Chapter 2 Flashcards
How does Mo change is the polymer is not a homo polymer?
Mo becomes the MW of the repeating unit divided by the number of monomers in each repeating unit. For nylon, the MW of the RU is divided by 2 for example
Third way of writing the Mw equation
sum(WiMi)/sumWi
Average poly-dispersity
1.5-2.0
Equation for polydispersity
Mw/Mn
Pros and cons of membrane osmometry
Simple but is time consuming. Also no membrane can block all small molecules and so, it works best with ME between 20,000 and 50,000
Equation for osmotic pressure with units
OP = pgh
p = density kg/dm2
g = 9.8 ms-2
h = height in m
What do you plot following membrane osmometry to find what
OP/C vs c to find Mn
Light source for light scattering
high intensity polarized or filtered mercury lamp
What does light scattering method allow us to calculate
Mw
For what kind of polymer samples is light scattering usually used
for dilute polymer samples
What is plotted following a light scattering experiment
Kc/R(theta) vs sin^2(theta/2) to find 1/Mw
Pro and con of light scattering
Don’t need to know the chain conformation before hand.
Its difficult, expensive and highly specialised
What do you plot following a viscometry experiment
ni/c vs c, the intercept is n
Equipment used for viscometry
Ostwald-Fenske, Ubbelohde capillary viscometer
What is the gel-permeation column packed with?
insoluble, small, highly porous beads (SiO2) modified with ether or diol linkages
