Aliphatic/aromatic copolyesters containing biobased u-hydroxyfatty acids: Synthesis and structureeproperty relationships Annamaria Celli a, * , Paola Marchese a , Simone Sullalti a , Jiali Cai b , Richard A. Gross b, * a Department of Civil, Environmental and Materials Engineering, University of Bologna, Via Terracini 28, 40131 Bologna, Italy b Center for Biocatalysis & Bioprocessing of Macromolecules, Polytechnic Institute of NYU, Six MetroTech Center, Brooklyn, NY 11201, USA article info Article history: Received 9 March 2013 Received in revised form 27 April 2013 Accepted 1 May 2013 Available online 28 May 2013 Keywords: u-Hydroxyfatty acid Biobased copolyesters Thermo-mechanical properties abstract A family of unique aliphaticearomatic copolyesters was prepared by bulk condensation co- polymerizations of bio-derived u-hydroxytetradecanoic acid (H) with 1,4-butanediol (B) and dimethyl terephthalate (DMT). 1 H NMR analysis showed the copolyesters have random repeat-unit sequence distributions. Thermal properties strongly depend on molar composition. Melting temperatures are lower than 70  C for compositions rich in H-units; T m varies from about 140 to 180  C for copolymers with high butylene terephthalate (BT) content. Crystal lattice structures shift from the crystal phase of poly(u-hydroxytetradecanoate) (PH) to that of PBT with increasing BT copolymer content, while the minor component is trapped in the crystallizable domains as defects. The amorphous phase is homo- geneous for all compositions and T g increases from 21  C (PH homopolymer) to 61  C (PBT). Also, mechanical properties vary in a continuous way, according to copolymer composition. Therefore, the combination of aliphatic and aromatic units enables molecular design of partially biobased materials with adjustable thermal and physicalemechanical properties. Thus, by judicious selection of copolymer composition, material properties can be fine-tuned to attain the desired balance of material rigidity, ductility, melting point and biobased content. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Strong drivers exist for commercial, government and academic scientists and engineers to develop next-generation biobased al- ternatives to petroleum-derived plastics [1e3]. These drivers include, but are not limited to environmental pollution, climate change and a finite global supply of fossil fuel that is subject to disruptive price fluctuations. Important fundamental and applied research is focused on developing ‘new to the world’ as well as ‘drop in’ replacements for current petroleum based plastics. New to the world biobased plastics must offer physical properties that are unique, superior or at least on par with existing materials while being cost-competitive [4,5]. Biobased and petroleum-derived aliphatic polyesters can lead to useful materials that also provide the property of biodegradability [6]. Important examples include poly(ε-caprolactone) [7], microbial polyesters or polyhydroxylalkanoates (PHAs) [8,9], poly(lactic acid) (PLA) [10,11], poly(butylene succinate) [12]. These polymers are all commercially available and offer useful properties. However, for reasons that are well understood, the market penetration of these aliphatic polyesters has been limited [6]. For example, PLA suffers from poor hydrolytic stability that limits its shelf life; it also has inadequate impact strength and a low heat distortion temperature [13,14]. PCL has excellent ductility, but has low melting point (about 60  C) and poor strength (low modulus). PHAs vary in structure but generally are expensive and require improvement in melt strength and crystallization rates [15]. A unique family of aliphatic biodegradable polyesters have emerged that share structural and physical characteristics highly valued by polyethylene manufacturers and users. These polyesters have long methylene (e(CH 2 ) x e) sequences separated by ester groups. The PE-like character of such polymers will depend on the length of e(CH 2 ) x e units [16,17]. Elegant chemical approaches have been developed to prepare bifunctional building blocks with e(CH 2 ) x e units from readily renewable vegetable oils [1,5,18]. Important examples of these methods include the use of metath- esis [19e21], thiol-ene reactions [22,23], methoxycarbonylation [24,25], ozonolysis and reduction [26] chemistries. However, these * Corresponding authors. E-mail address: rgross@poly.edu (R.A. Gross). Contents lists available at SciVerse ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymer.2013.05.007 Polymer 54 (2013) 3774e3783