Centre for Textile Science and Engineering (CSTE), Department of Materials, Textiles and Chemical Engineering, Faculty of Engineering and Architecture, Ghent University (UGent) , Technologiepark 907, 9052 Ghent, Belgium.
Laboratory for Chemical Technology (LCT), Department of Materials, Textiles and Chemical Engineering, Faculty of Engineering and Architecture, Ghent University (UGent) , Technologiepark 914, 9052 Ghent, Belgium.
ACS Appl Mater Interfaces. 2017 Jul 19;9(28):24100-24110. doi: 10.1021/acsami.7b05074. Epub 2017 Jul 6.
With increasing toxicity and environmental concerns, electrospinning from water, i.e., waterborne electrospinning, is crucial to further exploit the resulting nanofiber potential. Most water-soluble polymers have the inherent limitation of resulting in water-soluble nanofibers, and a tedious chemical cross-linking step is required to reach stable nanofibers. An interesting alternative route is the use of thermoresponsive polymers, such as poly(N-isopropylacrylamide) (PNIPAM), as they are water-soluble beneath their lower critical solution temperature (LCST) allowing low-temperature electrospinning while the obtained nanofibers are water-stable above the LCST. Moreover, PNIPAM nanofibers show major potential to many application fields, including biomedicine, as they combine the well-known on-off switching behavior of PNIPAM, thanks to its LCST, with the unique properties of nanofibers. In the present work, based on dedicated turbidity and rheological measurements, optimal combinations of polymer concentration, environmental temperature, and relative humidity are identified allowing, for the first time, the production of continuous, bead-free PNIPAM nanofibers electrospun from water. More specifically, PNIPAM gelation was found to occur well below its LCST at higher polymer concentrations leading to a temperature regime where the viscosity significantly increases without compromising the polymer solubility. This opens up the ecological, water-based production of uniform PNIPAM nanofibers that are stable in water at temperatures above PNIPAM's LCST, making them suitable for various applications, including drug delivery and switchable cell culture substrates.
随着毒性和环境问题的增加，从水中进行电纺丝，即水基电纺丝，对于进一步挖掘所得纳米纤维的潜力至关重要。大多数水溶性聚合物都存在固有局限性，即只能得到水溶性纳米纤维，并且需要繁琐的化学交联步骤才能得到稳定的纳米纤维。一种有趣的替代方法是使用温敏聚合物，如聚（N-异丙基丙烯酰胺）（PNIPAM），因为它们在低于其低临界溶液温度（LCST）下是水溶性的，允许在低温下进行电纺丝，而所得的纳米纤维在 LCST 以上是水稳定的。此外，PNIPAM 纳米纤维在许多应用领域具有很大的潜力，包括生物医学领域，因为它们结合了 PNIPAM 的众所周知的开/关切换行为，这要归功于其 LCST，以及纳米纤维的独特性质。在本工作中，通过专门的浊度和流变学测量，确定了聚合物浓度、环境温度和相对湿度的最佳组合，首次允许从水中连续、无珠地生产 PNIPAM 纳米纤维。更具体地说，发现 PNIPAM 凝胶化在较高聚合物浓度下远低于其 LCST 发生，导致在不影响聚合物溶解度的情况下，粘度显著增加的温度范围。这为生态友好、基于水的均匀 PNIPAM 纳米纤维的生产开辟了道路，这些纳米纤维在高于 PNIPAM LCST 的温度下在水中稳定，使其适用于各种应用，包括药物输送和可切换的细胞培养底物。
