Polymers: Lecture 1 - Unit 3a

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Questions and Answers

What is the significance of having two functional groups in a monomer?

  • It allows the formation of a branched chain polymer.
  • It results in the formation of cyclic polymer structures.
  • It leads to the creation of a three-dimensional network polymer.
  • It enables the monomer to form linear or straight chain polymer molecules. (correct)

Which of the following monomers is classified as bifunctional?

  • Melamine
  • Amino acid (correct)
  • Polystyrene
  • Hexamethylene diamine (correct)

When a trifunctional monomer is combined with a bifunctional monomer, what type of polymer is formed?

  • Linear polymer
  • Branched chain polymer (correct)
  • Cyclic polymer
  • Three-dimensional network polymer

Which of the following statements about the functionality of monomers is true?

<p>Two functional groups in a monomer contribute to bifunctionality. (C)</p> Signup and view all the answers

What would you expect if only bifunctional monomers are used in polymerization?

<p>Production of linear or straight chain polymers (D)</p> Signup and view all the answers

What is a polymer primarily composed of?

<p>Small molecules called monomers (B)</p> Signup and view all the answers

What does the degree of polymerization (DP) indicate?

<p>The number of repeat units in a polymer (C)</p> Signup and view all the answers

Which statement correctly describes the relationship between chain length and mobility of molecules in polymers?

<p>Longer chains result in restricted movement of molecules. (C)</p> Signup and view all the answers

What minimum requirement must a molecule meet to behave as a monomer?

<p>Possess at least two functional groups (C)</p> Signup and view all the answers

What is the primary feature of vinyl monomers?

<p>They are bifunctional due to the presence of a double bond. (A)</p> Signup and view all the answers

What happens to the properties of paraffin as its molecular chain length increases?

<p>It develops solid-like properties due to molecular entanglement. (C)</p> Signup and view all the answers

Which of the following substances is least likely to act as a monomer?

<p>Acetic acid (C)</p> Signup and view all the answers

What is the effect of increasing the degree of polymerization in polyethylene?

<p>It turns into a strong, brittle solid. (A)</p> Signup and view all the answers

Flashcards

Bifunctional Monomer

A molecule with two functional groups capable of forming bonds, leading to the creation of linear or straight chain polymers.

Functionality

The number of functional groups present in a molecule that can react with another molecule to form a polymer chain.

Linear Polymer

A polymer with a long chain of repeating units connected in a straight line.

Network Polymer

A polymer with a three-dimensional structure formed by cross-linking of multiple chains.

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Branched Polymer

A polymer with branches extending from the main chain.

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Polymer

A large molecule formed by linking together thousands of smaller molecules called monomers.

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Monomer

The small molecules that combine to form polymers.

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Polymerization

The process of joining monomers together to create a polymer.

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Degree of Polymerization (DP)

The number of repeating monomer units in a polymer chain.

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Monomer Requirement

A monomer must have at least two reactive sites to participate in polymerization.

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Monofunctional Molecules

A molecule with only one reactive site cannot form a polymer.

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Bifunctional Molecules

A molecule with two reactive sites, like vinyl monomers, can participate in polymerization.

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Study Notes

Polymers: Lecture 1 - Unit 3a

  • Polymer Definition: A polymer is a long molecule formed by joining thousands of small molecules (monomers) chemically. Its large size makes it a macromolecule.

  • Polymerization: The chemical process that creates polymers from monomers.

  • Monomers: Small molecules that combine to form larger polymer molecules.

  • Example: n(CH2=CH2) → (CH2-CH2)n (ethene → polyethylene)

  • Degree of Polymerization (DP): The number of repeat units (monomers) in a polymer chain. Different polymers have varying DP values. For example, cellulose has a DP of 250, and vinyl polymers have a DP of 400.

  • Polymer Properties: The long-chain structure of polymers gives them unique properties.

  • Ethane (CH3-CH3): A gas at room temperature; its small size allows it to move freely.

  • Butane (CH3-CH2-CH2-CH3): A liquid, with a longer chain length than ethane, butane molecules have lower mobility and interact more frequently.

  • Paraffin (CH3(CH2CH2)10CH3): A waxy substance; the entanglement of long polymer molecules significantly affects its physical properties.

  • Polyethylene (CH3(CH2CH2)2000CH3): A strong, brittle solid; the extremely long chains become entangled.

  • Functionality: The number of reactive sites on a monomer molecule used for bonding. A monomer must have at least two functional groups to form a polymer.

    • Example Functional Groups: Double bonds, triple bonds, −NH2, −OH, −COOH, −SH.
  • Vinyl Monomer (CH2=CHX): A bifunctional monomer; the double bond is a reactive site, breaking to form two single bonds and two reactive sites.

  • Side Groups/Functional Groups: The side groups attached to the basic polymer chain affect the polymer's properties.

Monomer Functionality and Polymer Types

  • Bifunctional Monomers: Lead to linear polymers (e.g., ethylene glycol, vinyl monomers, adipic acid).

  • Trifunctional Monomers: Form three-dimensional network polymers (e.g., phenol, melamine).

  • Mixed Functionality: Combining bifunctional and trifunctional monomers creates branched polymers.

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