exam 3 lecture 4

Question 1

molecular weight

Answer 1

number average (Mn)
weight average (Mw)

Question 2

molecular weight distribution

Answer 2

monodispersed: Mn = Mw –> narrow distribution
polydispersed: Mw&raquo_space; Mn –> broad distribution

Question 3

crystalline

Answer 3

linear polymer
polymer can pack together in regular arrays at T<Tm
manifests sharp Tm
good barrier to drug diffusion

Question 4

amorphous

Answer 4

more common
polymers with irregular structure
polymers forms “glass” at T«Tg
softens over a wide temperature range

Question 5

Tg (glass transition temp)

Answer 5

temperature range where polymer changes from hard, rigid, glassy to pliable, compliant, rubbery state
T«Tg = hard glass
T»Tg = rubbery and flow

Question 6

chewable dosage forms Tg

Answer 6

have low Tg –> the gum softens at mouth temperature
ex - nicotine gum

Question 7

factors affecting Tg

Answer 7

polymer length: longer is higher Tg
side chains: bulkier is higher Tg
crosslinking: more crosslinked is higher Tg
plasticizers: increase entropy and mobility of polymer chains –> lower Tg when included in polymer products

Question 8

plasticizers

Answer 8

increase entropy and mobility of polymer chains –> lower Tg when included in polymer products

Question 9

mechanical properties graph

Answer 9

stress (force/area) vs strain (deformation)

Question 10

mechanical properties (EXAM QUESTION)

Answer 10

slope (stress/strain): modulus (stiffness)
area under the curve: toughness
elastic polymers: fibers or highly crosslinked polymers
- linear stress vs strain curve up to a break point
rubbers or elastomers:
- may deform 10-15 times their original lengths

Question 11

hydrogels

Answer 11

crosslinked hydrophillic polymers
- chemical gels + physical gels
swell rapidly when placed underwater
- chain-water interaction, electrostatic repulsion, osmotic forces
retain large volume of water in their structures

Question 12

cellulose-based polymers

Answer 12

ethylcellulose (tab coating)
carboxymethyl cellulose ( superdisintigrant ; emulsifier)
hydroxypropyl methyl cellulose (tablet binder, coating)

Question 13

hydrocolloids

Answer 13

alginic acid (thickening agent in suspension)
chitosan (mucoadhesive dosage forms)

Question 14

water-soluble synthetic polymers

Answer 14

poly (ethylene glycol) (plasticizer, suppository base, stealth coating)
poly(vinyl alcohol) (tablet binder, coating)

Question 15

water- insoluble synthetic polymers

Answer 15

poly(lactic-coglycolic acid) (controlled drug release)
polylactic acid (controlled drug release