Ive got a question i am trying to answer, its in 4 parts and i have been able to answer 3 of these. the question/s is/are:
What is the intrinsic viscosity of a polysaccharide of M = 96000 with Mark-Houwink parameters
(K = 1.4*10-6 m3 / kg, and a = 0.69)?
[n] = KMa = (1.4*10-6 m3/kg)(96000)0.69 = 3.8*10-3 m3/kg
Calculate the hydrodynamic volume
VH = [n]M/2.5NA
= KMa+1 / 2.5NA
= ((1.4*10-6 m3/kg)(96kg/mol)0.69+1) / ((2.5)(6.022*1023mol-1))
What concentration of the polysaccharide is needed to completely fill a solution with polymer coils?
VH = hydrodynamic volume = volume of one polymer chain = 2.1*10-27m3 / chain = 2.1*10-24L/chain
#of polymer chains per liter = 1 / (2.1*10-24L / chain)= 4.8*1023 chain /L
the concentration of polysacharide in a solution completely filled with polysacharide coils = conc. max = 4.8*1023 chain /L
alternatively, conc. max = 1/(VH*NA)
= 1/((2.1*10-24L/poly. chain)(6.022*1023chain/mol))
What might you expect to happen to the viscosity of the solution as the concentration increases beyond this level?
This has got me puzzled, this is what ive come up with.
There is a maximum concentration of 4.8*1023 poly. chains / L, therefore the viscosity of the solution will not increase, this is the point of maximum viscosity.
Its got me puzzled because I cant understand how you could have a concentration higher than 4.8*1023 poly. chains / L of this polysacharide when thats all you can fit in a liter? does that make sense?
Any help would be much appreciated (im starting to have nightmares about polymers)