Synthesis and meticulous molecular, morphological and thermal characterization of linear and star-shaped polycaprolactones

Abstract

In this study, linear and star-shaped polycaprolactones with varying numbers of arms are synthesized by ring opening of ε-caprolactone. The polymers were characterized in detail to obtain information of by-products in the samples. Size exclusion chromatography could not differentiate products with similar molar mass but different architecture and if there are any by-products in the sample. Liquid chromatography at critical conditions (LCCC) on NP and RP columns provided more insight into the product composition with regard to number of arms and possible by-products. MALDI-TOF MS analysis confirmed the structures and successful separation of targeted product from unwanted by-product. 2D-LC by coupling of LCCC to SEC in the second dimension demonstrated the similar size of the products that are separated successfully by LCCC. The purity and analysis of star-shaped precursor is imperative for further synthesis of star-block copolymers that is not given much attention in published literature. Thermal and morphological properties of the polycaprolactones with similar molar mass but different architectures are evaluated by DSC, TGA and AFM.