Polymer

9 Key excerpts on "Polymer"

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  eBook - PDF

  Introduction to Biopolymer Physics

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

    (Publisher)

  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). Proteins catalyze biochemical reactions (enzymes), have structural or mechanical functions or are important in cell signalling and immune responses. The structural components of plants are primarily composed of the polysaccharide cellulose. Bacteria excrete polysaccharides for adhesion to surfaces and to avoid dehydration. Examples of these polysaccharides are dextran, xanthan and pullulan, which have found wide-spread applications in pharmacy, biotechnology and the food industry. The classification according to the functioning of the bioPolymers is also not unique. An important exception is the ribosome; an organelle on which proteins are assembled. A ribosome contains 65% RNA and 35% protein. It can be considered an enzyme, but its active site is made of RNA. However, the functioning and purpose of bioPolymers in the machinery of life is beyond the scope of this book. Here, we intend to explore the extent to which their properties can be understood in terms of concepts from physics and mathematics. Like every Polymer, bioPolymers are strings or sequences of monomeric units or monomers for short. In many cases these strings are linear, but sometimes they are closed and circular, branched or even cross-linked. In the latter case, we are dealing with a gel. In this book, we will primarily focus on linear Polymers, but we will also discuss star-branched Polymers, spherical Polymer brushes and closed circular, supercoiled DNA. The structure of any bioPolymer is determined by the nature of the building blocks ( i.e . the monomeric units) in combination with environmental conditions such as the temperature, the solvent (water) and the presence of salts and/or other molecular components.

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  The Fundamentals of Materials chemistry

  • Saeed Farrokhpay(Author)
  • 2023(Publication Date)
  • Arcler Press

    (Publisher)

  FUNDAMENTALS OF PolymerIC MATERIALS 4 CONTENTS 4.1. Introduction ...................................................................................... 88 4.2. The History of the Concept of the Macromolecule ............................ 89 4.3. Classification of Polymers ................................................................. 91 4.4. Structure and Properties of Polymers ................................................. 93 4.5. Thermoplastic Polymers .................................................................... 93 4.6. Thermosetting Polymers .................................................................. 101 4.7. Naturally Occurring Polymers......................................................... 108 References ............................................................................................. 113 CHAPTER The Fundamentals of Materials Chemistry 88 4.1. INTRODUCTION A Polymer is a big molecule comprised of a lot of smaller ones. Complex molecules can be strongly linked, mildly branching, or straight. The structure in the first example becomes a vast three-dimensional (3D) network (Morgan and Gilman, 2013; Dhote et al., 2019). Monomers are tiny molecules that serve as the fundamental foundations of larger compounds. The economically important substance poly(vinyl chloride), for example, is made from the monomer vinyl chloride. The Polymer’s duplication component is usually the same as the monomer wherein the Polymer was made. Although, there are several exceptions. Vinyl alcohol (CH 2 CHOH) recurring units are correctly considered to make up Poly(vinyl alcohol), yet there is no such monomer like vinyl alcohol. The relevant molecular unit is found in the alternate tautomeric for methanal (CH 3 CHO). The Polymer poly(vinyl ethanoate) must first be made from the monomer vinyl ethanoate, and afterwards, the result must be hydrolyzed to create the Polymer ethanol (Bloembergen, 1996; Roth and Baglay, 2016).

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  Liquid Crystals, Laptops and Life

  • Michael R Fisch(Author)
  • 2004(Publication Date)
  • WSPC

    (Publisher)

  When we discuss Polymers in more detail, you will see the role carbon plays in Polymers. We will begin by discussing the basic chemistry of Polymers. An impor- tant difference between Polymers and materials such as fluids or metals is that Polymers are long-chain or network type molecules. We will illustrate this using cartoons. We will then discuss the major types of Polymers. From the materials viewpoint, there are two main types of Polymers: ther- moplastic Polymers that become less rigid when heated, and thermosetting Polymers that become more rigid when heated. Both types of Polymers are often used with additives that improve color, strength, and other physical and chemical properties. 9.3 What is a Polymer? The term Polymer literally means “many parts.” It is derived from Greek where poly means many and meros means unit or part; that is the simple, repeated building block of the chain or network. Thus, a Polymer is a large molecule made up of many smaller and simpler chemical units covalently bonded together. For example, polyethylene (CH3-(CHz),-CH3) is a long chain molecule composed of ethylene molecules (CHz=CH2), Notice how- ever that the terminal groups are CH3. This is a fairly standard occurrence - the terminal moieties2 are frequently different from the central moieties that make up the Polymer. Moreover, the two terminal groups need not be the same. Molecules with these general properties, that is, long chain molecules consisting of three different moities, a distinct one at each end and many repetitions of the central moiety, are ubiquitous. Such molecules occur in nature, and are also synthetically produced. This chapter will primarily focus on artificially produced Polymers. Syn- thetic Polymers often have a central structure of the form: -A-A-A-A-A-A-or -A-B-A-B-A-B-. –B—–B– .... ‘A plastic deformation is a permanent deformation that does not change upon re- ’A moiety is a sub-section of a molecule that has characteristic properties.

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  Biology for AP® Courses

  • Julianne Zedalis, John Eggebrecht(Authors)
  • 2018(Publication Date)
  • Openstax

    (Publisher)

  These large molecules are composed mainly of six elements—sulfur, phosphorus, oxygen, nitrogen, carbon, and hydrogen (SPONCH)—in different quantities and arrangements. Complex Polymers are built from combinations of smaller monomers by dehydration synthesis, a chemical reaction in which a molecule of water is removed between two linking monomers. (Think of a train: each boxcar, including the caboose, represents a monomer, and the entire train is a Polymer.) During digestion, Polymers can be broken down by hydrolysis, or the addition of water. Both dehydration and hydrolysis reactions in cells are catalyzed by specific enzymes. Dehydration reactions typically require an investment of energy for new bond formation, whereas hydrolysis reactions typically release energy that can be used to power cellular processes. The four categories of macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Evidence supports scientists’ claim that the organic precursors of these biological molecules were present on primitive Earth. Information presented and the examples highlighted in the section support concepts and Learning Objectives outlined in Big Idea 1 of the AP ® Biology Curriculum Framework. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP ® Biology course, an inquiry-based laboratory experience, instructional activities, and AP ® Exam questions. A learning objective merges required content with one or more of the seven Science Practices. Big Idea 1 The process of evolution drives the diversity and unity of life. Enduring Understanding 1.D The origin of living systems is explained by natural processes. Essential Knowledge 1.D.1 There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. Science Practice 1.2 The student can make claims and predictions about natural phenomena based on scientific theories and models.

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  Polymerization in Biological Systems

  • G. E. W. Wolstenholme, Maeve O'Connor, G. E. W. Wolstenholme, Maeve O'Connor(Authors)
  • 2009(Publication Date)
  • Wiley

    (Publisher)

  I hope, therefore, that at this symposium we shall find a common language to cope with the problems to be discussed. The layman often refers to this age as the age of plastics, in which nylon, polystyrene, polyvinylchloride and other synthetic Polymers are in everyday use. BioPolymers, such as proteins, nucleic acids and polysaccharides, play a major role in determining the most essential processes in living organisms. They have, in one form or another, been utilized since time immemorial, and by now even the man in the street is familiar with some of their specific biological properties, yet the interests of the molecular biologists are still rather different from those of the synthetic Polymer chemist. The Polymer chemist is mainly interested in the mechanical, electrical and other physical properties of the Polymers which he has produced. The molecular biologist is interested in nucleic acids, proteins and other bioPolymers because they store information, because some of them act as catalysts, and others possess recogni- tion patterns which allow them to recognize other molecules. There is much room for increased cooperation between the two groups of scientists with their somewhat divergent interests. 2 E. KATCHALSKI We are going to begin by discussing Polymerization mechanisms and the techniques used in the preparation of synthetic Polymers. In some cases, the mechanisms involved in the formation of synthetic Polymers resemble those observed in the biosynthesis of natural Polymers, e.g. condensation. However, the commonly used Polymerizations, in which radicals and carbonium ions participate as reactive intermediates, have no counterpart in nature. I wonder why this is so? Professor Fritz Lipmann, who most certainly is not a synthetic Polymer chemist, has divided the reactions by which bioPolymers are formed into two classes: the tail type of Polymerization and the head type of Polymerization (Lipmann 1968).

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  Biomaterials

  A Basic Introduction

  • Qizhi Chen, George Thouas(Authors)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  10.8 BIOLOGICAL PolymerS As introduced in Chapter 1, biomaterials encompass biological materials. Biomacromolecules can be classified into four groups: 1. Polysaccharides (Polymers with carbohydrate monomers) 2. Proteins (Polymers with amino acid monomers) 3. Lipids (i.e., fatty acids = short chain hydrocarbons, with mixed saturated and unsaturated C − C bonds, sometimes with trimester cross-links) 4. Polynucleic acids (i.e., DNA, RNA—purine and pyrimdine Polymers) More discussions on these biomacromolecules will be provided in the Advanced Topic section of this chapter and in Chapter 16. 10.9 CHAPTER HIGHLIGHTS 1. The biodegradation of Polymers proceeds in three major steps: Cleavage → Metabolism → Excretion. 2. Cleavage is initiated by abiotic mechanisms, which include hydrolysis and/ or oxidation. The kinetics of an abiotic process is determined by the physical accessibility of the Polymer structure to water or oxygen molecules. Abiotic mechanisms proceed in a diffuse manner. 3. Biodegradation rates of chemical bonds in Polymers: • C − C, C − H, C − F, Si − O: physiologically inert • HN − CO, peptide bond: hydrolyzable but very slowly, virtually impossible without enzyme activity • CO − O, ester bond: hydrolysis proceeds without enzyme activity, though can be accelerated by enzyme-mediation Polymer carrier Degraded Polymer Released drug Drug Figure 10.20 Controlled drug release. Bioresorbable Polymers 357 4. A rank of some polyesters, in terms of degradation kinetics, from faster to slow: PGLA PGA PDLLA PLLA PCL P3HB Degradation rate dec > > > > > reasing  →  which can be explained by the steric hindrance of side chains and crystallinity of these Polymers. 5. The degradation product of these polyesters is their monomers, that is, glycolic acid, lactic acids, or primelic acid. These chemicals are natural metabolites in the body and can be excreted by the physiological system.

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  Introduction to Biomaterials

  Basic Theory with Engineering Applications

  • C. Mauli Agrawal, Joo L. Ong, Mark R. Appleford, Gopinath Mani(Authors)
  • 2013(Publication Date)
  • Cambridge University Press

    (Publisher)

  Each molecule of a Polymer can consist of hundreds, thousands, or even millions of repeat units. Depending on the type of Polymeriza-tion, the repeat unit may contain exactly the same atoms as the starting molecule or monomer, or may contain a smaller number of atoms due to the elimination of some during the Polymerization reaction. In either case, a single repeat unit is known as the monomeric unit or monomer . Small chains of up to roughly 10 repeat units are called oligmers (from Greek oligos meaning few), although there is no hard and fast rule about the number of repeat units needed for the transition from oligmers to Polymers. The structural units terminating the ends of a Polymer chain molecule are known as end groups . The number of units in a Polymeric chain plays a signi fi cant role in determining its properties. Let us take the example of polyethylene, which is derived from the basic unit of ethylene gas. As the number of units in the chain increases, the product changes from a gas to a liquid and then to a brittle or waxy solid. As the number increases even more, the Polymeric chains become long enough to start entangling with each other and lead to the properties more commonly associated with Polymers. 135 6.1 Molecular structure of Polymers The units in a Polymer are usually held together by covalent bonds. Adjacent Polymeric chains or the different segments of the same chain may bond together by intermolecular forces or van der Waals bonds. In some cases, ionic bonds may also occur in Polymers. Covalent bonds are characterized by relatively high energy, fi xed angles, and short distances (0.11 – 0.16 nm), and they determine the mechanical, thermal, chemical and photochemical properties of a Polymer.

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  Plastic Films

  Technology and Packaging Applications

  • Wilmer A. Jenkins, Kenton R. Osborn(Authors)
  • 1992(Publication Date)
  • CRC Press

    (Publisher)

  CHAPTER I Polymers INTRODUCTION There is an almost bewildering array of plastic films for packaging that are commercially available today. Their evolution was driven by market need on the one hand and by advances in technology on the other. These technological advances included development of both the number of Polymers that are the current components of plastic films and the variety of processes for converting these Polymers into films and film structures. In this chapter, an understanding of these Polymers and how they are made will be developed. Polymers are very long molecules, and while a few of commercial in-terest are formed in nature, like cellulose, most are synthesized using a chemical process called Polymerization. In this process small molecules, called monomers, are joined together, end to end, in a growing chain. Eventually, the length of the Polymer chain reaches a point where com-mercially useful objects can be made from them. Films made from short chains are brittle, but above some critical length they become tough and ductile. This transition point is different for different classes of Polymers, but for polyethylene commercially useful chains have a minimum of 1000 to 2000 monomer units. Thus, the most important characteristic of Polymer molecules is their length since that determines whether they have any usefulness at all. The next most important characteristic is the chemical nature of the units making up the Polymer molecule. Degrees of toughness, stiffness, transparency, barrier to gases, etc. exhibited by films of chemically different Polymers vary widely. Additional variation is also caused by the specific conditions under which the Polymerization takes place. Also, combinations of monomer units can be caused to Polymerize together forming a coPolymer. Finally, different Polymer molecules can be mixed together or blended leading to further proliferation of the levels and com-binations of properties that are achievable in plastic films. 1

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  Chemical Sciences in the 20th Century

  Bridging Boundaries

  • Carsten Reinhardt(Author)
  • 2008(Publication Date)
  • Wiley-VCH

    (Publisher)

  His book, The Synthesis ofL& was an outcome of this work.[38] In 1963, Mark’s Journal of Polymer Science added a section on “BioPolymers,” which was superseded by a separate new journal, BioPolymers, with Mark, Melvin Calvin, Marshall Nirenberg, and Pauling on the editorial board. It would become a common practice that a textbook on Polymer science included, even to date, a chapter on biological macromolecules (such as polypeptides, proteins, nucleic acids, polysaccharides, and synthetic bioPolymers), discussing their structural details, conformations, and functions. I 12.5 The Problem of Interdisciplinary Science As Polymer science enlarged its scope, strengthening more and more its inter- disciplinary character, research activities within the discipline became increasingly specialized. The journal of Macromolecular Science, an American periodical estab- lished in 1967, aimed to “facilitate a complete overview of the science of macromole- cules.” Thus, the publisher Marcel Dekker stated: I 239 72.5 The Problem of Interdisciplinary Science A broad approach is intended, ranging through the chemical, physical, biological, and engineering sciences. It is the aim of the Journal of Macromolecular Science to create a new dialogue and broader awareness of inter- and intradisciplinary problems and progress. [39] The journal began serving as a means to unify the diverse knowledge in Polymer science. By the 1960s, there had been strong appeals from both academic and industrial scientists for the expansion of Polymer science education in America. The 1962 National Register of Scientijc and Technical Personnel, prepared by the National Science Foundation, listed 25% of all organic chemists in the United States as engaged in the chemistry of Polymers, such as plastics, resins, and rubber, and 15 % of all physical chemists in Polymer chemistry.

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