Palygorskite as Efficient Catalyst for Ring-Opening Polymerization of ϵ-Caprolactone

Abstract

Fiber-like high-surface-area and natural nanostructure clay mineral palygorskite (or attapulgite, ATP) containing lots of hydroxyl groups is found to efficiently catalyze the ring-opening polymerization (ROP) of ϵ-caprolactone (ϵ-CL). The products are subsequently characterized by FTIR, ¹H NMR, GPC, DSC, SEM and XPS analysis. The results show that porous PCL with relatively high molecular weight is obtained. A mechanism is proposed to illustrate that ϵ-CL is initiated by the constituent water in ATP and catalyzed by three active centers relate to hydroxyl groups on the surface of ATP. The ATP acts as a proton shuttle via its acidic hydrogen atoms and basic oxygen atoms. Moreover, there exists synergetic catalytic effect between the metal centers and Si centers.

Keywords:

• Caprolactone
• Catalyst
• Clay
• Palygorskite
• Polyester
• Ring-opening polymerization

ACKNOWLEDGMENTS

This work was supported by the Fundamental Research Funds for the Central Universities (CUG120118), the National Natural Science Foundation of China (50903077), the Natural Science Foundation of Hubei Province (2010BFA022, 2011CDA035, 2012FFA111),and the Public Service Project of the Chinese Ministry of Land and Resources (201311024).

Notes

^a Mass ratios of ε-CL to ATP. Conditions are all 3000:1, CL = 3 g.

^b Conversion (%) = (polymer yield)/(monomer feed), wt.%.

^c Determined by (GPC) in THF, using polystyrene as standards.