Polymer Chemistry View Article Online PAPER View Journal Structure/property relationships in copolymers comprising renewable isosorbide, glucarodilactone, Cite this: DOI: 10.1039/c7py00575j and 2,5-bis(hydroxymethyl)furan subunits† Leon M. Lillie, William B. Tolman * and Theresa M. Reineke * Carbohydrates and their derivatives have great potential as building blocks for the development of renew- able materials that are cost and performance competitive with conventional petroleum-based materials. D7ZLQ&LWLHVRQ To this end, the rigid carbohydrate-derived diols, glucarodilactone and isosorbide were functionalized with a castor oil derivative, 10-undecenoic acid, forming α,ω-dienes suitable for acyclic diene metathesis (ADMET) polymerization. Equimolar copolymerizations of these two monomers, glucarodilactone undecenoate (GDLU) and isosorbide undecenoate (GDLU), transform brittle homopolymers into elastic materials with shape memory capabilities. To understand the source of these properties, a series of copolymers consisting of a range of GDLU and IU compositions (100 : 0, 77 : 23, 76 : 24, 52 : 48, 48 : 52, 18 : 82, 0 : 100 mol percent GDLU to IU) was synthesized. The material and chemical properties were characterized by uniaxial tensile testing, small-amplitude oscillatory shear rheology, X-ray scattering and hydrolytic degradation testing. Small compositional changes in this family were shown to have a drastic impact on the observed mechanical performance and degradability of these materials. Rheological measurements of GDLU-containing copolymers found evidence for the presence of transient networking within these materials. We posit that the transient network within this material is responsible for the elasticity and shape memory abilities of the GDL-containing materials. In confirmation of these properties, Received 6th April 2017, anovelα,ω-diene 2,5-bis(hydroxymethylfuran) undecenoate (BHMFU) was developed and served as a Accepted 11th May 2017 direct replacement for either GDLU or IU in copolymerizations. The replacement of GDLU resulted in a DOI: 10.1039/c7py00575j total loss of the elasticity and shape memory of the copolymers, supporting the role of GDLU in the rsc.li/polymers mechanical performance. 3XEOLVKHGRQ-XQH'RZQORDGHGE\8QLYHUVLW\RI0LQQHVRW Introduction sorbides and examined as adhesives.9 Incorporation of iso- sorbide facilitates polymers and blocks within these structures 3,6–10 Polyesters have attracted widespread attention due to their with high glass transition temperatures (Tg). tunable mechanical properties and potential susceptibility to In previous work, we have focused on incorporating a less- 1–4 hydrolytic degradation. Obtaining polyesters from novel bio- studied structural analog of isosorbide, D-glucaro-1,4:6,3-di- derived monomers is of great interest to meet consumer lactone (GDL, Scheme 1) into polyesters.11 Previous reports demands for high-performance and sustainable materials.5 exploring GDL have been limited to hydroxylated nylons,12,13 Isosorbide, a rigid bicyclic sugar derivative directly derived polyurethanes,14,15 and methacrylate-based thermosets.16,17 – from glucose, has found use in a wide array of materials.6 8 Its The latter work described the formation of a GDL-containing ability to serve as a direct replacement for rigid diols like α,ω-diene (GDLU) through the functionalization of GDL with bisphenol A (BPA) has encouraged its use for step growth poly- the biofeedstock 10-undecenoic acid. This sustainable merizations to create sustainable polycarbonates, polyesters, α,ω-diene and its congener, isosorbide undecanoate (IU), are and polyurethanes.6 Moreover, this structure has been functio- well suited for acyclic diene metathesis (ADMET) polymeriz- nalized and used to create block polymers with pendant iso- ation, which yielded linear polyesters of moderate molecular − weight (30–60 kg mol 1).11 In the case of GDLU, ADMET polymerization allowed for the polymerization chemistry to Department of Chemistry and Center for Sustainable Polymers, University of occur away from the dilactone core, mitigating potential degra- Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431, USA. dation that was observed with conventional condensation E-mail: [email protected], [email protected] 11,15,16 †Electronic supplementary information (ESI) available. See DOI: 10.1039/ polymerization methods. Yet, the reactivity of the intact c7py00575j GDL core served an important function, facilitating degra- This journal is © The Royal Society of Chemistry 2017 Polym. Chem. View Article Online Paper Polymer Chemistry and shape memory properties into this material class, and that these properties are critically dependent on the compo- sition. Herein, we also demonstrate more economical and environmentally-friendly routes for the synthesis of GDLU and IU feedstocks. Experimental Materials Calcium D-saccharate tetrahydrate was obtained from Carbosynth Limited (Compton, Berkshire, UK). D-Glucaro- 1,4:6,3-dilactone was synthesized using previously reported 18 procedures. Deuterated chloroform (CDCl3) was obtained from Cambridge Isotope Laboratories (Tewskbury, MA, USA). 2,5-Bis(hydroxymethyl)furan was purchased from Polysciences Inc. (Warrington, PA, USA). 10-Undecenoyl chloride was D7ZLQ&LWLHVRQ purchased from ACROS Organics, through Fisher Scientific (Pittsburgh, PA, USA). All other reagents were purchased from Sigma-Aldrich (St Louis, MO, USA). The purchased compounds were used directly without further purification. All glassware was oven-dried prior to use. Scheme 1 Synthesis of monomers and polymers. Synthesis conditions: Characterization methods (a) esterification of rigid diols with 10-undecenoic acid, 10-undecenoyl 1H NMR and 13C NMR spectra were obtained in deuterated chloride, or 10-undecenoic acid anhydride, (b) ADMET polymerization chloroform on a Bruker Avance HD-500. 1H NMR spectra were using Grubbs’ second generation catalyst (1.0 mol percent) and 1 mol% methyl 10-undecenoate in toluene (0.33 M) at 80 °C for 16 h under obtained with at least 64 scans with a 5 second acquisition vacuum. time and 10 second delay time. All spectra were referenced to tetramethylsilane (TMS). Polymer molecular weights (Mw, Mn) and dispersities (Đ) were calculated after performing size dation upon exposure of the polymer to strong basic hydrolytic exclusion chromatography (SEC) using an Agilent 1260 Infinity conditions.11,15 Additionally, we showed in preliminary studies instrument with a Wyatt DAWN Heleos II 10-angle light that the thermal and mechanical behavior of these polyesters scattering detector at 662.6 nm and a Wyatt Optilab EX RI vary based on the identity of the building block (IU vs. GDLU, detector. The instrument was setup using Waters Styragel Scheme 1). Notably, we observed elasticity and shape memory HR6, HR4, HR1 columns with a tetrahydrofuran mobile phase −1 3XEOLVKHGRQ-XQH'RZQORDGHGE\8QLYHUVLW\RI0LQQHVRW in the 50 : 50 copolymer of GDLU and IU. at 25 °C with a 1.0 mL min flow rate. Inductively coupled Herein, we present the results of studies aimed at answer- plasma mass spectrometry (ICP-MS) of P(GDLU52-co-IU48)was ing two main questions that arose from our previous work. performed by Robertson Microlit Laboratories. First, how does changing the ratio of GDLU and IU influence Thermogravimetric analysis (TGA) was performed on a TA the thermal, chemical, and mechanical properties of the Instruments Q500 under a nitrogen atmosphere with a heating − ADMET-derived copolymers? To address this question, we syn- rate of 10 °C min 1 using samples of 8–15 mg. Samples were thesized a family of copolymers with varying ratios of GDLU heated from room temperature (RT) to 550 °C. Differential and IU and characterized the analogs through thermo- Scanning Calorimetry (DSC) was performed on a TA gravimetric analysis, differential scanning calorimetry, size- Instruments Q-1000. Samples were tested in hermetically exclusion chromatography, uniaxial extensional testing, hydro- sealed aluminum pans. Each sample was equilibrated to − lytic degradation testing, small-angle oscillatory shear rheol- −50 °C and then heated to 125 °C at a rate of 10 °C min 1. The − ogy, and synchrotron X-ray scattering measurements. Second, samples were then cooled to −50 °C at a rate of −10 °C min 1. − we sought to answer the question: which carbohydrate build- Lastly, the samples were heated to 150 °C at 10 °C min 1. ing block was most important in promoting the elasticity and Glass transition temperatures and melting temperatures were shape-memory abilities observed with this class of materials? measured during the second heating ramp. To address this question, we replaced either GDL or isosorbide Tensile testing was performed on a Shimadzu AFS-X tensile with a different sustainable diol, 2,5-bis(hydroxymethyl)furan tester at room temperature with tensile bars possessing (BHMF), and synthesized the homopolymer of 2,5-bis(hydroxy- approximate gauge dimensions of 10 mm × 4 mm × 0.2 mm. − methyl)furan undecenoate (BHMFU), along with select compo- Samples were each extended at 50 mm min 1 and at least six sitions of BHMFU : GDLU and BHMFU : IU copolymers. We replicate runs were performed for each polymer sample. found that GDLU is responsible for imparting both elasticity Hysteresis testing was performed on the same Shimadzu AFS-X Polym. Chem. This journal is © The Royal Society of Chemistry 2017 View Article Online Polymer Chemistry Paper − tensile tester at 50 mm min 1 to either 67% or 200% strain, allowed to reflux for 2.5 h. The reaction