Polymers Flashcards
Polymers
Large molecule composed of repeating structural units.
Monomers
Building blocks of more complex molecules called polymers
Two types of Polymers
Natural and Synthetics
Two types of Synthetic Polymers
Homopolymers and Copolymers
Homopolymers
Single type of repeating units
Copolymers
Mixture of repeating units
7 types of Addition Polymers
polyethyle, polyvinyl chloride (PVC), polstyrene (PS), polytetrafluoroethylene (PTFE), polypropylene, polyacrylanitrate (acrylics), polyvinylacetate (PVA).
Polyethylene
C2H4 is the repeating unit
Two types of Polyethylene
Low Density (LDPE) and High Density (HDPE)
Low Density (LDPE) Polyethylene
- Branch like chains
- This Branching prevents the chains from packing closely together
- This results in the polymer that is softer and more flexible, but also a lower tensile strength and lower melting point
- Weaker dispersion forces
- Amorphous structure
- Flexible
High Density (HDPE) Polyethylene
- Chains are more linear (like a wave ocean type thing)
- Chain are packed together more results in stronger intermolecular forces between the polymere chains
- Has greater tensile strength and higher melting points that LDPE
LDPE Uses
- Plastic bags
- Packaging
- Films
HDPE Uses
- Plastic Utensils
- Bottles
- Toys
Halogenation
Substitute Cl for H in ethene to make Vinyl Chloride
Polyvincly Chloride
- The polymer of vinyl chloride
- Chlorine atoms are randomly orientated along the chain
- Shapeless (amorphous)
- Large size due to the way Chlorine sticks out of chain
- Hard and Rigid
- C-Cl is a polar bond due to Cl being highly electronegative
- Dipole-Dipole forces add to dispersion forces between chains to make longer intermolecular forces which holds chain more strongly together
- Plasticers can be inserted in between the chain to weaken intermolecular forces between them.
Uses of Polyvinyl Chloride
Construction; pipes, window frames however flexible Polyvinyl Chloride can be used for cling wrap and cable and wire.
Styrene
Substitute of Benzene for H in ethene
Polystyrene
- Polymer of Styrene
- Benzyl ring randomly orientated across the chain
- Mainly amorphous due to the way the ring sticks out and large size
- Symmetry means no polar bonds
- Only weak dispersion are acting to hold the chain together
- Large ring prevents polymer chain packing closely together
- Large ring prevents ability of chain to flop around so it tends to be hard and brittle
- Readily softened, moulded on heating but becomes rigid when cooled
Polypropylene
- Polymer of propene
- Manufacturing this polymer requires catalysts like Zieger-Natta
- There are three variations of the structure of polypropylene and each one has different properties
- The variations differ in the placement of the -CH3 alkyl group
Atactic
- Variant of polypropylene
- Side group are randomly placed
- In the random atactic arrangement, the chains cannot lie close together so the forces of attraction are weaker
- This results in softer polymer with lower melting point
- The atactic version formed during the manufacture of the isotactic polymer is considered a waste product and is a soft rubbery polymer, which has limited use mainly as roofing materials and sealants.
