Introduction to Polymers
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Questions and Answers

What is a polymer?

A polymer is a molecular compound that can be distinguished by a high molar mass, ranging into thousands and even millions of mass and they are made up of many repeating units.

What are the two main types of polymers and provide an example for each?

The two main types of polymers are thermoplastic and thermosetting polymers. Thermoplastics can be melted and reshaped repeatedly, such as polyethylene. Thermosetting polymers harden permanently when heated, such as epoxy resin.

Natural polymers have been around since life itself began.

True

How are polymers created from monomers?

<p>Polymers are created from monomers through a process called polymerization, where monomers link together to form long chains.</p> Signup and view all the answers

What is the name given to a polymer that is made up of only one type of monomer? (Select all that apply)

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

What are the two main types of homopolymers?

<p>Two main types of homopolymers are polyethylene and poly(vinyl chloride) (PVC).</p> Signup and view all the answers

What is a common raw material used for the production of synthetic polymers?

<p>Crude oil is a common raw material for the production of synthetic polymers.</p> Signup and view all the answers

What is the name given to the gigantic molecules in polymers?

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

What is the backbone of a carbon-chain polymer?

<p>The backbone of a carbon-chain polymer is a string of carbon atoms.</p> Signup and view all the answers

What type of bond connects the atoms within a polymer molecule?

<p>Covalent interatomic bonds.</p> Signup and view all the answers

What is the chemical formula for ethylene?

<p>C2H4</p> Signup and view all the answers

What is the name of the process that transforms ethylene gas into polyethylene?

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

What type of material is polyethylene?

<p>Polyethylene is a solid polymeric material.</p> Signup and view all the answers

What is an active center in polymerization?

<p>An active center is formed by the reaction between an initiator or catalyst species and the monomer.</p> Signup and view all the answers

What is the chemical formula for tetrafluoroethylene?

<p>C2F4</p> Signup and view all the answers

What is the trade name for polytetrafluoroethylene?

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

What is the chemical formula for vinyl chloride?

<p>CH2CHCl</p> Signup and view all the answers

What is the meaning of the letter "R" in the general formula for polymers?

<p>The &quot;R&quot; represents either an atom like H or Cl or an organic group such as CH3, C2H5, and C6H5.</p> Signup and view all the answers

What four types of molecular structures are described in the text?

<p>The four types of molecular structures are linear, branched, cross-linked, and network.</p> Signup and view all the answers

What type of polymer structure is characterized by repeat units joined together end to end in single chains?

<p>Linear polymers</p> Signup and view all the answers

What type of polymer structure is characterized by side branches?

<p>Branched polymers</p> Signup and view all the answers

What type of polymer structure is characterized by adjacent linear chains joined together by covalent bonds?

<p>Crosslinked polymers</p> Signup and view all the answers

What type of polymer structure is characterized by multifunctional monomers forming three or more active covalent bonds, creating a three-dimensional network?

<p>Network polymers</p> Signup and view all the answers

What is the other name for partially crystalline polymers?

<p>Semicrystalline polymers</p> Signup and view all the answers

What is an amorphous region in a polymer?

<p>An amorphous region is the result of chain disorder or misalignment in the polymer.</p> Signup and view all the answers

What is the name of a unit cell for polyethylene?

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

The length of polymer chains has no effect on polymer properties.

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

Polymers with very short chains or a low molecular weight exist as liquids at room temperature.

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

Polymers with molecular weights of approximately 1000 g/mol exist as waxy solids or soft resins.

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

What is the range of molecular weights for polymers that are sometimes termed high polymers?

<p>10,000 to several million g/mol</p> Signup and view all the answers

What is the molecular weight of the repeat unit of PVC?

<p>62.50 g/mol</p> Signup and view all the answers

What is the degree of polymerization of PVC?

<p>338.4</p> Signup and view all the answers

What is the weight-average molecular weight of PVC?

<p>23200 g/mol</p> Signup and view all the answers

What is the name for a polymer that is composed of two or more different repeat units?

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

What are the four types of copolymer arrangements described in the text? (Select all that apply)

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

Synthetic rubbers are usually copolymers?

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

The atomic arrangement in polymers is simpler than in metals and ceramics.

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

What is polymer crystallinity?

<p>Polymer crystallinity is the packing of molecular chains to produce an ordered atomic array.</p> Signup and view all the answers

The degree of crystallinity in polymers can range from completely amorphous to almost entirely crystalline.

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

Which type of material typically exhibits a higher degree of crystallinity: metals or polymers?

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

The degree of polymer crystallinity can significantly affect its properties.

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

What are the two most common types of polymers that form with linear structures?

<p>Polyethylene and poly(vinyl chloride) or PVC</p> Signup and view all the answers

Study Notes

Polymers

  • Polymers are molecular compounds characterized by high molar masses (ranging into thousands and even millions).
  • They are composed of repeating units.
  • Synthetic polymers were developed in the early 20th century, significantly impacting various applications.
  • Natural polymers have existed since life's origin; examples include cellulose, starch, natural rubber, and DNA.
  • Monomers (mono meaning "one"; meros meaning "unit") are small molecules used to synthesize polymers.
  • A polymer's structure influences its behavior under heat.
  • Homopolymers are created from one type of monomer, while copolymers are made from two or more different monomers.
  • Examples of homopolymers include polyethylene and poly(vinyl chloride) (PVC). Teflon is an example of a homopolymer.
  • Polymers can be sourced from crude oil, a vital raw material in producing various carbon-based products.
  • Polymer molecules are large and referred to as macromolecules.
  • Within each molecule, atoms are bonded by covalent interatomic bonds in a polymer chain.
  • Carbon atoms frequently bond to two adjacent carbon atoms.
  • Ethylene (C2H4) is a gas that can be transformed into polyethylene (PE) under specific conditions.
  • Polymer chains are formed by the sequential addition of monomer units.
  • Additional properties are affected by the length of polymer chains. For very lengthy polymer chains with a large molecular weight (around 100,000 g/mol), the melting/softening point increases).
  • With smaller molecular weights (around 1000 g/mol) the polymers exist as a wax or soft resin.

Molecular Weight and Degree of Polymerization

  • Polymer chains vary in length, leading to a distribution of molecular weights.
  • Average molecular weight (Mn) is calculated from the measurement of physical characteristics like viscosity and osmotic pressure.
  • The number-average molecular weight (Mn) takes into account the number of chains within each size range.
  • The weight-average molecular weight (Mw) considers the weight/mass fraction of molecules in each size range.
  • The degree of polymerization (DP) represents the average number of repeat units in a polymer chain, related to the number-average molecular weight.

Thermoplastic and Thermosetting Polymers

  • Polymer behavior with heat defines thermoplastic and thermosetting polymers.
  • Thermoplastics soften when heated, liquefy, and harden when cooled. This process is reversible, repeating many times.
  • For thermoplastics, high temperatures can cause irreversible degradation.
  • Thermosetting polymers do not soften when heated. These are network polymer chains with covalent crosslinks. This structure makes them permanently hard after formation.
  • Excessively high heats during thermoset processing will cause the severing of bonds, degrading the polymer.

Copolymers

  • Copolymers are made from two or more different monomers.
  • Different arrangements (random, alternating, block, or graft) of repeat units can affect the copolymer's properties.

Polymer Crystallinity

  • Crystalline polymers have complex atomic arrangements unlike metals and ceramics, which involve molecules rather than atoms or ions.
  • Crystalline structures are based on unit cells (often complex).
  • Polyethylene's unit cell structure has an orthorhombic geometry.
  • Amorphous regions are common in polymers due to chain misalignments, hindering strict ordering.
  • Crystallinity can vary from completely amorphous to nearly 95% crystalline.

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Description

Dive into the fascinating world of polymers, molecular compounds with high molar masses. Explore the differences between synthetic and natural polymers, and learn about monomers and their role in polymer synthesis. This quiz will help you understand the structures, types, and applications of various polymers.

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