Investigation of wettability and moisture sorption property of electrospun poly( N -isopropylacrylamide) nanofibers
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Investigation of wettability and moisture sorption property of electrospun poly(N-isopropylacrylamide) nanofibers Anupama Sargur Ranganath, V. Anand Ganesh, Kostiantyn Sopiha, Rahul Sahay, and Avinash Baji* Division of Engineering Product Development, Singapore University of Technology and Design (SUTD), Singapore - 487372. Corresponding Author: [email protected] ABSTRACT Poly(N-isopropylacrylamide) (PNIPAM) has been used extensively for numerous biomedical applications. However, there is not enough information in the literature on the wettability and hygroscopic properties of electrospun PNIPAM fibers, relevant for water harvesting applications. This study focuses on investigating the wettability and hygroscopic properties of electrospun PNIPAM fibers at room temperature and elevated temperature. The wettability properties of electrospun PNIPAM fibers were compared to spin-coated PNIPAM thin films. The wettability properties of the electrospun fibers were enhanced by 56% compared to spin-coated films. Water contact angle (WCA) measured on electrospun fibers was determined to be 137° at elevated temperatures while WCA on spin cast PNIPAM film was determined to be 81° at elevated temperatures. Furthermore, hygroscopic properties of the electrospun PNIPAM fibers were studied using thermogravimetric analysis (TGA). The PNIPAM fibers are seen to exhibit moisture absorption capacity of about 16.6 wt. % under humid conditions. INTRODUCTION Stimuli responsive functional surfaces with switchable properties have attracted huge amount of interest among researchers due to their numerous industrial applications. Some of the applications include self-cleaning surfaces, micro-fluidic tools, tunable optical lenses and lab-onchip systems. [1, 2]. Among all known stimuli-responsive polymers, polymers that respond to temperature stimulus have found widespread applications, as temperature stimulus is easy to apply and monitor externally. Poly(N-isopropylacrylamide) is a well-known thermo-responsive system. It shows a low critical solution temperature (LCST) at around 32 °C in aqueous solution. Below LCST, PNIPAM exhibits hydrophilic property due to extended random coil conformation. Above LCST, it is hydrophobic due to compressed molecular chain conformation. This tunable wettability makes it suitable for various applications such as rheological (enhanced tertiary/oil recovery) and biological (hydrogels for drug delivery) applications [3-8]. PNIPAM fibers are widely considered for numerous applications including drug delivery, immuno-separation, micro-actuators, sensors and membranes. As the fibers can have significant impact on designing, it is essential to know their water sorption properties.
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Water sorption behavior of PNIPAM thin films is widely investigated. However, to the best of our
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