Hi,

In the chloromethylation reaction of polysulfone (PSU), I am required to use paraformaldehyde and trimethylchlorosilane as the chloromethylating agent while stannic chloride as the catalyst. I followed the same protocol of many papers such as this one attached.

During the experiment, PSU was first dissolved separately in solvent (e.g dichloromethane and chloroform) then paraformaldehyde (PFA) was added in form of solid. For both solvent and at two different dissolution temperatures (25 and 60 °C), the PFA was not fully dissolved.

I tried to dissolve PFA separately in solvent than add it to the dissolved PSU, this slightly improved the degree of chlore in the produced chloromethylated PSU (C-PSU), however it was not dissolved and gelation as well as non-homogeneity was obtained. Moreover, the obtained C-PSU was not soluble in many solvents (e.g. NMP, DMAc, DMSO, Toluene, DMF), which can be caused by the low degree of functionalization ( -CH2Cl) and the precipitation of insoluble cross-linked polymer.

I am aware that PFA is

  • slightly soluble in alcohol
  • soluble via depolymerization by heating PFA in distilled water at 60°C followed by a titration with NaOH

Which I already tried and it was successful in terms of PFA dissolution. The problem is that I don’t want water in my reaction due to the future application of the system.

I would appreciate if you could help me to improve my system by providing some suggestions on how to achieve a good homogeneous PFA/solvent solution. Any ideas on how to increase the degree of chloromethylation of PSU are very welcomed.

Thank you

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