title: Crystallization and its effect on the mechanical properties of a medium chain length polyhydroxyalkanoate.
abstract: Medium chain length polyhydroxyalkanoates (mcl-PHAs) could play a role in the growing demand for highly elastic and biodegradable materials in the medical field. In this study, a poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (P(3HO-co-3HH)) was first fully characterized in terms of molecular weight, microstructural chain parameters and chemical structure by means of gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR). As determined by NMR, the synthesized polymer contained 94.3% and 5.7% molar content of 3-hydroxyoctanoate and 3-hydroxyhexanoate, respectively. Since mechanical properties are closely related to thermal history, the effect of crystallization on tensile properties was also investigated in the present study. Three crystallization temperatures were selected (0, 23 and 37°C), the conclusion reached is that the maximum crystallization rate for this copolymer was achieved at 0°C. On the other hand, evolution of tensile properties of P(3HO-co-3HH) films stored at room temperature demonstrated that, as crystallization occurred toward the equilibrium state, the polymer underwent a stiffening process. In this sense, secant modulus and tensile strength increased respectively from 8.3 ± 1.0 MPa and 6.4 ± 0.8 MPa after 1 day stored at room temperature to 36.2 ± 3.3 MPa and 16.3 ± 2.1 MPa after 16 weeks.
authors.affiliation: University of the Basque Country (EHU-UPV), Department of Mining-Metallurgy Engineering and Materials Science & POLYMAT, School of Engineering, Alameda de Urquijo s/n, 480130 Bilbao, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Larrañaga
authors.affiliation: University of the Basque Country (EHU-UPV), Department of Mining-Metallurgy Engineering and Materials Science & POLYMAT, School of Engineering, Alameda de Urquijo s/n, 480130 Bilbao, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Fernández
authors.affiliation: University of the Basque Country (EHU-UPV), Department of Mining-Metallurgy Engineering and Materials Science & POLYMAT, School of Engineering, Alameda de Urquijo s/n, 480130 Bilbao, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Vega
authors.affiliation: Department of Polymer Science and Technology, Institute of Polymer Materials, University of the Basque Country (EHU-UPV), M. de Lardizabal 3, 20018 Donostia, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Etxeberria
authors.affiliation: Neol Biosolutions S.A. Avda. de la Innovación 1, 18016 Granada, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Ronchel
authors.affiliation: Neol Biosolutions S.A. Avda. de la Innovación 1, 18016 Granada, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Adrio
authors.affiliation: University of the Basque Country (EHU-UPV), Department of Mining-Metallurgy Engineering and Materials Science & POLYMAT, School of Engineering, Alameda de Urquijo s/n, 480130 Bilbao, Spain. Electronic address: jr.sarasua@ehu.es.
authors.forename: J R
authors.initials: JR
authors.lastname: Sarasua
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry*; D002208:Caproates / Q000737:chemistry*; D002850:Chromatography, Gel; D003460:Crystallization; D004548:Elasticity; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D008970:Molecular Weight; D011091:Polyesters / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011312:Pressure; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013696:Temperature; D013718:Tensile Strength; D013816:Thermodynamics; D000094122:Polyhydroxybutyrates
chemical_list: D020155:3-Hydroxybutyric Acid; D001672:Biocompatible Materials; D002208:Caproates; D011091:Polyesters; D011108:Polymers; C115940:poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); D000094122:Polyhydroxybutyrates
keywords: Crystallization; Hydroxyhexanoate; Hydroxyoctanoate; Mechanical properties; Polyhydroxyalkanoates