Polymers

Question 1

Polyethylene (PE)

Answer 1

No bulky pendant groups, lack of Van der Waal forces/H bonds/ionic forces

Question 2

Poly(methyl methacrylate) (PMMA)

Answer 2

Bulky pendant group, no H bonds

Question 3

Polytetrafluoroethylene (PTFE)

Answer 3

Fluorinated, can greatly elongate

Question 4

Poly(hydroxyethyl methacrylate) (PHEMA

Answer 4

Bulky pendant group, capability of H bonding

Question 5

Polypropylene (PP)

Answer 5

Slightly bulkier than PE, but more Van der Waal forces

Question 6

Poly(ethylene terephthalate) (PET)

Answer 6

Aromatic ring, pi system

Question 7

Poly(ether ether ketone) (PEEK)

Answer 7

Lots of aromatic rings (high tensile modulus)

Question 8

Poly(vinylidene fluoride) (PVDF)

Answer 8

Again, some Fluorine molecules

Question 9

Polyurethanes

Answer 9

• used in blood contacting applications, mechanical stability/biocompatibility
• has hard and soft segments (diols are soft, diisocyanates and chain extenders are hard)
• elastomeric properties AND good fatigue resistance

Question 10

Silicones

Answer 10

• excellent biocompatibility/biodurability
• used in soft-tissue implants (hydrophobicity leads to fibrous capsules)
• alternating silicon-oxygen backbone
• low Tg, is elastomeric and gas/drug permeable (sealants and adhesives)
• liquid polymer solutions are ‘cured’ at room temperature to form 3D crosslinking network (high bond strength between Si and O)
• PDMS, for example, is thermoset (can’t be further processed after polymerization)
• suboptimal yield strength, but used as a filler

Question 11

Fluorinated Polymers

Answer 11

• hydrocarbons with significant amounts of pendant fluorine atoms (perfluorocarbons – all pendant groups are F)
• high electronegativity… inert, highly tensile and temperature resistant, hydrophobic, low interfacial energy/coefficient of friction
• very lubricious (PTFE for example), but can cause creep if in load bearing
• prefers to coat an air-exposed surface

Question 12

PHEMA

Answer 12

• popular hydrogel, used in contact lenses
• significant swelling, withstands heat sterilization
• adding methacrylic acid reduces swelling in the resultant PMAA, as MAA incurs hydrophobic interactions

Question 13

Poly(vinyl alcohol) (PVA)

Answer 13

• highly hydrophilic, used as drug delivery matrix
• repeated freeze thaw cycles
• blood contacting hydrogel

Question 14

Poly(ethylene glycol) (PEG or PEO)

Answer 14

• biologically intert and ‘stealthy’, as it resists protein adsorption
• used often in tissue engineering as crosslinking constituent

Question 15

Poly(N-isopropylacrylamide)

Answer 15

• smart biomaterial, phase separates/precipitates out of aqueous solution due to temperature change