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Abstract:It is highly desirable to develop simple organocatalysts for the controlled ring-opening alternating copolymerization(ROAC) of epoxides and cyclic anhydrides, leading to high molecular weight polyesters. Hence, a phosphazenium salt, namely tri[tris(dimethylamino)phosphoranylidenamino]phosphonium chloride(P_4~+Cl~-), is developed as a catalyst for the ROAC of epoxides and cyclic anhydrides. Surprisingly, the combination of P_4~+Cl~-with a protonic initiator, such as 1,4-benzenedimethanol(BDM)exhibited high efficiency in the copolymerization of propylene oxide(PO) and phthalic anhydride(PA). This led to the production of polyester with an exceptional high molecular weight(M_n) of up to 126 k Da, which represented a rare example of poly(PO-alt-PA) with Mnsurpassing 100 k Da. Note that the core P atom is trivalent status and the tris[tris(dimethylamino)]phosphoranyl group will share one proton in the P_4~+Cl~-salt. Once combined with protonic species, the P_4~+Cl~-will not only serve as a proton acceptor but also as a hydrogen bonding donor for the cyclic anhydrides. Therefore, it was assumed that the P_4~+plus proton served dual role in mimic of base/urea pair to effectively catalyze ROAC, which was supported by density functional theory(DFT) calculations.
Volume:v.67
Issue:09
Translation or Not:no