Abstract
Polycaprolactone (PCL) is a biodegradable synthetic polymer that is currently widely used in many pharmaceutical and medical applications. In this paper we describe the coordination ring-opening polymerization of ε-caprolactone in the presence of two newly synthesized catalytic systems: diethylzinc/gallic acid and diethylzinc/propyl gallate. The chemical structures of the obtained PCLs were characterized by 1H- or 13C-NMR, FTIR spectroscopy and MALDI TOF mass spectrometry. The average molecular weight of the resulting polyesters was analysed by gel permeation chromatography and a viscosity method. The effects of temperature, reaction time and type of catalytic system on the polymerization process were examined. Linear PCLs with defined average molecular weight were successfully obtained. Importantly, in some cases the presence of macrocyclic products was not observed during the polymerization process. This study provides an effective method for the synthesis of biodegradable polyesters for medical and pharmaceutical applications due to the fact that gallic acid/propyl gallate are commonly used in the pharmaceutical industry.
Highlights
We have reported a new and effective zinc-based catalytic system for the ring-opening polymerization (ROP) of ε-caprolactone (CL)
The catalytic systems were prepared from diethylzinc and gallic acid (ZnEt2/GAc) or propyl gallate (ZnEt2/PGAc) for the first time
ZnEt2/GAc or ZnEt2/PGAc catalytic systems were quite effective in the ROP of CL
Summary
Polycaprolactone (PCL) is an important biomedical polyester due to its physicochemical properties as well as good biocompatibility and biodegradability [9,10]. PCL is a hydrophobic and semi-crystalline polymer. It was one of the earliest polymers synthesized, by the Carothers group in the early 1930s [9]. PCL can biodegrade in a time-span ranging from several months to several years, depending on its molecular weight, degree of crystallinity and the condition of biodegradation process [10]. Due to its multiple biomedical applications, the synthesis of PCL has received increased attention in the last years [9,10]. There are two methods for the preparation of biomedical PCLs: the polycondensation of
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