Sulfonated poly ether ether ketone (SPEEK) was used to fabricate proton exchange membrane (PEM) due to its adaptable proton conductivity. However, PEM cannot simultaneously enhance its conductivity and stability. To solve the problem mentioned above, phosphotungstic acid (HPW) with strong inherent proton conductivity was chosen to add to the SPEEK matrix, but it still faces the leaky problem. NH 2 -UiO-66 (NU6) with a large surface area and chemical stability was synthesized in situ on the surface of polyimide (PI) nanofiber to create NU6@PI nanofiber, which can be used to anchor HPW. Meanwhile, the stability of proton transport channel may be further enhanced by the sandwich structure, which may be advantageous for proton transport. The NU6@PI/SPEEK + HPW-20 exhibited a conductivity of 174.9 mS·cm −1 and a swelling ratio of 19 % at 60 °C and 100 % RH. After 6 weeks of testing, its conductivity decreased to 151.2 mS·cm −1 which was 24 % higher than that of SPEEK, while the swelling ratio increased to 31 % which was lower than that of SPEEK. The outcome demonstrates that the sandwich-structure NU6@PI/SPEEK + HPW membrane may really boost proton conductivity and stability at the same time. By using XPS and TEM, it is possible to confirm the acid-base interaction and acid-rich layer that exist at the interfaces of NU6@PI nanofiber and HPW/SPEEK matrix. After 6-weeks of usage, the sandwich-structure composite membrane with nanofiber at both the top and bottom of PEM can still maintain high proton conductivity and high stability, offering a novel research idea for resolving the issue that PEM cannot simultaneously achieve significant proton conductivity as well as elevated stability.
Li Shaoping,Jia Cancan,Han Haitong,Yang Yuqing,Xiaowen Yundeng,Chen Zhiyu
Background Polyetheretherketone (PEEK) is well known for its excellent physical–chemical properties and biosafety. The study aimed to open up a new method for clinical application of PEEK to reconstruct large-scale bone defects.Methods A bilayer scaffold for bone regeneration was prepared by combining a sulfonated PEEK barrier framework (SPEEK) with a hydrogel layer loaded with aspirin (ASA) and nano-hydroxyapatite (nHAP) by the wet-bonding of Polydopamine (PDA).Results The hydrogel was successfully adhered to the surface of SPEEK, resulting in significant changes including the introduction of bioactive groups, improved hydrophilicity, and altered surface morphology. Subsequent tests confirmed that the bilayer scaffold exhibited enhanced compression resistance and mechanical compatibility with bone compared to a single hydrogel scaffold. Additionally, the bilayer scaffold showed stable and reliable bonding properties, as well as excellent biosafety verified by cell proliferation and viability experiments using mouse embryo osteoblast precursor (MC3T3-E1) cells.Conclusion The bilayer bone regeneration scaffold prepared in this study showed promising potential in clinical application for bone regeneration.
Ning Liu,Shuguang Bi,Ying Ou,Hai Liu,Yi Zhang,Chunli Gong
Proton exchange membranes with high ionic conductivity and good chemical stability are critical for achieving high power density and long lifespan of direct methanol cells (DMFCs). Herein, a zwitterionic molecule was grafted onto the surface of polyvinylidene fluoride (PVDF) nanofibers to obtain functionalized PVDF porous substrate (SBMA-PDA@PVDF). Then, sulfonated poly(ether ether ketone) (SPEEK) was filled into the pores of SBMA-PDA@PVDF, and further ionic cross-linked via H 2 SO 4 to prepare the composite membrane (SBMA-PDA@PVDF/SPEEK). The basic groups on the zwitterionic interface could not only establish ionic cross-linking with SPEEK to increase chemical stability and reduce swelling, but also serve as the adsorption sites for subsequent H 2 SO 4 cross-linking to significantly enhance proton conductivity. Super-high proton conductivity (165.34 mS cm −1 , 80 °C) was achieved for the membrane, which was 2.12 times higher than that of the pure SPEEK. Moreover, the SBMA-PDA@PVDF/SPEEK membrane exhibited remarkably improved oxidative stability of 91.6 % mass retention after soaking in Fenton’s agent for 12 h, while pure SPEEK completely decomposed. Satisfactorily, the DMFC assembled with SBMA-PDA@PVDF/SPEEK exhibited a peak power density of 99.01 mW cm −2 , which was twice as much as that of commercial Nafion 212 (48.88 mW cm −2 ). After 235 h durability test, only 11 % voltage loss was observed.
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