Changping Zhu

Hydrophobic modification of sodium alginate and its application in drug controlled release.

Sodium alginate was hydrophobically modified by coupling of polybutyl methacrylate onto the alginate. The polybutyl methacrylate was previously prepared through polymerization of butyl methacrylate in the presence of 2-amino-ethanethiol as a chain transfer agent. The structure of the product was characterized by Fourier-transformed infrared spectrometry, nuclear magnetic resonance (1HNMR) and thermogravimetry. The result of fluorescence analysis showed that the hydrophobicity of the modified alginate was obviously increased. The modified alginate conjugate was used for immobilization of bovine serum albumin in the presence of calcium chloride. In addition, the release behavior of the drug-loaded alginate in deionized water and Tris–HCl buffer solution (pH 7.2) was investigated. It was found that the modified sodium alginate possessed prolonged release behavior compared to unmodified sodium alginate, and it had potential application in controlled release as a drug carrier.

Syntheses of silsesquioxane (POSS)-based inorganic/organic hybrid and the application in reinforcement for an epoxy resin

A new inorganic/organic hybrid material containing silsesquioxane was prepared by the reaction of caged octa (aminopropyl silsesquioxane) (POSS-NH(2)) with n-butyl glycidyl ether (nBGE) and 1,4-butanediol diglycidyl ether (BDGE). The copolymers of POSS, nBGE, and BDGE could be obtained with varied feed ratio of POSS-NH(2), nBGE, and BDGE in the preparation. The hybrid material was added into an epoxy resin (E51) for enhancing the toughening and thermal properties of the epoxy resin. The results showed that the toughening and the thermal properties of the cured epoxy resin were greatly improved by the addition of the hybrid. The enhancement was ascribed to nano-scale effect of the POSS structure and the formation of anchor structure in the cured network. The investigation of kinetics for the curing process of the hybrid-modified epoxy resin revealed that two kinds of curing reactions occurred in different temperature ranges. They were attributed to the reactions between amino groups of the curing agent with epoxy groups of E51 and with residue epoxy groups in the hybrid. The reacting activation energies were calculated based on Kissingers and Flynn-Wall-Ozawas methods, respectively.

Grafting Polymerization of N-isopropylacrylamide on the Surfaces of Silica by ATRP and Its Application in HPLC

Poly(N-isopropylacrylamide) was grafted on the surface of ultrafine silica beads through Atom Transfer Radical Polymerization (ATRP). The synthetic included the introduction of initiator and ATRP polymerization. Scanning electron microscopy revealed that a homogeneous and smooth poly(N-isopropylacrylamide (PNIPAm) layer was formed on the silica surface. The differential scanning calorimetry indicated the composite particles were thermosensitive. The polymer (PNIPAm) was cleaved from the silica composites to be analyzed. The molecular weight of the PNIPAm can be well-controlled by adjusting the feed ratio of the monomers and the polydispersity index was very narrow. The PNIPAm-modified silica particles were used as packing materials in high performance liquid chromatography (HPLC) for separating organic compounds. The result indicated that the satisfactory separations could be successfully achieved only by controlling the temperature of the column.

Investigation of cavitation bubble collapse near rigid boundary by lattice Boltzmann method

The dynamics of the bubble collapse near a rigid boundary is a fundamental issue for the bubble collapse application and prevention. In this paper, the bubble collapse is modeled by adopting the lattice Boltzmann method (LBM) and is verified, and then the dynamic characteristics of the collapsing bubble with the second collapse is investigated. The widely used Shan-Chen model in the LBM multiphase community is modified by coupling with the Carnahan-Starling equation of state (C-S EOS) and the exact difference method (EDM) for the forcing term treatment. The simulation results of the bubble profile evolution by the LBM are in excellent agreements with the theoretical and experimental results. From the two-dimensional pressure field evolution, the dynamic characteristics of the different parts during the bubble collapse stage are studied. The role of the second collapse in the rigid boundary damage is discussed, and the impeding effect between two collapses is demonstrated.

Reduction-responsive zwitterionic nanogels based on carboxymethyl chitosan for enhancing cellular uptake in drug release

Stimuli-responsive nanoparticles as drug carriers have promising applications in chemotherapy. To increase stability of nanogels in the bloodstream and to enhance intracellular drug uptake, reduction-responsive zwitterionic nanogels were prepared using carboxymethyl chitosan as a material. The preparation included modification of carboxymethyl chitosan and crosslinking by of N,N-Bis(acryloyl) cystamine. The nanogels possessed zwitterions of carboxyl and amino groups, and showed excellent non-fouling behavior against protein adsorption. In the presence of a reduction agent such as glutathione (GSH), the nanogels were dissociated due to scission of disulfide bonds in the crosslinking structure, leading to drug release in tumor cells. The nanogels were non-cytotoxic, biocompatible, biodegradable, and would be potentially used as anticancer drug delivery carriers in controlled release for enhancing cellular drug uptake.

Degradation of Alginate and Polymerization of Styrene Initiated by Alginate Macroradicals under Ultrasonic Irradiation

Ultrasonic irradiation is a promising method used for polymer degradation and polymerization. In this study, the degradation of alginate under ultrasonic irradiation was investigated. The macroradicals produced in the degradation process were used to initiate polymerization of styrene without adding any initiators and surfactants, and copolymers of styrene and alginate were obtained. The amphiphilic copolymers could form nano particles in aqueous solutions. A hydrophobic drug, ibuprofen, was loaded onto the copolymer gels for controlled release. The results showed that the hydrophobically modified alginate had higher drug loading and prolonged release time compared to those of the neat alginate.

Degradation of Sodium Polystyrene Sulfonate and the Radical Initiated Polymerization of Styrene Under Ultrasonic Irradiation

Amphiphilic block copolymer of sodium polystyrene sulfonate (PSS) and polystyrene(St) was prepared under ultrasonic irradiation. The PSS fragment radicals created during the degradation process was used to initiate the polymerization of styrene(St), and a diblock copolymer of poly(SS-b-St) was obtained when the degradation of PSS and the polymerization of St occurred simultaneously. The block copolymers underwent self assembly in aqueous solution, and formed stable nano micelles with diameters of 95–128 nm. The influence of ultrasonic irradiation on the formation of the block copolymers and micelles were investigated.

Image denoising via expected patch log likelihood with Gaussian model identification

In this paper, a new strategy is proposed for the existing expected patch log likelihood (EPLL) algorithm to deal with image denoising, where the Gaussian model identification is incorporated to improve the likelihood estimation for patches. In detail, the noisy patches are first divided into two categories, i.e., smooth and unsmooth groups. Sequentially, in the iteration of the likelihood estimation, these two groups are separately performed via the Gaussian models with the corresponding covariance parameters. Experiments show that, with this Gaussian model identification for patches, the proposed method can achieve the better performance than the traditional EPLL algorithm.

Preparation of poly(N-Butyl Acrylate-Co-Glycidyl Methacrylate) and its Application in Enhancement of Epoxy Resin

The epoxy-functionalized copolymers were prepared by copolymerization of n-butyl acrylate (nBA) and glycidyl methacrylate (GMA) in a solution. The structures of the copolymers were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and gel-permeation chromatography. The copolymers were added to epoxy resin E44 for modifying the properties of the cured epoxy resin. The results showed that some properties of the cured epoxy resin were apparently improved through the addition of the copolymers. The kinetic studies indicate that the curing process was continuous with average activation energy of 51.13 kJ/mol, which was calculated based on Kissinger and Ozawa models.

Modeling of collapsing cavitation bubble near solid wall by 3D pseudopotential multi-relaxation-time lattice Boltzmann method:

Understanding the dynamic characteristic of the cavitation bubble near a solid wall is a fundamental issue for the bubble collapse application and prevention. In the present work, an improved three-dimensional multi-relaxation-time pseudopotential lattice Boltzmann model is adopted to investigate the cavitation bubble collapse near the solid wall. With respect to thermodynamic consistency, Laplace law verification, the three-dimensional pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. By the theoretical analysis, it is proved that the model can be regarded as a solver of the Rayleigh–Plesset equation, and confirmed by comparing the results of the lattice Boltzmann simulation and the Rayleigh–Plesset equation calculation for the case of cavitation bubble collapse in the infinite medium field. The bubble collapse near the solid wall is modeled using the improved pseudopotential multi-relaxation-time lattice Boltzmann model. We find the lattice Boltzmann simulation and the experimental results have the same dynamic process by comparing the bubble profiles evolution. Form the pressure field and the velocity field evolution it is found that the tapered higher pressure region formed near the top of the bubble is a crucial driving force inducing the bubble collapse. This exploratory research demonstrates that the lattice Boltzmann method is an alternative tool for the study of the interaction between collapsing cavitation bubble and matter.