In this work, we report on the development of slit-surface electrospinning – a process that co-localizes two solutions along a slit surface to spontaneously emit multiple core-sheath cone-jets at rates of up to 1 L/h. To the best of our knowledge, this is the first time that production of electrospun core-sheath fibers has been scaled to this magnitude. Fibers produced in this study were defect-free (i.e. non-beaded) and core-sheath geometry was visually confirmed under scanning electron microscopy. The versatility of our system was demonstrated by fabrication of (1) fibers encapsulating a drug, (2) bicomponent fibers, (3) hollow fibers, and (4) fibers from a polymer that is not normally electrospinnable. Additionally, we demonstrate control of the process by modulating parameters such as flow rate, solution viscosity, and fixture design. The technological achievements demonstrated in this work significantly advance core-sheath electrospinning towards commercial and manufacturing viability.

ABSTRACT:The development of self-assembled ZnO nanoparticles within a diblock copolymer matrix using wet chemical processing specific to ZnO is reported. Diblock copolymers consisting of polynorbornene and poly(norbornene-dicarboxcylic acid) (NOR/NORCOOH) were synthesized with a block repeat unit ratio of 400 for the first block and 50 for the second block, to obtain spherical microphase separation. The block copolymer self-assembly was used to template the growth of ZnO nanoparticles by introducing a ZnCl 2 precursor into the second polymer (NORCOOH) block at room temperature and processing the copolymer by wet chemical methods to substitute the chlorine atoms with oxygen. X-ray photoemission spectroscopy (XPS) verified the conversion of ZnCl 2 to ZnO by monitoring the disappearance of the Cl 1s peak and the shift in the binding energy of the Zn 2p 3 peak in the high-resolution spectra. The substitution of Cl by O was found to be a highly preferential process, whereby only one approach using a weak base (NH 4 OH) succeeded in effectively replacing Cl with O to result in spherical ZnO nanoparticles having a size ranging from 7 to 15 nm, as determined by transmission electron microscopy. The development of such block copolymer-templated ZnO nanoparticles% is important in enabling the functionalization of large-area nanodevice technologies.

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