Chapter 9 - Polymers Flashcards
what are polymers
large molecules made by joining smaller molecules, called monomers together.
what are monomers
small molecules that either go through addition or condensation polymerisation to be strung together into very long chains called polymers
what are thermoplastic polymers
also known as themosoftening polymers
polymers that can be repeatedly melted and reshaped due to the absence of cross links.
what are thermosetting polymers
polymers that do not melt but char at high temperatures. the cross links present do not allow the chains to become loose therefore not letting the substance be re moulded.
define addition polymerisation
an addition reaction where many monomers separate a multiple bond between carbons to join to many of the same monomers. monomers must have a double bond and there is never a bi product.
what affects the properties of polymers
extent of branching arrangement of side branches cross linking degree of crystallinity length of chains addition of plasticisers
what is the vulcanisation of rubber
where isoprene (natural rubber) is bonded with sulfur. sulfur forms cross links between chains of isoprene giving the substance elastic properties.
condensed formula of isoprene
CH2C(CH3)C(H)CH2
steps to forming polymers from monomers
- make the monomer look like an ethene molecule.
- add lines to show bonds on each end of the monomer
- if you need to add monomers together, you may want clean it up by rearranging where side branches are etc.
describe the affect of extent of branching on a polymer
more branching = softer/ less dense material
as the branches keep the chains from getting close to each other, the dispersion forces are weak and therefore create a softer substance.
describe the affect of arrangement of side branches on a polymer
isotactic polymers are where the few side branches are all on one side of the polymer chain. this allows chains to get closer to each other and make a denser harder substance
atactic polymers have side branches occurring on both sides of the chain irregularly. this limits how close the chains can be and therefore creates a softer material.
describe the affect of cross-linking on a polymer
a polymer
describe the affect of degree of crystallinity on a polymer
crystalline polymers are molecules arranged in regularly arranged lines
amorphous polymers have no particular order or arrangement
more crystalline regions = more opaque as crystalline reflects light
describe the affect of chain length on a polymer
larger chain length = higher points, strength
describe the affect of addition plasticisers on a polymer
small molecules called plasticisers push the polymer chains further apart. ultimately, they create a softer, flexible polymer.
