Polymers II

Question 1

What is viscosity defined as?

Answer 1

A measure of the resistance to flow of a system under an applied stress.

Question 2

What are the four sub-categories of viscosifiers?

Answer 2

Synthetic cellulose derivatives, natural polymers/gums, synthetic polymers, inorganic hydrocolloid particles.

Question 2

What disentangles the polymer chains in shear-thinning systems?

Answer 2

Vigorous agitation.

Question 3

What are two examples of synthetic cellulose derivatives?

Answer 3

Methylcellulose and hypromellose.

Question 4

What are three examples of natural polymers/gums?

Answer 4

Acacia, tragacanth, xanthan gum.

Question 5

What are two examples of synthetic polymers?

Answer 5

Carbomer, poloxamer.

Question 6

Give one example of an inorganic hydrocolloid particle.

Answer 6

Bentonite clay.

Question 7

Semi-synthetic cellulose derivatives are extracted and refined from different types of plants, where _______, a natural polysaccharide of _____ serves as the main structural polymer.

Answer 7

Cellulose; B-D-glucose.

Question 8

Natural cellulose is ________ branched and fibrous.

Answer 8

Minimally.

Question 9

Define a Type I gel.

Answer 9

Chemical gel, formed from covalently cross-linked polymers, sometimes referred to as hydrogels, mechanically rigid, high viscosities at rest.

Question 10

Define a Type II gel.

Answer 10

Physical gel, physical interaction at junction zones by non-covalent interactions, demonstrated shear-thinning rheology.

Question 11

What is a single-phase gel?

Answer 11

No apparent boundaries exist between the dispersed molecules and the medium in which they are dispersed.

Question 12

What is a hydrogel?

Answer 12

A macromolecular network interpenetrated by high quantities of water molecules.

Question 13

When the mesh size is larger than the diffusant, drugs diffuse freely through the hydrogel and D is independent of rmesh. How long does release take?

Answer 13

1-24 hours.

Question 14

When the drug radius is approximately the same size as the mesh, how long does release take?

Answer 14

Days.

Question 15

In the case of extremely small mesh sizes or extremely large API, drug can’t freely diffuse through the hydrogel. How long does release take?

Answer 15

Weeks to months.

Question 16

In situ gelling hydrogels are injected as aqueous solutions which then under-go what type of transition inside the body?

Answer 16

Sol-gel.

Question 17

What type of synthetic polymers form gels with increasing temperature?

Answer 17

Thermo-reversible.

Question 18

Macroscopic hydrogels are typically on the order of?

Answer 18

Millimeters to centimeters.

Question 19

Where are macroscopic hydrogels typically implanted?

Answer 19

Surgically or placed into contact with the skin.

Question 20

Microgels and nanogels are not a contiguous body but rather a?

Answer 20

Dispersion of very small hydrogel particles loaded with drug.