Viscosity & Solubility

Question 1

viscosity definition

Answer 1

resistance to flow in units poise

Question 2

solubility

Answer 2

like dissolves like

mixing breaks up solvent-solvent and molecule-molecule interactions

allows molecule-solvent interactions

Question 3

with a polymer the dimensions are different

Answer 3

polymer is “large”

solvent is “small”

Question 4

solubility/dissolving occurs in ___ stages

Answer 4

two

Question 5

stage 1

Answer 5

solvent molecules diffuse through polymer matrix to form a swollen mass (gel)

Question 6

stage 2

Answer 6

gel breaks up or molecules are dispersed in solution

slow process

some dissolve readily, others need time + temp

Question 7

do network polymers (cross-linked) dissolve?

Answer 7

no

usually swell

Question 8

do all linear polymers dissolve?

Answer 8

no

Question 9

how to calculate best solvent

Answer 9

use a handbook

gibbs free energy want small delta H and large delta S

best solvent has good affinity for that polymer

Question 10

polymer behavior in solvent

Answer 10

size/hydrodynamic volume depends on how well interacts w/ solvent

depends on chain branching

conformations arising from polarity/sterics of substituents

could be gauche but have h-bonding

Question 11

good solvent effects

Answer 11

strong intermolecular forces btw polymer + solvent

polymer uncoils and spreads out

higher hydrodynamic volume

higher viscosity due to higher volume “drag”

Question 12

poor solvent effects

Answer 12

intramolecular forces cause polymer to shrink in volume (become more compact)

reduced viscosity