Controlling the Isothermal Crystallization of Isodimorphic PBS-ran-PCL Random Copolymers by Varying Composition and Supercooling.

Maryam Safari,Manuela Zubitur,Alejandro J Müller,Antxon Martínez De Ilarduya,Agurtzane Mugica,Sebastián Muñoz-Guerra

doi:10.3390/polym12010017

Abstract

In this work, we study for the first time, the isothermal crystallization behavior of isodimorphic random poly(butylene succinate)-ran-poly(ε-caprolactone) copolyesters, PBS-ran-PCL, previously synthesized by us. We perform nucleation and spherulitic growth kinetics by polarized light optical microscopy (PLOM) and overall isothermal crystallization kinetics by differential scanning calorimetry (DSC). Selected samples were also studied by real-time wide angle X-ray diffraction (WAXS). Under isothermal conditions, only the PBS-rich phase or the PCL-rich phase could crystallize as long as the composition was away from the pseudo-eutectic point. In comparison with the parent homopolymers, as comonomer content increased, both PBS-rich and PCL-rich phases nucleated much faster, but their spherulitic growth rates were much slower. Therefore, the overall crystallization kinetics was a strong function of composition and supercooling. The only copolymer with the eutectic composition exhibited a remarkable behavior. By tuning the crystallization temperature, this copolyester could form either a single crystalline phase or both phases, with remarkably different thermal properties.

Highlights

Biocompatible and biodegradable polymers are being developed for a wide range of applications due to their potential to solve the environmental concerns caused by traditional nondegradable plastics [1,2,3,4]
We speculate that this may drive the enhancement of nucleation, but more in-depth work, we studied the nucleation kinetics by determining the nucleation density as a function of time studies would be needed to ascertain the exact reason for this behavior
It is clear that the dominant factor to the left of the eutectic point is the is the growth rate, as the results presented in Figures 6a and 7a imply an overall crystallization rate growth rate, asPCL

Summary

Introduction

Biocompatible and biodegradable polymers are being developed for a wide range of applications due to their potential to solve the environmental concerns caused by traditional nondegradable plastics [1,2,3,4]. The properties of crystallizable random copolymers constituted by two semicrystalline parent components have been recently reviewed [12] Depending on their ability to share crystal lattices, three different cases have been reported [12,13,14]: (a) total comonomer exclusion occurs when the chemical repeat units are very different and the crystal lattice of each one of the components cannot tolerate the presence of the other; (b) total comonomer inclusion or isomorphic behavior can only be obtained in cases where the components can cocrystallize in the entire composition range (as their chemical structures are very similar), forming a single crystal structure [15,16]; (c) an intermediate and complex case, where a balance between comonomer inclusion and exclusion occurs, leading to isodimorphic copolymers

Methods

Results

Conclusion