Hi All,

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:

**(1)**

*What is the intrinsic viscosity of a polysaccharide of M = 96000 with Mark-Houwink parameters *

(K = 1.4*10^{-6} m^{3} / kg, and a = 0.69)?

**[n] = KM**^{a} = (1.4*10^{-6} m^{3}/kg)(96000)^{0.69} = 3.8*10^{-3} m^{3}/kg

**(2)**

*Calculate the hydrodynamic volume*

**V**_{H} = [n]M/2.5N_{A}

= KM^{a}M/2.5N_{A}

= KM^{a+1} / 2.5N_{A}

= ((1.4*10^{-6 }m^{3}/kg)(96kg/mol)^{0.69+1}) / ((2.5)(6.022*10^{23}mol^{-1}))

= 2.1*10^{-27}m^{3}/chain

**(3)**

*What concentration of the polysaccharide is needed to completely fill a solution with polymer coils?*

V_{H} = hydrodynamic volume = volume of one polymer chain = 2.1*10^{-27}m^{3} / chain = 2.1*10^{-24}L/chain

#of polymer chains per liter = 1 / (2.1*10^{-24}L / chain)= 4.8*10^{23} chain /L

the concentration of polysacharide in a solution completely filled with polysacharide coils = conc. max = 4.8*10^{23} chain /L

alternatively, conc. max = 1/(V_{H}*N_{A})

= 1/((2.1*10-24L/poly. chain)(6.022*10^{23}chain/mol))

= 0.791mol/L

**(4)**

*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*10^{23} 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*10^{23} 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)

cheers,

Mad