Synthesis of biocompatible and thermally sensitive poly(N‐vinylcaprolactam) nanogels via inverse miniemulsion polymerization: Effect of the surfactant concentration

The goal of this study was to develop a new route to prepare thermally responsive polymer nanogels. Poly(N‐vinylcaprolactam) nanogels were prepared via inverse miniemulsion polymerization (W/O) at 70 °C using n‐hexadecane as a nonpolar continuous phase, potassium persulfate as an initiator, and N,N′‐methylenebisacrylamide as a crosslinker. Sorbitan monooleate (Span 80) was used as surfactant and its influence on the polymerization kinetics and on the colloidal characteristics of the nanogels were principally investigated. It was observed that the addition of a strong “lipophobe” is required to stabilize the resulting miniemulsion. The nanogels were characterized in terms of morphology, size, zeta potential, and thermoproperties using transmission electron microscopy and dynamic light scattering. It was observed that all the nanogels obtained collapsed when the lower critical solution temperature (LCST) was raised. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3932–3941, 2010     

铈离子氧化还原引发体系与铈离子引发接枝或嵌段共聚合研究的新进展

本文介绍Ce⁴⁺/酰胺引发体系;Ce⁴⁺/聚酰胺、带酰苯胺侧基的聚合物引发接枝共聚合;Ce⁴⁺/氨基甲酸酯引发体系;Ce⁴⁺/聚醚氨酯引发接枝共聚合;Ce⁴⁺/羰基化合物引发体系;Ce⁴⁺引发嵌段共聚合6个方面的研究新进展.     

铈离子与乙酰乙酸乙酯体系引发烯类聚合的研究

<正> 铈离子与醇、醛、酮、α-羟基酸等组成的体系能引发烯类单体进行自由基聚合。关于铈离子与酯类化合物体系文献报道甚少。孙燕慧发现脂肪酸酯或芳香酸酯对铈离子引发丙烯酰胺(AAM)聚合能起促进作用,提高聚合速度只R_(p)但活性较小,相对聚合速度只,为1.3左右。本文研究了二元酸酯、乙酰乙酸乙酯(EACAC)分别与铈离子组成的体系引发AAM聚合,实验结果表明EACAC有很高的活性,它与铈离子组成的体系为一氧化还原引发体系。应用自由基捕捉技术和ESR波谱研究,能检测到由EACAC组分反应产生的自由基,从聚合物端基的FT-IR光谱分析,证实了该自由基能引发单体聚合而成为聚合物的端基。从而讨论了引发机理。     

Application of thermal analysis to study the macroredox polymerization of styrene with hydroxy-terminated polybutadiene

Ceric ammonium nitrate-hydroxy-terminated polybutadiene macroredox initiator has been investigated for the polymerization of styrene in nitric acid medium at 35 °C. Water inhibited the polymerization of styrene using this macroredox system. The products obtained were crosslinked and insoluble in water and organic solvents. A probable mechanism for the copolymerization reaction has been inferred from differential scanning calorimetry. Kinetic parameters for thermal degradation have been calculated by thermogravimetry (TG).     

Ceric ammonium nitrate (CAN) mediated esterification of N-Boc amino acids allows either retention or removal of the N-Boc group

Reaction of N-Boc amino acids with ceric ammonium nitrate in an alcohol as the solvent at room temperature resulted in the esterification of N-Boc amino acids with Boc group retention. When the reaction was conducted at reflux temperature, esterification was accompanied with simultaneous removal of the Boc group. Both reactions gave the desired products in good yields.     

Branched polymers through redox emulsion polymerization using peroxide monomer as the branching agent

Redox emulsion polymerization to branched vinyl polymers in the presence of 2-(tert-butylperoxy)ethyl methacrylate (BPEMA), ferrous sulfate, and sodium formaldehyde sulfoxylate (SFS) is reported in this paper. The peroxide monomer BPEMA containing alkyl peroxide was designed for high stability during preparation and storage. Nuclear magnetic resonance spectroscopy (NMR), Raman, and triple-detection size-exclusion chromatography (TD-SEC) measurements were used to reveal the polymerization procedure and provide evidence of branching structure. In the case of polymerization at St₁₀₀-BPEMA_1.0-FeSO_{4 0.5}-SFS_0.2, the molecular weight increased and decreased with conversion below and above 75% monomer conversion, respectively. The decreasing of molecular weight with monomer conversion came from the increased viscosity of the micelle, which makes it difficult for the formed macromolecules containing vinyl group to participate into polymerization. Finally, the molecular weight reached a value of M_{n. SEC} = 439,200 g/mol at 92.2% conversion. In addition, the Zimm branching factor, g', also decreased and increased with conversion below and above 60% conversion, respectively, and then the g' finally attends a value of 0.41, showing high degree of branching. Branched poly(methyl methacrylate) was also prepared through this strategy, showing a versatile approach to branched vinyl polymers.     

Effects of reaction conditions on quinone/diquinone product ratios in the oxidation of 1,4-dimethoxybenzene derivatives with ceric ammonium nitrate

Proper choice of reaction conditions allows formation of either the quinone or corresponding diquinone as the major product upon treatment of 2-alkyl-1,4-dimethoxybenzenes with ceric ammonium nitrate.     

Synthesis of core-shell latexes by redox initiation at ambient temperatures

Core-shell polymer composites made by two-stage emulsion polymerizations are useful in many applications. In systems involving a hydrophilic/hydrophobic polymer pair, a core-shell arrangement is thermodynamically unfavorable and may be difficult to achieve. To counteract the thermodynamic forces in such a system, the mobility of the phases can be reduced to such an extent that a core-shell morphology is achieved. This was accomplished in a PMMA/PS two-stage system by lowering the second-stage polymerization temperature to room temperature using a redox initiator. At this relatively low temperature, a core-shell morphology was obtained even when the second-stage was carried out as a batch polymerization. © 1992 John Wiley & Sons, Inc.     

Synthesis of Benzo[c][2,7]Naphthyridines by One-Pot Multicomponent Reaction Using Ceric(IV) Ammonium Nitrate

A new, one-pot, three-component reaction for the synthesis of benzo[c][2,7]naphthyridines has been achieved from aromatic amines, aromatic aldehydes, and N-carbethoxy-4-piperidone in the presence of a catalytic amount of ceric ammonium nitrate in good yields at room temperature. The advantages of this procedure are mild reaction conditions, low toxicity, and the use of inexpensive reagents. Apart from milder and environmentally benign conditions, this method involves a simple, reliable approach to give good yields of the desired products and is compatible with a wide range of functional groups.     

反相乳液聚合法制备丙烯酰胺-丙烯酸铵共聚物

以煤油为连续相,水为分散相,Span-80/Tween-80为复配乳化剂,过硫酸铵为引发剂,丙烯酰胺、丙烯酸和氨水为原料,采用反相乳液聚合法合成了丙烯酰胺-丙烯酸铵共聚物絮凝剂.考察了乳化剂种类及用量、引发剂浓度、单体浓度、EDTA用量、聚合温度等对共聚物特性黏数的影响.确定了最佳实验条件,利用FTIR对样品进行了表征.     

Oxidation of 4-methoxyanilines to 1,4-benzoquinones using ceric ammonium nitrate (CAN)

Treatment of substituted 4-methoxyanilines with ceric ammonium nitrate in a 1:1 mixture of water and acetonitrile resulted in the formation of 1,4-benzoquinones in acceptable yields.     

A facile procedure for the one-pot synthesis of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles

Unsymmetrically 2,5-disubstituted 1,3,4-oxadiazoles were efficiently synthesized from the cyclization-oxidation reaction of acyl hydrazones. Also, the synthesis of the title compounds was achieved by the condensation of acyl hydrazides and aromatic aldehydes in the presence of ceric ammonium nitrate in dichloromethane.     

Synthesis of Nanosized (<20 nm) Polymer Particles by Radical Polymerization in Miniemulsion Employing in situ Surfactant Formation

A novel method for synthesis of ultrafine polymeric nanoparticles of diameters less than 20 nm has been developed. The method is based on miniemulsion polymerization exploiting combination of the in situ surfactant generation approach (whereby the surfactant is formed at the oil–water interface by reaction between an organic acid and a base) and ultrasonication. Conventional radical polymerization and nitroxide‐mediated radical polymerization of styrene have been conducted in miniemulsion using oleic acid/potassium hydroxide, demonstrating that particles with diameters less than 20 nm can be obtained by this approach at surfactant contents much lower than traditionally required in microemulsion polymerizations.

     

Relative Rates of Branching in Emulsion and Miniemulsion Polymerization

This communication describes the potential advantages of using a miniemulsion rather than an emulsion process for the polymerization of synthetic rubbers in which the polymerization is ended (short‐stopped) considerably before full conversion in order to limit excessive branching brought on by a high polymer‐to‐monomer ratio in the polymer particles. Because the polymer‐to‐monomer ratio in the particle at low monomer conversion is much lower in a miniemulsion, a miniemulsion can be polymerized to a significantly higher conversion than a conventional emulsion while maintaining an equivalent degree of branching. Short‐stopping at a higher monomer conversion will result in substantially reduced processing costs associated with recovery and recycle of unpolymerized monomer.     

Effect of unmodified kraft lignin concentration on the emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid to produce polymer hybrid latex

The introduction of non‐modified kraft LignoBoost® lignin (KL) to produce polymer hybrid latex has received much attention in recent years because it is derived from renewable resources. The focus of this work is to develop a polymer hybrid latex by emulsion and miniemulsion copolymerization of styrene with n‐butyl acrylate and methacrylic acid in the presence of different concentrations of KL furnished by the pulp and paper industry. The study intends to substitute a styrene in the system to understand the effect of non‐modified KL on the properties not only of the latexes, but also on the copolymers themselves. Each polymerization was carried out by shot‐process of tertbutyl hydroperoxide and sodium formaldehyde sulfoxylate as the redox system. The polymer latexes were characterized in relation to overall conversion, particle diameter, particle morphology, coagulum formation, surface tension, zeta potential, and atomic force microscopy. The polymers were evaluated through gel permeation chromatography, water absorption, and thermal properties. The results show that the addition of non‐modified KL results in inhibition of the polymerization and that KL acts as a colloid stabilizer. Small particles were generated in the initial stages of the polymerizations. The presence of the KL altered the color of the latexes; the increase in KL concentration resulted in increase in the absorption of water of the polymer films; the increase in KL concentration resulted in decrease of the molar mass of the copolymers.     

Surface modification of monodisperse hydroxyl functionalized polymeric microspheres using ceric ammonium nitrate

The surface modification of monodisperse hydroxyl functionalized polymeric microspheres was carried out by utilizing a redox initiation system. Styrene, divinylbenzene and hydroxyethyl methacrylate were used as the second monomer in the seeded polymerization. An excessive amount of the second monomer emulsion was swollen into the polystyrene (PS) seed particles completely by controlling the medium solvency and swelling temperature. The hydroxyl functional groups were radicalized by the ceric ammonium nitrate in nitric acid solution, and the methyl methacrylate was reacted uniformly on the surface of microspheres. From the SEM, and FE-TEM measurements, highly monodisperse microspheres having a smooth surface, and polymethylmethacrylate (PMMA) coating layer were observed, respectively. The surface characteristics of the PS seed particles, hydroxyl functionalized and surface-modified polymeric microspheres were confirmed by utilizing FT-IR, XPS and thermal analysis.     

Functional benzoxazines containing ammonium salt of carboxylic acid: Synthesis and highly activated thermally induced ring‐opening polymerization

1,3‐Benzoxazine monomers having ammonium salt of carboxylic acid have been developed. These 1,3‐benzoxazines 1a and 1b were easily synthesized from the corresponding tetrabutylammonium salts of glycine and β‐alanine, respectively. The glycine‐derived benzoxazine 1a exhibited remarkably high reactivity, which allowed its thermally induced ring‐opening polymerization in bulk at 100 °C, at which N‐methyl‐1,3‐benzoxazine 1d did not undergo the polymerization at all. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

功能高分子聚丙烯酸铵的研制

以环己烷为连续相、水为分散相、氨水部分中和的丙烯酸为单体、K2S2O8为引发剂，N，N－亚甲基双丙烯酰胺为交联剂，采用反相悬浮聚合法合成了功能高分子材料－聚丙烯酸铵高吸水性树脂。研究了乳化剂、引发剂和交联剂用量、pH值、反应湿度等对吸水率的影响，得到的高吸水性树脂最大吸水率为1237mL/gR,其最大吸生理盐水率为114mL/gR。利用SEM，IR对其进行了表征。SEM分析表明，如果采取适当的工艺可以得到粒状产品。     

Ceric Ammonium Nitrate as the Novel Oxidizing Agent for the Facile Synthesis of (Dichloroiodo)arenes

Ceric ammonium nitrate (CAN) has been found to be a remarkable oxidizing agent for the oxidative conversion of iodoarenes to (dichloroiodo)arenes in acetic acid using aqueous HCl. The reaction of CAN with HCl generates in situ molecular chlorine, which is responsible for the oxidation. This method avoids the use of hazardous, toxic, and corrosive gaseous chlorine.     

Synthesis of cationic polyacrylamide via inverse emulsion polymerization method for the application in water treatment

In order to improve the flocculent efficiency of wastewater treatment, a cationic flocculant poly (acrylamide-[2-(methacryloyloxy) ethyl] trimethyl ammonium chloride) (P (AM-DMC)) (CPAM) has been synthesized successfully via an inverse emulsion polymerization. Acrylamide (AM) and [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride (DMC) were served as monomers. The molecular structure of CPAM was characterized by Fourier transform infrared spectra (FT-IR) and ¹H nuclear magnetic resonance spectrum (¹H-NMR). The morphology of CPAM particles has been investigated by transmission electron microscope (TEM). Results showed that CPAM was the copolymer of AM and DMC and the particles of CPAM were uniform spheres (the size was about 200?nm). The synthetic conditions of CPAM have been studied and optimized by single-factor experiments. An optimized product was obtained at an intrinsic viscosity of 560?mL/g with a total monomer concentration of 25% and initiator concentration V50 of 0.2% (based on the total monomer mass). The amount of emulsion was 6% and the HLB (Hydrophile-Lipophile-Balance) of emulsion was 7.3. In addition, the flocculation property of CPAM was evaluated with kaolin suspension using jar test, and the result demonstrated that the flocculation property of CPAM performed better than kaolin flocculation.