Zhanxiong Li

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Organization: Soochow University

Department: National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering

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Chemicals
References

Self-assembled perfluoroalkylsilane films on silicon substrates for hydrophobic coatings

Co-reporter:Lu Cai, Anqi Liu, Yanhua Yuan, Li Dai, Zhanxiong Li

Progress in Organic Coatings 2017 Volume 102(Part B) pp:247-258

Publication Date(Web):January 2017

DOI:10.1016/j.porgcoat.2016.10.022

•Silicon substrates with hydrophobic coatings were prepared by self-assembled perfluoroalkylsilane films.•Assembling time has a great effect on the surface properties of self-assembled films.•Annealing process facilitated the migration of fluoroalkyl groups to the outmost surface.•Triazole group is somewhat helpful to the regular arrangement of fluoroalkyl chains.•Two fluoroalkyl groups packing densely in one molecule resulted in lower surface free energy.In this work, four novel perfluoroalkylsilanes were included to fabricate hydrophobic coatings on silicon substrates by the method of self-assembled films. The surface chemical compositions and structures of self-assembled perfluoroalkylsilane films were analyzed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectrometer, and results showed that perfluoroalkylsilane molecules have uniformly assembled onto the surface of hydroxylated silicon substrate successfully. Water contact angles and surface free energy were tested to characterize the surface wettability of self-assembled perfluoroalkylsilane films. Results showed that the self-assembled bisfluorooctyltrichlorosilane film with annealing process (BPFOTS-Si-heat) had the highest water contact angle as 117.6 ± 0.9° and hexadecane contact angle as 76.7 ± 1.3°. This may be attributed to the incorporation of two longer perfluoroalkyl groups into the silane molecule. On the other hand, annealing process also contributed much to improve the hydrophobicity of self-assembled films. The adhesive force of annealed self-assembled perfluoroalkylsilane films was lower than that of untreated ones. Dynamic contact angle measurement showed that the BPFOTS-Si-heat had the smallest water contact angle hysteresis (14 ± 2°) and hexadecane contact angle hysteresis (10 ± 2°). Surface morphology of self-assembled films with different assembling time was obtained through atomic force microscopy, and the surface was found to be gradually covered by dense sharp peaks with the extension of assembling time.

A facile strategy for fabricating PCL/PEG block copolymer with excellent enzymatic degradation

Co-reporter:Haipeng Wang, Dejin Tong, Lei Wang, Lei Chen, Na Yu, Zhanxiong Li

Polymer Degradation and Stability 2017 Volume 140(Volume 140) pp:

Publication Date(Web):1 June 2017

DOI:10.1016/j.polymdegradstab.2017.04.015

Poly(ω-caprolactone) (PCL) has been the focus in many research initiatives, especially regarding various ways though which to introduce reactive sites to the polyester chains. In this work, hydroxyl groups were covalently introduced into the chain of PCL by reacting ester groups with 6-amino-1-hexanol. Poly(ethylene glycol) (PEG) was crosslinked to the PCL chain through esterification, by using N,N’-carbonyldiimidazole (CDI) as catalyst. The prepared PCL-PEG copolymers were characterized by various analytical techniques such as Fourier transform infrared spectroscopy (FT-IR), 1H NMR and X-ray photoelectron spectroscopy (XPS). Static water contact angles measurement indicated that hydrophilicity of the copolymer films modified by PEG has improved considerably. The copolymer films were prepared by casting the polymer solution onto a stainless plate. The degradation of the copolymer samples, in a phosphate buffer solution containing a type of Lipase (Aspergillus Oryzae), was observed at different time intervals. The results of weight loss ratio, during the degradation process, indicated that blocking PEG chains onto the PCL chains can effectively accelerate the process of enzymatic degradation of the resulting copolymer. The changes in molecular weight of the copolymer films were investigated by Gel Permeation Chromatography (GPC) and the copolymers were characterized by 1H NMR during degradation. Surface morphology of PCL and PCL-PEG polymers, before and after degradation, was observed by Scanning electron microscopy (SEM), and emphasized that the enzymatic degradation of PCL-PEG copolymers occurred faster by comparison with PCL, starting from the surface layer of the films.

Coating of poly(carborane-carbosilane-phenylacetylene) on carbon fibers with excellent oxidation protection

Co-reporter:Dejin Tong, Haipeng Wang, Lei Wang, Lei Chen, Zhanxiong Li

Surface and Coatings Technology 2017 Volume 319(Volume 319) pp:

Publication Date(Web):15 June 2017

DOI:10.1016/j.surfcoat.2017.04.014

•Poly(carborane-carbosilane-phenylacelene) was synthesized according to Grignard reaction mechanism.•The precursor polymer can provide a protective barrier via PIP process.•Heating pre-treatment has a great effect on the formation of the ceramic coatings.•The mechanism of thermo-oxidative stability was analyzed.Linear carborane-carbosilane-phenylacetylene co-polymer has been synthesized as precursor for thermosets and ceramics for the protection of carbon fibers from oxidation in an oxidizing environment. The novel linear co-polymers can be processed conveniently and converted into thermoset or ceramics since they are either liquids or low melting solids at room temperature and are soluble in most organic solvents. Treatment of carbon fibers with poly(carborane-carbosilane-phenylacetylene) by precursor infiltration and pyrolysis (PIP) process can provide a protective barrier at elevated temperatures. Tensile strength measurement revealed that the coated carbon fiber maintained 81.39% of its original strength. It was found that the novel co-polymer is highly efficient in protecting the carbon fibers from oxidation breakdown when used as a matrix material (ceramic). Boron and CC group appear to be the key to the unique oxidative stability of the composite compositions. The derived ceramic coatings on carbon fibers were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Anti-oxidation studies were performed by thermogravimetric analyses (TGA). The results showed that the oxidation resistance of carbon fibers has been promoted obviously by the ceramic coatings.Download high-res image (126KB)Download full-size image

Synthesis of novel polymethacrylates with siloxyl bridging perfluoroalkyl side-chains for hydrophobic application on cotton fabrics

Co-reporter:Lu Cai, Li Dai, Yanhua Yuan, Anqi Liu, Li Zhanxiong

Applied Surface Science 2016 Volume 371() pp:453-467

Publication Date(Web):15 May 2016

DOI:10.1016/j.apsusc.2016.03.010

Highlights

•: Novel polymethacrylates with multi-perfluoroalkyl groups were reported.
•: TFSMA monomer in the polymer contributed much to the lower surface free energy.
•: PSD and TEM showed a broader size distribution with the increasing fluorine content.
•: EDS and XPS revealed migration of perfluoroalkyl chains under high temperature.

Self-assembled monolayers of perfluoroalkylsilane on plasma-hydroxylated silicon substrates

Co-reporter:Lin Wu, Lu Cai, Anqi Liu, Wei Wang, Yanhua Yuan, Zhanxiong Li

Applied Surface Science 2015 Volume 349() pp:683-694

Publication Date(Web):15 September 2015

DOI:10.1016/j.apsusc.2015.05.073

Highlights

•: A novel kind of fluoroalkylsilane monomers with different fluoroalkyl chain length was synthesized.
•: The fluoroalkyl-terminated self-assembled monolayers (SAMs) on silanol-terminated silicon substrates were chemically fabricated using the liquid phase deposition method.
•: Fluoroalkylsilanes were used for the self-assembly rather than the silane coupling agents and fluorochemicals to fabricate controllable, ordered SAMs.
•: The angle-dependent XPS study was conducted to investigate the changes of surface structures as well as elemental compositions of the SAMs.
•: The results indicated that fluoroalkyl groups would migrate from the inner part of the monolayers to the outermost interface after heat treatment, resulting into the microphase separation of the SAMs surface.

Synthesis and surface properties of novel fluoroalkylsilyl methacrylate copolymers

Co-reporter:Lu Cai, Zhanxiong Li

Journal of Fluorine Chemistry 2015 Volume 178() pp:187-194

Publication Date(Web):October 2015

DOI:10.1016/j.jfluchem.2015.07.026

•Silyl was introduced as bridging group to construct MFSA, BFSA and TFSA monomers.•Increasing fluorinated monomers in emulsion polymerization affected emulsion stability.•TFSA monomer in the copolymer contributed much to the lower surface free energy.•Thermal migration of fluoroalkyl chains improved the surface roughness.The syntheses of novel mono(1H,1H,2H,2H-tridecafluorooctyl) dimethylsilylpropyl methacrylate (MFSA), bis(1H,1H,2H,2H-tridecafluorooctyl)methylsilylpropyl methacrylate (BFSA) and tris(1H,1H,2H,2H-tridecafluorooctyl)silylpropyl methacrylate (TFSA) were achieved in two steps each in good yields. These fluoroalkylsilyl methacrylate monomers (MFSA, BFSA and TFSA) readily reacted with methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA) to form their corresponding fluoroalkysilyl methacrylate copolymers via continuous emulsion polymerization. The structures of fluoroalkylsilyl methacrylate monomers and copolymers were characterized by FT-IR, 1H NMR, 13C NMR and 19F NMR. The stability of copolymer emulsions was determined by measuring their particle size and zeta potential, and the thermal stability of copolymers was also evaluated by using thermo-gravimetric analysis. In addition, it was observed that improving fluorine content, increasing the packing density of fluoroalkylsilyl segments, and annealing process could enhance the excellent water and oil repellency of fluoroalkylsilyl methacrylate copolymers. The surface free energies of copolymer films were calculated. Moreover, an enrichment of fluoroalkyl chains at the copolymer surface was directly verified by measuring contact angles and using atomic force microscopy.In this paper, mono(1H,1H,2H,2H-tridecafluorooctyl)dimethylsilylpropyl methacrylate, bis(1H,1H,2H,2H-tridecafluorooctyl)methylsilylpropyl methacrylate and tris(1H,1H,2H,2H-tridecafluorooctyl)silylpropyl methacrylate monomers were synthesized via hydrosilylation and Grignard reaction. These monomers were employed in continuous emulsion polymerization with other acrylic monomers to obtain corresponding copolymers. Subsequently the properties of the copolymer films were examined by using thermal analysis, contact angle measurements, and atomic force microscopy.

Preparation of fluoroalkylsilyl polymethacrylates and their waterproof application on cotton fabrics

Co-reporter:Lu Cai

Fibers and Polymers 2015 Volume 16( Issue 10) pp:2094-2105

Publication Date(Web):2015 October

DOI:10.1007/s12221-015-5505-5

Three novel fluoroalkylsilyl polymethacrylates, namely mono(fluoroalkyl)silyl polymethacrylate (PMFSA), bis(fluoroalkyl)silyl polymethacrylate (PBFSA) and tris(fluoroalkyl)silyl polymethacrylate (PTFSA), were synthesized via emulsion polymerization in this study. Subsequently, those fluoroalkylsilyl polymethacrylates were applied onto the surface of cotton fabric to make the fabric water-repellent. Particle size, zeta potential and transmission electron microscopy (TEM) were employed to analyze the emulsion stability and particle morphology. The surface properties of the coated cotton fabrics were confirmed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Thermal properties of fluoroalkylsilyl polymethacrylates and coated cotton fabrics were evaluated by thermal gravity analysis (TGA). Contact angle measurement (CA) demonstrated that the incorporation of more fluorinated segments into the fluoroalkylsilyl methacrylate comonomer molecule and increasing fluorine content can improve the water repellency of treated cotton fabrics. In addition, the fabric’s washing durability was found to be prominent. Even after 15 household machine washes, the water contact angles could be maintained as 132.7 °, 133.9 ° and 128.9 °, respectively.

Bilayered vascular grafts based on silk proteins

Co-reporter:Shanshan Liu, Chaofei Dong, Guozhong Lu, Qiang Lu, Zhanxiong Li, David L. Kaplan, Hesun Zhu

Acta Biomaterialia 2013 Volume 9(Issue 11) pp:8991-9003

Publication Date(Web):November 2013

DOI:10.1016/j.actbio.2013.06.045

Abstract

A major block in the development of small diameter vascular grafts is achieving suitable blood vessel regeneration while minimizing the risk of thrombosis, intimal hyperplasia, suture retention, and mechanical failure. Silk-based tubular vessels for tissue engineering have been prepared by molding, dipping, electrospinning, or gel spinning, however, further studies are needed to improve the mechanical and blood compatibility properties. In the present study a bilayered vascular graft based on silk fibroin (SF) was developed. The graft was composed of an inner silk fiber-reinforced SF tube containing heparin and a highly porous SF external layer. Compared with previously fabricated SF tubes the fiber-reinforcement provided a comparable or higher mechanical strength, burst pressure, and suture retention strength, as well as mechanical compliance, to saphenous veins for vascular grafts. Heparin release was sustained for at least 1 month, affording blood compatibility to the grafts. The outer layer of the grafts prepared through lyophilization had a highly porous structure in which the macropore walls were composed of nanofibers similar to extracellular matrix, which offered an excellent environment for cell growth. In vitro studies showed good cytocompatibility and hemocompatibility.