The Effect of Cyclodextrins in Polymer Particles Synthesis

The free radical polymerization of styrene in water in the presence of β-cyclodextrin (β-CD) is described. It is found that β-CD could greatly accelerate the polymerization, enhance the final conversion of monomer. The particle-size distribution of the final polymer is also improved than that without β-CD in the system.

Effect of stirring on preparation of hollow copolymer particles by alkali/cooling method

Hollow particles were prepared by the treatment of styrene-metbacrylic acid copolymer particles with alkali/cooling method. The influences of stirring position （in aqueous phase or at the interface of O/W） and stirring speed （90, 110 and 240 r/min） on the formation of hollow particles were investigated. It is found that the soft stirring in aqueous phase at 90 r/min leads to the formation of monohollow particles, while the violent stirring at the interface of O/W and 240 r/min gives non-hollow products. In contrast, the weak stirring in aqueous phase at 110 r/min results in sterically heterogeneous dispersion of methacrylic acid-rich regions within the original particles, and hence the formation of multihollow particles. Further investigation indicates that the change of stirring efficiency provides a way to tune the diffusion behavior of monomer styrene, and therefore influences the distribution of methacrylic acid units in the original particles as well as the morphology of the treated particles.

Large scale manufacture of magnetic polymer particles using membranes and microfluidic devices

Magnetic polymer particles have found applications in diverse areas such as biomedical treatments, diagnosis and separation technology. These applications require the particles to have controlled sizes and narrow size distributions to gain better control and reproducibility in use. This paper reviews recent developments in the preparation of magnetic polymer particles at nano- and micro-scales by encapsulating magnetic components with dissolved or in situ formed polymers. Particle manufacture using emulsification and embedment methods produces magnetic polymer particles at micro-scale dimensions. However, the production of particles in this range using conventional emulsification methods affords very limited control over particle sizes and polydispersity. We report on alternative routes using membrane and microfluidics emulsification techniques, which have a capability to produce monodisperse emulsions and polymer microspheres （with coefficients of variation of less than 10%） in the range from submicrometer to a few 100 μm. The performance of these manufacturing methods is assessed with a view to future applications.

Nanoscale coordination polymer Fe-DMY downregulating Poldip2-Nox4-H2O2 pathway and alleviating diabetic retinopathy

Diabetic retinopathy(DR)is a prevalent microvascular complication of diabetes and the leading cause of blindness and severe visual impairment in adults.The high levels of glucose trigger multiple intracellular oxidative stress pathways,such as POLDIP2,resulting in excessive reactive oxygen species(ROS)production and increased expression of vascular cell adhesion molecule-1(VCAM-1),hypoxia-inducible factor 1a(HIF-1a),and vascular endothelial growth factor(VEGF),causing microvascular dysfunction.Dihydromyricetin(DMY)is a natural flavonoid small molecule antioxidant.However,it exhibits poor solubility in physiological environments,has a short half-life in vivo,and has low oral bioavailability.In this study,we present,for the first time,the synthesis of ultra-small Fe-DMY nano-coordinated polymer particles(Fe-DMY NCPs),formed by combining DMY with low-toxicity iron ions.In vitro and in vivo experiments confirm that Fe-DMY NCPs alleviate oxidative stress-induced damage to vascular endothelial cells by high glucose,scavenge excess ROS,and improve pathological features of DR,such as retinal vascular leakage and neovascularization.Mechanistic validation indicates that Fe-DMY NCPs can inhibit the activation of the Poldip2-Nox4-H_(2)O_(2) signaling pathway and downregulate vital vascular function indicators such as VCAM-1,HIF-1a,and VEGF.These findings suggest that Fe-DMY NCPs could serve as a safe and effective antioxidant and microangio-protective agent,with the potential as a novel multimeric drug for DR therapy.

DuaI-Functionalized Hollow Polymer Particle as a pH-Responsive Adsorbent for Selective Removal of Basic Dye

In the present work,novel dual-functionalized hollow polymer particles （DF-HPP） with high density of carboxylate and amino dual functional groups have been specially designed and fabricated to serve as high-performance adsorbent for selective removal of basic dye （methylene blue,b-MB,as a model dye）.Due to both the high surface area and the extremely high density of carboxylate and amino groups,the DF-HPPs exhibited excellent adsorption property for methylene blue （b-MB）,including high adsorption capacity,fast adsorption/desorption rates,unique pH-sensitivity and easy recovery.The equilibrium adsorption data of b-MB on the DF-HPPs were evaluated using Freundlich and Langmuir isotherm models,and the equilibrium isotherm was better fit with Langmuir model with a maximum adsorption capacity of 538.8 mg/g at pH 12.More interestingly,the DF-HPPs showed a significant pH-dependent equilibrium adsorption capacity,which decreased dramatically from 516.1 mg/g to 24 mg/g as the solution pH decreased from 12 to 3.The dye-adsorbed DF-HPPs can be facilely and rapidly regenerated under mild condition （under weak acidic solution,pH 3,in 30 min） to recover both b-MB and the DF-HPPs,and the regenerated DF-HPPs can be reused for dye removal with high efficiency,indicating the exceptional recyclability of the DF-HPPs.

PREPARATION OF SULPHONATE-CONTAINING POLYMER PARTICLES VIA SEMI-CONTINUOUS EMULSION COPOLYMERIZAION OF STYRENE AND SODIUM STYRENE SULPHONATE

Submicron-sized P（St-NaSS） latexes were prepared via a semi-continuous emulsion copolymerization of styrene （St） and sodium styrene sulphonate （NaSS） in the presence of anionic surfactant, in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time. The hydrodynamic diameter of the latex particles was measured by dynamic light scattering （DSL） method, and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis. Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96% in the absence of crosslinker, and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h. The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time, and both of them increased with the increase of NaSS/St mole ratio in the charge. The introduction of divinyl benzene （DVB） could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol% DVB of total NaSS and St were used in the recipe, and the monomer feeding time was 3 h in copolymerization, the NaSS unit content of the purified copolymer reached 7.31 mol%.

Preparation of Fe_3O_4/PS Magnetic Particles by Dispersion Polymerization

Fe_3O_4/PS magnetic particles with core/shell structure has been prepared in the presence of Fe3O4 magnetic fluid in ethanol/water mixture.Magnetic particles with diameter size range from 5. 54 t0 187. 32 μm were obtained by different reaction conditions.Some parameters such as ethanol, PEG and monomer which affect particle size diameter and size distribution are discussed briefly in this paper.

PREPARATION OF HOLLOW LATEX PARTICLES BY ALKALI-ACID TREATMENT

Hollow polymer latex particles were prepared by seeded emulsion polymerization. A seed latex consisting of styrene (St), butyl acrylate(BA) copolymer was first prepared, and seeded terpolymerization of St BA MA(methacrylic acid) were then carried out in the absence of surfactant. Final latex was treated by a two step treatment under alkaline and acidic conditions, thus, the particles with hollow structure were obtained. We discussed the effects of pH value, temperature and time in alkali and acid treatment processes on hollow structure within the polymer latex particles and amount of carboxylic group on particle surface. The results show that the hollow polymer latex particles with the largest hollow size can be obtained under a certain condition (pH12.5, 90°C, 3 h in alkali treatment stage and pH2.5, 85°C, 3 h in acid treatment stage).

BRITTLE-DUCTILE TRANSITION OF POLYMERS AND ITS PERCOLATION MODEL

The brittle-ductile transition (BDT) of particlc toughened polymers was extensively studied in terms ofmorphology, strain rate, and temperature. The calculation results showed that both the critical interparticle distance (ID_c) andthe brittle-ductile transition temperature (T_(BD)) of polymers were a function of strain rate. The ID_c reduced nonlinearly withincreasing strain rate, whereas T_(BD) increased considerably with increasing strain rate. The effects of temperature andplasticizer concentration on BDT were discussed using a percolation model. The results were in agreement with theexperiments.

Synthesis of crystals and particles by crystallization and polymerization in droplet-based microfluidic devices

The recent advances in crystallization and polymerization assisted by droplet-based microfluidics to synthesize micro-particles and micro-crystals are reviewed in this paper.Droplet-based microfluidic devices are powerful tools to execute some precise controls and operations on the flow inside microchannels by adjusting fluid dynamics parameters to produce monodisperse emulsions or multiple-emulsions of various materials.Major features of this technique are producing particles of monodispersity to control the shape of particles in a new level,and to generate droplets of diverse materials including aqueous solutions,gels and polymers.Numerous microfluidic devices have been employed to generate monodisperse droplets of range from nm toμm,such as T junctions,flow-focusing devices and co-flow or cross-flow capillaries.These discrete,independently controllable droplets are ideal microreactors to be manipulated in the channels to synthesize the nanocrystals,protein crystals,polymer particles and microcapsules.The generated monodisperse particles or crystals are to meet different technical demands in many fields,such as crystal engineering,encapsulation and drug delivery systems.Microfluidic devices are promising tools in the synthesis of micron polymer particles that have diverse applications such as the photonic materials,ion-exchange and chromatography columns,and field-responsive rheological fluids.Processes assisted by microfluidic devices are able to produce the polymer particles(including Janus particles)with precise control over their sizes,size distribution,morphology and compositions.The technology of microfluidics has also been employed to generate core-shell microcapsules and solid microgels with precise controlled sizes and inner structures.The chosen“smart”materials are sensitive to an external stimulus such as the change of the pH,electric field and temperature.These complex particles are also able to be functionalized by encapsulating nanoparticles of special functions and by attaching some special groups like targeting ligands.The nucleation kinetics of some crystals like KNO_(3)was investigated in different microfluidic devices.Because of the elimination of the interactions among crystallites in bulk systems,using independent droplets may help to measure the nucleation rate more accurately.In structural biology,the droplets produced in microfluidic devices provide ideal platforms for protein crystallization on the nanoliter scale.Therefore,they become one of the promising tools to screen the optimal conditions of protein crystallization.

PREPARATION OF MICRON-SIZED NONSPHERICAL POLYSTYRENE/POLY(STYRENE-co-ETHYLENEGLYCOL DIMETHACRYLATE) PARTICLES BY SEEDED SOAP-FREE EMULSION POLYMERIZATION

Micron-sized nonspherical polymer particles having different morphologies were synthesized by seeded soap-free emulsion polymerization of styrene （St） and ethyleneglycol dimethacrylate （EGDMA, used as a crosslinker） on spherical, linear polystyrene （PS） seed particles. The morphology of the resulting PS/poly（St-co-EGDMA） particles was dependent on the crosslinker concentration and polymerization temperature.

Selective removal of phenol by spherical particles of α-,β- and γ-cyclodextrin polymers： kinetics and isothermal equilibrium

Spherical particles of α-,β- and γ-cyclodextrin （CD） polymers to efficiently remove phenol from waste water were prepared by reverse suspension polymerization with epichlorohydrin as crosslinker in liquid paraffin. By controlling the amounts of crosslinker and water, well- defined spherical polymer particles with controllable size were obtained. Due to the selective inclusion associations between CD groups and phenol, these CD spherical polymer particles were demonstrated to be ideal candidates for removal of phenol. Among them β-CD polymer particles showed the best performance. The kinetics and isothermal equilibrium models were used to fit the experimental data of phenol removal from aqueous solution using these CD polymer particles. It was found that the kinetics followed the Ho and Mckay equation, suggesting that the adsorption process of phenol was controlled by diffusion and the host-guest interaction between CD and phenol. Equilibrium isothermal data can be well fitted by the Freundlich equation. The negative free energy change indicated the spontaneous nature of adsorption of phenol by α-,β- and γ-CD spherical polymer particles, while the lowest free energy for β-CD polymer reflected its best adsorption ability, compared to α- and γ- CD polymer particles.

Synthesis of magnetic polyphosphazene-Ag composite particles as surface enhanced Raman spectroscopy substrates for the detection of melamine

Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and milk samples.5,5’-Dithiobis-(2-nitrobenzoic acid)(DTNB) was used as model analyte to test the SERS activity of the MPZS-Ag particles.The prepared MPZS-Ag particles possess both magnetic responsiveness and excellent SERS properties.SERS detection of different concentrations of melamine aqueous solutions and spiked milk samples were performed by the MPZS-Ag particles.The limit of detection(LOD) of the melamine in aqueous solutions was 10^-7 mol/L(0.0126 mg/L) and 0.6 mg/L in real milk samples using the MPZS-Ag particles as SERS substrates.The LOD of the melamine are much lower than the safety values of Food and Drug Administration and Codex Alimentarius Commission.These results indicate that the MPZS-Ag particles have promising application prospect for SERS analysis in food safety fields.

Preparation and characterization of conducting polymer-coated thermally expandable microspheres

The thermally expandable microspheres（TEMs） were prepared via suspension polymerization with acrylonitrile（AN）, methyl methacrylate（MMA） and methyl acrylate（MA） as monomers and n-hexane as the blowing agent. Meanwhile, a novel type of functional and conductive thermal expandable microsphere was obtained through strongly covering the surface of microsphere by conductive polymers with the mass loading of 1.5%. The optimal conditions to prepare high foaming ratio and equally distributed microcapsules were investigated with AN-MMA-MA in the proportion of 70%/20%/10%（m/m/m）, and 25 wt% of n-hexane in oil phase. The further investigation results showed that the unexpanded TEMs were about 30 μm in diameter and the maximum expansion ratio was nearly 125 times of original volume. The polypyrrole（PPy） was smoothly coated on the surface of the TEMs and the expansion property of PPy-coated TEMs was almost the same as the uncoated TEMs. Moreover, the structure and expanding performance of TEMs and PPy-coated TEMs were characterized by scanning electron microscopy（SEM）, laser particle size analyzer and dilatometer（DIL）.

Antibacterial Nanoparticles with Universal Adhesion Function Based on Dopamine and Eugenol

In this work,dopamine methacrylamide(DMA)and eugenyl methacrylate(EMA)were used to synthesize polymeric particles of Poly(DMA-co-EMA)by free radical precipitation copolymerization.These two monomers were modified from dopamine(consisting of the catechol moieties adhering to various materials)and eugenol(with antibacterial property),respectively.The proton nuclear magnetic resonance(^(1)H NMR)and Fourier transform infrared(FT-IR)spectroscopy were applied to confirm the successful synthesis of the two monomers and copolymer.The scanning electron microscope(SEM)images showed the size and morphology of the polymer particles.The results indicated that regular particles with uniform size could be obtained with a monomer feeding ratio of 5꞉5.The results of antibacterial activity test indicated that the obtained polymer particles have an antibacterial rate over 90%to Eugenia coli.