[green-goblin]

Hi everyone.

I have been trying to convert some mole percent values into weight percent for a terpolymer system and was hoping you could help.

I have a terpolymer system containing three different monomer units A, B and C.

{A}_x{B}_y{C}_z

A has a RMM of 170 g/mol
B has a RMM of 95   g/mol
C has a RMM of 110 g/mol

I know that C makes up 85 wt % of the polymer.

Out of the remaining 15 wt %, 80 mole % is made up from monomer A and 20 mol % from monomer B.

I would like to know the concentration of all the monomer units in either mol % or wt % but not in this mixture of the two.

Can I first treat monomer A and B like a copolymer, ignoring C, and say that there is an average repeat unit molecular weight which is a weighted average of the both of their molecular weights? i.e:

Average RMM of AB = (0.80*170g)+(0.20*95g) = 155g/mol

Then going back to the terpolymer, If I had say 100g of terpolymer I have:

85g of C and 15 g of AB

85g of C = 85g/110g/mol = 0.773 moles of C

15 g of AB is 15g/155g/mol = 0.097 mole of AB repeat units

As AB is 80 mol % A and 20 mol % B

A= 0.097 * 0.8 = 0.0776 moles of A and

B= 0.097 * 0.2 = 0.0194 moles of B


so in 100g:

moles of A = 0.0776, B = 0.0194 and C= 0.773

as mole % = number of moles of repeat unit/ total number of moles:

mol % of A= 8.92, B=2.23 and C = 88.85

Is this all valid? I have carried out similar calculations on coplymer systems before, where an average repeat unit RMM is used when calculating the concentration of a particular repeat unit to help calculate reactant amounts but never of a ter-polymer system where I only know a mixture of wt% and mol %.

I hope I haven't made that too horrendously complicated. Any help/advice would be appreciated.