Thermal Properties of Degradable Polymers

Question 1

Degradable polymers

Answer 1

Designed to degrade within the body body after performing their functions.
Degradation refers to the chemical process resulting in the cleavage of covalent bonds.
polymers degrade either by hydrolysis or by enzymatic action into non-toxic products

Question 2

Advantages of biodegradable medical devices

Answer 2

Useful in short term applications (no removal surgery needed)
Circumvent safety problems of permanent devices
Do not elicit foreign body reactions

Question 3

What is usually the morphology of polymers?

Answer 3

Semicrystalline or amorphous

Question 4

What are the two important transitions in polymers?

Answer 4

Tm - Melting temperature

Tg - Glass transition temperature

Question 5

Which polymers only have a glass transition temperature?

Answer 5

fully amorphous polymers

Question 6

Which polymers undergo both Tg and Tm?

Answer 6

Semi-crystalline polymers

Question 7

Relation between degradation rate and crystallinity

Answer 7

Both are inversely related. Amorphous states absorb more water, leading to faster degradation

Question 8

Polylactide (PLA)

Answer 8

Based on -[-O-CHR-CO-]-n where R = CH3

Replacing H with CH3 produces more hydrophobic polyesters resulting in a lower water uptake and lower hydrolysis rates

Question 9

Polyglycolide (PGA)

Answer 9

Based on -[-O-CHR-CO-]-n, where R=H
At high molar mass it is a hard, tough semicrystalline polymer
Short degradation time

Question 10

Poly alpha hydroxyesters

Answer 10

Group of degradable polymers where repeating unit is based on -[-O-CHR-CO-]-n, derived from monomers that are alpha-hydroxy acids Polyesters containing the groups (-CO_O-) in the polymer backbone that can be hydrolyzed causing chain scission.
Ex: PGA and PLA, and their copolymers