What do you mean by contrast? Do you want to study the nanoscale microstructure using TEM or a scattering technique?

in fact, I want to observe morphology of ternary blends using SEM.

morphology is core-shell.(core is SEBS and shell is SAN)

I want to solve SAN without making change in SEBS

The mutual solubility/insolubility of SAN/SEBS blends much depends on the composition of both polymers. The more styrenic (rich in styrene monomer) the polymers are, the more difficult it is to separate them by using sufficient solvent systems.

Dear Pawel

SAN is a SAN24 by AN amount(24 wt% AN) and SEBS is Kraton which styrene content is 30%

do you know any solvent or mixture of solvent appropriate for this aim?

Acetone may be useful in removing SAN from the SAN/SEBS blend since it readily dissolves styrene-rich SAN random copolymers (e.g. SAN 24) and only swells SEBS triblock copolymers (e.g. Kraton G) without dissolving it.

Certainly, you can predict that behavior based on the solubility parameter values of both polymers, being 21.6 and 17.0 (J/cm3)^0.5 for SAN and SEBS respectively. The SAN copolymer is also much more polar than SEBS with larger contributions to the solubility parameter from polar components (10.0 and 3.5 (J/cm3)^0.5, for SAN and SEBS respectively).

For a better result, I would try extracting the blend with the solvent at a low temperature (-20 to 0 deg C). Ethyl acetate might be sufficient to do so as well.

Dear Dusan

I think you are right. I read in a text that MEK is a appropriate solvent. but, there is some other papers demonstrating MEK also solve SEBS.

did you test it experimentally?

SEBS are G1652 and, FG1901x

You mentioned preferential dissolution as a tool for revealing morphology. This could be successful but it has its challenges as in removing the dissolved material so it does not redeposit also the possibility of structural collapse . Selective Etching in which the polymer is degraded in to more soluble sections using an oxidising agent in which the soluble sections can easily be transported from the surface without redeposition give a much higher resolution image. Equally staining, for example SEBS will stain with Ruthenium Tetroxide (make a thorough review of the H & S procedures before starting) and looking at a sample in the TEM or at a push in a SEM using back scattered electrons is probably your best approach.

Any new morphology revealing procedure needs to be extensively validated otherwise you think you have succeeded when you have images that match your expectations.

Dear Dusan

the material is SAN not PAN.

SEBS is a block copolymer with 30/70 ratio toward ethylene-buthylene/styrene.

Dear Dusan

Thanks for your guidance.

If any one has a comment or an alternative way it is requested to discuss that.

Staining is your best way forward as described above

yes, of course.but, as you know it is expensive method. thus, I am willing to do that with SEM or FESEM.