Bozhen Wu

Effect of allantoin on the stabilization efficiency of Ca–Zn thermal stabilizers for poly(vinyl chloride)

The influence of allantoin (ALL) combined with zinc stearate (ZnSt2), calcium stearate (CaSt2), and ZnSt2–CaSt2 (1:1), respectively, in different mass ratios on thermal stability of poly(vinyl chloride) (PVC) was investigated by Congo red test, discoloration test, and thermogravimetric analysis. The results indicated that ALL behaved as a good long-term thermal stabilizer for PVC, which was attributed to its ability to absorb hydrogen chloride released from the degradation of PVC. Moreover, ALL was able to extend the stabilization time of PVC containing ZnSt2–CaSt2 and postpone “zinc burning.” Fourier transform infrared spectra confirmed that ALL can react with ZnCl2 to produce an inert complex, which is responsible for postponing “zinc burning.”

Novel organic antibacterial thermal stabilizers for transparent poly(vinyl chloride)

A novel kind of antibacterial thermal stabilizers for transparent poly(vinyl chloride), bis-uracil compounds with different alkyl chain length, was synthesized by the condensation of 6-amino-1,3-dimethyluracil with aliphatic aldehydes and characterized with 1H NMR spectra. Not only high stabilization efficiency which increased with the increasing of alkyl chain length was obtained to prevent PVC from degradation, special antibacterial properties could also be acquired in the mean time of keeping PVC highly transparent. The results of discoloration test, thermogravimetric analysis, Fourier transform infrared spectra, visible spectroscopy and scanning electron microscopy revealed that the bis-uracil compounds could absorb HCl through acid–base reaction and chemical bonding, and the amine group played a key role in reacting with the inherent structural defects in PVC chains, meanwhile the long alkyl chain of the bis-uracil compounds could reduce their melting points and improve the compatibility with PVC. Comparing with the referential films stabilized by 6-amino-1,3-dimethyluracil and Ca/Zn stabilizers, PVC films stabilized with bis-uracil compounds had excellent transparency. In addition, the measurement of antimicrobial activity suggested that the bis-uracil compounds had the biological activity to inhibit growth of bacteria. We believe that PVC stabilized by such multifunctional stabilizers may widen its applications in biomedical field.

Highly efficient and antibacterial zinc norfloxacin thermal stabilizer for poly(vinyl chloride)

A novel kind of highly efficient and antibacterial thermal stabilizer, zinc norfloxacin (Zn(C16H17FN3O3)2·4H2O, represented as ZnNo2), for poly(vinyl chloride) (PVC) was first reported in this paper; the structure of which was characterized by Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), elemental analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and laser particle size analysis. ZnNo2 extended the thermal stability of PVC and had good synergetic effects with calcium stearate (CaSt2) on decreasing the releasing rate of HCl from PVC, which were confirmed by the results of thermal stability research including the Congo red test, discoloration, dehydrochlorination test and visible spectroscopy. The thermal stability mechanism of ZnNo2 and CaSt2 on PVC was proposed in this paper. The best auxiliary thermal stabilizer was the compound of dibenzoylmethane (DBM), pentaerythritol (PET) and triphenylphosphate (TPP) for ZnNo2/CaSt2 with both acceptable initial color and long-term stability for PVC products. Importantly, the inhibition zone test showed that ZnNo2 had good antibacterial activity against Escherichia coli and Staphylococcus aureus, even in PVC with low concentrations.

The key effect of the self-assembly mechanism of dendritic gelators: solubility parameters, generations and terminal effects

The key effect of the self-assembly mechanism of dendritic gelators is researched by a comprehensive investigation of the gelation behavior of L-lysine dendritic gelators with different structures of three generations in 20 different solvents. The solvents investigation, 1H NMR, tube inversion method, DSC, rheology, FTIR and rheological measurements show that the reported dendritic gelators self-assemble through the main driving force of hydrogen bonds and the second driving force of π–π stackings. So the key effect of the self-assembling mechanism is that these factors can influence the driving force of the self-assembly process. This is the reason that L-lysine dendritic gelators tend to gelate in solvents with low α and β parameter values, which have less influence on the formation of hydrogen bonds between the gelators. Higher generations provide a much greater hydrogen bond density in the gelators, which makes them have a higher gelation ability. The benzyl terminal groups provide the second driving force of π–π stacking, making the Bzl-Gly-Lys gelators have much stronger gelation ability. This research reports a comprehensive insight into the precise ways in which the solubility parameters of the solvents, the gelator generation and the terminal group effects can influence the self-assembly and gelation of dendritic gelators. Gaining this type of fundamental understanding is essential if the key effect of this important class of self-assembling soft materials is to be truly understood.

Stretchable light scattering display based on super strong liquid crystalline physical gels with special loofah-like 3D gel networks

A unique stretchable liquid crystal light scattering display is reported in this paper with clear images shown at a maximum strain of 145% of the original length, based on super strong liquid crystalline physical gels with special loofah-like 3D gel networks.

Drug-mediation formation of nanohybrids for sequential therapeutic delivery in cancer cells

In order to overcome the multidrug resistance (MDR) of tumor cells, it is very important to develop nanocarriers which can effectively load drugs while releasing them in a sequential way. Herein, nanohybrids with such properties have been fabricated by a first loading of one anticancer drug onto a silicate nanodisk (Laponite (LP), 25 nm in diameter and 0.92 nm in thickness) and a subsequent assembly with a pH sensitive poly(N-vinylpyrrolidone) (PVP) as a protective layer, followed by a loading of with another anticancer drug. The resulting nanohybrids (LDPM) present a high drug encapsulation efficiency and long-term colloidal stability. However, if the two drugs are loaded onto LP before PVP decoration, the formed particles tend to form microsized aggregates with poor colloidal stability. In vitro release study indicates that LDPM can deliver the anticancer drugs in a sequential way, which can be further accelerated under acidic microenvironments mimicking both solid tumor and endo-lysosomal compartments, exerting synergistic anticancer cytotoxicity. The drug-mediated formation of nanocarriers may enlighten a design of novel nanoplatform for co-delivery of therapeutic agents, beyond anticancer drugs, in a combinative way for drug delivery applications.

Topological structure influences on the gel formation process and mechanical properties of L-lysine based supramolecular gels

The influence of a minor modification of the topological structure of a gelator’s core on the mechanism of the gel formation process and the resultant gel properties were researched by comparing the gelation ability of three L-lysine based gelators with the same arm structures and totally different topological core structures, one of which has a cubic topological polyhedral oligomeric silsesquioxane (POSS) core, one has a regular tetrahedron topological pentaerythritol core and the other has an organic linear topological dodecane core (denoted as POSS-Lys, PER-Lys and C12-Lys). Gelation tests, DSC, rheology measurements, SEM and POM investigations indicate that the gel obtained from C12-Lys with an organic linear topological dodecane core in the same solvent has a much greater strength of hydrogen bonding formed between the gelator molecules and much higher mechanical strength. What is more, POSS-Lys with a cubic topological core has a rather strong recovery ability, while PER-Lys cannot form a gel in any of the solvents tested. The key effect of such an obvious difference is in the self-assembly mechanisms which are influenced by the topological structure of the gelators.

High transparency and toughness PMMA nanocomposites toughened by self-assembled 3D loofah-like gel networks: fabrication, mechanism, and insight into the in situ polymerization process

Novel types of transparent PMMA composites were toughened with 3D loofah-like gel networks obtained via the in situ polymerization of methyl methacrylate (MMA) gel with POSS-based supramolecular POSS-Lys(BOC) gelators that have excellent compatibility with the polymerized matrix for the nanoscale nature of supramolecular gel fibers. The “gel networks-energy dissipation” toughening mechanism was investigated using SEM, tensile testing and DMA, the results of which demonstrate that a favorable architecture formed by the gel nanofibres through hydrogen bonding interactions contributes to the toughness improvement in these nanocomposites. In particular, UV-Vis spectrometry and haze meter tests indicate that the PMMA nanocomposites maintain the advantage of good optical transparency. In addition, the physical self-assembly nature of the gel networks allows them to be easily extracted from the polymer matrix, the result of which clearly demonstrates the framework formed by the nanofibres has not only been retained during the in situ polymerization process, but also has an outstanding capacity for the dissipation of energy. As a result, a special type of nanoporous materials with stable pore shapes was obtained, which has potential applications in optical sensors, energy storage and as a Li-ion battery separator.

pH sensitive mesoporous nanohybrids with charge-reversal properties for anticancer drug delivery

The surface/interface state of nanomaterials plays a key role on their biomedical applications. Nanotechnology offers a versatile means to develop nanoparticles with well-defined architecture. In this study, mesoporous silica nanoparticles were firstly loaded with an anticancer drug (doxorubicin, DOX), which were then decorated with a cationic oligomer (low molecular weight polyethyleneimine, LPEI) to acquire an increased surface charge. The resulting particles were further self-assembled with negative-charged bovine serum albumin (BSA) as natural protein nanoblocks to offer surface charge tunability. The resulting mesoporous nanohybrids (MDPB) acquired charge-reversal ability, which presented negative charge under biological conditions (beneficial to biocompatibility), while displaying a positive-charged state under acidic conditions mimicking the tumor extracellular microenvironment (favoring cell uptake or tumor penetration). Furthermore, the nanohybrids not only allowed for an effective loading of DOX drug, but also accelerated its release under acidic tumor microenvironments in a sustainable way. In vitro biological study indicated that the DOX-free nanoparticles were biocompatible, while MDPB exerted good cytotoxicity against cancer cells, suggesting their promise for therapeutic delivery application.

Microencapsulation of 1-hexadecanol as a phase change material with reversible thermochromic properties

Herein, a novel approach for generating a microencapsulated reversible thermochromic phase change material (RTPCM) is described. The system described uses a spirolactone derivative color former, phenolic hydroxyl compound color developer, and 1-hexadecanol as the phase change material and co-solvent. The microencapsulation is achieved by complex coacervation of modified gelatin containing vinyl groups and gum arabic. This is followed by the crosslinking reaction between vinyl groups on modified gelatin and a divinyl crosslinker and subsequent crosslinking reaction with glutaraldehyde to improve stability and encapsulation efficiency. The influence of various key parameters on properties of the microcapsules (encapsulation efficiency, morphology, and particle size) are reviewed including the substitution degree of vinyl groups on modified gelatin, the type and amount of divinyl crosslinkers, and the core/shell ratio. Thermal properties and reversible color reliability of the generated microcapsules were found to be stable after 100 thermal heating and cooling cycles. Such microcapsules are well suited for latent heat storage and as an indicator for the states of energy saturation and consumption in phase change material applications directly through color change.