************ The 4th Lab Seminar ***************************************

Title : Characterization of Methyl-Substituted Polyamides Used for 
Reverse Osmosis Membranes by Positron Annihilation Lifetime Spectroscopy 
and MD Simulation
J. Appl. Polym. Sci., 2009, 113, 1757-1762.

Speaker : Suzuki Yuichi

Date : Fri. July. 5th, 1:30 pm

Abstract :
Three kinds of polyamides were synthesized from three diamines and 1,3,5-
benzenetricarbonyl tri-chloride (TMC). The diamines used were m-phenyl-
enediamine, N-methyl- m-phenylenediamine, and N,N'-dimethyl-m-phenyl-
enediamine. The average free volume sizes of the polyamides were measured 
by positron annihilation lifetime spectroscopy (PALS), and the free 
volume fractions were evaluated by molecular dynamics (MD) simulations. 
The methyl substitution on amino groups of diamines brought about an 
increase in interstitial space of molecular chains of the polyamides. In 
addition, reverse osmosis (RO) membranes were prepared by interfacial 
polymerization from the three diamines and TMC. The increase in the 
degree of methyl-substitution of diamines led to increased chlorine 
resistance and decreased salt rejections of the polyamide RO membranes.
Thus, the methyl-substitution of diamines significantly influenced 
membrane performance. The vacancy sizes and fractional volumes in poly-
amides evaluated by PALS measurement and MD simulation were well 
correlated with salt rejection of polyamide RO membranes.


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