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204 results on '"Wei, Dafu"'

14. Effect of silphenylenesiloxane units on the thermal stability of poly[methyl(trifluoropropyl)siloxane].

Author

You, Yang, Wei, Dafu, Xu, Xiang, Guan, Yong, Chen, Jianding, and Xiao, Huining

Subjects
SILOXANES, THERMAL stability, FOURIER transform infrared spectroscopy, GEL permeation chromatography, NUCLEAR magnetic resonance, POLYCONDENSATION
Abstract

A series of poly[methyl(trifluoropropyl)siloxane‐co‐silphenylenesiloxane] (PMTFPS‐co‐SPS) was synthesized by condensation polymerization of methyltrifluoro‐propylsiloxanediol and 1,4‐bis(dimethylsilyl)benzene. Their chemical structures were investigated using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and dynamic thermomechanical analysis (DMA). The effect of silphenylenesiloxane (SPS) units on the thermal stability of poly[methyl(trifluoropropyl)siloxane] (PMTFPS) was studied by thermogravimetric analysis (TGA), isothermal degradation tests, quantum chemical calculation, and pyrolysis‐gas chromatography–mass spectrometry (Py‐GCMS). The results showed that the thermal stability of PMTFPS improved with the introduction of SPS units into the backbone. The temperature for 5% mass loss in PMTFPS increased by 63°C under a nitrogen atmosphere. Additionally, the mechanism by which the SPS units improve the thermal stability of PMTFPS was also investigated. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Transparent, High-Strength, and Antimicrobial Polyvinyl Alcohol/Boric Acid/Poly Hexamethylene Guanidine Hydrochloride Films.

Author

Zhang, Shaotian, Wei, Dafu, Xu, Xiang, and Guan, Yong

Subjects
GUANIDINIUM chlorides, BORIC acid, POLYVINYL alcohol, CYCLOHEXANE, HYDROGEN bonding interactions, TENSILE strength
Abstract

It is still crucial to improve the mechanical characteristics of polyvinyl alcohol (PVA) films without resorting to chemical cross-linking. In this study, boric acid (BA) was used to enhance the mechanical characteristics of PVA films while maintaining their excellent transparency and biodegradability. The hydrogen bond interaction between PVA and BA resulted in a 70% increase in tensile strength (from 48.5 to 82.1 MPa) and a 46% increase in elongation at break (from 150 to 220%). To introduce antibacterial properties, polyhexamethylene guanidine hydrochloride (PHMG) was incorporated into PVA/BA composite films resulting in PVA/BA/PHMG composite films. The PVA/BA/PHMG films exhibited 99.99% bacterial inhibition against Escherichia coli and Staphylococcus aureus with negligible leaching of PHMG. The PVA/BA/PHMG films maintained a tensile strength of 75.3 MPa and an elongation at a break of 208%. These improved mechanical and antimicrobial properties make PVA/BA and PVA/BA/PHMG films promising for applications in food and medicinal packaging. [ABSTRACT FROM AUTHOR]

Published
2023
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25. Antibacterial Mechanism of N‐PMI and the Characteristics of PMMA‐Co‐N‐PMI Copolymer**

Author

Qixin Zhuang, Pengfei Zhan, Tao Wu, Anna Zheng, Han Shi, Xu Xiang, Yong Guan, and Wei Dafu

Subjects
Polymers, Chemistry, technology, industry, and agriculture, Bioengineering, macromolecular substances, General Chemistry, General Medicine, Biochemistry, Anti-Bacterial Agents, Maleimides, Anti-Infective Agents, Polymer chemistry, Copolymer, Polymethyl Methacrylate, Molecular Medicine, Molecular Biology, Mechanism (sociology)
Abstract

Aiming at the excellent killing effect of N-phenylmaleimide (N-PMI) on microorganisms, this paper used structural simulation analysis, fluorescence analysis, confocal laser scanning microscope and SEM to find that the double bond in N-PMI could interact with the sulfur groups in the membrane protein, changing its conformation, rupturing the plasma membrane of the cell, leaking the contents, and ultimately causing the death of the microorganisms. Therefore, once the double bond participated in the polymerization, N-PMI loosed its antimicrobial function. N-PMI could achieve azeotropic copolymerization with MMA through reactive extrusion polymerization, and didn’t follow the law of reactivity ratio of classic copolymerization. N-PMI with a content of 5% can be evenly inserted into the PMMA chain segment during the copolymerization reaction, thereby increasing the Tg of pure PMMA by up to 15°C, which provided the PMMA-co-PMI copolymer with resistance to boiling water sterilization advantageous conditions. In addition, the copolymer was superior to the commercially available pure PMMA in terms of bending strength and modulus. At the same time, N-PMI with a content of 5% has little effect on the transparency of PMMA after participating in the copolymerization. Moreover, the trace amount of residual N-PMI made the material have excellent antimicrobial function, and the bacteriostatic zone is extremely small, which provided an excellent guarantee for the safety and durability of the material. As a medical biological material, the PMMA-co-PMI copolymer has a good industrialization application prospects.

Published
2022

29. Ultrasonic dispersion of multi-walled carbon nanotubes aided by pyrene-polyether dispersants and Al2O3 particles.

Author

Guan, Yong, Liu, Xingyu, Xu, Xiang, and Wei, Dafu

Subjects
MULTIWALLED carbon nanotubes, DISPERSING agents, DISPERSION (Chemistry), ALUMINUM oxide, BUTYRIC acid, ELECTROMAGNETIC shielding
Abstract

Carbon nanotube (CNT) aqueous suspensions are attracting considerable attention in conductive, antistatic, electromagnetic shielding coatings and films owning to their environmental safety. However, stable CNT suspensions are difficult to prepare because of the remarkable entanglement between CNTs and their intrinsic hydrophobicity. A new class of amphiphilic dispersants—pyrene butyric acid polyethylene glycol monoester (Py-mPEG)—were prepared through the esterification reaction between 1-pyrene butyric acid and polyethylene glycol monomethyl ether. Varieties of multi-walled carbon nanotubes (MWCNTs) aqueous suspensions were prepared by ultrasonic method using the following dispersants: Py-mPEG, sodium dodecyl benzene sulfonate (SDBS), Py-mPEG/Al2O3, and SDBS/Al2O3. The concentrations of suspended MWCNTs were determined by UV–vis absorption spectroscopy, and the state of suspensions was characterized by scanning electron microscopy (SEM). The non-covalent interactions between MWCNTs and Py-mPEG were investigated by fluorescence emission spectroscopy, and density functional theory calculations. The results showed that MWCNTs were more readily dispersed in Py-mPEG solutions than in SDBS solutions, whereas the Al2O3 particles could further improve the dispersion effect. Particularly, the MWCNT concentration reached 1.363 mg/mL using Py-mPEG (1000 ppm)/Al2O3 (particle size: 5–6 µm) as dispersant. A large number of individual MWCNTs were observed from the SEM images of the suspensions. A diffusion experiment on ink showed that the Al2O3 particles with particle size of 5–6 µm were highly responsive to ultrasound. The entangled MWCNTs could be disintegrated by the collision of particles. [ABSTRACT FROM AUTHOR]

Published
2022
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