title: A novel shortened electrospun nanofiber modified with a 'concentrated' polymer brush.
abstract: We report the fabrication of shortened electrospun polymer fibers with a well-defined concentrated polymer brush. We first prepared electrospun nanofibers from a random copolymer of styrene and 4-vinylbenzyl 2-bromopropionate, with number-average molecular weightMn=105 200 and weight-average molecular weightMw=296 700 (Mw/Mn=2.82). The fibers had a diameter of 593±74 nm and contained initiating sites for surface-initiated atom transfer radical polymerization (SI-ATRP). Then, SI-ATRP of hydrophilic styrene sodium sulfonate (SSNa) was carried out in the presence of a free initiator and the hydrophobic fibers. Gel permeation chromatography confirmed thatMnandMw/Mnvalues were almost the same for free polymers and graft polymers.Mnagreed well with the theoretical prediction, andMw/Mnwas relatively low (<1.3) in all the examined cases, indicating that this polymerization proceeded in a living manner. Using the values of the graft amount measured by Fourier transform infrared spectroscopy, the surface area, andMn, we calculated the graft density σ as 0.22 chains nm-2. This value was nearly equal to the density obtained on silicon wafers (σ=0.24 chains nm-2), which is categorized into the concentrated brush regime. Finally, we mechanically cut the fibers with a concentrated poly(SSNa) brush by a homogenizer. With increasing cutting time, the fiber length became shorter and more homogenous (11±17 μm after 3 h). The shortened fibers exhibited excellent water dispersibility owing to the hydrophilic poly(SSNa) brush layer.
authors.affiliation: World Premier International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Yoshikawa
authors.affiliation: World Premier International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.affiliation: World Premier International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Ewelina
authors.initials: E
authors.lastname: Zawadzak
authors.affiliation: Bomaterials Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan; CREST, JST, Sanbancho, Chiyoda, Tokyo 102-0075, Japan.
authors.forename: Hisatoshi
authors.initials: H
authors.lastname: Kobayashi
keywords: concentrated polymer brush; electrospinning; fiber cutting; nanofiber; surface-initiated atom transfer radical polymerization