Manufacture of electrospun all-aqueous poly(vinyl alcohol)/cellulose nanocrystal composite nanofibrous mats with enhanced properties through controlling fibers arrangement and microstructure Siqi Huan 1 , Long Bai 1 , Wanli Cheng, Guangping Han * College of Material Science and Engineering, Northeast Forestry University, Harbin 150040, PR China article info Article history: Received 27 January 2016 Received in revised form 8 March 2016 Accepted 26 March 2016 Available online 30 March 2016 Keywords: Cellulose nanocrystals Poly(vinyl alcohol) nanofibers Electrospinning nanocomposite Micromechanical properties abstract Uniform fibers composed of two concentrations of poly(vinyl alcohol) (PVA) separately reinforced with up to 20 wt% cellulose nanocrystals (CNCs) were successfully produced by electrospinning. The CNCs were well dispersed in both 5 wt% PVA (5PVA) and 7 wt% (7PVA) aqueous solution prior to nanofiber manufacture. Composite nanofibers with controllable ultra-thin diameters of around 200 nm were generated reproducibly at all CNC contents investigated, and the nanofiber diameter turned out to be much smaller at higher CNC content. Interestingly, with the same CNC loading, nanofibrous mats pro- duced from 7PVA reinforced with CNC nanoparticles had higher degree of crystallinity than nano- composite with 5PVA as the matrix due to the more orderly stack of 7PVA nanofibers as well as the stronger interactions between PVA molecular chains and CNC nanoparticles. High mechanical perfor- mance nanocomposite fibrous mats were successfully fabricated by electrospinning an all-aqueous system for their potential application in biological field. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Polymer nanocomposites have been a subject of increasing in- terests as part of the development of novel structural and func- tional heterogeneous materials that occur at nanoscale [1,2]. Incorporation of mechanically robust nanoscale fillers, e.g. gra- phene, carbon nanotubes and inorganic nanoparticles, into poly- mer matrices has been widely investigated to fabricate high- performance nanocomposites [3]. Recently, one strong trend is the utilization of renewable or naturally derived nanoscale fillers to develop green nanocomposite materials with diverse advanced functionalities in response to environmental and economical de- mands [4e6]. Cellulose nanocrystals (CNCs), one of the strongest and stiffest natural polymers, are promising green nanofillers to improve the properties and versatility of polymer nanocomposites since they offer a unique combination of desirable properties and environmental benefits [7e10]. CNCs are rod-like, highly crystalline particles that are readily isolated through the controlled acid hy- drolysis of cellulosic materials [11]. The main motivation to develop CNCs as reinforcing agents are their low density, large specific surface area, as well as the ability to act as a significant enhance- ment at low loading levels [12]. Particularly, CNCs are usually used to reinforce the mechanical properties of polymer materials due to their high elastic modulus and mechanical strength obtained from the densely and orderly crystallized structure after acid hydrolysis [13,14]. Furthermore, along with the good biocompatibility, bioac- tivity and non-toxicity of cellulose derivatives [15,16], CNC- reinforced biocomposites can also be widely utilized in the bio- logical fields, e.g., tissue engineering [17]. However, although CNCs have been successfully incorporated into many polymers as effec- tive nanofillers, including poly (lactic acid) [18], poly (ethylene oxide) [19], and poly (vinyl acetate) [20], full exploitation of the intrinsic properties of CNCs to controllably tune and predict the performances of nanocomposites remains to be solved. One-dimension (1D) polymer nanomaterials, especially poly- meric nanofibers, have received growing attentions as a result of their distinct properties and applications superior to their bulk counterparts [21,22]. Electrospinning of polymer solutions or melts is a highly versatile technique that can be used to generate continuous 1D polymeric nanofibers [23], a process of whipping of polymer solutions under electrostatic forces [24]. Owing to their small fiber diameter, high surface-to-volume ratio and controllable porous structures, electrospun nanofibrous mats have been studied for a * Corresponding author. E-mail address: guangping.han@nefu.edu.cn (G. Han). 1 Siqi Huan and Long Bai contributed equally to this work. Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer http://dx.doi.org/10.1016/j.polymer.2016.03.082 0032-3861/© 2016 Elsevier Ltd. All rights reserved. Polymer 92 (2016) 25e35