NARROW MOLECULAR-WEIGHT DISTRIBUTION OF CONDENSATION POLYMERS ACHIEVED BY ADDING MONOMERS IN MANY BATCHES

The Z transform method has been used to calculate the molecular weight distribution (MWD) of condensation polymers. The MWD obtained by usin g Z transform is explicitly discrete. The method is illustrated for tw o cases: (1) further polycondensation of AB prepolymers with certain i nitial MWD, and (2) polycondensation of AB and Ar (r is the number of A type functional groups) monomers where AB monomers are added in seve ral batches. In the latter case, it is found that the resulting MWD is much narrower than that of one-batch polycondensation. The trick of p roducing narrow MWDs of condensation polymers is merely a consequence of keeping AB monomer concentration as low as possible during the reac tion in order to suppress the condensation reaction between monomeric AB molecules. The theoretical prediction has been confirmed by Monte C arlo simulation. Therefore, it provides a new possible technique for o btaining narrow MWD polymers through polycondensation reactions.