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Polymer
Macromolecule generated through sequential reaction of elementary units
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Monomer
Molecule with minimum functionality of 2 that reacts to form the structural units of a polymer
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Oligomer
Short chains synthesized from reaction of several monomers
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Repeat Units
Structure of minimal size to generate polymer
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Degree of Polymerization (DP)
- Number of repeat units
- DPn=Xn=Mn/Mo
- Mn=number average MW
- Mo=MW of repeat Unit
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Natural Polymers
- Of biological origin
- (Proteins, polysaccharides, etc.)
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Polysaccharides
Very limited processability, as melting temperature and poor solubility
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Homopolymer
- Polymer with 1 repeat unit
- AAAAAAAA
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Copolymer
Polymer with more than 1 repeat unit
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Random Copolymer
- AAABABAAABBBBAA...
- poly(A-ran-B)
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Block Copolymers
- AAAABBBB
- AB blockcopolymer
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Thermoset
Initial mixture of reactive low molecular mass compounds react upon heating mold to from insoluble network
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Thermoplastic
Becomes fluid upon heating
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Isotactic
All chiral centers are the same
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Syndiotactic
Chiral centers alternate
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Atactic
Chiral centers are random
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Chain Entanglement
Allows long chains to act as they were longer. Causes multiple chains to act together
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Glass Transition Temperature (Tg)
Flexibility of amorphous polymers is reduced when they are cooled below a temperature
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Melting Temperature (Tg)
Temperature range where total or whole polymer chain mobility occurs
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Polydispersity Index (PDI)
- PDI=Mw/Mn
- Mw≥Mn
- Measures the distribution on molecular mass in a sample closer to 1, more uniform the polymers
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Step-Growth Polymerization
Many monomers react at once
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Chain-Growth
Growth occurs one unit at a time
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Trommsdorff Effect
Viscosity of the solution increases the rate of termination decreases, large rate of polymerization leads to an explosion
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Ideal Copolymerization Rates
r1=r2=1
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Alternating Copolymerization Rates
r1•r2=0
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Block Copolymerization Rates
r1>1, r2>1
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Can you melt a thermoplastic?
No
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Does every polymer have a Tg?
Yes
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A soft polymer has a ____ Tg
Low
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If you increase the number of small chains in your polymer sample, Mn will:
Decrease
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What is cotton composed of?
Cellulose
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Which polymerization technique is the fastest to provide high MW polymers?
Chain Growth
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Unreacted Monomers are an issue for which polymerization method?
Chain Growth
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For chain growth polymerization: higher temperature leads to ____ DPn
Lower
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The molecular weight of the polymer produced is too high so what can you change?
- Increase initiator
- Increase Temperature
- Increase the chain transfer agent concentration
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What is the ceiling temperature (Tc)?
It is the temperature when the rate of polymerization equals the rate of depolymerization
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Rank the Tg, Tm and Tc
Tg<Tm<Tc
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Give the name of one technique to measure the MW distribution of a polymer?
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Which technique gives the larger number end-group analysis or viscosity?
Viscosity (Mv)
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Why is the Trommsdorff effect is only problematic once the monomer conversion is high?
At high conversion the solution becomes viscous where the reaction releases more heat and causes autoacceleration
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What can you do in a batch process to ensure that you reach 100% conversion?
Increase concentration of initiator
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What process change would you do to reach 100% conversion at a lower cost for a batch reactor?
Feed initiator continuously
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What are the parameters used to slow down the rate of polymerization?
- Decrease Temperature
- Decrease Initiator
- Decrease Monomer
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Why is losing the temperature control of a radical polymerization be bad?
The reaction is exothermic so losing control of the temperature can increase the reaction and lead to a runaway reaction and the Trommsdorff effect
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Why aren't polymers produced with the highest MW possible?
The longer the polymer the more viscous it is making it difficult to process
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What is the difference between suspension polymerization and emulsion polymerization?
- Suspension: Mechanical mixing required
- Emulsion: Chemically stabilized particle
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In copolymerization studies, the monomer reactivity ratio provides information on?
The instantaneous composition of the copolymer knowing the monomer composition
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When the degree of crosslinking goes up the MW of the polymer
Increases
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The crosslinking density of an elastomer is ____ than the one of a thermoset
Lower
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A 10w% solution of polystyrene in toluene is ___ viscous than a 30% polylstyrene
More
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Which one of these PP is industrially relevant?
Attactic
Isotactic
Syndiotactic
Isotactic
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Rank the polydispersities of the following polymers. (Polyethylene, Nylon 6,6, Polybutadiene)
- Largest: Polyethylene
- Middle: Nylon 6,6
- Smallest: Polybutadiene
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What does the polymer ABS stand for?
- A: Acrylonitrile (CH2CHCN)
- B: Butadiene
- S: Styrene
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Emulsion Polymerization Phase I (Micelles, Monomer droplets, Particle number, Particle Size)
- Micelles: Present
- Monomer Droplets: Present
- Particle Number: Increase
- Particle Size: Increase
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Emulsion Polymerization Phase II (Micelles, Monomer droplets, Particle number, Particle Size)
- Micelles: Absent
- Monomer Droplets: Present
- Particle Number: Constant
- Particle Size: Increase
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Emulsion Polymerization Phase III (Micelles, Monomer droplets, Particle number, Particle Size)
- Micelles: Absent
- Monomer Droplets: Absent
- Particle Number: Constant
- Particle Size: Constant
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What does HDPE, UHMWPE and LLDPE stand for?
- HDPE: High density polyethylene
- UHMWPE: Ultra high molecular weight polyethylene
- LLDPE Linear Low density polyethylene
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Which one has the lowest crystallinity? (HDPE, UHMWPE, LLDPE)
LLDPE
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How is the degree crystallinity of LLDPE controlled?
Control the amount of olefins and the lengths of them
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Why is it impossible to make copolymer of propylene and acrylic acid via insertion polymerization?
Acrylic acid has oxygen which kills the propylene catalyst
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Why is preparing high molecular weight polymers difficult with cationic polymerization?
They are unstable and terminates easily
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How can you synthesize a polymer with amine groups at both ends of the chain?
Use an excess of diamines
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Carother could not prepare high molecular polyester because he couldn't control the stoich between the monomers. What solution did he find?
He precipitated the monomers as a salt with a 1:1 stoic ratio
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Polymer: LLDPE
Initiator:
Reaction Type:
- Initiator: Z-N
- Reaction Type: Insertion
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Polymer: LDPE
Initiator:
Reaction Type:
- Initiator: ROOR
- Reaction Type: Radical
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Polymer: 1,2 Polybutadiene
Initiator:
Reaction Type:
- Initiator: nBuLi anionic
- Reaction Type: Anionic
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Polymer: PS
Initiator:
Reaction Type:
- Initiator: ROOR
- Reaction Type: Radical
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Polymer: PEG 4000
Initiator:
Reaction Type:
- Initiator: NaOH
- Reaction Type: Anionic
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Polymer: PVC
Initiator:
Reaction Type:
- Initiator: ROOR
- Reaction Type: Radical
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Polymer: HDPE
Initiator:
Reaction Type:
- Initiator: Z-N
- Reaction Type: Insertion
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Polymer: Syndiotactic PP
Initiator:
Reaction Type:
- Initiator: Z-N
- Reaction Type: Insertion
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Polymer: 1,4 cis butadiene
Initiator:
Reaction Type:
- Initiator: nBu-Li
- Reaction Type: Anionic
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Average degree of polymerization equation (non stoichiometric)
- Xn=(1+r)/(1+r-2rp)
- [Ao]/[Bo]=r
- A<B
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Average degree of polymerization (Stoichiometric)
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Extent of Reaction equation (p)
(No-N)/No
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DP vs. Temp for step growth
- Higher Temp, Higher DP
- Linear Lines
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DP vs. Temp for Chain growth
- Higher Temp, Lower DP
- Straight Lines
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