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NSWChemistryQuick questions
Module 7: Organic Chemistry
Quick questions on Addition and condensation polymers explained: HSC Chemistry Module 7
11short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is addition polymers?Show answer
The $\pi$ bond of an alkene opens; the carbons join in a long chain. The general scheme:
What is condensation polymers?Show answer
Two monomers, each with two reactive groups, react head-to-tail-to-head-to-tail. A small molecule (water) is expelled at each linkage.
What is structure-property relationships?Show answer
Chain length. Longer chains give greater dispersion forces overall, higher melting point and stronger material. Industrial polymers are typically 1000 to 10,000 monomer units long.
What is chain length?Show answer
Longer chains give greater dispersion forces overall, higher melting point and stronger material. Industrial polymers are typically 1000 to 10,000 monomer units long.
What is branching?Show answer
Linear chains pack closely (HDPE, drawn nylon fibre); branched chains pack loosely (LDPE). Closer packing means more dispersion force contact and higher density.
What is functional groups in the chain?Show answer
Hydrogen-bond-capable groups (amide, hydroxyl) raise melting point and tensile strength considerably. Halogen substituents add dipole-dipole forces. Aromatic rings add rigidity.
What is crystallinity?Show answer
Regular, regularly-spaced chains can crystallise (form ordered regions); irregular chains stay amorphous. Crystalline regions are stronger and more dense. HDPE is about 90% crystalline; LDPE only about 50%.
What is crosslinking?Show answer
Covalent bonds between adjacent chains turn a thermoplastic into a thermoset (vulcanised rubber, epoxy). Not usually examined at HSC but worth a mention.
What is writing water as a byproduct of addition polymerisation?Show answer
Addition has no byproduct. Only condensation produces water (or sometimes HCl, etc.).
What is naming the monomer of polyethylene as "ethylene"?Show answer
Ethylene is the older name; HSC prefers ethene. Same molecule.
What is confusing PVC with polystyrene?Show answer
PVC has C-Cl side groups, polystyrene has C-phenyl side groups.