polymers revised

Question 1

Mn

Answer 1

numer average

Question 2

Mw

Answer 2

weight average

Question 3

polydispersity

Answer 3

when Mw > Mn
greater than 1

Question 4

glass transition temperature

Answer 4

temp range where a polymer changes from a hard, rigid, or glassy state to a more pliable, compliant, or rubbery state
T < Tg then hard stiff glassy
T > Tg then rubbery flowly

Question 5

crystalline

Answer 5

linear polymer
can pack together is regular arrays at T < Tm
mainfests a sharp Tm
good, durable barrier to drug diffusion

Question 6

amorphous

Answer 6

polymers with irregular structure
softens over a wide temperature range

Question 7

mechanical properties

Answer 7

stress (force/area) vs strain (deformation)
slope (stress/strain): modulus or stiffness
area under the curve: toughness
elastic polymers (stress vs strain to breaking point)
rubbers or elastomers (deform 10-15x)

Question 8

factors increasing Tg

Answer 8

longer length of polymer
bulkier side chains
more crosslinking
less plasticizers

Question 9

plasticizers

Answer 9

molecules that increase the entropy and mobility of polymer chains
example - water

Question 10

features of hydrogels

Answer 10

crosslinked networks of hydrophilic networks
swell rapidly when placed in water
retain large volume of water in their structures

Question 11

how are chemical gels crosslinked?

Answer 11

covalently

Question 12

how are physical gels crosslinked?

Answer 12

via hydrogen bonding, hydrophobic interactions, or complexation

Question 13

why do hydrogels swell rapidly when placed in water?

Answer 13

chain-water interactions
electrostatic repulsion
osmotic forces