Polymer Structure and Properties

Overview

This lecture introduces polymers, focusing on their structure, how to represent them, and why they are solid at room temperature.

Polymers are large molecules made by joining many small units called monomers.
Polypropylene is a common polymer formed from propene (C3H6) monomers.
Polymer chains can be thousands of atoms long by continual addition of monomers.

A polymer can be identified by finding a repeating section (the monomer unit) in its structure.
To represent a polymer, draw the repeating unit inside curved brackets with an 'n' in the corner to show repetition.
For reactions, use the repeating unit and state the number of monomers (e.g., n or 400) instead of drawing the full polymer chain.
Show bonds extending through the curved brackets in the repeating unit.

Covalent bonds within polymer chains are very strong but are not broken during melting or boiling.
To change state, only the weaker intermolecular forces between separate polymer molecules are overcome.
Polymers have higher melting and boiling points than simple molecular substances but lower than giant covalent or ionic substances.
High surface area of long polymer chains increases total intermolecular forces, making most polymers solid at room temperature.

Polymer — A large molecule made of repeating monomer units.
Monomer — A small molecule that can join with others to form a polymer.
Intermolecular Forces — Weak attractions between molecules, weaker than covalent or ionic bonds.
Repeating Unit — The specific arrangement of atoms that repeats in a polymer chain.
Addition Polymer — A polymer formed by joining monomers without losing atoms (to be covered separately).
Condensation Polymer — A polymer formed by joining monomers with loss of small molecules like water (to be covered separately).