Electrospinning of plant oil-based, non-isocyanate polyurethanes for biomedical applications Donald C. Aduba, Jr., 1,2 Keren Zhang, 2,3 Akanksha Kanitkar, 2,4 Justin M. Sirrine, 2,3 Scott S. Verbridge, 2,4 Timothy E. Long 2,3 1 Department of Mechanical Engineering, Virginia Tech, Blacksburg Virginia 24061 2 Macromolecules Innovation Institute, Virginia Tech, Blacksburg Virginia 24060 3 Department of Chemistry, Virginia Tech, Blacksburg Virginia 24061 4 Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg Virginia 24061 Correspondence to: T. E. Long (E - mail: telong@vt.edu) ABSTRACT: Non-isocyanate polyurethanes (NIPU) have rapidly emerged as a sustainable, less toxic, and environmentally friendly alternative to traditional isocyanate-based thermoplastic polyurethane (TPU) synthesis. TPU is widely used in the medical industry due to its excellent mechanical properties and elasticity. However, little work has been done to synthesize and electrospin NIPU into fibrous mats for biomedical applications. In this work, melt polymerization of a plant oil-based cyclic carbonate monomer with poly- ether soft segments and various diamines yielded isocyanate-free, segmented poly(amide hydroxyurethane)s (PAHUs). Electrospinning of segmented PAHUs afforded ductile, free-standing fibrous mats with Young’s modulus values between 7 and 8 MPa, suitable for tis- sue scaffold applications. PAHU fiber mats exhibited 3–4 times greater water uptake than the electrospun TPU control, demonstrating potential utility in drug delivery. Fibroblasts adhered to electrospun PAHU fibrous mats with viability values over 90% after 72-h, val- idating its biocompatibility. The results highlight the high performance and potential of electrospun isocyanate-free polyurethanes mats for biomedical application. V C 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46464. KEYWORDS: biomaterials; electrospinning; fibers; polyurethane Received 13 December 2017; accepted 10 March 2018 DOI: 10.1002/app.46464 INTRODUCTION The production of polyurethanes without the use of isocyanates is a significant area of research. 1–5 Conventional thermoplastic poly- urethanes (TPUs) are ubiquitously used as polymers for bedding, packaging, insulation, coating, electronic, and automotive applica- tions. 6–8 The global market size of polyurethane foams was esti- mated at $48.55 billion dollars in 2015. 6 Their high demand is due to their durability, elasticity, and inert properties. Also, they are rel- atively simple to synthesize from reagents that are readily commer- cially available. Traditional TPU synthesis employs polyols (commonly hydroxyl-terminated polyethers), diisocyanates, and chain extenders; the step-growth reaction of these reactants affords polyurethanes or segmented polyurethanes. However, the use of isocyanates poses safety concerns, as they are highly reactive and cause severe damage to the eyes and the respiratory system. 9 TPU synthesis also requires the use of phosgene gas that has harmful effects including death. 9 Thus, non-isocyanate polyurethanes (NIPU) is synthesized as a less toxic alternative that addresses these environmental and health concerns. NIPUs are synthesized by polycondensation, step growth polyaddition, or ring-opening polymerization. 10 NIPU synthesis most commonly employs the ring-opening of cyclic carbonates with primary amines to form hydroxyurethane bonds. 10–14 However, linear NIPUs, while pos- sessing high elongation often do not have sufficient mechanical strength for practical applications and crosslinked NIPU lack pro- cessability. 15 Thus, there is a need to use polymer processing meth- ods to develop NIPU systems that leverage their biocompatibility, mechanical properties, and processability. Electrospinning is a well-established polymer processing tech- nique used to fabricate NIPUs into fibrous meshes. 16 Electrospin- ning is widely used because of its ability to construct micro- scaled fibrous biomaterials from synthetic and naturally derived polymers dissolved in organic solvents. 17 In addition to biomate- rial uses, materials processed by electrospinning enable very recent uses in gas storage, 18 water desalination, 19 energy harvest- ing, 20 and electronics. 21 Successful electrospinning is highly dependent on factors such as chain entanglement concentra- tion, 22 electrical conductivity, 23 and humidity. 24 Polyurethane elastomers are soluble in many organic solvents, enabling the fac- ile preparation of electrospinning solutions. Electrospinning these V C 2018 Wiley Periodicals, Inc. J. APPL. POLYM. SCI. 2018, DOI: 10.1002/APP.46464 46464 (1 of 11)