Polymers: 1. Introduction 2. The variety of Polymeric Materials

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Polymers1. Introduction2. The variety of
Polymeric Materials

• Dept. Phys., Tunghai Univ.
• C. T. Shih

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Introduction

• Polymers a giant molecule, made up of many
  repeat units covalently joined together
• Common characteristics long, string-like
  molecules
• Living polymers long-chain objects whose
  subunits are joined by physical bonds, e.g.,
  actin filaments

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Variety of Polymeric Materials

• Polymer chemistry
• Stereochemistry
• Architecture
• Homopolymers and Copolymers
• Physical state

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Polymer chemistry

• Most polymers contains carbon atoms. Simplest
  polymer polyethylene (???)

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Polymer chemistry (conti.)

• The main chain can have different side groups
  polymethyl methacrylate(????????)

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Polymer chemistry (conti.)

• The main chain can incorporate non-carbon atoms,
  e.g., Nylon

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Polymer chemistry (conti.)

• The main chain can involve loops, e.g., amylose
  (??)

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Polymer chemistry (conti.)

• The polymer can be multiply connected, forming a
  ladder structure, e.g., poly(dioctyl fluorene)

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Polymer chemistry (conti.)

• The main chain can contain no carbon atoms at
  all, e.g., PDMS (silicone oil)

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Stereochemistry

• If a polymer has more than one type of chemical
  group attached to each main chain (carbon) atom,
  then different arrangement of the groups in 3D
  are possible isotactic, syndiotactic, and
  atactic.

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Quenched disorder ? Glasses
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Architecture

• Linear vs. Branched polymers
• Linear polymers can be characterized by N, the
  number of repeated units degree of
  polymerization
• N is proportional to the relative molecular mass
  M
• Degree of polymerization is not a constant for a
  group of polymers a distribution
• PDI polydispersity index
• (weight average)/(number average)

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PDIMw/Mn

• Number average
• Weight average
• Standard error

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Branched Polymer

• The polymers may be branched
• The branched points introduce quenched disorder,
  and hinder the formation of crystals
• A lot of branch points a network

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Copolymers

• The building units are all the same
  homopolymers
• Different building units copolymers
• Phase separation and microphase separation
• DNA and proteins are copolymers

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Physical States

• Liquid melts and solutions, usually very
  viscous/viscoelastic
• Glass is common because of the difficulty of
  crystallization
• Crystalline usually incomplete/small due to
  quenched disorder
• Liquid crystal