Induced insolubility of electrospun poly(N-vinylcaprolactam) fibres through hydrogen bonding with Tannic acid

Water-insoluble poly(N-vinylcaprolactam) (PVCL) electrospun nanofibres have been prepared for the first time by direct electrospinning with Tannic acid (TA) in apolar protic solvents. The PVCL/TA nanofiber mats have been fabricated through a facile one-step procedure which will increase their potential applications in the biomedical field where material stability in an aqueous environment is crucial. Hydrogen bonding between TA and PVCL resulted in nanofibers that are non-water soluble after drying, and the TA/PVCL interactions were confirmed through rheological and infrared spectroscopy measurements. In addition, the optimal ratio of TA and PVCL essential for the production of uniform, insoluble fibres in the range of hundreds of nanometres was established. The contact angle measurements confirmed that the roughness induced by the fibrous morphology of the TA/PVCL mats resulted in hydrophobic surfaces (CA>120°) from materials that otherwise exhibited hydrophilic behaviour (CA<90°) on flat surfaces. This method of using TA as a crosslinker for direct electrospinning of PVCL fibres requires no chemical modification or complex post-synthesis steps, thus facilitating the potential use of these novel PVCL nanofibers for applications as biomedical scaffolds in aqueous environments.