Haipeng Yang

Size dependence of SiO2 particles enhanced glucose biosensor

A wide size range of SiO(2) particles were synthesized and were used as enzyme immobilization carriers to fabricate glucose biosensors. The size of the particles was in the range of 17-520 nm. These biosensors could be operated under physiological conditions (0.1M phosphate buffer, pH 7.2). Particle size could affect the performance of SiO(2) modified glucose biosensors drastically. The smaller particles had higher performance. The smallest SiO(2) modified biosensor could work well in the glucose concentration range of 0.02-10 mM with a correlation coefficient of 0.9993. Its sensitivity was 2.08 microA/mM and the detection limit was 1.5 microM glucose.

Development of zwitterionic polyurethanes with multi-shape memory effects and self-healing properties

Recently, multi-shape-memory polymers have attracted significant attention due to their technological impact. This study reports novel zwitterionic multi-shape-memory polyurethanes (ZSMPUs) from N-methyldiethanolamine (MDEA), hexamethylene diisocyanate (HDI) and 1,3-propanesultone (PS). The ZSMPUs feature excellent multi-shape-memory properties that are capable of remembering four different shapes, and shape recovery decreases with increasing sulfobetaine content. Ionic interactions greatly influence the structure, morphology and properties. Increasing the sulfobetaine content promotes the phase mixing and zwitterions serve as organic fillers in the zwitterionic polyurethane. Immersing the zwitterionic polyurethane in moisture-rich conditions and drying at low temperature preserves the shape-memory capabilities and demonstrates good self-healing properties. Furthermore, both the shape memory effect and self-healing effects are repeatable. The self-healing mechanism is ascribed to the spontaneous attraction of zwitterions, followed by slower re-entanglement.

Electro-deposition of CoNi2S4 flower-like nanosheets on 3D hierarchically porous nickel skeletons with high electrochemical capacitive performance

Ternary cobalt nickel sulfide (CoNi2S4) flower-like nanosheets are directly grown on three dimensional (3D) hierarchically porous nickel skeletons by one-step electro-deposition. The resultant 3D porous Ni/CoNi2S4 composites could serve as binder-free integrated electrodes for supercapacitors, which exhibit higher capacitance than those of 3D porous Ni/Co9S8, 3D porous Ni/Ni3S2, Ni foam/CoNi2S4 and smooth Ni/CoNi2S4 electrodes. Furthermore, the 3D porous Ni/CoNi2S4 electrodes demonstrate better electrochemical reversibility and excellent rate capability. The super electrochemical capacitive behavior might be attributed to the highly interconnected conductive networks of 3D hierarchically porous Ni scaffold supported CoNi2S4 flower-like nanosheets with a large specific area and highly active sites.

Development of supramolecular liquid-crystalline polyurethane complexes exhibiting triple-shape functionality using a one-step programming process

Supramolecular liquid crystalline polymers and shape memory polymers are attracting increasing interest as materials. In this paper, we describe the development of a supramolecular liquid crystalline shape memory polyurethane (SLCSMPU) complex that exhibits both liquid crystalline properties and shape memory properties. The complex is formed by incorporating 4-hexadecyloxybenzoic acid (HOBA) into a pyridine-containing shape memory polyurethane (PySMPU). The HOBA is tethered to the PySMPU by strong hydrogen bonding between the pyridine rings and the COOH of the HOBA, forming a SLCSMPU complex. Heat treatment plays an important role in the formation of hydrogen-bonded supramolecular liquid crystalline structures in these SLCSMPU complexes. Thus, the SLCSMPU complex not only maintains the intrinsic liquid-crystalline properties of HOBA, but can also form a stable polymeric film for various shape memory applications. Additionally, the SLCSMPU complex forms a two-phase separated structure composed of an amorphous polyurethane matrix and a HOBA crystalline phase, which includes the hydrogen-bonded crystalline HOBA phase and the free HOBA crystalline phase. Therefore, a simple one-step programming process is developed that produces SLCSMPU complexes with excited triple-shape functionalities due to their multiple phase transitions, especially when the molar ratio of HOBA/BINA is less than 0.8.

Development of liquid-crystalline shape-memory polyurethane composites based on polyurethane with semi-crystalline reversible phase and hexadecyloxybenzoic acid for self-healing applications

Shape memory materials and self-healing materials have attracted considerable attention in recent years. This paper reports the development of a liquid-crystalline shape-memory-polyurethane (LC-SMPU) composite based on SMPU and hexadecyloxybenzoic acid (HOBA) for self-healing applications. The results demonstrate that HOBA is physically mixed with SMPU resulting in a semi-crystalline reversible phase and forming LC-SMPU composites. The two-phase separated structure comprises an SMPU matrix and a HOBA phase. The HOBA phase exhibits a reversible nematic phase within a temperature range of 101–130 °C, while the SMPU matrix acts as a stable polymeric film for various applications. Both the semi-crystalline soft phase of the SMPU matrix and the HOBA crystalline phase can be used to trigger shape memory effects. The LC-SMPU composites display not only triple-shape memory behaviours but also self-healing behaviours due to the heating-induced “bleeding” behaviour of HOBA in the liquid crystalline state and their subsequent recrystallisation upon cooling.

New insights into multi-shape memory behaviours and liquid crystalline properties of supramolecular polyurethane complexes based on pyridine-containing polyurethane and 4-octyldecyloxybenzoic acid

Both liquid crystalline polymers and shape memory polymers are attractive to researchers. This paper describes the development of a supramolecular liquid crystalline complex exhibiting a multi-shape memory effect and liquid crystalline properties. 4-n-Octyldecyloxybenzoic acid (OOBA) is connected to a pyridine-containing polyurethane (PySMPU), forming a new PySMPU/OOBA complex. The results of this study demonstrate that the complex maintains the intrinsic crystallization and liquid-crystalline properties of OOBA and combines the shape memory effects of PySMPUs. Shape memory investigations demonstrate that the PySMPU/OOBA complexes have a good multi-shape memory effect, exhibiting triple- and quadruple-shape memory behaviours. For the triple-shape memory behaviours, the strain fixity at the first stage is lower than that at the second stage, while the strain recovery at the first stage is higher than that at the second stage. Overall, increasing the OOBA content improves the strain fixity but reduces the strain recovery due to the lubrication of the OOBA long chains. The successful combination of the liquid crystalline properties and multi-shape memory effect makes the PySMPU/OOBA complexes potentially applicable in smart optical devices, smart electronic devices and smart sensors.

Exploring the Biocompatibility of Zwitterionic Copolymers for Controlling Macrophage Phagocytosis of Bacteria.

This paper provides a biomaterial derived from zwitterionic polymer for controlling macrophage phagocytosis of bacteria. A series of zwitterionic copolymers, named DMAPS-co-AA, are synthesized with 3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS) and acrylic acid (AA). The biocompatibility of DMAPS-co-AA copolymers can be adjusted by adjusting the DMAPS-content or pH value. As the DMAPS-content increases, the biocompatibility of zwitterionic copolymer increases. The zwitterionic copolymers with DMAPS content above 30 wt% have higher biocompatibility. Moreover, the biocompatibility also increases significantly as the pH increases from 3.4 to 7.2. By adjusting the pH above 5.8, the zwitterionic copolymer with lower DMAPS-content also shows higher biocompatibility. Importantly, after incubation with the DMAPS-co-AA copolymer solutions at different pH values, phagocytosis behavior of macrophage RAW264.7 cells can also be adjusted. The phagocytosis of bacteria is enhanced at pH = 7.2. Thus, it is proposed that zwitterionic copolymers can be used for controlling phagocytosis of bacteria.