What is Polymer Chemistry?
Polymers are giant molecules made of repeating monomer units linked together. From plastic bags to DNA, polymers are everywhere. Understanding how they form and behave is polymer chemistry.
A polymer is a chain of identical or near-identical monomers bonded together. Two main pathways: addition polymerization (monomer + monomer, no byproduct) and condensation polymerization (release of water or other small molecule).
- 1↓MonomersSmall molecules with double/triple bonds or functional groups ready to react. Example: ethene (C₂H₄).
- 2↓InitiationA catalyst or heat/light provides energy to 'open' the first monomer's double bond.
- 3↓PropagationMore monomers continuously add to the growing chain. Repeat hundreds to millions of times.
- 4↓TerminationChain growth stops when reacting radicals or other monomers run out.
- 5Polymer productA long macromolecule with thousands of monomer units. Example: polyethene (−CH₂−CH₂−)ₙ.
Step-by-step worked examples
Ethene (C₂H₄) undergoes addition polymerization. Write the monomer and resulting polymer.
Monomer: CH₂=CH₂ (ethene) During addition polymerization, the C=C double bond opens: Polymer: −(CH₂−CH₂)−ₙ (polyethene) No byproduct—only monomer units joined.
Phenol (C₆H₅OH) and formaldehyde (CH₂O) react to form Bakelite. Is this addition or condensation?
Two functional groups (phenolic −OH and formaldehyde) bond together. A small molecule (water, H₂O) is released as a byproduct. This is CONDENSATION polymerization (releases H₂O).
Nylon is made from hexamethylene diamine and adipic acid. Does this release any byproduct?
Hexamethylene diamine (H₂N−(CH₂)₆−NH₂) + adipic acid (HOOC−(CH₂)₄−COOH) The amino and carboxyl groups form amide bonds (−CO−NH−) and release H₂O. Nylon is a CONDENSATION polymer (releases water).
Flashcards
Quick quiz
Q1.Which of these undergoes addition polymerization?
Q2.In condensation polymerization, what usually happens?
Q3.Polyethene is made from ethene. How many atoms are lost per monomer?
Q4.What does a catalyst do in polymerization?
The full card deck, worked steps and AI-tutor support for “What is Polymer Chemistry?” are in Notek — study by hand before your exam.
Common mistakes
Condensation polymers have water chemically bonded inside. — Correct: Water is released as a byproduct and leaves the reaction—it is NOT part of the final polymer.
All plastics are addition polymers. — Correct: Plastics can be addition (polyethene, PVC) OR condensation (polyester, polyurethane).
A polymer stops growing only when the heat runs out. — Correct: Polymerization terminates when radicals or monomers run out, or when temperature/catalyst is removed.
Bigger polymers are always stronger. — Correct: Polymer strength depends on chain length (MW), cross-linking, and crystal structure—not just size alone.
FAQ
Why is polyethene slippery but nylon is stronger?
Polyethene (addition) has linear chains with weak van der Waals forces. Nylon (condensation) has amide bonds—stronger, polar, and can hydrogen-bond.
Can you recycle all polymers?
Thermoplastics (polyethene, PVC) can melt and reflow → recyclable. Thermosets (Bakelite) cross-link permanently → harder to recycle.
What is 'molecular weight' in polymers?
The average mass of a polymer chain. Higher MW usually means higher strength and melting point. (MW = n × monomer mass)
What is polymerization degree (DP)?
The average number of monomer units in one polymer chain. DP = 1000 means ~1000 monomers per chain.