Browsing by Subject "Main-chain polybenzoxazines"

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Open Access
Main-chain polybenzoxazine nanofibers via electrospinning
(Elsevier, 2014-01-30) Ertas, Y.; Uyar, Tamer
Here we report the successful production of nanofibers from main-chain polybenzoxazines (MCPBz) via electrospinning without using any other carrier polymer matrix. Two different types of MCPBz (PBA-ad6 and PBA-ad12) were synthesized by using two types of difunctional amine (1,6-diaminohexane and 1,12-diaminododecane), bisphenol-A, and paraformaldehyde as starting materials through a Mannich reaction. 1H NMR and FTIR spectroscopy studies have confirmed the chemical structures of the two MCPBz. We were able to obtain highly concentrated homogeneous solutions of the two MCPBz in chloroform/N,N-dimethylformamide (DMF) (4:1, v/v) solvent system. The electrospinning conditions were optimized in order to produce bead-free, uniform and continuous nanofibers from these two MCPBz by varying the concentrations of PBA-ad6 (30–45%, w/v) and PBA-ad12 (15–20%, w/v) in chloroform/DMF (4:1, v/v). The bead-free fiber morphology was evidenced under SEM imaging when PBA-ad6 and PBA-ad12 were electrospun at solution concentration of 40% and 18% (w/v), respectively. The nanofibrous mats of MCPBz were obtained as free-standing material, yet, PBA-ad12 mat was more flexible than and PBA-ad6 mat. Furthermore, the curing studies of these MCPBz nanofibrous mats were performed to obtain cross-linked materials.
Open Access
Polybenzoxazine-based nanofibers by electrospinning
(Elsevier Inc., 2017) Ertaş, Yelda; Uyar, Tamer; Ishida, H.; Froimowicz, P.
In this chapter recent progress in the production of polybenzoxazine-based nanofibrous mats by electrospinning is highlighted. The benzoxazine monomers could easily form thermosetting polybenzoxazines by in situ thermally initiated ring-opening polymerization, hence, they are promising materials for both the surface modification of polymeric nanofibrous mats and the production of polybenzoxazine-based composite nanofibers. After curing, polybenzoxazines provide hydrophobic characteristic for the modified polymeric nanofiber surfaces by in situ polymerization of the benzoxazines because of their highly cross-linked structure. Also, they allow for the further functionalization of the surfaces as superhydrophobic and superleophilic by the incorporation of SiO2 nanoparticles into the benzoxazine solution. In addtion, benzoxazine monomers could be directly added into electrospinning solutions and the thermal curing of the obtained nanofibrous mat could yield hydrophobic composite nanofibers. Moreover, because of outstanding properties, such as near-zero volumetric change upon curing, low water absorption, high glass transition temperature, high char yield, and no by-products without any catalysts during curing, polybenzoxazines are good a candidate as a precursor for the production of carbon nanofibers. In addition, the molecular structure of polybenzoxazines facilitates immense design flexibility, which enables the tailoring of the properties of the cured material. Therefore, suitable polybenzoxazines can be synthesized, and cross-linked polybenzoxazine nanofibers, with enhanced thermal and mechanical properties, can be obtained by electrospinning without the blending of other polymers. By combining the unique properties of nanofibers and the facinating properties of polybenzoxazines, highly cross-linked polybenzoxazine-based nanofibrous mats can be obtained and these materials are quite useful, especially in filtration applications. © 2017 Elsevier Inc. All rights reserved.