BME 6210 E2 TEST WITH
COMPLETE SOLUTION
Three types of polymers - ANSWER - Linear
- Branched
- Cross-Linked
Linear Polymers - ANSWER Long strand of single molecule
Typically proteins
VDW or H bonding
Thermoplastics
Branched Polymers - ANSWER Randomized combination of molecules
therefore there are different side chain lengths
Cannot be 'packed' as densly
Typically thermoplastics but can be thermoset
Cross-Linked Polymers - ANSWER 3D network of molecules where sidechains
link backbones
Covalently bonded therefore thermosets
Thermoplastics - ANSWER Material will flow with increased heat and
pressure allowing for reshaping
Linear and branched polymers
,Thermosets - ANSWER Dont flow with heating therefore cannot be recast
Melt or degrade with increased heat
Styrofoam
Addition Polymerization - ANSWER Growing a polymer from a single initiator
site
3 Steps:
Initiation
Propagation
Termination
Add. Poly. Initiation - ANSWER - Mix of initiator molecules and molecule
- Initiator is stable until enthalpy change to form free radical initiators that
react with monomers
- Initiators love double bonds
Add. Poly. Propagation - ANSWER Free radical transfers to monomer so
monomer can react with other monomers and increase chain length
Add. Poly. Termnation - ANSWER - Coupling
- Disproportionation
Coupling - ANSWER 2 growing chains with free radicals react to form
covalent bond
MW doubles
Disproportionation - ANSWER Chain steals free radical hydrogen from
, another chain
Donating chain can no longer propagate (not even if another free radical
comes)
MW doesn't change
Initiators - ANSWER Begin polymerization
Since there are more monomers than initiators, chance of initiator ending a
chain in unlikely
Additive Polymerization - ANSWER Free radical
Cationic
Anionic
RAFT
Ring opening
RAFT Polymerization - ANSWER Reversible Addition Fragmentation-chain
Transfer
Used to control length of polymer but not well understood
Ring Opening - ANSWER High strain cyclic polymer pops open into a reactive
species that makes other polymer rings pop open to form linear chain
Copolymers - ANSWER Different monomers
Random
Alternating
Block
COMPLETE SOLUTION
Three types of polymers - ANSWER - Linear
- Branched
- Cross-Linked
Linear Polymers - ANSWER Long strand of single molecule
Typically proteins
VDW or H bonding
Thermoplastics
Branched Polymers - ANSWER Randomized combination of molecules
therefore there are different side chain lengths
Cannot be 'packed' as densly
Typically thermoplastics but can be thermoset
Cross-Linked Polymers - ANSWER 3D network of molecules where sidechains
link backbones
Covalently bonded therefore thermosets
Thermoplastics - ANSWER Material will flow with increased heat and
pressure allowing for reshaping
Linear and branched polymers
,Thermosets - ANSWER Dont flow with heating therefore cannot be recast
Melt or degrade with increased heat
Styrofoam
Addition Polymerization - ANSWER Growing a polymer from a single initiator
site
3 Steps:
Initiation
Propagation
Termination
Add. Poly. Initiation - ANSWER - Mix of initiator molecules and molecule
- Initiator is stable until enthalpy change to form free radical initiators that
react with monomers
- Initiators love double bonds
Add. Poly. Propagation - ANSWER Free radical transfers to monomer so
monomer can react with other monomers and increase chain length
Add. Poly. Termnation - ANSWER - Coupling
- Disproportionation
Coupling - ANSWER 2 growing chains with free radicals react to form
covalent bond
MW doubles
Disproportionation - ANSWER Chain steals free radical hydrogen from
, another chain
Donating chain can no longer propagate (not even if another free radical
comes)
MW doesn't change
Initiators - ANSWER Begin polymerization
Since there are more monomers than initiators, chance of initiator ending a
chain in unlikely
Additive Polymerization - ANSWER Free radical
Cationic
Anionic
RAFT
Ring opening
RAFT Polymerization - ANSWER Reversible Addition Fragmentation-chain
Transfer
Used to control length of polymer but not well understood
Ring Opening - ANSWER High strain cyclic polymer pops open into a reactive
species that makes other polymer rings pop open to form linear chain
Copolymers - ANSWER Different monomers
Random
Alternating
Block
