A new way to nanostructure hydrogels: Electrospun Thermo-responsive Islands-in-the-Sea Nanofibres
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A new way to nanostructure hydrogels: Electrospun Thermo-responsive Islands-in-the-Sea Nanofibres Jing Wang, Alessandra Sutti, Xungai Wang and Tong Lin Institute for Technology Research and Innovation, Deakin University, 75 Pigdons Rd, Waurn Ponds, VIC 3216, Australia ABSTRACT An effective strategy to produce thermo-responsive islands-in-the-sea hydrogel nanofibres was developed using a single needle electrospinning setup. The produced hydrogel nanofibre mats not only showed excellent temperature response and high response speed, but also showed nanostructured surfaces. INTRODUCTION Stimuli-responsive hydrogel nanofibers are lately receiving increased levels of attention, due to their “smart response” to external stimuli [1-4]. Characterised by large surface area and fast response thanks to the small polymer domains [5], stimuli-responsive hydrogel nanofibres have typically poor mechanical properties. In an effort to overcome this limitation, reinforced hydrogel nanofibres have been investigated in literature [6-11]. Reinforcement strategies which have shown good potential include: the integration of functional nanoparticles in the polymer solution to be electrospun, the use of interpenetrating polymer networks, the use of copolymers[12], which chain is composed of stimuli-responsive and other units which provide reinforcement, the use of blends of stimuli-responsive and reinforcing polymers[13]. These strategies are compatible with single-needle electrospinning setups, but can result in materials in which a compromise is reached between the extent and rate of the response to external stimuli and the structural and mechanical properties (due to the interpenetration of the polymer domains at the molecular level). In addition to the above-mentioned strategies, the co-axial electrospinning of multicomponent nanofibres is a valid reinforcement approach, which also constitutes a means to produce nanostructured nanofibres. Typically, two polymer solutions are co-electrospun through specialized spinnerets, which keep the polymer flows unmixed[14]. In the resulting fibres, the domains of one polymer (e.g. stimuli-responsive) are physically separated from the domains of the second (e.g. reinforcing) polymer. The most common electrospinning configurations include side-by-side[14] and sheath–core[13], while “islands-in-the-sea”[15], citrus fibres, segmentedpie, etc are more rare. The separation of polymer domains ensures high control over the composition of the hydrogel, without having to compromise on their response speed, as with the previously mentioned approaches. Nonetheless, co-axial electrospinning typically requires specialized spinnerets and a high level of control on the flow rate of the two polymer solutions[16]. In this work stimuli-responsive hydrogel nanofibres with a particular multi-domain morphology (islands-in-the-sea) were produced using a single-needle electrospinning setup, in the absence of specialized spinnerets, combining the advantages of the reinforcement approaches explained above. With the aim to pr
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