Kinetic Study of Radical Polymerization VIII. A Comprehensive Study of Solution Copolymerization of Vinyl Acetate and Methyl Acrylate by 1H‐NMR Spectroscopy

Radical copolymerization reaction of vinyl acetate (VA) and methyl acrylate (MA) was performed in a solution of benzene‐d₆ using benzoyl peroxide (BPO) as the initiator at 60°C. Kinetic studies of this copolymerization reaction were investigated by on‐line ¹H‐NMR spectroscopy. Individual monomer conversions vs. reaction time, which was followed by this technique, were used to calculate the overall monomer conversion, as well as the monomer mixture and the copolymer compositions as a function of time. Monomer reactivity ratios were calculated by various linear and nonlinear terminal models and also by simplified penultimate model with r _2(VA)=0 at low and medium/high conversions. Overall rate coefficient of copolymerization was calculated from the overall monomer conversion vs. time data and k _p  . k _t ^?0.5 was then estimated. It was observed that k _p  . k _t ^?0.5 increases with increasing the mole fraction of MA in the initial feed, indicating the increase in the polymerization rate with increasing MA concentration in the initial monomer mixture. The effect of mole fraction of MA in the initial monomer mixture on the drifts in the monomer mixture and copolymer compositions with reaction progress was also evaluated experimentally and theoretically.     

Grafting of 4‐Vinyl Pyridine onto Nylon‐6 Initiated by Cu(III)

In this article, the graft copolymerization of 4‐vinyl pyridine (4VP) onto nylon‐6 (PA6) using potassium diperiodacuprate (III) (DPC)–PA6 redox system as initiator is investigated in an alkaline medium. The structure and the properties of graft copolymer are confirmed by Fourier transfer infrared spectroscopy (IR), X‐ray diffraction and thermogravimetric analysis (TGA). The mechanism is proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, ratio of 4VP to PA6, pH, as well as reaction temperature and time are investigated. Graft copolymers with high grafting efficiency (>95%) were obtained, which indicated that the DPC–PA6 redox system was an efficient initiator for this graft copolymerization. The quaternized PA6‐g‐P4VP (QPAVP) is proven to be an excellent adsorbent to heavy metal ions.     

Novel Copolymers of Vinyl Acetate and Alkyl Ring‐Substituted 2‐Phenyl‐1,1‐dicyanoethylenes

Electrophilic trisubstituted ethylene monomers, alkyl ring‐substituted 2‐phenyl‐1,1‐dicyanoethylenes, RC₆H₄CH?C(CN)₂ (where R is 2‐methyl, 3‐methyl,4‐methyl, 4‐ethyl, 4‐isopropyl, 4‐butyl, and 4‐t‐butyl), were synthesized by piperidine catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and malononitrile, and characterized by CHN elemental analysis, IR, ¹H‐ and ¹³C‐NMR. Novel copolymers of the ethylenes and vinyl acetate were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C‐NMR, GPC, DSC, and TGA. High T_g of the copolymers, in comparison with that of polyvinyl acetate, indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 190–700°C range.     

Heavy Metal Removal from Synthetic Solutions with Magnetic Beads Under Magnetic Field

The aim of this study is to prepare magnetic beads which can be used for the removal of heavy metal ions from synthetic solutions. Magnetic poly(ethylene glycol dimethacrylate‐vinyl imidazole) [m‐poly(EGDMA‐VIM)] beads were produced by suspension polymerization in the presence of magnetite Fe₃O₄ nano‐powder. The specific surface area of the m‐poly(EGDMA‐VIM) beads was found to be 63.1 m²/g with a size range of 150–200 µm in diameter and the swelling ratio was 85%. The average Fe₃O₄ content of the resulting m‐poly(EGDMA‐VIM) beads was 12.4%. The maximum binding capacities of the m‐poly(EGDMA‐VIM) beads were 32.4 mg/g for Cu²⁺, 45.8 mg/g for Zn²⁺, 84.2 mg/g for Cd²⁺and 134.5 mg/g for Pb²⁺. The affinity order on mass basis is Pb²⁺>Cd²⁺>Zn²⁺>Cu²⁺. Equilibrium data agreed well with the Langmuir model. pH significantly affected the binding capacity of the magnetic beads. Binding of heavy metal ions from synthetic wastewater was also studied. The binding capacities were 26.2 mg/g for Cu²⁺, 33.7 mg/g for Zn²⁺, 54.7 mg/g for Cd²⁺ and 108.4 mg/g for Pb²⁺. The magnetic beads could be regenerated up to about 97% by treating with 0.1 M HNO₃. These features make m‐poly(EGDMA‐VIM) beads a potential candidate for support of heavy metal removal under magnetic field.     

紫外光谱法测定乙酸乙烯酯中的对苯二酚

采用紫外光谱法测定乙酸乙烯酯中对苯二酚含量时,乙酸乙烯酯中的有机杂质会对测试结果产生影响.其中乙醛、丙酮对测试结果的影响程度基本呈线性递增关系,而醋酸甲酯、醋酸乙酯对测试结果不会产生影响.     

Fragrance encapsulation in polymeric matrices by emulsion electrospinning

We present the successful application of emulsion electrospinning for the encapsulation of a model for highly volatile fragrances, namely (R)-(+)-limonene in a poly(vinyl alcohol) (PVA) fibrous matrix. The influence of the emulsion formulation and of its colloidal properties on the fiber morphology, as well as on the limonene encapsulation efficiency, is described. The release profile of the fragrance from the electrospun nanofibers over a fifteen days range shows that this type of nanofibrous matrices with a high fragrance loading capacity is of great potential for applications in various fields, such as cosmetics or food packaging.     

Hypervalent Iodine in Synthesis XXXIV: Palladium-Catalyzed Coupling Reaction of o-Hydroxyarylaldehydes with Hypervalent Iodonium Salts Via Cleavage of the Aldehyde C-H Bond

A novel way of preparation for o-hydroxyarylketones with mild conditions and good yields by palladium-catalyzed coupling reaction of o-hydroxyarylaldehydes with hypervalent iodonium salts via the cleavage of the aldehyde C-H bond has been reported.     

Stereoselective Bromination of 2-Vinyl Chromones Using NBS

A simple one-step synthetic methodology for stereoselective synthesis of E- and Z-3-bromo-2-vinyl chromones in quantitative yield in polar solvents under ambient conditions without the use of catalysts is reported.     

Polymer colloids formed by polyelectrolyte complexation of vinyl polymers and polysaccharides in aqueous solution

The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry, static and electrophoretic light scattering, and elementary analysis. Sodium salts of polyacrylate (PA) and heparin (Hep) were chosen as the polyanion, and hydrochloric salts of poly(vinyl amine) (PVA) and chitosan (Chts) as the polycation. Although these vinyl polymers and polysaccharides have remarkably different backbone chemical structures and linear charge densities, all the four combinations PA-PVA, PA-Chts, Hep-PVA, and Hep-Chts provide almost stoichiometric polyelectrolyte complexes which are slightly charged owing to the adsorption of the excess polyelectrolyte component onto the neutral complex. The charges stabilize the complex colloids in aqueous solution of a non-stoichiometric mixture, and the aggregation number of the complex colloids increases with approaching to the stoichiometric mixing ratio. The mixing ratio dependence of the aggregation number for the four complexes is explained by the model proposed in the previous study.     

Dispersion production by semi-continuous radical vinyl acetate emulsion polymerization with silane co-monomer and characterization of final products

Vinyl acetate radical emulsion polymerization in water with GF51 silane co-monomer was performed by semi continuous way. The GF51 impacts on dispersion rheology as well on films and bonding strength properties were determined. It should be stated that even low quantities of GF51 (up to 6% from VAc) determined high viscosity of dispersions. The GF51 modified films have low water absorption and high affinity to glass. Molecular mass and thermal properties of GF51 modified polymers were determined accordingly.