Synthesis,Characterization And Applications In Rop Of Cyclic Esters Of Schiff Base Sodium And Zinc Complexes

Polymer materials play an important role in each department of the national economy and our life after 21 century. However, polymer materials not only improve our life, but also have done greatly harmful to our environment. With the increasingly shortage of the petroleum resources and serious White Pollution in the environment, the clean, safe and renewable polymers are urgently sought for us. In the last few years, biodegradable polymers are rapid developed, due to their applications in agriculture, packaging materials, garment and fiber, biomedical and pharmaceutical devices. The most excellent biodegradable polymer materials are polyesters, such as polylactide(PLA), polyglycolide(PGA), polycaprolactone (PCL) and their copolymers (PLGA). Therefore, studies on the ring opening polymerization of cyclic esters by Schiff base sodium and zinc complexes to obtain polyesters are presented in this paper.This paper can be divided into four parts as follows:1. A brief review of ring opening polymerization of cyclic esters in the last few years was given.2. Two Salen [N, N-bis(3,5-di (tert-butyl)salicylaldimine)-1,2-propylenediamine] sodium complexes and one Salen zinc complex were synthesized and characterized. The two Salen sodium complexes(1 and 2) are used as the effective catalysts in the ring opening polymerization(ROP) of L-lactide(L-LA), but the zinc complex(3) is almost not able to catalyze the ROP of L-LA. The two Salen sodium complexes show different catalytic activity:complex(1) is more active than complex(2). The obtained polymer is mainly cyclic PLA for a short PLA chain, but a mixture of cyclic and linear PLA for a long PLA chain.3. Four Schiff base zinc complexes were synthesized and characterized. The Schiff base [(E)-2-(((2-(dimethylamino)ethyl)imino)methyl)-6-methoxyphenol] benzyloxy zinc complex(4) is an efficient initiator for the ring opening polymerization(ROP) of L-lactide(L-LA) in a living and controlled fashion. Experimental results show that the introduction of an electron donor methoxy at ortho-phenoxy substituent leads to a decrease of the polymerization rate. In addition, it is found that the polymerization reaction proceeds with a first-order rate in both monomer and initiator in the kinetic study with the ROP of L-LA. The two Schiff base [(E)-2-(((furan-2-ylmethyl)imino) methyl)phenol] and (E)-2-(((furan-2-ylmethyl)imino)methyl)-6-methoxyphenol] zinc complexes(5 and 6) are almost not able to catalyze the ROP of L-LA, but can catalyze the ROP of trimethylene carbonate(TMC) in toluene at 100℃.4. Three Schiff base sodium complexes were synthesized and characterized. While trying to synthesize Schiff base [(E)-2-(((furan-2-ylmethyl)imino)methyl)-6-methoxy phenol] sodium alkoxy complexes, a bridged bicyclic compound is unexpectedly obtained. Schiff base sodium complex(7) has a cube of Na-O bond in its crystal structure and is a well air-stable complex. Preliminary experimental results of the ring opening polymerization(ROP) of cyclic esters show that its different catalytic activity has been displayed when this sodium complex(7) catalyzes the ROP of different cyclic esters. The catalytic activity is high, but the polymerization is not controlled fashion.