1
Q
Ozonolysis
A
Cleaves double bonds.
2
Q
Addition Polymer table
A
3
Q
Poly(vinyl alcohol) - PVA
A
Produced by polymerization of vinyl acetate (small double-bonded carbon monomer with acetate group) to form polyvinyl acetate, followed by hydrolysis to clip the acetate groups.
4
Q
Polymethyl Methacrylate (PMMA)
A
- Hard, transparent polymer
- Methyl methacrylate is a methacrylate ester in which the group attached (R in the figure below) can be any alkyl group or even aryl group
- PMMA is vinyl polymer, made by free radical vinyl polymerization from the monomer methyl methacrylate.
- Mostly atactic, not crystalline and behave like glassy materials
- If isotactic, chain twists to relieve the “steric strain,” the relatively big carboxy methyl groups bang into each other so the chain twists in a way to stop that - forms a helical conformation.
5
Q
Teflon (polytetrafluoroethylene)
A
- Useful for medical - biocompatible
- Vinyl - similar to polyethylene in structure
- free radical vinyl polymerization
- Fluorine doesn’t like to interact with others, especially something other than F
- repel everything, non-stick
- less protein adhesion?
- High Tm
- Inert
- Really strong bonds to backbone
- Not even O2 reacts
- Really strong bonds to backbone
6
Q
Poly(vinylidene chloride)
A
- Saran plastic wrap that food comes in at the grocery store.
- Monomer is vinyl chloride with and extra Cl on the alpha carbon.
7
Q
PMMA with copolymer of PV-alcohol and PV-acetate
A
PMMA, is a hard, tough, and shiny plastic, but hydrophobic. It doesn’t dissolve in water, and a lot of paints are water based.
In hydrolysis of polyvinyl acetate to polyvinyl alcohol, leave 20% of acetate groups to form random copolymer (in image).
Hydrophobic acetate groups in center, while hydrophilic alcohol forms ring outside.
PMMA hides in the hydrophobic center of the coiled polymer. By doing this, it can stay suspended in water based paints. Latex.
8
Q
Mn, Mw and PDI
A
9
Q
Acrylates
A
Vinyl polymers from acrylate monomers (usually esters which contain vinyl groups, that is, two carbon atoms double-bonded to each other, directly attached to the carbonyl carbon of the ester group).
Because of the very polar nature of the carbonyl, pulling electron density away from the normally electron-rich vinyl group, the alpha carbon is more electron poor than the beta carbon. This has a huge effect on the reactivity of the monomer.
Anionic polymerization becomes possible for acrylates (and methacrylates as well), and this gives polymers with very different backbone tacticities and very different physical properties such as being more crystalline.
10
Q
Poly(acrylic acid)
A polyelectrolyte.
A
- Each repeat unit has an ionizable group. In this case, it’s a carboxylic acid group.
- Superabsorber: they absorb many times their own weight in water with no problem, even hundreds of times more.
- In baby diapers!
- Scientists not sure exactly how they work
11
Q
Polyacetate vs Polyacrylate
A
Acrylate:
-(COO-R)
Acetate:
-(OCO-R)
12
Q
Polyacrylates with nitrogen
(Polyacrylamide and polyacrylonitrile)
A
Polyacrylamide
- Will dissolve in water and is used industrially in many applications needing this ability.
- Even crosslinked polyacrylamides can absorb water.
- Crosslinked polymers can’t really dissolve, if you think about it, but that doesn’t stop water from wanting to interact with it through hydrogen bonding.
- These gels of water-swollen crosslinked polymer are used to make things like soft contact lenses.
- It’s the absorbed water in them that makes them soft, but you need other comonomers or polymers mixed in with them to help with things like oxygen permeability.
13
Q
Modifying polyacrylates
A
Modify the ester
- HEMA
- Monomer has reactive -OH attached as the R of the ester.
- Reactive and likes to bond with lots of other polar functional groupa
Modify the vinyl
- MHMA
- Monomer has reactive alcohol attached to alpha carbon of the vinyl.
- ECMA
- Monomer has reactive chloromethyl group attached to alpha carbon of the vinyl.
- Two functional groups extending from alpha carbon. More control over properties and chain linking, even ring structures.
14
Q
Polyisobutylene (synthetic rubber)
A
- synthetic rubber, or elastomer
- should be crystalline but it’s not
- Most polymers with highly symmetrical backbones like PIB are crystalline. Take isotactic polypropylene or polystyrene. Both are high melting, crystalline polymers.
- Polymers with disubstituted carbons in backbone usually have higher Tgs (> room temp) b/c chain mobility decreases
- Ex: PMMA Tg > PMA Tg b/c methyl on alpha carbon makes it have less chain mobility, i.e. glass at room temp rather than rubber PMA
- only rubber that’s gas impermeable, can hold air for long periods of time
- fixed tires so they retain air for longer
- cationic vinyl polymerization
- copolymerize with isoprene
- small amount (1%) of isoprene is added to the isobutylene and reaction is fast, done at low temp to allow for control
- isoprene has double bond, can be crosslinked by vulcanization
15
Q
Polyisoprene (natural rubber)
A
- Elastomer: recovers its shape after being stretched or deformed.
- Treated to enable crosslinks, better elastomer
- diene polymer: two C=C bonds (C=C-C=C)
- Ziegler-Natta polymerization
- polybutadiene: same but without the methyl on C2
16
Q
Polybutadiene
(elastomer)
A
- Synthetic elastomer, diene
- isoprene without methyl on C2
- Very low Tg
- good in cold temps, used as copolymer element
- chains are mobile, linked to absence of the methyl
17
Q
Poly(styrene-butadiene-styrene)
SBS hard rubber
A
- Durable and rubbery
- 3 segments in backbone
- Block copolymer with polystyrene(long)-polybutadiene-polystyrene(long)
- Polystyrene
- tough and hard - gives it durability
- Polybutadiene
- elastomer, very low Tg - gives it rubbery
- Polystyrene chains clump together
- When one styrene group of one SBS molecule joins one clump, and the other polystyrene chain of the same SBS molecule joins another clump, the different clumps become tied together with rubbery polybutadiene chains.
- This gives the material the ability to retain its shape after being stretched.
- Thermoplastic
- Most types of rubber are difficult to process because they are crosslinked.
- But SBS and other thermoplastic elastomers manage to be rubbery without being crosslinked, making them easy to process into nifty useful shapes.
18
Q
Thermoplastic
A
- These are materials that behave like elastomeric rubbers at room temperature, but when heated, can be processed like plastics.
- Most types of rubber are difficult to process because they are crosslinked. But SBS and other thermoplastic elastomers manage to be rubbery without being crosslinked, making them easy to process into nifty useful shapes.
19
Q
Poly(vinyl chloride)
PVC
A
- plastic for piping
- resists fire (chlorine atoms released inhibit combustion)
- water-resistant
- vinyl polymer
- free radical polymerization
- semi-crystalline domains
- regions that have a much higher softening point (Tm) than the other amorphous domains (Tg) that make up the solid polymer.
- The crystalline domains act as physical crosslinks to give the product you make toughness and strength.
- This means you can process PVC as a thermoplastic to make all those wonderful pipes and clear plastic seals around stuff you buy that you can’t tear or cut easily.
- So what kind of crystallinity does PVC have?
- Think about size: chlorine atoms have many more electrons than hydrogen and that makes it bigger.
- As a vinyl chloride monomer approaches the radical chain end during polymerization, the bigger chlorine wants to be further away from the chlorine already there.
- That leads to more syndiotactic placement than atactic or even isotactic.
- Those syndiotactic segments (3, 4, 5 or more repeat units) can get together with similar segments on other polymer chains and form small domains of crystalline material. Good properties.
- Increase syndiotacticity?
- Lower the temperature and the steric effects during monomer addition increase.
- Chain twists to achieve a conformation that will minimize the steric strain caused by larger side groups.
- Or you can do the polymerization like normal but add a “complexing agent” (aldehyde) that makes the chlorines look even bigger than they are.
20
Q
Semi-crystalline
A
Semi-crystalline domains or regions have a much higher softening point (Tm) than the other amorphous domains (Tg) that make up the solid polymer.
21
Q
Polyethylene
A
Vinyl polymer (ethylene monomer)
Linear = HDPE (200k
- Stronger
- Ziegler-Natta polymerization
- UHMWPE (3mil
- Kevlar fibers
- Metallocene catalysis polymerization
Branched = LDPE
- Cheaper, easier to make
- Flexible
- free radical vinyl polymerization
- linear-LDPE can also be made with Ziegler
- copolymerize ethylene with alkyl-branched comonomer
22
Q
Nylon
A
- Polyamide (just like silk protein)
- Very polar amide groups that H-bond to each other
- Also, backbone is regular and symmetrical
- Crystalline, make fibers
- Thermoplastic
- Nylon 6,6 means one repeat unit has 6 C stretches on each side separated by the amide group in the middle
- Condensation polymerization
- Made from diacid chloride (or adipic acid - switch Cl for OH) and diamine
- Nylon 6 is made from ring opening polymerization
- Hydroxy bonds with carbocation, nitrogen steals H from carbonyl and breaks off
- Then, next round acid loses its H, and the N in NH2 from broken chain bexome nucleophile, bonding to carbocation, giving ammonium.
- Now amine of one become an amide to the carbonyl of the other
- https://www.pslc.ws/mactest/nysix.htm
23
Q
Polyester
A
- Plastics and fibers
- Hydrocarbon chains with ester linkages
24
Q
Poly(ethylene terephthalate)
PET
A
- ester groups are polar (C+ : O-)
- +/- charges of different ester groups are attracted to one another, crystallization in chains - strong fibers
- Tg is low, is soft at higher temps
- Monomers
- dimethyl terephthalate and ethylene glycol
- OR, terephtalic acid and ethylene glycol with acid catalyst
25
Poly(ethylene naphthalate)
PEN
* Bulkier backbone, less mobile, Tg higher
* Higher Tg than PET
* Even mixing some in as a copolymer to PET increases the Tg
26
Glass transition temperature
Tg
* Temp at which polymer becomes soft
* Glass below this
* Rubber/flexible above
27
Transesterification for making polyester
Alcohol + ester
* O-CH3 of ester switches place with -O-CH2-CH2-OH of ethylene glycol
* then,
[https://www.pslc.ws/mactest/petsyn.htm](https://www.pslc.ws/mactest/petsyn.htm)
Or, if done in lab can do with picture monomers instead
28
Polycarbonate of bisphenol A
* Clear plastic
* Monomers
* Bispenol A and phosgene
* Thermoplastic
29
Chains with carbonate-containing groups
Thermosets
* Light
* High refractive index
* Free radical vinyl polymerization
* **Crosslinked with allyl groups**
* Very strong
* **Thermoset**
* Strong and heat resistant
30
Thermosets
* Do not melt, and they can't be remolded
* Strength and heat resistance
* Form physical or chemical bonds between chains in heated state that are permanent (crosslinks)
31
Polystyrene
* Inexpensive
* Hard, plastic
* Vinyl polymer
* Long HC chain with phenyl group on alpha C
* Free radical vinyl polymerization
* monomers = styrene
* Hard, durable component of SBS
* Syndiotactic state is crystalline (high Tm) because order allows the chains to arrange for maximum packing and minimal steric strain requiring bending
* $$$
* Metallocene catalysis polymerization
* Atactic normal state can be used to make high-impact
32
High-impact polystyrene
* Atactic state of polystyrene + polybutadiene undergoes free radical polymerization to form a graft copolymer
* Backbone is polystyrene and polybutadiene chains grow from it
* Polybutadiene chains
* rubbery
* doesn't mix with polystyrene backbone
* phase separate and form globs
* absorb energy on impact: resilience
* stronger, not as brittle
* only some chains are branched, lots of plain for both
* immiscible blend
33
PET and PVA
* Sheets: lamellar morphology.
* PET makes the bottle strong.
* PVA keeps CO2 from passing.
34
Immiscible morphology
* Immiscible
* Shape made by two phases of polymers.
* Control?
* With relative amounts.
* Large differences will cause little globs like with HIPS.
* Balanced leads to co-continuous phase
* Processed by biaxial stress of blow molding
* Flattened domains leads to flattened rods and lamellae
* Smaller SA of spheres, less they touch, bigger spheres at few numbers more stable
* Two Tgs, weaker as a mix, major component drives mechanical properties - absorbs stress and loads
* When processed like rods, act as fibers of a composite - makes it stronger in that direction
* Stronger at equal concentrations
* **Compatibilizer**
* [https://www.pslc.ws/mactest/iblend.htm](https://www.pslc.ws/mactest/iblend.htm)
* bonds phases more tightly (HIPS)
* a block copolymer introduced that sits at phase boundaries and **allow for energy transfer** because they are bound together - minor improves major
* Also, **lowers energy of the phase boundaries**, need to minimize contact decreases, **spheres can be smaller** and this is good for **mechanical properties** as more **phase boundary area leads to more efficient energy transfer**
35
Silicones
* Inorganic
* No carbon, rather silicone and oxygen backbone with organic groups branching from silicone
* Elastomers since backbone is flexible with Si-O bonds, angle opens easily
* Formation driven by entropy
36
Polyurethane
* Foams, spandex
* Versatile
* Elastomers, fibers, or adhesives
* Urethane linkage in backbone
* Monomers:
* diisocyanates and di-alcohols (ethylene glycol) like how PET does
* Hydrogen bond very well - crystalline
* Combined with soft rubbers to form block copolymers - thermoplastic elastomers
* Very rigid sections form fibers and clump
* Rubbery links
37
Tg factors
Transition from glass to rubber is not sharp.
Chain length
* Longer chain length in R means lower Tg, more flexible because it arranges to keep them spread out?
Tacticity
* when polymers have a regular arrangement of their atoms it is very easy for them to pack together into crystals and fibers.
* This is because molecules pack best with other molecules of the same shape and size.
* metallocene catalysis vinyl polymerization = syndiotactic
* Ziegler Natta = isotactic
* Free radical = atactic
Chain flexibility
* Reduced flexibility leads to higher Tg
* Prevent backbone from moving
IMFs
* Strong IMFs like H-bonds or dipole-dipole give higher Tg
MW
* Inverse relationship.
* Polymer having low molecular weight has more number of chain ends in compare of polymer having high molecular weight.
* Chain ends have less strain and become more active than the chain backbone and causes greater molecular mobility.
* Therefore increase in molecular weight decreases the glass transition temperature of polymer.
Pendant groups
* Bulky pendants like a benzene ring can restrict rotational freedom, causing less mobility, will stay glass and take lower temps to cool it, higher Tg
Co-polymerization
* C
Cross-links
* Restrict rotational freedom and raise Tg
Plasticizer
* Promote flexibility, weaken IMFs, decrease Tg
38
Crosslinked polymers
* Molded and shaped before crosslinking - thermosets.
* Can't dissolve in, but can absorb solvents
* ex: hydrogel - polyacrylamide (absorb water)
* Increases strength
Thermoplastics (secondary IMFs - Hbonds/ionic)
* Elastomers (lightly crosslinked)
* _Ex:_ Polyisoprene, Polybutadiene, Polyisobutylene, Polychloroprene, Acrylates, Methacrylates
* Ionomers and copolymers
* Polar ionic groups vibrate at high temp and are forced out of their cluster
* PB acts as crosslink for PS in SBS rubber
* Also atactic (amorphous) and isotactic (crystalline) blocks of same monomer
Thermosets (covalent)
* Highly crosslinked
* _Ex:_ Epoxy resins, Polydicyclopentadiene, Polycarbonates
39
PMMA vs PMA
PMMA adds another methyl group above the acrylate.
Poly(methyl acrylate) is a white rubber at room temperature, but poly(methyl methacrylate) is a strong, hard, and clear plastic.
How soft or hard a polymer is at a given temperature is determined by what we call chain mobility, that is, how well the polymer chains wiggle past and around each other. The more they can move, the softer the polymer is.
Anything bigger than a methyl stops the polymerization in its tracks. Steric hindrance becomes too great for the incoming monomer to add on to the end of the reactive polymer chain.
40
Addition Polymerization (chain)
* Entire monomer becomes part of polymer
* Polyethylene
41
Condensation Polymerization (step)
* Part of monomer (condensate: H2O or HCl) is kicked out in polymer formation and condenses elsewhere
* Less mass in polymer than monomers separately
* Nylon 6,6
42
Chain-growth
* Monomers become part of polymer one at a time
* Ex: anionic polymerization of styrene to make polystyrene
* Only the monomer can react with the chain, growing chains cannot react with one another
43
Step-growth
* Growing chains may react with monomers or each other to form even longer chains rapidly
* Addition: Polyurethane
* Condensation: PET
* Ex: terephthaloyl chloride and ethylene glycol, to make poly(ethylene terephthalate) PET
* Monomers form dimer
* But then that dimer can react with another monomer or with another ethylene glycol or with another dimer
Forms
* Ester
* Amide
44
MW with conversion
* conversion: how fast one or more of reactants is used up
* Step-growth
* Main reactant (monomer or reactive species) used up early, before high MW needed for useful properties
* Chain-growth
* chain growth to high molecular weight is fast for any GIVEN growing chain
* molecules that are present in a typical chain growth polymerization are only either monomer or high molecular weight polymer
* Radical polymerizations behave this way.
* And near the end of polymerization, when the rate of reaction (i.e., conversion of monomer to polymer) slows way down, you STILL have monomer around.
* It's almost impossible to get rid of all of it.
45
Addition
Free radical vinyl polymerization
* vinyl monomers
* polystyrene, poly(methyl methacrylate), poly(vinyl acetate) and branched polyethylene.
* Initiator: AIBN
* split into fragments and electrons in their bonds separate
* [https://pslc.ws/macrog/radical.htm](https://pslc.ws/macrog/radical.htm)
*
46
Initiators for free radical poly
47
Branched polymer formation through free radical polymerization
Chain transfer to polymer by radical end pulling and H from middle of chain and occurs in polyethylene.
* This is why linear non-branched polyethylene can't be made by free radical polymerization
48
Anionic vinyl polymerization
Living
[https://pslc.ws/macrog/anionic.htm](https://pslc.ws/macrog/anionic.htm)
vinyl monomers
initiator is anion (butyl lithium with carbanoin)
perpetuated carbanion formation by forcing electrons from double bond onto end carbon
stops when monomer runs out
polystyrene (add H2O to stop)
living polystyrene and butadiene to form SBS
49
Cationic vinyl polymerization
* initiator
* AlCl3 (needs 2 electrons to fill octet), bonds with O in water, an H then reacts with double bond of the vinyl
* carbocations
* polyisobutylene
* electrons from double bond leave and form bond with cation to make 1 molecule, shifting + charge to end C
* ends by chain transfer - same as free radical poly or termination with Cl capping
50
Poly(vinyl ethers)
PVE
* Size of a side group can be so big that it promotes stereoregularity, which is done by the bend of the chain to allow for minimized steric strain, greater organization can allow for higher crystallinity (may be why but\>meth for PMMA alternates)
51
Ziegler-Natta Vinyl polymerization
* Allows you to specify tacticity
* Linear polyethylene and isotactic polypropylene
* transition metal catalyst, like TiCl3
* co-catalysts are involved, group III metals like aluminum
* Ti-metal complex undergoes migration to form different structure
* Isotactic b/c incoming monomers can only react in that direction
* Can also give syndiotactic
* The catalysts initiate free radical for PVC and anionic for acrylates so they don't follow through just start another type - don't work.
52
Metallocene catalysis polymerization
* High MW polymers
* Specific tacticities: iso and syndio
* Metallocene is a positively charged metal ion sandwiched between two negatively charged cyclopentadienyl anions.
* [https://pslc.ws/macrog/mcene.htm](https://pslc.ws/macrog/mcene.htm)
* thermoplastic, elastomeric polypropylene
53
Tg graphs
In semi-crystalline, the crystalline regions will go straight to crystal formation below Tm, whereas the amorphous will gradually become less stiff as T increases above Tg.
54
Controlling polymer MW
* Temp increase : increase rxn rate : increase or decrease MW
* If polymer loses solubility at a particular MW, may crash out.
55
Differential scanning calorimetry
Differential scanning calorimetry is a technique we use to study what happens to polymers when they're heated. We use it to study what we call the thermal transitions of a polymer
56
Tg and Tm
Above Tg, the mobility is sufficient (if no crystals are present) that the polymer can flow as a highly viscous liquid.
The viscosity decreases with increasing temperature and decreasing molecular weight.
There can also be an elastic response if the entanglements cannot align at the rate a force is applied.
Semi-crystalline is viscoelastic above Tm
57
Pendant groups
Boat anchors
* get caught on things and limit
Elbow room
* big pendant groups limit how closely the polymer chains can pack together. The further they are from each other, the more easily they can move around. This lowers the Tg, in the same way a plasticizer does. The fancy way to say that there is more room between the polymer chains is to say there is more free volume in the polymer. The more free volume, the lower the Tg generally.
* PMMA and butyl PMMA
58
PLA, PGA, PCL
Biomaterials
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