Materials scienceLesson 1 of 1 in the course Polymers

Polymerization Mechanisms, Heat Control, and Photopolymerization

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Polymerization is the chemical process that joins small molecules called monomers into larger molecules called polymers. This lesson introduces the basic vocabulary of polymerization and compares its two main mechanisms: step-growth and chain-growth polymerization.

A monomer is a small molecule that can react with other molecules to form a larger structure. During polymerization, monomers join to create long chains or three-dimensional networks called polymers. The reaction mechanism depends on the monomers' functional groups and on factors such as the spatial crowding, or steric effects, around reactive sites.

All flashcards

What is polymerization?
A chemical process in which monomer molecules react together to form polymer chains or three-dimensional networks.
How do homopolymers and copolymers differ?
A homopolymer is built from repeated units of one monomer type. A copolymer contains units derived from more than one monomer type.
What happens during step-growth polymerization?
Pairs of molecules with reactive functional groups combine, and the partners can be of any size. Long chains generally form late, so high molecular weight requires very high conversion.
What are the three broad stages of chain-growth polymerization?
Initiation creates an active center, propagation adds monomers to the growing chain, and termination ends growth at the active center.
Why is step-growth polymerization not always condensation polymerization?
Condensation polymerization releases a small molecule during chain formation, but some step-growth reactions do not. Polyurethane formation, for example, is step-growth addition polymerization and does not release water.

Quiz questions

  1. What is a monomer?Answer: A small molecule that can react with other molecules to form a larger structure.
  2. What distinguishes a copolymer from a homopolymer?Answer: A copolymer contains units derived from more than one monomer type.
  3. In photopolymerization, what does a photosensitizer do?Answer: It absorbs light and transfers energy to the monomer.
  4. How can photopolymerization produce a raised image?Answer: Polymer forms in illuminated regions, and unexposed monomer can then be removed.
  5. Why can a polymerization method that uses a solvent or dispersed reaction system require additional processing?Answer: The polymer may need to be separated and isolated from the reaction system.

Based on the Wikipedia article Polymerization, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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