Vinyl Polymerization. 386. Polymerization of Methyl Methacrylate Initiated by Imidazole in Aqueous Solution of Copper(II) Chloride

The radical polymerization of methyl methacrylate (MMA) was carried out with the system of imidazole (Im), copper(n) chloride, and water at 85°C. The effects of the amount of each component on the conversion of MMA were investigated. The polymerization proceeded through a radical mechanism. The overall activation energy was estimated to be 28.7 kJ/mole. The conversion of MMA showed a maximum at pH 8-9 of the aqueous solution. The formation of a complex of CuCl₂ with Im, water, and MMA was confirmed by electronic spectra. An initiation mechanism was proposed.     

CHARACTERIZATION OF MELT-MIXED POLY(ETHYLENE-2,6-NAPHTHALATE) (PEN)/POLYCARBONATE (PC) BLENDS

ABSTRACT

Melt blending of poly(ethylene naphthalate) (PEN) and bisphenol A polycarbonate (PC) was performed without the addition of catalyst in a batch mixer at 290°C at various compositions. All the blends prepared exhibited a biphasic character and had very good mechanical properties, in some cases, even better than those of the respective pure constituents. This behavior was attributed to a copolymer formation in the mesophase, which effectively compatibilizes the system. The formation of a PEN/PC block copolymer was considered to be due to transesterification reactions between PEN and PC and was verified by extraction experiments and examination of the soluble and insoluble fractions by various spectroscopic techniques.     

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.     

Phosphorylated silica/polyamide 6 nanocomposites synthesis by in situ sol–gel method in molten conditions: Impact on the fire-retardancy

Polyamide 6 (PA6)/phosphorylated silica nanocomposites were synthesized during PA6 extrusion through in situ formation of the inorganic phase without solvent. This synthesis is based on the hydrolysis-condensation reactions of diethylphosphatoethyltriethoxysilane (SiP) as a functional inorganic precursor in combination with or without tetraethoxysilane (TEOS) dispersed in the molten PA6. This synthesis is carried out during PA 6 matrix extrusion that means at high temperature and under shear. The characterization of the in situ synthesized PA6/phosphorylated silica nanocomposites by solid ²⁹Si Nuclear Magnetic Resonance (NMR), Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) coupled with Energy Dispersive X-ray spectroscopy (EDX) demonstrated the possibility to directly create in less than 5 min at 220 °C a phosphorylated silica uniformly dispersed in the PA6, i.e. in the form of well dispersed particles or aggregates of sub-micron range. The influence of silicon and phosphorus on the thermal and fire retardant behaviour was investigated by thermogravimetric analysis (TGA), cone calorimeter and UL94 tests. The fire retardant behaviour was modified with a formation of a char and a peak heat release rate (PHRR) decrease by more than 50% for the SiP based nanocomposite compared to the pure PA6.     

Liquid crystalline banana‐shaped monomers derived from 2,7‐naphthalene: synthesis and properties

Three banana‐shaped monomers, i.e. 2,7‐naphthalene bis[4‐(4‐allyloxyphenylazo)‐benzoate], 2,7‐naphthalene bis[4‐(4‐allyloxy‐3‐fluorophenylazo)benzoate] and 2,7‐naphthalene bis{4‐[4‐(10‐undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7‐dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans‐azobenzene groups displays a high‐intensity π–π* transition at about 365 nm and a low‐intensity n–π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana‐shaped liquid crystals molecules.     

采用反应挤出三次加料法合成苯乙烯/异戊二烯/苯乙烯

以同向啮合双螺杆挤出机为反应器,采用苯乙烯和异戊二烯为聚合单体,以正丁基锂为引发剂,采用三次加料法合成苯乙烯/异戊二烯/苯乙烯(SIS)三嵌段热塑性弹性体.氢核磁共振(1H NMR)谱分析结果表明,共聚物中聚异戊二烯嵌段以1,4-结构为主.采用四氧化锇催化双氧水氧化降解聚合物分子链,利用凝胶渗透色谱对氧化降解后的聚苯乙烯碎片进行分析,证明共聚物分子为(聚苯乙烯-聚异戊二烯-聚苯乙烯)(PS-PI-PS)三嵌段结构.动态力学分析(DMA)及透射电子显微镜(TEM)分析结果表明,SIS具有两相分离结构.拉伸试验结果表明,共聚物拉伸强度与苯乙烯含量有关.     

Formation of the Interphase of a Cured Epoxy Resin Near a Metal Surface: Reactive Coarse-Grained Molecular Dynamics Simulations

Mesoscale molecular dynamics simulations are performed to analyze the curing process of an epoxy resin with polyfunctional amines on a generic surface. The coarse grained potentials were derived from all-atomistic molecular dynamics simulations using iterative Boltzmann inversion. The reactive scheme incorporates cross-linking between an epoxy resin and an amine, as well as amine adsorption on the surface. The structure of the cured network is examined and compared with equilibrium properties of the uncured system. Special attention has been paid on the implications of the surface that is believed to play a crucial role in the performance of epoxy systems.     

Phenylethynyl-terminated Imide Oligomers Modified by Reactive Diluent for Resin Transfer Molding Application

To meet the processing requirements of resin transfer moulding(RTM)technology,reactive diluent containing m-phenylene moiety was synthesized to physically mixed with phenylethynyl terminated cooligoimides with well-designed molecular weights of 1500-2500 g/mol derived from 4,4’-(hexafluoroisopropylidene)diphthalic anhydride(6 FDA),3,4’-oxydianiline(3,4’-ODA)and m-phenylenediamine(m-PDA).This blend shows low minimum melting viscosity(<1 Pa·s)and enlarged processing temperature window(260–361℃).FPI-R-1 stays below 1 Pa·s for2 h at 270℃.The relationship between the molecular weight of the blend and its melting stability was first explored.Blending oligoimides with lower molecular weights exhibit better melting stability.Upon curing at 380℃for 2 h,the thermosetting polyimide resin demonstrates superior heat resistance(T_g=420-426℃).     

Acrylation of biomass: A review of synthesis process: Know-how and future application directions

Over the years, eco-friendly raw biomass is being investigated to develop novel green monomer and oligomer components for sustainable polymer materials synthesis. The use of naturally obtained biomass can reduce the dependence on petrochemical suppliers and the impact of petroleum prices. Polymer materials obtained from biomass are a competitive alternative comparing with those made from petrochemicals. Domestically and industrially used vegetable oil derivatives are considered widely available, while cellulose derivatives are the most abundant natural polymers. Biobased acrylic polymers developed from vegetable oils and cellulose are very popular nowadays. Using acrylic derivatives of vegetable oils and cellulose as naturally obtained materials leads to long-lasting biopolymers with a wide range of high exploitation properties and applications. The characteristics of vegetable oil- and cellulose-based acrylate resins of high-biorenewable carbon content are suitable for industrial application, while their role is still underestimated. A brief analysis of biomass-derived biopolymer resin compositions, properties, and applications is critically outlined herein.