1,3-propanediol (1,3-PD) has a molecular weight of ~76 daltons (Da), which is reasonably higher than that of water (the solvent in my case).

I have been trying to find online any commercial membranes with a molecular weight cut-off (MWCO) of 76 Da or less, but I couldn't find any. However, I came across an RO membrane by DOW FILMTEC Membranes (FT30) that has a MWCO of 100 Da. This size is larger than that of 1,3-PD, but according to the product specification sheets (both attached), this membrane has a high rejection rate for even smaller molecules. 

What specifically caught my attention is that this membrane has 90% rejection of isopropanol (60 Da), which is the most similar compound to 1,3-PD I could find in the lists attached. I was wondering if I could use this as a basis for 1,3-PD rejection (meaning, to assume that 90% of 1,3-PD can be rejected by this membrane), but I'm not sure if 1,3-PD and isopropnaol are chemically and physically similar enough for this assumption to hold. If not then what should I do in this case? Anyhow, can you recommend to me any commercial membranes that have the desired MWCO (76 Da) or lower?

Thank you.