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Polymers & Polymerization Reference cheat sheet - grade 11-12

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Chemistry Grade 11-12

Polymers & Polymerization Reference Cheat Sheet

A printable reference covering monomers, polymers, addition polymerization, condensation polymerization, degree of polymerization, and polymer properties for grades 11-12.

TopicsMaterials ScienceChemical ReactionsMoleculesChemistryStudy Guide
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Polymers are large molecules made of repeating units called monomers, and they are found in plastics, fibers, rubbers, proteins, and DNA. This cheat sheet helps students connect molecular structure to the materials they see in everyday life. It is useful for comparing polymerization reactions, recognizing repeating units, and predicting basic properties.

Grade 11-12 chemistry students need these ideas for organic chemistry, materials science, and reaction classification.

The main ideas are that monomers join to form long chains, and the structure of those chains controls strength, flexibility, melting behavior, and chemical resistance. Addition polymerization usually uses unsaturated monomers with C=CC=C bonds and produces no small molecule byproduct. Condensation polymerization joins monomers with functional groups and often releases a small molecule such as H2OH_2O or HClHCl.

Important formulas include degree of polymerization, number-average molar mass, and simple repeating-unit notation.

Key Facts

  • A polymer is a macromolecule made from many repeating units, often written as [−M−]n[-M-]_n, where MM is the repeating unit and nn is the number of repeats.
  • The degree of polymerization is DP=MpolymerMrepeat unitDP = \frac{M_{\text{polymer}}}{M_{\text{repeat unit}}} when the polymer chain mass and repeat-unit mass are known.
  • In addition polymerization, alkene monomers open their C=CC=C bonds to form a saturated polymer chain with no small molecule byproduct.
  • Polyethylene forms from ethene by n CH2=CH2→[−CH2−CH2−]nn\,CH_2=CH_2 \rightarrow [-CH_2-CH_2-]_n.
  • In condensation polymerization, two functional groups react repeatedly and usually release a small molecule such as H2OH_2O, HClHCl, or CH3OHCH_3OH.
  • A polyester linkage contains the ester group −COO−-COO-, and a polyamide linkage contains the amide group −CONH−-CONH-.
  • Number-average molar mass can be written as Mn=DPn×Mrepeat unitM_n = DP_n \times M_{\text{repeat unit}} for a polymer with one main repeat unit.
  • Cross-linking connects polymer chains together, which usually increases rigidity, thermal stability, and resistance to flow.

Vocabulary

Monomer
A small molecule that can chemically bond with other similar or different molecules to form a polymer.
Polymer
A very large molecule made of many repeating structural units joined by covalent bonds.
Repeating Unit
The smallest structural pattern that repeats along the backbone of a polymer chain.
Addition Polymerization
A polymerization reaction in which unsaturated monomers add together without forming a small molecule byproduct.
Condensation Polymerization
A polymerization reaction in which monomers with functional groups join while releasing a small molecule such as H2OH_2O.
Degree of Polymerization
The number of repeating units in a polymer chain, often calculated using DP=MpolymerMrepeat unitDP = \frac{M_{\text{polymer}}}{M_{\text{repeat unit}}}.

Common Mistakes to Avoid

  • Confusing monomers with repeating units, because the repeat unit in the polymer may not look exactly like the original monomer after bonds break or small molecules are removed.
  • Writing addition polymerization with a byproduct, because addition polymerization joins monomers directly and does not release H2OH_2O, HClHCl, or another small molecule.
  • Forgetting the brackets and subscript in polymer notation, because [−CH2−CH2−]n[-CH_2-CH_2-]_n shows that the unit repeats many times along the chain.
  • Using the monomer molar mass instead of the repeat-unit molar mass, because condensation polymerization often removes atoms when small molecules such as H2OH_2O are formed.
  • Assuming all polymers melt sharply like pure small molecules, because polymer samples contain chains of different lengths and often soften over a temperature range.

Practice Questions

  1. 1 Polyethylene has the repeating unit −CH2−CH2−-CH_2-CH_2- with molar mass 28.0 g mol−128.0\,\text{g mol}^{-1}. What is DPDP for a chain with molar mass 56,000 g mol−156{,}000\,\text{g mol}^{-1}?
  2. 2 A polymer has DP=850DP = 850 and a repeat-unit molar mass of 104 g mol−1104\,\text{g mol}^{-1}. Calculate MnM_n using Mn=DPn×Mrepeat unitM_n = DP_n \times M_{\text{repeat unit}}.
  3. 3 Classify the reaction n CH2=CHCl→[−CH2−CHCl−]nn\,CH_2=CHCl \rightarrow [-CH_2-CHCl-]_n as addition or condensation polymerization, and identify the repeating unit.
  4. 4 Explain why a highly cross-linked polymer is usually harder and less flexible than a mostly linear polymer.