Xinhua Yuan

An “active” and self-switchable nanoreactor

An “active” and self-switchable nanoreactor is reported. This nanoreactor was made of nickel nanoparticles and a unique polymer composite of poly(1-vinylimidazole) (PVIm) and poly(acrylic acid) (PAAc) that exhibited “self-healing” properties. This nanoreactor revealed a weak reactivity at relatively low temperatures due to the complementary interaction between the PVIm and PAAc, which inhibited access to the catalytic sites of the nickel. In contrast, the nanoreactor demonstrated significant reactivity at relatively high temperatures, resulting from the dissociation of the interpolymer interaction. Unlike conventional nanoreactors, which usually involve the thermal phase transition of PNIPAm, this novel nanoreactor has employed the “self-healing” properties of supramolecular building blocks. The proposed incorporation of “active” supports to metal nanoparticles creates a new protocol for developing catalytic nanoreactors.

Recognition of proteins and peptides: Rational development of molecular imprinting technology

The creation of tailor-made receptors which are able to recognize molecular targets with high affinity and selectivity has attracted much attention in the field of chemistry, physics, and biology. Molecular imprinting has proved to be an effective technique for generating specific recognition sites in synthetic polymers. The synthesis of molecular imprinted polymers specific for proteins and peptides has been a focus for many scientists working in the area of molecular recognition, since the creation of synthetic polymers that can specifically recognize biomacromolecules is a very challenging but potentially extremely rewarding work. These polymers with specificity for biological macromolecules have considerable potential for applications in the areas of solid phase extraction, catalysis, medicine, clinical analysis, drug delivery, environmental monitoring, and sensors. In this review, the authors discuss the developed approaches associated with the imprinting of peptides and proteins, and provide an overview of the significant progress achieved within this field. Finally, the possible mechanism of the molecular imprinting and recognition has been discussed.

One-Pot Pathway: Fabricating Ordered Hollow Silica Spheres Using Sodium Silicate as the Precursor

The preparation of hollow silica spheres via the sodium silicate route presents many advantages such as a low-cost silica source, and an environmentally friendly reaction system. Unfortunately, it is extremely hard to prepare the well-defined hollow silica spheres by using sodium silicate as the silica source owing to its rapid, disordered precipitation under the acid catalysis. As a result, we, in this paper, report a facile, economic, one-pot pathway for preparation of the ordered hollow silica spheres by employing a sodium silicate precursor. In this approach, the cationic polystyrene (CPS) templates can be first prepared via emulsifier-free emulsion polymerization by using the cationic monomer vinylbenzyltrimethylammonium chloride, then, the silica shells were attached on the surfaces of CPS particles via electrostatic interaction, finally CPS particles were in situ dissolved and removed by adding toluene to create ordered hollow silica spheres. Some modern techniques and instruments, including the transmission electron microscope, scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller theory were employed to monitor and characterize the resulting hollow silica spheres.

The Preparation of Monodisperse Cationic Polystyrene and its Application to the Synthesis of Hollow Silica Spheres

The fabrication of hollow spheres with well defined size and morphology has been attracting much attention due to their unique structures and related physicochemical properties. Among the synthetic methods, the template-directed method is particularly interesting and extensively employed to fabricate hollow spheres due to templates available of essentially any size, shape, and chemistry. As a result, a new monodispersed cationic polystyrene (PS) template in this paper was fabricated by using 2-(methacryloyloxy) ethyltrimethylammonium chloride as co-monomer via emulsifier-free polymerization. The template not only can easily be tuned to the size, but can combine the advantages of hard-templating and soft-templating methods. Subsequently, we used cationic PS particles as templates to prepare hollow silica spheres – the results indicated that cationic templates can attract the assembly of tetraethylorthosilicate hydrolyzate on their surface and that the dissolution of templates can be done in the system of silica encapsulation by modification of the reaction conditions.

An autonomic and “off–on–off”-switchable polymer microreactor

An originally designed autonomic and “off–on–off”-switchable polymer microreactor is reported. This polymer microreactor was made of nickel nanoparticles and a unique shape-memory polymer consisting of poly(acrylamide) and pendent dodecyl side chains that exhibited switchable domains. This reactor showed weak reactivity at relatively low temperatures due to the low mobility of molecular chains in the switchable domains, which inhibited the access of substrate to the encapsulated nickel nanoparticles (i.e., catalytic ‘off’ status). This reactor also showed weak reactivity at relatively high temperatures in response to the significantly increased hydrophobicity (viz., catalytic ‘off’ status). This reactor only demonstrated significant catalysis at modest temperatures, arising from the relative balance between the mobility of molecular chains and the hydrophobicity in the switchable domains (i.e., catalytic ‘on’ status). In this way, this polymer microreactor demonstrated the autonomic “off–on–off” catalytic ability. This novel design opens up the opportunity to develop smart polymer microreactors for controlled catalytic processes.

A convenient separation method for di(2-ethylhexyl)phthalate by novel superparamagnetic molecularly imprinted polymers

Through a surface molecular imprinting technique and coating superparamagnetic Fe3O4 nanoparticles with molecularly imprinted polymers (MIPs), a novel magnetic molecularly imprinted polymer (MMIP) was successfully fabricated for the convenient separation of di(2-ethylhexyl)phthalate (DEHP) with methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross linker and 2,2-azobis(isobutyronitrile) as initiator. A magnetic non-molecularly imprinted polymer (MNIP) was also prepared for comparison purposes. The morphology structure and the magnetic properties of MMIP were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction, vibrating sample magnetometry (VSM) and thermo gravimetric analysis (TGA). The adsorption properties of MMIP and MNIP were investigated by static and dynamic adsorption experiments. The results show that the diameter of the synthesized MMIP microspheres is about 300–500 nm with good dispersibility in solvent. The prepared MMIP shows superparamagnetic properties with the maximum saturation magnetic intensity of 43.97 emu g−1, and it can be conveniently separated using an external magnetic field. Compared with MNIP, MMIP has a higher adsorption capacity and better adsorption selectivity for DEHP, and the imprinting factor reaches 3.012. The regeneration adsorption experiment illuminates that the novel MMIP can be reused with good separation efficiency.

Synthesis and Properties of Phenylmethylsilicone/Organic Montmorillonite Nanocomposites by In-Situ Intercalative Polymerization

Using methylphenyl dichlorosilane, methyl trichlorosilane cetyltrimethylammonium bromide (CTAB) as organic treatment agent, phenylmethylsilicone/organic montmorillonite (OMMT) nanocomposites were prepared by in-situ intercalative polymerization. The internal structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Mechanical properties, high temperature resistance and barrier performance for gas and water were also studied. The results show that molecules of silicone chains insert into the layer of montmorillonite (MMT), and the interlayer distance of MMT is expanded effectively after polymerization of phenylmethylsilicone prepolymer and methyl methacrylate, even forming exfoliated nanocomposites.

The Fabrication and Progress of Hollow Structures

The fabrication of hollow particles is one of the fastest-growing fields of materials research, owing to their potential applications in catalysis, chromatography, separation, coatings, protection of bioactive agents, microelectronics and electrooptics. As reported in recent studies, a variety of chemical and physicochemical methods have been employed to prepare hollow spheres with hierarchical and well-defined morphologies. For this, a basic understanding of the mechanism and recent advances in the fabrication of hollow spheres is discussed, along with outstanding challenges, issues, and potentially future opportunities. Evidently, it will enable the development in the fabrication of hollow particles with unique and tailored properties.