title: The relevance of molecular weight in the design of amorphous biodegradable polymers with optimized shape memory effect.
abstract: The shape memory effect (SME) has long been the focus of interest of many research groups that have studied many facets of it, yet to the authors' knowledge some molecular parameters, such as the molecular weight, have been skipped. Thus, the aim of this work is to offer further insight into the shape memory effect, by disclosing the importance of the molecular weight as the relevant parameter dictating the extension of the rubbery plateau, which is the scenario where the entropic network of entanglements manifests. For this, a set of biodegradable amorphous poly(rac-d,l)lactides have been synthesised by ring opening copolymerization of a racemic mixture of L-and D-lactide. The analysis performed on the synthesised enantiomeric copolylactides includes the determination of molecular weights by means of Gel Permeation Chromatography (GPC), thermal properties by Differential Scanning Calorimetry (DSC), dynamic mechanical analysis (DMA) and rheological tests using small amplitude oscillatory flow analysis. Shape memory properties have been determined by means of specific cyclic thermo-mechanic test protocol. It has been shown that the recovery capacity of amorphous PDLLA is linked to the disentanglement time through an exponential law.
authors.affiliation: Department of Mining-Metallurgy Engineering and Materials Science, POLYMAT, University of the Basque Country, Alameda de Urquijo s/n, 48013 Bilbao, Spain. Electronic address: susana.petisco@ehu.eus.
authors.forename: S
authors.initials: S
authors.lastname: Petisco-Ferrero
authors.affiliation: Department of Mining-Metallurgy Engineering and Materials Science, POLYMAT, University of the Basque Country, Alameda de Urquijo s/n, 48013 Bilbao, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Fernández
authors.affiliation: Polymer Science and Technology Department, Faculty of Chemistry, POLYMAT University of the Basque Country (UPV/EHU), PO Box 1072, E-20080 Donostia-San Sebastian, Spain.
authors.forename: M M
authors.initials: MM
authors.lastname: Fernández San Martín
authors.affiliation: Polymer Science and Technology Department, Faculty of Chemistry, POLYMAT University of the Basque Country (UPV/EHU), PO Box 1072, E-20080 Donostia-San Sebastian, Spain.
authors.forename: P A
authors.initials: PA
authors.lastname: Santamaría Ibarburu
authors.affiliation: Department of Mining-Metallurgy Engineering and Materials Science, POLYMAT, University of the Basque Country, Alameda de Urquijo s/n, 48013 Bilbao, Spain.
authors.forename: J R
authors.initials: JR
authors.lastname: Sarasua Oiz
mesh_terms: D001672:Biocompatible Materials; D002152:Calorimetry, Differential Scanning; D002850:Chromatography, Gel; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D012212:Rheology
chemical_list: D001672:Biocompatible Materials; D011108:Polymers
keywords: Entanglement network; Glassy polymer; Polylactide; Reptation time; Shape memory