Preparation of monodisperse HPMC/PAA hybrid nanogels via surfactant-free seed polymerization

Herein we report a facile surfactant-free two-step method to prepare hydroxypropyl methylcellulose/poly(acrylic acid) (HPMC/PAA) hybrid nanogels. The HPMC/poly(N,N′-methylenebisacrylamide) (PMBA) nanoparticles were firstly prepared by free radical polymerization of N,N′-methylenebisacrylamide (MBA) in HPMC aqueous solution. In the second step, HPMC/PAA nanogels were synthesized by polymerization using the as-prepared HPMC/PMBA nanoparticles as the seeds and acrylic acid (AA) and MBA as the monomer and cross-linker, respectively. Dynamic light scattering (DLS) experiments indicated the nanogels were monodispersed with the nanogel sizes ranging from 95 to 310 nm and the polydispersity index (PDI) values ranging from 0.043 to 0.122. Transmission electron microscope (TEM) experiments demonstrated that nanogels have a core/shell structure. Furthermore, the monodisperse nanogels have a good temperature and pH sensibility, and the nanogel diameter was decreased with increasing temperature while increased with rising pH. This method provides a new way of preparation of monodisperse polymer nanogels with a core/shell structure.     

Preparation of thermosensitive nanogels by photo-cross-linking

 A novel method to prepare thermosensitive nanogels from photocross-linkable copolymers of N-isopropylacrylamide and dimethyl maleinimido acrylamide (DMIAAm) was developed. The colloidal nanogels were formed by UV irradiation of solutions of thermosensitive polymers in water at 45 °C. The compositions of the photopolymer solutions were varied by changing the amount of DMIAAm in the photopolymer chains (2–10 mol%) or by varying the sodium dodecyl sulfate (SDS) concentration. The resultant nanogel particles were rather spherical and showed large changes in hydrodynamic diameters in the vicinity of the phase transition temperature of the corresponding linear photopolymers. The particle sizes of the nanogels and their swellability could be controlled through the UV irradiation time, the chromophore content and the SDS concentration. An increase in the chromophore content and the SDS concentration resulted in nanogels with smaller dimensions. The hydrodynamic diameters of the nanogels decreased significantly from 2 to 10 min UV irradiation time but not significantly after that. The phase transition of the photopolymer solutions and the respective nanogels could be adjusted by the chromophore content or the SDS concentration. An increase in the chromophore content leads to lower phase-transition temperatures, whilst an increase in the SDS concentration elevated them. Pulsed-field-gradient NMR proved a useful tool to investigate the network formation in the nanogels by determining changes in the diffusion coefficients. Received: 14 May 2001 Accepted: 1 June 2001     

In-situ synthesis of PHEMA magnetic nanogels via photochemical method

One-pot synthesis of magnetic nanogels via photochemical method is reported in this paper. Poly(2-hydroxyethyl methacrylate)(PHEMA) magnetic nanogels are synthesized by in-situ polymeriza-tion of 2-hydroxyethyl methacrylate(HEMA) and N,N'-methylene-bis-(acrylamide)(MBA) in Fe3O4 aqueous suspension under UV irradiation. The structure and compositions of magnetic nanogels are characterized by FTIR,TGA,SEM,TEM and PCS. TGA measurement indicates that magnetic nanogels contain 90% magnetite. Both naked Fe3O4 and magnetic nanogels are superparamagnatic at room temperature according to magnetization curves. The swollen capability of the hydrogel shell is proved by contrasting the particles sizes obtained by SEM,TEM and PCS. Particle diameters can be manipu-lated by changing monomer concentration and irradiation time. A mechanism of the coating process is proposed.     

Lysozyme-dextran core-shell nanogels prepared via a green process

A novel method has been developed for preparing nanogels with a lysozyme core and dextran shell. The method involves the Maillard dry-heat process and heat-gelation process. First, lysozyme-dextran conjugates were produced through the Maillard reaction. Then, the conjugate solution was heated above the denaturation temperature of lysozyme to produce nanogels. The nanogels are of spherical shape having a hydrodynamic diameter of about 200 nm and swelling ratio of about 30. The nanogel solutions are stable against long-term storage as well as changes in pH and ionic strength. Ibuprofen has been used as a drug model to study the electrostatic and hydrophobic interactions with these nanogels at different pH values. The study reveals that the nanogels are more suitable for loading protonated ibuprofen. We have verified that the knowledge of the formation mechanism of lysozyme-dextran nanogels can be applied to prepare other globular protein-dextran nanogels.     

Stable amphoteric nanogels made of ovalbumin and ovotransferrin via self-assembly

Ovalbumin and ovotransferrin are two proteins in hen egg white with isoelectric points of 4.8 and 6.8, respectively. A convenient and green method was developed in this study to prepare ovalbumin-ovotransferrin nanogels: a mixture of the two proteins was adjusted to a certain pH and then heated. Heat induced denaturation and gelation of the proteins, but the negative charges of ovalbumin prevented the proteins from coagulating. Dynamic light scattering, transmission electron microscopy, and atomic force microscopy studies reveal the nanogels have a spherical shape in both the swell and dry forms. Their apparent hydrodynamic diameters are in the range of 100-220 nm depending on the protein concentration in the nanogel preparation process. The nanogels display an amphoteric property: they carry net positive charges at pH lower than 5.5 and net negative charges at pH higher than 5.5. They form redispersible secondary aggregates at pH 5.0-6.0. The nanogels are stable in the pH ranges of 2.0-4.0 and 7.0-11.0, and they exhibit pH unchangeable but thermoreversible hydrophobicity. Benzoic acid was used as a model drug to study the loading ability. The native ovalbumin and ovotransferrin cannot bind with benzoic acid, whereas the nanogels with the network structure and hydrophobic binding sites can load benzoic acid through hydrophobic and electrostatic interactions.     

Preparation of functionalized ketones via low temperature grignard reaction

δ-Chloroketones and 5-oxo-9-decenoic acid methyl ester were prepared from 5-chlorovaleryl chloride and methyl 4-(chloroformyl)-butyrate via Grignard reaction in tetrahydrofuran at ?70°.     

Synthesis of architecturally well-defined nanogels via RAFT polymerization for potential bioapplications

Nanogel synthesis by RAFT polymerization is an emerging field for the control of architectures and functions of polymeric nanomaterials for bioapplications. In this Feature Article, we review the recent development in nanogel synthesis using preformed RAFT polymers and by direct RAFT polymerizations.     

Novel approaches for the preparation of magnetic nanogels via covalent bonding

Here, novel methods to encapsulate magnetic nanoparticles (MNPs) into dual‐stimuli‐responsive nanogels via covalent bonding are reported. With the aim of strengthening the attachment of MNPs with the nanogels, primary amine‐ and epoxide‐functionalized stimuli‐sensitive poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA)‐based nanogels were firstly synthesized. Then, MNPs were incorporated into the nanogels by using different methods, obtaining different families of magnetic nanogels (MNGs). Those MNGs, showing pH‐sensitivity and high superparamagnetic response, could be considered to be widely useful as theranostic agents in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3573–3586     

In-situ synthesis of PHEMA magnetic nanogels via photochemical method

One-pot synthesis of magnetic nanogels via photochemical method is reported in this paper. Poly(2-hydroxyethyl methacrylate)(PHEMA) magnetic nanogels are synthesized by in-situ polymerization of 2-hydroxyethyl methacrylate (HEMA) and N,N′-methylene-bis-(acrylamide)(MBA) in Fe₃O₄ aqueous suspension under UV irradiation. The structure and compositions of magnetic nanogels are characterized by FTIR, TGA, SEM, TEM and PCS. TGA measurement indicates that magnetic nanogels contain 90% magnetite. Both naked Fe₃O₄ and magnetic nanogels are superparamagnatic at room temperature according to magnetization curves. The swollen capability of the hydrogel shell is proved by contrasting the particles sizes obtained by SEM, TEM and PCS. Particle diameters can be manipulated by changing monomer concentration and irradiation time. A mechanism of the coating process is proposed. Supported by the Shanghai Municipal Commission for Special Project of Nanometer Science and Technology (Grant No. 0452nm068)     

多频超声反应槽连续强化酸化油酯交换制备生物柴油研究

以平均酸值高达33.07 mgKOH/g不可食用的廉价酸化油为原料,利用自行设计的多频超声溢流槽连续强化酯交换反应生物柴油生产装置,先后经预酯化、酯交换两步反应,高效、低耗的制备生物柴油。主要考察了室温下物料流量(停留时间)、超声功率、超声频率及组合、KOH用量、醇油物质的量比对酯交换反应的影响及单位产品能耗。结果表明,多频组合超声辐射比单频更有利于生物柴油的制备;预酯化后的油料在流量为25 L/h(物料停留时间为54 min),催化剂(KOH)用量为1.2%(质量分数),醇油物质的量比为6∶1和各反应槽功率为200 W的条件下,甲酯产率达96.83%。50 L废弃酸化油能制得符合国标GB19147—2009的生物柴油48L,整个生物柴油制备过程总耗时和总耗电量仅为8.667 h、5.42 kWh。     

Preparation of polyamides via the phosphorylation reaction. X. A study of higashi reaction conditions

We report a study of the conditions of the phosphorylation reaction for the preparation of aromatic polyamides using the Higashi reaction medium. For poly(p-phenylene terephthalamide) (PPD-T), the optimum conditions are: reaction temperature, 115°C; monomer concentration, C = 0.083 mol/L; and ratio of triphenyl phosphite (TPP) to monomer, 2.0. These optimum conditions produce PPD-T having η_inh = 6.2 dL/g. At temperatures of 120°C and above PPD-T precipitates from the reaction mixture, leading to lower molecular weights. At lower temperatures the reaction mixture gels, and the gel time decreases with increasing reaction temperature. However, polycondensation continues in the gel state. Monomer concentrations C = 0.10 mol/L and above produce precipitation and yield polyamides of lower molecular weight. For the preparation of poly(p-benzamide) (PBA), the optimum ratio of TPP to monomer is 0.6 for either p- aminobenzoic acid or N-4-(4′-aminobenzamido)benzoic acid. In the former case the inherent viscosity of polymer prepared at 115°C showed little dependence upon the concentration of the monomer. The highest value, η_inh = 1.8 dL/g, was obtained with C = 0.40 mol/L and a TPP/monomer ratio of 0.6. However, for the same TPP/monomer ratio, the monomer containing a preformed amide linkage, N-4-(4′-aminobenzamido)benzoic acid, gave PBA with η_inh = 4.6 dL/g when the monomer concentration is 0.33 mol/L. This is the highest value reported for PBA using the phosphorylation reaction. In A?A + B?B polycondensation, examples in which one of the monomers contained one or two preformed amide linkages produced polyamides having η_inh = 7.8 and 8.9 dL/g, respectively.     

Bioreducible nanogels/microgels easily prepared via temperature induced self-assembly and self-crosslinking

A facile temperature induced self-assembly and self-crosslinking method has been developed for preparing bioreducible nanogels/microgels without need of any stabilizer, catalyst or additional crosslinking agent. The size of formed nanogels/microgels can be easily tuned via the polymer concentration.     

Enhanced mineralization of Reactive Black 5 by waste iron oxide via photo-Fenton process

Research on Chemical Intermediates - Advanced oxidation process is a promising technology for the treatment of azo dye wastewater, owing to its high degradation performance and less...     

Preparation of trifluoroiodomethane via vapor-phase catalytic reaction between hexafluoropropylene oxide and iodine

Based on our previous investigation on the reaction mechanism to produce difluorocarbene and subsequent CF₃I starting with CHF₃ and I₂, a new route for preparing CF₃I at a relative low temperature, 200 °C, has been developed via a vapor-phase catalytic reaction between hexafluoropropylene oxide with I₂ in the presence of KF supported on activate charcoal as a catalyst. The influence of reaction temperature and reaction time on the amount of CF₃I was investigated. In the reaction process, coke-formation was suggested on the surface of catalysts by means of BET, XPS and TG-DTA analysis. The process for the formation of CF₃I and by-products is also discussed.     

Preparation of hollow carbon nanospheres at low temperature via new reaction route

Hollow carbon nanospheres were obtained at 200 °C via a new reaction route, by using magnesium, hexachloroethane and aluminum trichloride as starting materials and benzene as solvent. The products were characterized with X-ray diffraction pattern, transmission electron microscope, high-resolution transmission electron microscope images and Raman spectrum. The reaction conditions are easy to be maintained and controlled. They may provide a new method to produce other carbonaceous materials. A possible mechanism of reaction was proposed.     

Preparation of initiator and cross-linker-free poly(N-isopropylacrylamide) nanogels by photopolymerization

Poly(N-isopropylacrylamide) or PNIPAm nanogels with diameter of 50–200 nm were prepared from N-isopropylacrylamide monomer by photopolymerization in the absence of initiator, cross-linker and surfactant. Morphology transition of the nanogels from branch to compact, global one was tuned with NIPAm(N-isopropylacrylamide) concentration in reaction. Reaction mechanism of the nanogels formation was proposed. The yield of prepared nanogels can increased from ca. 20 up to 86% when solution pH varied from neutral to 2. ESR signals confirmed that the existence of H⁺ in reaction could accelerate the polymerization of NIPAm.     

A novel route to prepare pH- and temperature-sensitive nanogels via a semibatch process

A novel method via a semibatch process in the absence of surfactant has been adopted to prepare pH- and temperature-sensitive nanogels. The shape, charge distribution, temperature, and pH-induced volume phase transition behavior of the latexes were investigated by scanning electronic microscopy, zeta potentials, dynamic laser light scattering, and UV/vis spectroscopy. It was found that, in the absence of surfactant, with increasing the amount of AAc from 5 to 20 mol% of N-isopropylacrylamide (NIPAM), the hydrodynamic diameters (D_H) decrease from 230 to 60 nm. With increasing pH value from 3 to 11, the D_H values increase slightly, which is different than the dramatic increase seen when using a conventional batch method with a range from 680 to 1700 nm. However, at pH 3, the turbidity curves of these kinds of particles increase dramatically at temperatures between 33 and 37 °C, while remaining constant at first and then increasing directly at pH 11. Furthermore, the distribution of carboxylic groups located not only on the interior but also on the exterior of colloidal particles as a result of adoption of the semibatch method, other than simple surface distribution of poly(NIPAM-co-AAc) latexes via the batch method.