Polymers

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Polymers

• Larry Scheffler

Version 1.0
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Definitions

• Polymer a long chain molecule made up of many
  small identical units.
• Monomer the smallest repeating unit of a polymer
  (propene in polypropylene).
• .

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IUPAC Definition

• A polymer is a substance composed of molecules
  characterized by the multiple repetition of one
  or more species of atoms or groups of atoms
  (constitutional repeating units) linked to each
  other in amounts sufficient to provide a set of
  properties that do not vary markedly with the
  addition of one or a few of the constitutional
  repeating units.

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Common Polymers

• Polymers are common in nature. Wood, rubber,
  cotton, silk, proteins, enzymes, and cellulose
  are all examples of polymers
• A wide variety of synthetic polymers have been
  produced, largely from petroleum based raw
  materials. These include polyurethane, teflon,
  polyethylene, polystyrene, and nylon.

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Common Polymers
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Polymer Recycling Codes

• Common household polymers

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Polymers

• The number code indicates the polymer type

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Polymers

• Types of synthetic and natural polymers.

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Addition Polymers

• Addition polymerization a reaction in which
  unsaturated monomers combine with each other to
  form a polymer
• Example Tetrafluoroethene can be polymerized to
  form polytetrafluoroethene, commonly known as
  Teflon

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Addition Polymers

• Some common addition polymers

• Many plastics are addition polymers made from
  hydrocarbon sources.
• The hydrocarbon must be unsaturated in order to
  polymerize

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Addition Polymers

• Polyvinyl chloride

• Polyvinyl chloride or PVC is wide used for pipes
  and other structural materials
• Vinyl chloride is also known as chloroethene

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Condensation Polymers

• Condensation polymers form from condensation
  reactions.
• In a condensation polymer a smaller molecule such
  as water is eliminated
• In order to form a condensation polymer the
  monomer must have two functional groups

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Example of a Condensation Polymer

• Nylon 6-6 is a condensation polymer

• It is also a copolymer since it is made from two
  different monomers

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Example of a Condensation Polymer 2

• Dacron is also a condensation polymer

Ethylene Glycol (1,2ethanediol) para
Terephthalic acid
Dacron is an example of a polyester

• It is also a copolymer since it is made from two
  different monomers

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Co-polymers

• Co polymers are made from than one monomer
• Many natural polymers are copolymers. For
  example, proteins are condensation polymers
  formed by joining as many as 20 different amino
  acids

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Polymer Structure

• Molecular Mass
• Polymers are high molecular mass structures
• Extremely large molecular weights are to be found
  in polymers with very long chains.
• Molecular Shape
• Polymer chain molecules are usually straight
  chains
• These chains may bend, coil and kink, leading to
  extensive intertwining and entanglement of
  neighboring chain molecules.
• These random coils and molecular entanglements
  are responsible for many of the important
  characteristics of polymers.

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The Polymer Structure Determines its
Characteristics

• The physical properties of a polymer, such as
  its strength and flexibility depend on
• Chain length - In general, the longer the chains
  the stronger the polymer
• Side groups - Polar side groups give stronger
  attraction between polymer chains, making the
  polymer stronger
• Branching - Straight, unbranched chains can pack
  together more closely than highly branched
  chains. These polymers are more crystalline and
  therefore stronger
• Cross-linking - If polymer chains are linked
  together extensively by covalent bonds, the
  polymer is harder and more difficult to melt.
•    

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Structure Linear Polymers

• Linear Polymers have monomer units that are
  joined together end to end in single flexible
  chain.
• Linear polymers have extensive van der Waals
  attractions between the chains.
• Examples polyethylene, polyvinyl chloride,
  polystyrene, and nylon

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Structure Branched Polymers

• Branched Polymers have side or branch chains are
  connected to the main ones.
• The branches, considered to be the part of the
  main-chain molecules, result from side reactions
  that occur during the synthesis of the polymer.
• The packing efficiency is reduced with the
  formation of side branches, which results in a
  lowering of the polymer density

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Structure Cross-Linked Polymers

• Adjacent linear chains are joined one to another
  at various positions by covalent bonds.
• The process of cross linking is achieved either
  during synthesis or by a nonreversible chemical
  reaction that is usually carried out at an
  elevated temperature.
• This cross linking is accomplished by additive
  atoms or molecules that are covalently bonded to
  the chains.
• Many of the rubber elastic materials are cross
  linked. In case of rubbers, it is called
  vulcanization

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Structure Network Polymers

• Network Polymers have trifunctional monomer
  units,
• Having three active covalent bonds allow these
  polymers to form three-dimensional networks
  instead of the linear chain framework
• Network polymers have distinctive mechanical and
  thermal properties.
• Examples include epoxies and other adhesives.

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Polymer Properties
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Polymer Microstructure

• Polyolefins with side chains have stereocenters
  on every other carbon

With so many stereocenters, the stereochemistry
can be complex. There are three main
stereochemical classifications for polymers.
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Microstructure and Properties

• Tacticity affects the physical properties
• Atactic polymers will generally be amorphous,
  soft, flexible materials
• Isotactic and syndiotactic polymers will be more
  crystalline, thus harder and less flexible.
• Polypropylene (PP) is a good example
• Atactic polypropylene is a low melting, gooey
  material
• Isoatactic polypropylene is is high melting
  (176º), crystalline, tough material that is
  industrially useful
• Syndiotactic polypropylene is has similar
  properties, but is very clear. It is harder to
  synthesize