Water resistance of photocrosslinked polyvinyl alcohol based fibers Yurong Liu a , Brian Bolger a , Paul A. Cahill b , Garrett B. McGuinness a, ⁎ a Materials Processing Research Centre, Dublin City University, Glasnevin, Dublin 9, Dublin, Ireland b Vascular Health Research Centre, Dublin City University, Glasnevin, Dublin 9, Dublin, Ireland abstract article info Article history: Received 18 September 2008 Accepted 30 October 2008 Available online 8 November 2008 Keywords: Polymers Photochemical technology Electrospinning Polyvinyl alcohol Styrylpyridinium Electrospinning and photocrosslinking were combined in this study to prepare water-insoluble fibers of polyvinyl alcohol (PVA) with the styrylpyridinium (SbQ) pendent group. The PVA-SbQ exhibited high photosensitivity in a spectroscopic study. Electrospun PVA and PVA-SbQ fibers were soluble and totally dissolved after water immersion. UV irradiation of the electrospun mat led to a significant decrease in the mass loss of PVA-SbQ fibers in water. This water insolubility was confirmed by the stable morphology of PVA- SbQ fibers during water immersion. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Electrospinning is a highly versatile method that can produce fibers on the micro- or nano-scale. Electrospun fiber mats have a large surface-to-volume ratio, tunable porosity, and relatively high produc- tion rates, and possess the potential for use in many technological areas [1,2]. In the biomaterials field, electrospun fibers have been successfully applied in wound dressing, in artificial blood vessels, and as vehicles for controlled drug delivery [3]. Polyvinyl alcohol (PVA), a synthetic polymer, has attracted great attention due to its hydrophilicity, good physical properties, biocom- patibility and chemical resistance [4]. PVA electrospun fibers could potentially have the merits of both the polymer and the nano-fibrous architecture. However, high hydrophilicity contributes to the dissolu- tion of PVA fibers, which limits its application in some areas, especially in biomedical engineering. There have been several studies related to the crosslinking of PVA [5–7]. Gohil et al. [5] crosslinked PVA using maleic acid with heat treatment. Ding et al. [6] crosslinked electrospun PVA/glyoxal fibers by heat treatment. Zeng et al. [7] synthesised a PVA derivative containing thienyl acrylate groups and photocrosslinked PVA-Thio electrospun fibers with UV irradiation. The crosslinked PVA in these studies showed less water solubility than non-crosslinked PVA. Another PVA derivative, PVA with pendent styrylpyridinium groups (SbQ), has been widely used as a photocrosslinkable material due to its water stability, high photosensitivity and good storage stability [8]. The photocrosslinking behaviour and mechanism of PVA- SbQ have been systematically investigated by Ichimura et al. [8,9], Shindo et al. [10–12] and Cockburn et al. [13]. The SbQ pendant groups undergo [2+2]-cycloaddition reactions which crosslink the PVA backbones (Fig. 1). The present study is the first to use PVA-SbQ as a photocrosslinkable polymer to prepare water-insoluble electrospun fibers. PVA-SbQ fibers were fabricated by the electrospinning process and then photocrosslinked with UV irradiation. The photoactivation, water resistance, and morphology of PVA-SbQ fibers were investigated in this study. 2. Experimental 13.3% PVA-SbQ (Mw= 45,000 and 4.1 mol% SbQ content) was purchased from Polysciences, Inc. PVA (Mw = 89,000–98,000 and 99 + % hydrolyzed) was purchased from Sigma-Aldrich, Inc. 10% PVA solution was prepared by dissolving PVA powder in distilled water and heating at 121 °C for 1 h. The prepared 10% PVA and 13.3% PVA-SbQ solutions were then transferred into a syringe equipped with a 19 gauge stainless blunt needle and infused at 0.35 ml/h with a syringe pump. A positive bias of 19 kV is applied to the needle. The collector position is 10 cm away from the needle. Electrospinning of PVA SbQ was conducted in a dark room. The electrospun PVA-SbQ was then irradiated by a 100-W UV lamp (B-100AP, UVP, Ireland) for 20 min. The PVA-SbQ fibers before and after irradiation were named as PVA-SbQ and PVA- SbQ-hv , respectively. The photoactivation of PVA-SbQ was evaluated by a UV–VIS spectrophotometer (Shimadzu UV-3100, Japan). The 13.3% PVA-SbQ was diluted to 3.3% and 10%, and then their UV absorbencies were measured in a UV disposable plastic cuvette (Fisher Scientific, Ireland). Distilled water was used as a control. The water solubility of PVA, PVA-SbQ and PVA-SbQ-hv fibers was studied by mass loss measurement. The fibers were immersed in 37 °C distilled water for 5 days. All samples were vacuum dried before Materials Letters 63 (2009) 419–421 ⁎ Corresponding author. Tel.: +353 1 7005423; fax: +353 1 7005345. E-mail address: garrett.mcguinness@dcu.ie (G.B. McGuinness). 0167-577X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2008.10.060 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet