Biobased Polyesters with Composition-Dependent Thermomechanical Properties: Synthesis and Characterization of Poly(butylene succinate-co-butylene azelate) Rosica Mincheva, Adrien Delangre, † Jean-Marie Raquez, † Ramani Narayan, ‡ and Philippe Dubois †, * † Laboratory of Polymeric and Composite Materials, Center of Innovation and Research in Materials and Polymers (CIRMAP), University of Mons (UMONS), Place du Parc 20, 7000 Mons, Belgium ‡ Department of Chemical Engineering and Materials Science, Michigan State University, 2527 Engineering Building/C-10 Engineering Research Complex, East Lansing, Michigan 48824, United States ABSTRACT: Environmentally friendly poly(butylenesuccinate- co-butyleneazelate) (P(BS-co-BAz)s) aliphatic copolyesters with composition-dependent thermomechanical properties were synthesized from succinic acid (SuA), 1,4-butanediol (BDO), and dimethylazelate (DMAz) through a two-step polyconden- sation reaction. The molar SuA/AzA ratio was varied from 4:1 to 1:4, and the chemical structure and molecular characteristics of resulting (co)polyesters were characterized by NMR and SEC, whereas thermal properties and crystallinity were studied by differential scanning calorimetry (DSC), dynamic mechan- ical thermal analyses (DMTA), and X-ray diffraction (XRD). A good agreement between theoretical and experimental SuA/AzA molar ratios in the copolyesters was achieved, together with the recovery of semicrystalline random copolymers of uniform composition along the chains. NMR, DSC, DMTA, and XRD results show that depending on their composition the P(BS-co-BAz) copolyesters might find applications from elastomers to high-impact thermoplastics. ■ INTRODUCTION During the past two decades, both university and industry have been developing (bio)degradable polymers of annually renew- able origin as an adequate response to the environmental and economic problems associated with the commodity petrochem- ical polymeric materials. 1 Among all, poly(lactic acid) (PLA) is nowadays considered as a valuable biobased alternative of high potentiality. Additionally, another aliphatic polyester, the poly(butylene succinate) (PBS), has gained more importance over the last years because the monomers for its synthesis can now be derived from biomass. 2-4 PBS is obtained through polycondensation reaction of suc- cinic acid (SuA, or its diester) and 1,4-butanediol (BDO) in the presence of titanium(IV)-based catalysts. 3 It was usually considered petro-based as both SuA and BDO were industrially obtained from acetylene, propylene oxide, or maleic anhy- dride. 3,4 Only recently, SuA and BDO were industrially pro- duced through biomass fermentation processes, and PBS became at least partially biobased polyester. 2-4 PBS is characterized by high crystallinity and flexibility, good processability, and considerable strength, and applications are expected in fields like disposable packaging, flushable hygiene products or in agriculture. 5-7 However, tuning the PBS properties is also needed for broadening its range of applications, and copoly- merization appears to offer promising advantages. 4 To date, PBS-based copolymers with various diacids (terephthalic, adipic, lactic, 2,5-furanedicarboxylic, etc. 8-14 ) or diols (ethylene, propylene, hexane 9,12,15 ) monomers have intensively been studied. Another interesting comonomer is azelaic acid (AzA), a C9 dicarboxylic acid. 16-20 AzA has been industrially produced by oxidative cleavage of biobased oleic acid (OA) through ozonolysis 21,22 and can be directly extracted in barley, rye, sorghum, or wheat through an adequate biocatalysis-based process. 23 AzA-based polyamide-6,9 is characterized by low water absorption and high-dimensional stability, 24 and poly- esteramide elastomers were found to have enhanced moduli. 25 Therefore, it seems interesting to incorporate AzA into PBS- based chains for modulating the thermal properties of PBS while targeting biobased and biodegradable copolyesters for environmental concerns. So far, there has been only one study reporting the synthesis of such a copolyester with a SuA/AzA composition equal to 50:50 mol/mol. 26 Moreover, the molar masses of the obtained copolymer were very low, that is, M ̅ W 13 000 g/mol, and unsuitable for any processing technique. Therefore, the present study aims at synthesizing random poly(butylenesuccinate-co-butyleneazelate) (P(BS-co-BAz)) co- polyesters with SuA/AzA molar ratio varied in the whole range via an adapted two-step melt-polycondensation. Copolyesters of desired composition and high molar mass were obtained. Their thermal properties and crystallinity were also studied. Received: December 20, 2012 Revised: January 29, 2013 Article pubs.acs.org/Biomac © XXXX American Chemical Society A dx.doi.org/10.1021/bm301965h | Biomacromolecules XXXX, XXX, XXX-XXX