Polymer Types and Structures: Addition vs Condensation Polymers

Polymer

large macromolecule made when many smaller monomers are joined together by covalent bonds.

Monomer

Small molecule that joins with other monomers to form a polymer.

Polymerisation

Many monomers joining together

Addition polymerisation

Monomers containing C=C double bonds join when the double bonds open, forming a polymer with no atoms lost.

Condensation polymerisation

Monomers with reactive functional groups join together and eliminate a small molecule, usually water.

Addition vs condensation polymerisation

Addition polymerisation opens C=C bonds and produces only the polymer; condensation polymerisation joins functional groups and releases a small molecule.

Main addition polymers

Polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS) and polytetrafluoroethylene (PTFE).

Polyethylene (PE) type of polymer, made from, formula, repeating unit

addition polymer made from ethene, CH2=CH2, with repeating unit -CH2-CH2-.

LDPE structure

Lots of branching prevents the polyethylene chains from packing closely together.

LDPE properties (forces, density, flexibility)

Weaker dispersion forces between chains make LDPE lower density, softer and more flexible.

LDPE uses

Plastic bags

HDPE structure

Little branching allows polyethylene chains to pack closely together.

HDPE properties (forces, strength, rigidity, melting point vs LDPE)

Stronger dispersion forces between closely packed chains make HDPE denser, stronger, more rigid and higher melting than LDPE.

HDPE uses

Bottles and buckets

Polyvinyl chloride (PVC) [type of polymer and formulae]

Addition polymer made from chloroethene, CH2=CHCl, with repeating unit -CH2-CHCl-.

PVC structure and properties (forces, strength/rigidity and why)

Polar C-Cl bonds produce dipole-dipole attractions and bulky chlorine groups restrict chain movement, making PVC strong and rigid.

PVC uses (plasticisers do what to it)

Pipes and gutters; plasticisers make it flexible for hoses

Polystyrene (PS)

Addition polymer from styrene, C6H5CH=CH2, bulky benzene rings as side group.

Polystyrene properties (side groups, strength)

Bulky benzene side groups restrict movement of the polymer chains, making polystyrene hard, rigid and brittle.

Polystyrene uses (expanded polystyrene?)

Rigid containers; expanded polystyrene is lightweight and used for insulation

Polytetrafluoroethylene (PTFE) [type of polymer, formula and repeating unit]

An addition polymer made from tetrafluoroethene, CF2=CF2, with repeating unit -CF2-CF2-.

PTFE properties [bonding, resistant to what, friction and stick levels are what?]

Very strong C-F bonds make PTFE chemically resistant and heat resistant; it also has very low friction and is non-stick.

PTFE uses

Non-stick cookware coatings

Nylon (repeating links?)

A condensation polymer called a polyamide because its chains contain repeating amide links, -CO-NH-.

Nylon formation

A diamine reacts with a dicarboxylic acid, forming amide links and releasing water.

Nylon properties (strength)

Hydrogen bonding between amide groups on neighbouring chains gives nylon high tensile strength, toughness

Nylon uses

clothing

Polyester (type of polymer and repeating unit)

A condensation polymer containing repeating ester links, -COO-.

Polyester formation

A diol reacts with a dicarboxylic acid, forming ester links and releasing water.

Polyester properties (types of bonding, strength, durability,

Polar ester groups produce dipole-dipole attractions between chains, making polyesters strong, durable

Polyester uses

Textiles

Nylon vs polyester

Nylon contains amide links and forms hydrogen bonds between chains; polyester contains ester links and mainly has dipole-dipole attractions.