If you work with a polymer of widely known chemical structure but unknown molecular weight, the easiest way to evaluate MW is doing viscometry followed by calculations of MW by Mark-Houwink-Sakurada equation. To get the chain contour length, divide MW of the polymer by the MW of the monomer unit and multiply by the length of the monomer unit. Tell more of your system to get more adequate or detailed answers :)

Dear Mattias,

the contour length is a length of a polymer chain in a maximally elongated conformation, without deformation of valent angles. The average end-to-end distance is hydrodynamic radius of a polymer coil, i.e a different and more realistic measure. Let us better wait before Van Tran makes her problem clearer.

Alexander

Depending on the polymer species or functional groups, you can try for Size Exclusion Chromatography (SEC), I suggest to look for this service, they'll ask for all the available information regarding your polymer, in order to get the best/fast result.

Yeah, I also knew the Mw of my polymer by Mark-Houwink-Sakurada equation. That's right, you two did talk about the lenght but I 'd like to know how to calculate or search the coil length. We all may know the salt can effect to the length of polymer. But when we want to coat polymer on the surface of nanoparticles or mesoporous, I think we must use the coil length, do we?

Dear Matthias,

thank you indeed for your remark on the obsolescent definition. This was perhaps a scientific reminder of my ageing ... :) Could you please send me and other participants a link to the new definition? Thank you in advance. As follows from Van's answer, she is more interested in evaluation of the coil dimensions.

Best regards

Alexander

Dear Van,

if you wish to compare the sizes of pores or nanoparticles with that of your polymer coil, you should probably use its hydrodynamic radius. I understand you work with a polyelectrolyte in aqueous solution. The coil size will depend then on both the pH and ionic strength. The more ionized is your polymer the larger radius it will have. It will also increase at lower salt concentrations. I cannot conceive, however, an easy technique to estimate the radius. Static light scattering is reliable but quite laborious. May anybody suggest something easier?

Alexander

I all thank to A.Ivanov and Arras ^_^ In my Lab, I have DLS machine, I may chech the radius gyration and its dependence in pH and salt concentration. That's a good advice :)

You are welcome, Van. DLS may give you too approximate value of MW. What you get from DLS is a mean diffusion coefficient (D). Check if your program uses adequate formula to transfer D into MW. The best would be to find in the literature a scaling dependence of D on MW for your polymer and the solvent. Use diluted polymer solution to avoid polymer associates.

Best wishes

Alexander