Polymers and Their Classification
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Questions and Answers

What is the glassy state of a polymer characterized by?

  • High thermal energy
  • Long range rotational motion
  • Short range vibrational motion (correct)
  • Flexible chain movement

    • Which of the following factors increases the glass transition temperature (Tg) of a polymer?

  • Increased chain mobility
  • Lower percentage of crystallinity
  • Heating the polymer above Tg
  • Presence of bulky side groups (correct)

    • What is the primary difference between the rubbery state and the glassy state of polymers?

  • Chain movement ability (correct)
  • Molecular weight
  • Temperature dependency
  • Color and appearance

    • How does the presence of aromatic rings affect the Tg of a polymer?

    <p>It increases Tg due to increased stiffness</p> Signup and view all the answers

    Which state is a polymer in when it is above its Tg?

    <p>Viscoelastic state</p> Signup and view all the answers

    What happens to the Tg of a polymer with increased crystallinity?

    <p>Tg increases due to reduced mobility</p> Signup and view all the answers

    What effect does chain stiffness have on the glass transition temperature (Tg)?

    <p>Stiff chains increase Tg</p> Signup and view all the answers

    Which of the following statements accurately describes the conditions for using hard plastics like polystyrene?

    <p>They are used in the glassy state at room temperature.</p> Signup and view all the answers

    What is the primary purpose of catalysts in thermosetting plastics?

    <p>To accelerate polymerization</p> Signup and view all the answers

    Which of the following substances can be used as catalysts in thermosetting plastics?

    <p>Benzoyl peroxide</p> Signup and view all the answers

    What role do antioxidants play in the processing of polymers?

    <p>They inhibit undesirable oxidation</p> Signup and view all the answers

    Liquid crystals are characterized by which of the following properties?

    <p>Anisotropy of properties without a crystal lattice</p> Signup and view all the answers

    Which of the following additives improves the thermal stability of polymers during processing?

    <p>Stabilizers</p> Signup and view all the answers

    Who is credited with the discovery of the liquid crystal phase?

    <p>Friedrich Reinitzer</p> Signup and view all the answers

    Which of these compounds is an example of a pigment used in polymers?

    <p>Antimony sulphide</p> Signup and view all the answers

    The term 'mesophase' in reference to liquid crystals describes which characteristic?

    <p>Their behavior between solid and isotropic liquid</p> Signup and view all the answers

    What is a characteristic feature of conductive element filled polymers?

    <p>They contain a polymer binder holding conducting elements.</p> Signup and view all the answers

    Which type of polymer is created by blending an insulator with a conducting polymer?

    <p>Blended conducting polymer</p> Signup and view all the answers

    In what application is polyaniline primarily used?

    <p>As a sensor for ammonia.</p> Signup and view all the answers

    Which polymer type shows increased conductivity when doped cis-forms are compared to their trans analogues?

    <p>Polyacetylenes</p> Signup and view all the answers

    What is one of the notable applications of conducting polymers in current technology?

    <p>For light weight rechargeable batteries.</p> Signup and view all the answers

    What characteristic do coordination conducting polymers exhibit due to the combination with coordination complexes?

    <p>They demonstrate conductive properties.</p> Signup and view all the answers

    Which of the following describes the process of forming polyacetylene?

    <p>It forms at the gas-liquid interface with acetylene and a catalyst.</p> Signup and view all the answers

    What is compounding of plastics primarily concerned with?

    <p>Adding additives to enhance characteristics of plastics.</p> Signup and view all the answers

    What action must occur for vertically polarized light to pass through a horizontal polarized filter?

    <p>The light must be rotated 90 degrees.</p> Signup and view all the answers

    What role does the liquid crystal layer play in a LCD?

    <p>It twists the molecules to control light orientation.</p> Signup and view all the answers

    What happens to the light when no voltage is applied between the electrodes?

    <p>The light passes through and appears white.</p> Signup and view all the answers

    How are different gray levels produced on the LCD screen?

    <p>By varying the amount of voltage applied between layers.</p> Signup and view all the answers

    What is the function of the color filters in front of the outer polarization plate?

    <p>To produce different color images by varying intensity.</p> Signup and view all the answers

    What causes a pixel to appear black when voltage is applied?

    <p>The liquid crystal molecules untwist and block the light.</p> Signup and view all the answers

    What is a characteristic of liquid crystal polymers?

    <p>They retain molecular order in both liquid and solid states.</p> Signup and view all the answers

    Which of the following is NOT a function of the electrodes in the liquid crystal display?

    <p>To create a color effect in pixels.</p> Signup and view all the answers

    What is a characteristic of long chain, linear polymers?

    <p>They retain their shape upon heating.</p> Signup and view all the answers

    Which type of polymerization results in the loss of small molecules?

    <p>Condensation polymerization</p> Signup and view all the answers

    What initiates the addition polymerization process?

    <p>Heat, light, pressure, or catalyst</p> Signup and view all the answers

    What happens to the structure of a polymer during heating above the glass transition temperature?

    <p>It softens into a viscous liquid.</p> Signup and view all the answers

    Which of the following is an example of a high molecular weight polymer?

    <p>Nylon 6,6</p> Signup and view all the answers

    What is a property of polymers formed by addition polymerization?

    <p>They yield an exact multiple of the monomer.</p> Signup and view all the answers

    Which of the following characteristics is true for high molecular weight polymers?

    <p>Hard and strong.</p> Signup and view all the answers

    What is the main difference between addition and condensation polymerization?

    <p>Addition focuses on unsaturated bonds; condensation does not.</p> Signup and view all the answers

    What is the effect of polar side atoms or groups on the glass transition temperature (Tg) of polymers?

    <p>They increase the intermolecular attractive interactions, raising Tg.</p> Signup and view all the answers

    How does increasing molecular weight affect Tg and Tm of polymers?

    <p>It increases Tg and Tm.</p> Signup and view all the answers

    What is the effect of plasticizers when added to polymers?

    <p>They decrease the brittleness of the polymer and lower Tg.</p> Signup and view all the answers

    What is the result of co-polymerization on the glass transition temperature?

    <p>It introduces disorder, which lowers Tg.</p> Signup and view all the answers

    How does the presence of flexible pendant groups in a polymer affect its Tg?

    <p>It enhances the rotational motion of the chains, lowering Tg.</p> Signup and view all the answers

    What characteristic of conducting polymers allows them to exhibit metallic conductivity?

    <p>Conjugated double bonds providing delocalized pi electrons.</p> Signup and view all the answers

    How does moisture content in a polymer influence its Tg?

    <p>It increases the distance between polymer chains, thus lowering Tg.</p> Signup and view all the answers

    What effect does cross-linking have on the glass transition temperature of polymers?

    <p>It increases the restriction and stiffness, raising Tg.</p> Signup and view all the answers

    Study Notes

    Polymers

    • A polymer is a large molecule formed by repeating small molecules (monomers)
    • Degree of polymerization is the number of repeating units in a polymer chain.
    • Functionality is the number of reactive sites in a monomer.
    • Functionality of 2 creates linear polymers, and functionality greater than 2 creates 3-D polymers.
    • Polymers are classified by availability (natural, semi-synthetic, synthetic), types of monomers (homopolymer, copolymer), chain structure (linear, branched, cross-linked), tacticity (isotactic, atactic, syndiotactic), and polymerization reaction (addition or condensation).
    • Natural polymers include protein, natural rubber, silk, and polysaccharides.
    • Examples of synthetic polymers include nylon, terylene, and PVC.
    • Homopolymers are made of identical monomers. Examples include polyethylene and PMMA.
    • Copolymers are made of different monomers. Examples include BUNA-S and nylon 66.

    Classification of Polymers

    • Based on availability: Natural, semi-synthetic, synthetic
    • Based on monomers: Homopolymer (same monomer), copolymer (different monomers)
    • Based on chain structure: Linear, branched, cross-linked
    • Based on tacticity: Isotactic, atactic, syndiotactic
    • Based on effect of heating: Thermoplastic, thermosetting

    Thermoplastic and Thermosetting Polymers

    • Thermoplastics: Soften on heating and harden on cooling. They are easily reshaped and reused. Formed by addition polymerization. Examples: PE, PVC, PMMA
    • Thermosetting polymers: Harden on heating and cannot be softened again. They are formed by condensation polymerization. Examples: Urea formaldehyde, phenol formaldehyde, epoxy resins, polyester.

    Types of Polymerisations

    • Addition polymerization: Chain polymerization in which no small molecules are eliminated. Monomers yield a polymer that is an exact multiple of the original molecule.
    • Condensation polymerization: Step-growth polymerization where small molecules like water are eliminated. It involves polyfunctional monomers and forms network polymers.

    Effect of Heat on Polymers

    • Glass Transition Temperature (Tg): The temperature at which a glassy/brittle polymer transitions to a viscous liquid/rubbery state.
    • Melting Point (Tm): The temperature at which a crystalline polymer melts to a liquid state.

    Factors Affecting Tg and Tm

    • Crystallinity
    • Polymer chain mobility
    • Chain stiffness
    • Presence of bulky side groups, multiple bonds, aromatic rings, or polar side atoms.
    • Co-polymerization
    • Cross-linking
    • Plasticizers
    • Water/moisture content

    Conducting Polymers

    • Some polymers can exhibit conductivity similar to semiconductors or metals.
    • Conductivity depends on delocalized π electrons.
    • Intrinsic conducting polymers (ICPs) have extensive conjugation in their backbone which is responsible for electron conduction.
    • Doped conducting polymers (DCPs): Increase in conductivity by addition or removal of electrons to give negative or positive charge on backbone.

    Liquid Crystals

    • Liquid crystals are a state of matter with properties in between liquids and solids.
    • They exhibit anisotropy of properties (e.g. optical) without a crystalline lattice.
    • Types of liquid crystals depend on factors like phase transition (thermotropic, lyotropic) and arrangement of molecules (nematic, smectic, cholesteric).1

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    Description

    This quiz explores the fascinating world of polymers, covering their definitions, formation, and various classifications. Test your knowledge on topics such as monomers, polymerization, and examples of natural and synthetic polymers. Discover the intricacies of polymer functionality and structure in this comprehensive quiz.

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