15.1 polymers

define polymers

covalent molecular substances composed of many small units (monomers) joined together

define polymerisation

the joining of monomers to create a large chain

what are some properties of synthesised polymers

can be hard, strong, malleable & ductile, insulators of electricity and heat

what are factors that affect the strength of intermolecular forces between polymer chains

-length of the polymer chain

-branching of polymer chain

-cross-linking between polymer chains

how does the length of polymer chain affect the strength of IMF

longer chain = strength of dispersion forces with neighbouring molecules increases resulting in harder and rigid material

how does branching of polymer chain affect the strength of IMF

formed when monomers react with sites on the side of the polymer chain instead of at the end.

causes molecules to be spread further apart, resulting in a less dens material

intermolecular attraction= weakened, increasing flexibility

explain what thermoplastic polymers are

straight chain and branched chain polymers.

are soften when heated, meaning they can be remoulde

how does cross linking affect the strength of IMF

polymer branches covalently bonded to the next polymer network

-cant be liquid because the polymer chains are held in place by cross links

-cross linking polymers= thermosetting polymers

define elastomers

formed when occasional cross links are present

chains move past each other when stretched but cross-links return to their og position once force is released

cross-links stop elastomers from completely melting