Crystallization and molecular mobility in renewable semicrystalline copolymers based on polycaprolactone and polyisosorbide. Issue 48 (25th November 2022)

• Record Type: Journal Article
• Authors: Bouyahya, Chaima; Bikiaris, Nikolaos D.; Zamboulis, Alexandra; Kyritsis, Apostolos; Majdoub, Mustapha; Klonos, Panagiotis A.
• Is Part Of: Soft matter. Volume 18:Issue 48(2022)
• Page Start: 9216
• Page End: 9230
• Publication Date: 2022-11-25
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/d2sm01198k
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Molecular dynamics and crystallization studies in renewable PCL-PIS block copolymers, assessed by thermodynamical and structural techniques. Abstract : A series of novel block copolymers based on two biodegradable polymers, poly(ε-caprolactone), PCL, and poly(isosorbide), PIS, with PIS fractions 5, 10, and 25 wt%, are studied herein. The aim is to assess the effects of the amorphous PIS phase on the properties of the semicrystalline PCL (majority), in addition to the synthesis strategy. The latter involved the polymerization of caprolactone onto initial PIS of low molar mass, resulting, thus, in gradually shorter PCL blocks when the starting amount of PIS is increased. The structure–property relationship investigation, with an emphasis on molecular mobility and crystallization, involves the following sum of complementary techniques: differential scanning calorimetry, dielectric spectroscopy, polarized optical microscopy and X-ray diffraction. The molecular mobility map for these PCL/PIS and initial PIS is drawn here for the first time. Despite the high glass transition temperature of PIS ( T g ∼ 51 °C) compared to that of PCL (−66 °C), the T g of the copolymers barely changes, as it is mainly ruled by crystallinity. The latter seems to be facilitated in the copolymers, in both the amount and the rate. The local molecular mobility of PCL and PCL/PIS consists of faster γ PCL relaxation which is unaffected in the copolymers, whereas the slower β PCL process arising from the backbone ester group rotation exhibits a systematic deceleration in the presence of PIS. A connection between such local motions and the corresponding segmental α relaxation, observed previously in other polyesters, is also found to be true here. Apart from that, the dielectric T g as well as the cooperativity of the polymer chains drop moderately, which indicates spatial confinement between the PCL crystals, whereas correlations with the looser lamellar chain packing within the spherulites are gained. The relaxations of initial PIS, i.e., γ PIS, β PIS and α PIS, could not be resolved within the copolymers. Along with other properties, such as ionic conductivity, we conclude to the homogeneity of our systems, with sufficient PCL/PIS distribution.