Qingzeng Zhu

Design and preparation of gels with excellent mechanical properties has garnered wide interest at present. In this paper, preparation of polyvinyl alcohol (PVA)–tannic acid (TA) gels with exceptional properties is documented. The crystallization zone and hydrogen bonding acted as physical crosslinkages fabricated by a combination of freeze–thaw treatment and a tannic acid compound. The effect of tannic acid on mechanical properties of prepared PVA–TA gels was investigated and analyzed. When the mass fraction of PVA was 20.0 wt% and soaking time was 12 h in tannic acid aqueous solution, tensile strength and the elongation at break of PVA–TA gel reached 5.97 MPa and 1450%, respectively. This PVA–TA gel was far superior to a pure 20.0 wt% PVA hydrogel treated only with the freeze–thaw process, as well as most previously reported PVA–TA gels. The toughness of a PVA–TA gel is about 14 times that of a pure PVA gel. In addition, transparent PVA–TA gels can effectively prevent ultraviolet-light-induced degradation. This study provides a novel strategy and reference for design and preparation of high-performance gels that are promising for practical application.

Protein micropatterning on microfabricated surfaces is a promising technology in applications for biochip microarrays, cell attachment, and biosensors. In the present work, a novel photoresponsive polymer based on light-triggered charge shifting bridged polysilsesquioxane (CBPS) is designed and prepared. The organic bridged units containing a photocleavable group of diethylaminocoumarin-4-yl in CBPS could be cleaved rapidly upon irradiation at 410 nm, resulting in the polymer surface switching from a positive charge to a negative charge property. The photoresponsive behavior of CBPS is studied using FTIR, UV–vis, SEM, fluorescence microscopy, and zeta potential analysis. Proteins are easily immobilized on the polymer surface via electrostatic interactions and released after irradiation as required. Combined with photopatterning techniques, accurate protein micropatterns are fabricated by covering a photomask upon irradiation. A gradient protein pattern is also spatially and temporally controlled by regulating irradiation parameters. This smart photoresponsive polymer surface provides a gentle and straightforward strategy to micropattern charged proteins. Moreover, the photoresponsive polymer holds permitting potential in biomedical applications such as conjugating biomolecules, guiding cell arrays, and resisting bacteria.

Precise control of target molecule release time, site, and dosage remains a challenge in controlled release systems. We employed a photoresponsive molecule release system via light-triggered charge reversal nanoparticles to achieve a triggered, stepwise, and precise controlled release platform. This release system was based on photocleavage-bridged polysilsesquioxane nanoparticles which acted as nanocarriers of doxorubicin loaded on the surface via electrostatic interaction. The nanoparticles could reverse into positive charges triggered by 254 nm light irradiation due to the photocleavage of the o-nitrobenzyl bridged segment. The charge reversal property of the nanoparticles could release loaded molecules. Doxorubicin was selected as a positively charged model molecule. The as-prepared nanoparticles with an average size of 124 nm had an acceptable doxorubicin loading content up to 12.8%. The surface charge of the nanoparticles could rapidly reverse from negative (−28.20 mV) to positive (+18.9 mV) upon light irradiation for only 10 min. In vitro release experiments showed a cumulative release up to 96% with continuously enhancing irradiation intensity. By regulating irradiation parameters, precisely controlled drug release was carried out. The typical “stepped” profile could be accurately controlled in an on/off irradiation mode. This approach provides an ideal light-triggered molecule release system for location, timing, and dosage. This updated controlled release system, triggered by near-infrared or infrared light, will have greater potential applications in biomedical technology.

Novel graphene‐oxide‐reinforced silicone composites (GOSC) are prepared by in situ polymerization of silanes and low concentrations (T _d improved by 100 °C). After covalently grafting onto silicone resins via in situ polymerization, the obtained GOSC exhibits greatly enhanced thermal stability (T _d up to 400 °C and T _g improved by 3–5 °C), increased storage modulus, loss modulus, and complex viscosity. The morphology, microstructure, interfacial adhesion of the developed GOSC coatings were carefully investigated. The GOSC coatings on metal exhibit good transparency (up to 90%), hydrophobicity, and excellent anticorrosion capability. This work provides a new strategy for developing high performance graphene‐based silicone composite materials.

α-Amine ketoximesilanes are proven to be effective crosslinkers in the preparation of ketone-oxime one-component room temperature vulcanized (RTV) silicone rubber without the use of toxic metal catalyst. This work aimed to investigate the hydrolysis kinetic of α-amine ketoximesilanes, which is vitally important for the preparation of RTV silicone rubber. Five kinds of α-amine ketoximesilanes, namely α-(N,N-diethyl)aminomethyltri(methylethylketoxime)silane (DEMOS), α-(N,N-di-n-butyl)aminomethyltri(methylethylketoxime)silane (DBMOS), α-(N-n-butyl)aminomethyltri(methylethylketoxime)silane (n-BMOS), α-(N-cyclohexyl)aminomethyltri(methylethylketoxime)silane (CMOS) and α-(β-aminomethyl)aminomethyltri(methylethylketoxime)silane (AEMOS), were successfully obtained and confirmed using Fourier transform infrared spectrometer (FT-IR) and hydrogen-1 nuclear magnetic resonance ( ¹H NMR). Kinetics of hydrolysis reactions were measured by FT-IR and conductivity. Our results illustrated that the kinetic constant rates ranged from 12.2 × 10⁻⁴ s⁻¹ to 7.6 × 10⁻⁴ s⁻¹, with the decreasing order of DEMOS > n-BMOS > DBMOS > CMOS > AEMOS at the given temperature and humidity. Better performances of thermal stability could be achieved when using the α-amine ketoximesilanes as crosslinkers in the preparation of RTV silicon rubber than that of RTV silicone rubber with the use of methyltri(methylethylketoxime)silane (MOS) as a crosslinker and organic tin as a catalyst.