交联壳聚糖树脂与Zn2+的配位作用

研究了甲醛、环氧氯丙烷交联壳聚糖树脂(Chitosan crosslinked by aldehyde and epichlorohydrin,AECTS)吸附Zn2 后对树脂结构及性能所产生的影响.用FTIR、XRD、TG、DSC和SEM对吸附产物进行了结构表征,并分析了AECTS与Zn2 之间的作用机理.结果表明,Zn2 与AECTS中的氨基发生配位而被吸附;AECTS吸附Zn2 后,结晶度下降、总体上热稳定性变差;Zn2 对AECTS的主链分解具有明显的催化功能;Zn2 的配位使得AECTS的表面形态发生了改变.     

Performance-Advantaged Stereoregular Recyclable Plastics Enabled by Aluminum-Catalytic Ring-Opening Polymerization of Dithiolactone

Chemically recyclable polymers that can depolymerize into their constituent monomers are attractive candidates to replace non-recyclable petroleum-derived plastics. However, the physical properties and mechanical strengths of depolymerizable polymers are commonly insufficient for practical applications. Here we demonstrate that by proper ligand design and modification, aluminum complexes can catalyse stereoretentive ring-opening polymerization of dithiolactone, yielding highly isotactic polythioesters with molar masses up to 45.5 kDa. This material can form crystalline stereocomplex with a T_m of 94.5 °C, and exhibits mechanical performances comparable to petroleum-based low density polyethylene. Exposure of the polythioester to aluminum precatalyst used to synthesized it resulted in depolymerization to pristine chiral dithiolactone. Experimental and computational studies suggest that aluminum complexes have appropriate binding affinity with sulfide propagating species, thereby avoiding catalyst poisoning and minimizing epimerization reactions, which has not been accessible using other metal catalysts. Overall, aluminum catalysis provides access to performance-advantaged stereoregular recyclable plastics as a promising alternative to petrochemical plastics, thus incentivizing improved plastic sustainability.