•A nanofibrous membrane of fluorinated hyperbranched PU was prepared.•High fluorine content was achieved on fluorinated PU membrane surface.•Superhydrophobicity with high adhesion to water was fabricated by electrospinning.The fluorination of hyperbranched polyurethane (HPU) was achieved by atom transfer radical grafting polymerization (ATRgP) of dodecafluoroheptyl methacrylate that was initiated from 2-bromoisobutyryl bromide-modified end groups of HPU. The nanofibrous membrane of fluorinated HPU was prepared by electrospinning. The structure of fluorinated HPU was characterized by Fourier-transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectrum (1H NMR). The surface of nanofibrous membrane was investigated with scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) analysis, respectively. The results suggested that compared with the reported linear fluorine-containing polyurethane materials, rather high fluorine content up to 29.14% was achieved on the surface of fluorinated HPU nanofibrous membrane. Meanwhile, a superhydrophobic surface (WCA 159.7°) with high adhesion to water was successfully fabricated via a convenient electrospinning process. The prepared material is promising for the application in microfluidic devices.Graphical abstract

The hydrophobic surface modification of chitosan gels was carried out using the amidating reaction of amido groups on a gel surface with stearic acid activated by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Lipases from Candida rugosa were adsorbed on the nascent chitosan gels (CS) and stearyl-modified gels (SCS) with different degrees of amidation. The increased surface hydrophobicity of chitosan gels improved the adsorption capacity and activity of the immobilized lipase. SCS with 31.46% amidation showed the maximum activity retention (83.43%). The experimental results suggest that the moderate surface hydrophilicity/hydrophobicity of chitosan gels is necessary for the improvement of the activity of immobilized lipase.