Facile synthesis of chromium chloride/poly(methyl methacrylate) core/shell nanocapsules by inverse miniemulsion evaporation method and application as delayed crosslinker in secondary oil recovery

Cr(III)ehydrolyzed polyacrylamide(HPAM)gels have been extensively studied as a promising strategy controlling waste water production for mature oilfields.However,the gelation time of the current technologies is not long enough for in-depth placement.In this study,we report a novel synthesis method to obtain chromium chloride/poly(methyl methacrylate)(PMMA)nanocapsules which can significantly delay the gelation of HPAM through encapsulating the chromium chloride crosslinker.The chromium chloride-loaded nanocapsules(CreNC)are prepared via a facile inverse miniemulsion evaporation method during which the hydrophobic PMMA polymers,pre-dispersed in an organic solvent,were carefully controlled to precipitate onto stable aqueous miniemulsion droplets.The stable aqueous nanodroplets(W)containing Cr(III)are dispersed in a mixture of organic solvent(O1)with PMMA and nonsolvent medium(O2)to prepare an inverse miniemulsion.With the evaporation of the O1,PMMA forms CreNCs around the aqueous droplets.The CreNCs are readily transferred into water from the organic nonsolvent phase.The CreNCs exhibit the tunable size(358-983 nm),Cr loading(7.1%-19.1%),and Cr entrapment efficiency(11.7%-80.2%),with tunable zeta potentials in different PVA solutions.The CreNCs can delay release of Cr(III)and prolong the gelation time of HPAM up to 27 days.

Monomer reactivity ratios for fluoroacrylate and butyl methacrylate in miniemulsion copolymerizations initiated by potassium persulphate

Miniemulsion copolymerization of butyl mathacrylate （BMA） with fluoroacrylate （HFMA, TFMA） was carried out at 70 ℃ by employing potassium persulphate （KPS） as initiator. Copolymer compositions at low conversion levels were determined by ^1H NMR spectra techniques. The reactivity ratios were evaluated by employing Kellen-Tudos （K-T） methods, which yields the apparent reactivity ratios, rBMA = 0.74, rHFMA = 0.87 and rBMA = 0.73, rTFMA = 0.75, respectively, and Q- and e-values of HFMA and TFMA were calculated by the Alfrey-Price method. The results show that HFMA and TFMA are more active than BMA, and the cross-propagation rate constant is greater than the self-propagation one in these two copolymerizations.

The reversible addition-fragmentation chain transfer(RAFT) miniemulsion polymerization of vinyl acetate mediated by xanthate

The reversible addition-fragmentation chain transfer （RAFT） miniemulsion polymerization of vinyl acetate （VAc） mediated by methyl （methoxycarbonothioyl） sulfanyl acetate （MMSA） was carried out. The results showed that polymerizations initiated by AIBN and KPS proceeded in a controlled way. The RAFT miniemulsion polymerization of VAc initiated by KPS showed the shorter inhibition period, higher propagation rate coefficient and final conversion than those in experiment initiated by AIBN. When the monomer conversion reached 25%, the polydispersity index （PDI） of polymer became broad, which was related to chain transfer reaction in RAFT miniemulsion of VAc.

Synthesis of polystyrene-styrene/butadiene diblock copolymers via reversible addition-fragmentation chain transfer miniemulsion polymerization

Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer （RAFT） miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ^1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.

RAFT Miniemulsion Polymerization of MMA with Cumyl Dithiobenzoate as Chain Transfer Agent

Reversible addition-fragmentation transfer （RAPT） miniemulsion polymerizations for PMMA with cumyl dithiobenzoate （CDB） as a chain transfer agent （CTA） has been carried out. Higher temperature made the polymerization much faster and the PDI remained below 1.20, when the temperature was upon 70 ℃.

The Role of Surfactant and Costabilizer in Controlling Size of Nanocapsules Containing TEGDMA in Miniemulsion

Nanocapsules with triethylene glycol dimethacrylate （TEGDMA） as core material and polyurethane as wall material used for self-healing bonding resin were prepared by interfacial polycondensation in miniemulsion. The influence of surfactant and costabilizer concentration on nanocapsules size and stability of nanocapsules was investigated. The size and its polydispersity of the nanocapsules were measured by light-scattering particle size analyzer. When the concentration of SDS were increased from 2.5wt% to 10wt%,the size decreases from 340.5 nm to 258.3 nm, PDI decreased from 0.210 to 0.111. As the concentration of HD increased, the size and PDI were both decreased, When reaching 10wt%,the size was 258.0 nm,PDI was 0.130. SDS and HD play important effect in synthesis of Nanocapsules containing TEGDMA.By changing the surfactant and costabilizer concentration it was possible to synthesize a wide variety of nanocapsules sizes. The performance and technical parameters of nanocapsules had been researched preliminarily, which built the solid foundation for the application to the self-repairing bonding resin.

Effect of ionic liquids on stability of O/W miniemulsion for application of low emission coating products

Room temperature ionic liquids(RTILs) are non-volatile organic salts. They may replace conventional coalescing agents in latex coating thus reducing volatile organic compounds(VOCs) emission as well as improving performance of latex coating products such as better thermal stability, conductivity, and antifouling property. The formation of latex coating containing RTILs can be achieved by encapsulation of RTILs inside particles via miniemulsion polymerization. In this study, the role of RTILs and its concentration on stability of miniemulsion during storage and polymerization were investigated. It has been found that, above a critical concentration(10 wt%), adding more RTILs to oil phase may weaken miniemulsion stability during storage as well as polymerization. Such observations were consistent with the zeta potential measurement for miniemulsions prepared at the similar conditions. The results obtained here would be a useful guideline for the development of new waterborne coating products with desirable functions and particle sizes.

Precipitation of metal oxide nanoparticles using a miniemulsion technique

A method to precipitate nanoparticles using a miniemulsion technique is described, in which miniemulsion droplets between 100 and 1000 nm in size serve as nanoreactors enabling both the control of particle formation and particle growth. The application of miniemulsion droplets to synthesise nanoparticles comprises three advantages： first, the size of the precipitated particles is limited by the reactant concentration within the emulsion droplet; second, particle agglomeration is prevented as nanoparticle collision outside the nanoreactor is avoided; and third, easy technical scale up can be realized by increasing emulsion volume and thus the number of nanoreactors, while local conditions within the reactors are not changed, The miniemulsion technique is an easy scalable process which allows defined synthesis of particles by precipitation reactions. The miniemulsion technique involves first the preparation of a stable water-in- oil miniemulsion by high pressure homogenisation. Whereas a water soluble reactant is provided within the aqueous droplets, another oilas well as water-soluble reactant can be introduced to the emulsion after homogenisation. The precipitation reaction is induced by the diffusion of the second reactant into the emulsion droplet. Together with this contribution, a method is described and discussed which uses a high pressure homogenisation process to produce stable water-in-oil miniemulsions serving as a reaction medium to precipitate metal oxides.

Preparation of Organic Nanoacid Catalyst for Urethane Formation

Metal-free catalysts are preferred during these days in organic synthesis or in polymeriza- tions. Sulfonic acid is reported to be efficient in catalyzing reactions between isocyanates and alcohols. In this work, synthesis of sulfonic acid immobilized organic nanoparticles （nanoacid） and its application in catalyzing urethane formation, are elaborated. The nanoacid can be simply prepared by miniemulsion polymerization with a reactive surfacrant, namely sodium 4-（（perfluoronon-8-en-l-yl）oxy）benzenesulfonate, followed by an acidification. From the images of scanning electron microscope, the nanoacid obtained is found to be narrowly dispersed and the average diameter is around 90 nm. The measured sulfur content is 0.5%, from which the content of sulfonic acid in the nanoparticles is calculated to be 0.16 mmol/g. When catalyzing urethane formation based on hexamethylene diisocyanate and n-butanol, the nanoacid catalyst exhibits considerable efficiency.

AQUEOUS STABLE FREE RADICAL POLYMERIZATION PROCESSES

An overview of aqueous polymerizations, which include emulsion, miniemulsion and suspension polymerizations, under stable free radical polymerization (SFRP) conditions is presented. The success of miniemulsion and suspension SFRP polymerizations is contrasted with the difficulties associated with obtaining a stable emulsion polymerization. A recently developed unique microprecipitation technique is referenced as a means of making submicron sized particles that can be used to achieve a stable emulsion SFRP process.

Synthesis and application of green solvent dispersed organic semiconducting nanoparticles

Organic photovoltaic semiconductors have made significant progress and have promising application prospects after decades of development.When compared with traditional semiconductors,the solution method for preparing photovoltaic semiconductors shows the advantages of low cost and convenient preparation.However,because of the extremely poor solubility of the polymers used to prepare semiconductors,toxic solvents must be used when using the solution method,which has significant negative effects on the environment and operators and severely limits its development prospects.Organic nanoparticles(NPs),on the other hand,can avoid these issues.Because NPs are typically water or alcohol-based,no toxic solvents are used.Furthermore,NPs have been used in organic solar cells,hydrogen catalysis,organic light-emitting diodes,and other fields after nearly two decades of development,and their preparation methods have been developed.We describe the preparation,optimization,and application of NPs in photovoltaic semiconductors in this review.

Preparation and study of photoswitchable fluorescence nanoparticles based on spirobenzopyran

The preparation and performance characterization of〈50 nm spirobenzopyran-based photochromic nanocomposites with photoswitchable fluorescence are presented.The nanocomposites were fabricated by means of a modifed miniemulsion polymerization process,in which the hydrophobic spirobenzopyran was covalently attached to the polymer chains and the matched fluorescent dyes were noncovalently embedded in the nanoscale cross-linked polymeric matrix,respectively.The obtained nanocomposites with a high relative fluorescence quantum yield（Q）exhibited superior fluorescent photoswitchable performance due to the effective photo-induced intermolecular energy transfer.The stability of photomerocyanine was also improved.

Facile and Convenient Fabrication of Color-controlled Colloidal Magnetically Assembled Photonic Crystals

A facile, convenient and flexible method to tune the structural color of the colloidal magnetically assembled photonic crystals（CMA-PCs） was proposed. The mechanism to tune structural color could be attributed to the significant influence of the surfactant sodium dodecyl sulfate（SDS） concentration on the particle size, especially on the magnetite content of the superparamagnetic composite nanoparticles（MCNPs）. By adjusting SDS concentra- tion in miniemulsion polymerization of MCNPs, CMA-PCs with desired diffraction colors could be obtained.