeating design, though random, recognizes the randomness and repetitiveness of the structure of polymers.

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  Bionanocomposites

  Green Synthesis and Applications

  • Khalid Mahmood Zia, Farukh Jabeen, Muhammad Naveed Anjum, Saiqa Ikram(Authors)
  • 2020(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 3

  Natural Polymers as constituents of bionanocomposites

  Aqdas Noreen, Salma Sultana, Tayyaba Sultana, Shazia Tabasum, Khalid Mahmood Zia, Zaeema Muzammil, Mudassir Jabeen, Ansab Zaeem Lodhi and Sitwat Sultana,    Government College University, Faisalabad, Pakistan

  Abstract

  Renewable Natural Polymers like polysaccharides, protein fibers, biopolyester fibers, polynucleotides, and polyisoprene fibers, show biodegradability, biocompatibility, cost-effectiveness, and nontoxicity. In addition, Natural Polymers have enormous structural abilities for chemical modifications to produce unique properties. Bionanocomposites are hybrid nanostructrured materials based on Natural Polymers with enhanced functional and structural properties. This chapter provides a comprehensive overview of the properties and applications of Natural Polymers that are constituents of bionanocomposites. This chapter also covers the applications of natural polymer-based bionanocomposites in biomedical, pharmaceutical, electrical, and food packaging fields.

  Keywords

  Bionanocomposites; polysaccharides; proteins; Polyhydroxyalkanoates; polyisoprene fibers

  3.1 Introduction

  The use of materials based on polymers has increased tremendously in the last few decades. These materials have not only made human life simple but have also affected all aspects of our civilization. Nowadays they are used in household to aerospace applications and are part of our everyday life. Different kinds of polymeric materials, including elastomers, polymer composites, plastics, artificial fibers, and many others, are being developed that have a polymer chain as an integral part. These materials are also custom-made for specific industrial applications. Being low cost, availability, and easy processing of polymers, they have replaced the traditional materials like glass and metals. Nevertheless a decrease in the petroleum sources, environmental awareness, and health concerns have given rise to the growth of new types of biodegradable materials [1] . Different biopolymers are obtained from many renewable sources including proteins (collagen, silk, fibrin gels, cutin, gelatin, and suberin), biofibers (lignocelluloses), and polysaccharides (starch, cellulose, pectin, chitosan, hylauronic acid derivatives, and alginate) (Fig. 3.1 ) [2 –4]

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  Tissue Engineering

  • Jan De Boer, Clemens van Blitterswijk, Peter Thomsen, Jeffrey Hubbell, Ranieri Cancedda, J.D. de Bruijn, Anders Lindahl, Jerome Sohier, David F. Williams(Authors)
  • 2008(Publication Date)
  • Academic Press

    (Publisher)

  Chapter contents 6.1 Introduction 146 6.2 Natural Polymers 146 6.3 Polysaccharides 149 6.4 Proteins 167 6.5 Polyhydroxyalkanoates 178 6.6 Future developments 180 6.7 Summary 180 Manuela Gomes, Helena Azevedo, Patrícia Malafaya, Simone Silva, Joaquim Oliveira, Gabriela Silva, Rui Sousa, João Mano and Rui Reis Chapter 6 Chapter objectives: ● To understand the origin, structure and properties of Natural Polymers used in tissue engineering applications ● To identify the characteristics that make Natural Polymers interesting for TE applications ● To understand possible factors that may affect cells/tissue response to Natural Polymers based scaffolds ● To understand the possible specific applications of each natural polymer in the context of tissue engineering ● To understand the processing possibilities of the different natural origin polymers for TE applications ● To recognize the most important achievements in this research field attained by different scientists ● To understand the versatility obtained by combining natural origin polymers with other materials in Tissue Engineering applications Natural Polymers in tissue engineering applications 146 Chapter 6 Natural Polymers in tissue engineering applications 6.1 Introduction Life as we know it could not exist without Natural Polymers. Just think of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). They are natural poly-mers essential in so many life processes. In fact, long before there were plastics and synthetic polymers, nature was using Natural Polymers to make life pos-sible. In the early 1900s, scientists began to under-stand the chemical makeup of Natural Polymers and how to make synthetic polymers with properties that complement those of natural materials. Nevertheless, for many purposes, we still don ’t think of Natural Polymers in the same way as we think about syn-thetic polymers.

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  Introduction to Biopolymer Physics

  • Johan R C van der Maarel(Author)
  • 2007(Publication Date)
  • WSPC

    (Publisher)

  1 C HAPTER 1 BIOPOLYMERS In this chapter, the basic properties of biopolymers will be briefly discussed. We will group them according to nucleic acids, proteins and polysaccharides and we will summarize their main biological functions. Biopolymers have the unique feature that they exhibit a hierarchy in their molecular structures. Associated with these structures, their biological functions emerge almost naturally. In the latter context, think about the importance of the double-helical structure of DNA for the replication process. It is important to realize that these biological functions are based on the way the building blocks (nucleotides, amino acids, carbohydrates, etc. ) are assembled. We will subsequently present the primary, secondary and some tertiary structures of nucleic acids, proteins and polysaccharides and show how they are stabilized by interactions. However, a detailed discussion of the chemical composition of the various biopolymers and their biological functions is beyond the scope of this book and for this purpose the reader is referred to the dedicated literature (see, for instance, the textbooks of Mathews, van Holde and Ahern and Bloomfield, Crothers and Tinoco). 1,2 1.1 Introduction Biopolymers or biomacromolecules can be roughly classified according to three different categories: nucleic acids, proteins and polysaccharides (carbohydrates). It should be born in mind that this classification is not strict and that there are important exceptions. An example is glycoprotein, which is a combination of protein and carbohydrate and plays a role in, among others, immune cell recognition and tissue adhesion. The biological functions of nucleic acids, proteins and polysaccharides are also different. Nucleic acids are 2 Introduction to Biopolymer Physics involved with the storage of the genetic code (DNA) and the translation of the genetic information into protein products (RNA).

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  Fibrous Materials

  • Krishan Chawla(Author)
  • 2016(Publication Date)
  • Cambridge University Press

    (Publisher)

  in industrial and nonindustrial applications has always been quite large because of their many attributes such as the wear-comfort of cotton and the fact that all natural fibers represent a renewable resource. The main disadvantage of natural fibers is the immense variability in their physical, chemical, and mechanical attributes. First, in order to understand the processing, structure, and properties of polymeric fibers, the main focus of Chapters 3 and 4, it will be useful to review some general and basic concepts regarding the structure of polymeric materials, and especially some of the important features associated with the macromolecular chains that do not have their counterparts in metals and ceramics. Readers more versed in these aspects of polymers may skip straight to Section 3.2. In what follows, we first examine the salient structural aspects of polymers and then describe the processing, structure, and properties of some important natural polymeric fibers. 3.1 Structure and properties of polymers Polymers, natural or synthetic, are characterized by an extended chain structure. Giant molecules called macromolecules are formed by joining the chain elements in different ways. Each unit or building block of the chain is called a monomer and a polymer results when we join many monomers to form a long chain. We describe below some important classes of polymers, their structure, and some of their important attributes. 3.1.1 Classification of polymers Polymers can be classified in many ways. An easy way to classify polymers is based on the processing used to make them. There are two main types of process: (i) Condensation polymerization. In this polymerization, a stepwise polymerization reaction of molecules takes place with a molecule of a simple compound forming at each step. Generally, the simple by-product is a water molecule. (ii) Addition polymerization. In this process, polymerization occurs without the forma- tion of any by-product.

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  Micro- and Nanostructured Polymer Systems

  From Synthesis to Applications

  • Sabu Thomas, Robert Shanks, Jithin Joy, Sabu Thomas, Robert Shanks, Jithin Joy(Authors)
  • 2016(Publication Date)
  • Apple Academic Press

    (Publisher)

  The large quantities of the petroleum-based polymeric materials raised a negative effect on the environment. Nanotechnology has a great potential in the development of high-quality biopolymer-based products. Biopolymers are attracting considerable attention as a potential replacement for petroleum-based plastics due to an increased consciousness for sustainable development and high price of crude oil. Biopolymers ideally maintain the carbon dioxide balance after their degradation or incineration. By using biodegradable grades, they will also save energy on waste disposal. Bio-reinforced materials are attractive and an alternative low-cost substitute and widely available. This chapter deals with the preparation, characterization, and applications of natural polymer blends and their composites in a systematic and detailed way. 1.1 INTRODUCTION Natural Polymers have attracted an increasing attention over the past two decades, mainly due to their abundance and low cost in addition to environmental concerns, and the anticipated depletion of petroleum resources. This has led to a growing interest in developing chemical and biochemical processes to acquire and modify Natural Polymers, and to utilize their useful inherent properties in a wide range of applications of industrial interests in different fields (Zhao, Jin, Cong, Liu, & Fu, 2013). The development of commodities derived from petrochemical polymers has brought many benefits to mankind. However, it is becoming more evident that the ecosystem is considerably disturbed and damaged as a result of the non-degradable plastic materials used in disposable items. Therefore, the interest in polymers from renewable resources has recently gained exponential momentum and the use of bio-degradable and renewable materials to replace conventional petroleum plastics for disposable applications is becoming popular (Yu, Dean, & Li, 2006).

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  Polymeric Biomaterials

  Structure and Function, Volume 1

  • Severian Dumitriu, Valentin Popa(Authors)
  • 2013(Publication Date)
  • CRC Press

    (Publisher)

  In general, natural nonspecific polymers can offer a range of advantages when compared with synthetic polymer-based materials. Natural Polymers are usually biocompatible, whereas synthetic polymers can contain a residue of initiators and other compounds/impurities that do not allow cell growth. Synthetic polymers possess good mechanical properties and thermal stability, much better than several naturally occurring polymers. There is also a limitation in the performance of several Natural Polymers in comparison to synthetic polymers. New polymeric materials in many cases should be biocompatible, and at the same time they should possess good thermal and mechanical properties. For this reason, blends of natural poly-mers and synthetic polymers have become promising materials for biomedical applications. That is why the new materials designed should contain both Natural Polymers and synthetic ones.* New materials based on blends of natural and synthetic polymers are a rapidly growing research area [5–44]. Intensive research is currently underway in areas in which biopolymeric–polymeric materials can be used in the engineering of bone, tissue, and organs [5]. New materials based on the blends of Natural Polymers and man-made polymers can also be applied as packaging materials for drugs and medical devices. They can also be applied in the food packaging industry. The biodegradability of Natural Polymers is very useful in the packaging industry. Blends of synthetic and Natural Polymers are required in this field as bacteria start to degrade the natural polymer and therefore decrease the natural component making it easier to degrade the synthetic component. The blends of Natural Polymers and synthetic polymers can more readily undergo photodegradation than synthetic polymers. Natural Polymers possess many chemical groups (chromophores) absorbing UV light from the sun.

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  Renewable Resources for Functional Polymers and Biomaterials

  Polysaccharides, Proteins and Polyesters

  • Peter Williams(Author)
  • 2015(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  CHAPTER 1 Natural Polymers: Introduction and Overview PETER A. WILLIAMS Glyndwr University, Plas Coch, Mold Road, Wrexham LL11 2AW, UK

  This chapter introduces the aim and scope of the book and presents an overview of the subject of Natural Polymers, mainly polysaccharides and proteins, but also microbial polyesters and nucleic acids. Details of the types, names and functions of individual polysaccharides and proteins are provided together with examples of their structural and physicochemical characteristics. It also highlights the main functional properties of these polymers including their rheological behavior, mechanisms of gelation, emulsification characteristics and film formation. The main applications of polysaccharides and proteins in medical and industrial sectors are also outlined with market size and trends.

  1.1 Introduction to Biopolymers

  Proteins and polysaccharides are found abundantly in nature and are major constituents of plants, animals and micro-organisms serving a number of important functions.

  1 ,2

  Proteins are composed of amino acids and although there are hundreds of different proteins they all consist of linear chains of the same twenty L -α-amino acids which are linked through peptide bonds formed by a condensation reaction. Each amino acid contains an amino group and carboxylic acid group with the general formula:

  The R group differs for the various amino acids and can impart polar, non-polar, anionic or cationic characteristics. The amino acid units are linked together through a peptide bond to form a polypeptide chain as illustrated below:

  Proteins consisting of between 15 and 10 000 amino acids are known. Since proteins contain both cationic and anionic charges due to the presence of ionisable groups, notably amine and carboxyl, they have a characteristic isoelectric point which corresponds to the pH at which the molecules have a net zero charge.

  There are various levels of protein structure. The protein primary structure is defined by the characteristic sequence of amino acids of the polypeptide chain. Certain amino acids within the chain give rise to local secondary structures such as the α helix and the pleated sheet. There is a tendency for the more hydrophobic amino acids present to reside within the core of the molecule so that they are less exposed to the aqueous environment, and the overall shape of the protein that is formed (the tertiary structure) is stabilised by a range of interactions including hydrogen bonds, disulfide bonds and salt bridges. The protein molecules may self-associate to create a larger assembly referred to as quaternary structures.

  Proteins tend to have either a linear or globular conformation and have a unique characteristic molecular mass. Linear proteins function as structural elements in the connective tissue of animals. The polypeptide chains are arranged in parallel forming long fibres. Fibrous proteins are insoluble in aqueous environments and are mechanically strong. Examples include collagen, found in tendons, cartilage and bone, and keratin, found in hair, skin and nails. Other proteins tend to fold into compact spherical or globular conformations. Globular proteins tend to be soluble in aqueous environments and are involved in transport processes or in dynamic functions in the cell. There are also special classes of proteins such as enzymes which are able to selectively cleave covalent bonds in biomacromolecules and antibodies which can attach to specific binding sites. Table 1.1

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  Natural Polymers

  Volume 1: Composites

  • Maya J John, Sabu Thomas(Authors)
  • 2012(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  In recent years, there has been growing interest in the use of biodegradable polymers for different applications in order to reduce different forms of environmental pollution. Eco-benign polymers and their derivatives are diverse, abundant and important for life. These polymers are mostly pro-duced from living organisms or through non-toxic precursors and reactions. They exhibit fascinating properties and are of increasing importance for dif-ferent applications. These polymers are broadly classified into two main areas: renewable and non-renewable polymers. Essentially, renewable biodegradable polymers utilize a renewable resource ( i.e ., animal or plant by-products) 35 in the development of the polymer, rather than a non-renewable ( i.e ., petroleum-based) resource. 36 Obviously, long-term research and development focuses on the utilization of various renewable/biodegradable polymers for a variety of applications, including as composites. Some of the environmentally friendly polymers include cellulose, starch, chitin, chitosan, proteins, peptides, alginate, gelatin, poly(lactic acid), locust bean gum, pectin, plant exudate gums, poly(3-hydroxybutyrate), polyamide, etc . Originally, biopolymers were intended to be used in packaging, 37 farming 38 and other industries with low strength requirements. The performance limitations and high cost of biopolymers are major barriers for their widespread acceptance as substitutes for traditional non-biodegradable synthetic polymers. The high cost of some eco-benign polymers compared with traditional polymers is not due to the raw material costs for biopolymer synthesis but mainly to the low volume of production. New and advanced synthetic procedures for preparing biopolymers need to be developed for their high-value applications.

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