Electron-beam charging of poly(methyl methacrylate)

The charging of bulk poly(methyl methacrylate) by irradiation with electrons of 2 MeV energy at room temperature in vacuum was studied. The experimental data obtained using the split Faraday cup are compared with the results of numerical simulation assuming one-dimensional geometry with allowance for the spatial distribution of dose rate and injected-electron current, nonlinear properties of radiation-induced conductivity in the prebreakdown electric-field region, and the intrinsic conductivity of poly(methyl methacrylate). It was shown that published data on the electric field strength measured by means of the electro-optical Kerr effect in electron-beam charged poly(methyl methacrylate) agree satisfactorily with the calculation results.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 183–189.Original Russian Text Copyright © 2005 by Sadovnichii, Tuytnev, Milekhin.     

On the Involvement of Geminate Pairs in Radiation-Induced Conductivity of Polystyrene

Basic parameters of the generalized Rose–Fowler–Weisberg theory were experimentally determined for polystyrene. The obtained data were used to comprehensively analyze the evolution of geminate pairs in this polymer. It was shown that the generation of the prompt component of radiation-induced conductivity occurs by the trapping mechanism with two charge carrier states involved, the quasi-free and trapped. This generation under equilibrium transport conditions (diffusivity and mobility of carriers are constant) reportedly ensured by the geminate recombination itself was not observed in a real experiment. With allowance for dispersive transport of holes (the major carriers), the lifetime of geminate pairs were found to be as long as a few hundred of milliseconds at 300 K. The published data on the formation and decay kinetics in doped polystyrene upon its pulse radiolysis or photolysis were thoroughly analyzed. It was shown that, at ultrashort times before localization of generated carriers, the contribution of electrons to the observed conductivity prevails, although the basic contribution is made by holes in later times.     

Oxygen diffusion in poly(methyl methacrylate) at low temperatures

Oxygen diffusion in atactic poly(methyl methacrylate) has been studied by anthracene luminescence quenching in geminate pairs anthracene-oxygen at 77–130 K. Analysis of the experimental data shows that the luminescence quenching is well accounted for by a polychromatic model assuming a log-normal diffusion coefficients distribution due to inhomogeneity of polymer structure. Energy activation is equal to 30 ± 1 KJ/mol. All diffusion coefficients data in the range 77–300 K demonstrate a good linear Arrhenius law. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 127–131, 1998     

Formation and reaction of polymer ions in solutions studied by pulse radiolysis

Formation and reaction of polymer anions in solutions of poly(methyl methacrylate), poly(ethyl methacrylate), poly(n-butyl methacrylate), poly(isobutyl methacrylate) and poly(4-vinylbiphenyl) in hexamethylphosphorictriamide and 2-methyltetrahydrofuran were studied by nanosecond pulse radiolysis. The rate constants of the reactions of the polymers with solvated electrons were determined and they were compared with those of the corresponding low molecular-weight molecules. Besides, the decay reactions as well as the electron transfer reactions of the anion radicals of these polymers were investigated. The time-profile of the poly(4-vinylbiphenyl) anion observed in 2-methyltetrahydrofuran at room temperature showed a spike which was followed by a slow decay. The fast decaying component was tentatively attributed to geminate recombinations within micro domains in the solution where the polymers were entangled.     

Molecular interaction in some polymeric additive solutions containing styrene-hydrogenated butadiene copolymer

The miscibility of styrene-hydrogenated butadiene copolymer (SHB) with different constituents of polymer additives for lubricating mineral oils was studied in dilute solution regime, using xylene as model solvent, at 30 °C, in a wide range of polymer blend compositions. The systems studied were SHB/poly(ethylene-co-propylene) (EPC), SHB/poly(methyl methacrylate) (PMMA), SHB/poly(dodecyl methacrylate) (PDDMA) and SHB/polystyrene (PS). The viscometric interaction parameters were calculated according to the Krigbaum–Wall and Catsiff–Hewett models of ideal viscometric behavior. Strong repulsive interactions were found in SHB/PMMA and SHB/PDDMA systems pointing to immiscibility. SHB/EPC and SHB/PS deviated much less from ideality. The results were compared to the theoretical estimation of interaction in polymer blends in the absence of solvent, using the Coleman–Graf–Painter approach. No correlation was observed between the interaction in the bulk and in solution.     

Effect of Tacticity of Poly(Methyl Methacrylate) on Conductivity of Poly(Ethylene Oxide)-Poly(Methyl Methacrylate) Blend-Based Polymeric Electrolytest

Abstract

Polymer electrolytes based on blends of poly(ethylene oxide) (PEO) with various stereoisomers of poly(methyl methacrylate) (PMMA) were studied by means of impedance spectroscopy and DSC. It was found that isotactic poly(methyl methacrylate) (1PMMA)-based electrolytes exhibit ambient temperature conductivities at least one order of magnitude higher than the electrolytes containing other stereoisomers of PMMA. The highest value of room temperature conductivity equal to 9 × 10^?5 S/cm was measured for a sample containing 30 wt% IPMMA. The effect observed results from the presence of a flexible amorphous phase in PEO-IPMMA blends which is favorable for fast ionic transport. A small increase of ionic conductivity with decreasing molecular weight of the added atactic poly(methyl methacrylate) was also observed.     

Influence of pressure and chemical structure on the thermal conductivity of vitreous poly(alkyl methacrylates). I

The influence of pressure on the thermal conductivity K of four vitreous poly(alkly methacrylate) polymers has been measured by steady state techniques. The measurements were made under pressures up to 2 kbar and over a temperature range between 173 and 300°K. For each member of the homologous series, K was found to increase with applied pressure. Shifts in thermal conductivity transition temperatures (attributed to glass transition phenomena) of 25, 26, and 16°C per kbar of applied pressure were observed for poly(methyl methacrylate), poly(ethyl methacrylate), and poly(n-isobutyl methacrylate).     

Synthesis of Carboxylated Monodisperse Latexes and Their Self-Organization in Thin Films

The capability of carboxylated latexes of poly(methyl methacrylate) and copolymers of styrene with glycidyl methacrylate or methacrylic acid for self-organization in thin films was studied in relation to the compositions of the dispersion medium and polymer and to the latex particle size.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 161–167.Original Russian Text Copyright © 2005 by Men’shikova, Shabsel’s, Evseeva, Shevchenko, Bilibin.     

Mesogen‐controlled ion channel of star‐shaped hard–soft block copolymers for solid‐state lithium‐ion battery

Novel star‐shaped hard–soft triblock copolymers, 4‐arm poly(styrene)‐block‐poly [poly(ethylene glycol) methyl ethyl methacrylate]‐block‐poly{x‐[(4‐cyano‐4′‐biphenyl) oxy] alkyl methacrylate} (4PS‐PPEGMA‐PMAxLC) (x = 3, 10), with different mesogen spacer length are prepared by atom‐transfer radical polymerization. The star copolymers comprised three different parts: a hard polystyrene (PS) core to ensure the good mechanical property of the solid‐state polymer, and a soft, mobile poly[poly(ethylene glycol) methyl ethyl methacrylate] (PPEGMA) middle sphere responsible for the high ionic conductivity of the solid polyelectrolytes, and a poly{x‐[(4‐cyano‐4′‐biphenyl)oxy]alkyl methacrylate} with a birefringent mesogens at the end of each arm to tuning the electrolytes morphology. The star‐shaped hard–soft block copolymers fusing hard PS core with soft PPEGMA segment can form a flexible and transparent film with dimensional stability. Thermal annealing from the liquid crystalline states allows the cyanobiphenyl mesogens to induce a good assembly of hard and soft blocks, consequently obtaining uniform nanoscale microphase separation morphology, and the longer spacer is more helpful than the shorter one. There the ionic conductivity has been improved greatly by the orderly continuous channel for efficient ion transportation, especially at the elevated temperature. The copolymer 4PS‐PPEGMA‐PMA10LC shows ionic conductivity value of 1.3 × 10^?4 S cm^?1 (25 °C) after annealed from liquid crystal state, which is higher than that of 4PS‐PPEGMA electrolyte without mesogen groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4341–4350     

Ion conductivity studies of blends of poly(methyl methacrylate)-g-poly(ethylene glycol) and poly(ethylene glycol) complexed with LiCF3 SO3

Polymer electrolytes which are adhesive, transparent, and stable to atmospheric moisture have been prepared by blending poly(methyl methacrylate)-g-poly(ethylene glycol) with poly(ethylene glycol)/LiCF₃ SO₃ complexes. The maximum ionic conductivities at room temperature were measured to be in the range of 10⁻⁴ to 10⁻⁵ s cm⁻¹. The clarity of the sample was improved as the graft degree increased for all the samples studied. The graft degree of poly(methyl methacrylate)-g-poly(ethylene glycol) was found to be important for the compatibility between the poly(methyl methacrylate) segments in poly(methyl methacrylate)-g-poly(ethylene glycol) and the added poly(ethylene glycol), and consequently, for the ion conductivity of the polymer electrolyte. These properties make them promising candidates for polymer electrolytes in electrochromic devices. © 1996 John Wiley & Sons, Inc.     

Preparation of poly(methyl methacrylate)/CaCO3/SiO2 composite particles via emulsion polymerization

A novel method to prepare organic/inorganic composite particles, i.e. poly(methyl methacrylate)/CaCO₃/SiO₂ three-component composite particles, using emulsion polymerization of methyl methacrylate with sodium lauryl sulfate as a surfactant in an aqueous medium was reported. CaCO₃/SiO₂ two-component inorganic composite particles were obtained firstly by the reaction between Na₂CO₃ and CaCl₂ in porous silica (submicrometer size) aqueous sol and the specific surface area of the particles was measured by the Brunauer–Emmett–Teller (BET) method. The results show that the BET specific surface area of the CaCO₃/SiO₂ composite particle is much smaller than that of the silica particle, indicating that CaCO₃ particles were adsorbed by porous silica and that two-component inorganic composite particles were formed. Before copolymerization with methyl methacrylate, the inorganic composite particles were coated with a modifying agent through covalent attachment. The chemical structures of the poly(methyl methacrylate)/CaCO₃/SiO₂ composite particles obtained were characterized by Fourier transform IR spectroscopy and thermogravimetric analysis. The results show that the surface of the modified inorganic particles is grafted by the methyl methacrylate molecules and that the grafting percentage is about 15.2%.     

New initiator system for the anionic polymerization of (meth)acrylates in toluene. IV. Random copolymerization of (meth)acrylates in toluene initiated by s-BuLi ligated by lithium silanolates

Copolymerization of binary mixtures of alkyl (meth)acrylates has been initiated in toluene by a mixed complex of lithium silanolate  (s-BuMe₂SiOLi) and s-BuLi (molar ratio > 21) formed in situ by reaction of s-BuLi with hexamethylcyclotrisiloxane (D₃). Fully acrylate and methacrylate copolymers, i.e., poly(methyl acrylate-co-n-butyl acrylate), poly(methyl methacrylate-co-ethyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(methyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate), poly(isobornyl methacrylate-co-n-butyl methacrylate) of a rather narrow molecular weight distribution have been synthesized. However, copolymerization of alkyl acrylate and methyl methacrylate pairs has completely failed, leading to the selective formation of homopoly(acrylate). As result of the isotactic stereoregulation of the alkyl methacrylate polymerization by the s-BuLi/s-BuMe₂SiOLi initiator, highly isotactic random and block copolymers of (alkyl) methacrylates have been prepared and their thermal behavior analyzed. The structure of isotactic poly(ethyl methacrylate-co-methyl methacrylate) copolymers has been analyzed in more detail by Nuclear Magnetic Resonance (NMR). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2525–2535, 1999     

Morphological studies of spin-coated films of poly(styrene-block-methyl methacrylate) copolymers by atomic force microscopy

The surface structure of very thin (15–20 nm) spin-coated films of a symmetrical poly(styrene-b-methyl-methacrylate) block copolymer on silicon and mica is analyzed by atomic force microscopy (AFM). The films show a surface corrugation of a very regular 100 nm lateral periodicity and 6–8 nm amplitude. Film thickness is measured by AFM at induced film defects and checked by ellipsometry. XPS shows that both blocks are at the film surface. Selective degradation of the methyl methacrylate block is used for contrast enhancement and allows to assign poly(styrene) to the elevated surface regions and poly(methyl methacrylate) to the substrate/film interface.Friction interactions of the AFM tip with the film surface may be used to induce high orientational ordering of the morphological pattern perpendicular to the fast scan direction.     

Highly enhanced electrical and mechanical properties of methyl methacrylate modified natural rubber filled with multiwalled carbon nanotubes

Developing conductive networks in a polymer matrix with a low percolation threshold and excellent mechanical properties is desired for soft electronics applications. In this work, natural rubber (NR) functionalized with poly(methyl methacrylate) (PMMA) was prepared for strong interfacial interactions with multiwalled carbon nanotubes (MWCNT), resulting in excellent performance of the natural rubber nanocomposites. The MWCNT and methyl methacrylate functional groups gave good filler dispersion, conductivity and tensile properties. The filler network in the matrix was studied with microscopy and from its non-linear viscoelasticity. The Maier-Göritze approach revealed that MWCNT network formation was favored in the NR functionalized with PMMA, with reduced electrical and mechanical percolation thresholds. The obvious improvement in physical performance of MWCNT/methyl methacrylate functionalized natural rubber nanocomposites was caused by interfacial interactions and reduced filler agglomeration in the NR matrix. The modification of NR with poly(methyl methacrylate) and MWCNT filler was demonstrated as an effective pathway to enhance the mechanical and electrical properties of natural rubber nanocomposites.     

Synthesis, electropolymerization and electrochemical characterization of some new acrylate substituted thiophene derivatives

In this work, three new acrylate substituted thiophene monomers, (3-thienyl) methylacrylate, 6-(3-thienyl)methoxy-hexylacrylate and 11-(3-thienyl)methoxy-undecylacrylate were synthesized and electropolymerized. Electrochemical polymerisation by a potential step technique leads to the formation of an electroactive film on a Pt electrode in each case. The polymerization involves evidently only the thiophene ring, as no sign of polyacrylate formation could be detected. The oxidation of each polymer was studied by in situ external reflectance FTIR spectroscopy, which showed several bands assigned to (bi)polaron type charge carriers in the region 1500–1000 cm⁻¹. The evolution of the conductivity was studied in situ by the contact electric resistance technique. The conductivity of poly(3-thienyl methacrylate) was found to be higher in aqueous solutions than in acetonitrile. The surface of poly((3-thienyl) methacrylate) was found to have a granular structure observed for many polythiophenes, as studied by atomic force microscopy (AFM).     

Excited-state proton-transfer dynamics of 1-methyl-6-hydroxyquinolinium embedded in a solid matrix of poly(2-hydroxyethyl methacrylate)

The excited-state intrinsic proton transfer and its geminate recombination, as well as the ground-state equilibria, of 1-methyl-6-hydroxyquinolinium embedded in a solid matrix of poly(2-hydroxyethyl methacrylate) have been studied by measuring time-resolved and steady-state fluorescence spectra along with absorption and excitation spectra. Proton transfer takes place within 3.3 ns to form ion pairs while its back-reaction occurs on the time scale of 3.7 ns. The ion pairs in the rigid alcoholic matrix go through neither diffusion to form free ions nor subsequent electronic rearrangement to form the keto species within their excited-state lifetimes.     

Electrooptical and Molecular Properties of Fullerene-Containing Poly(Methyl Methacrylates) Prepared by Introducing Fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript> into the Polymer Structure by Different Methods

Poly(methyl methacrylate) samples and their analogs containing covalently bound fullerenes C₆₀ and C₇₀ were prepared under varied synthesis conditions. The molecular weights and the electrooptical characteristics of the polymers in solutions were determined. The influence of the fullerenes on the molecular properties of poly(methyl methacrylate) was elucidated, and the most efficient method of its modification with fullerenes was proposed.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 139–145.Original Russian Text Copyright © 2005 by Evlampieva, Lopatin, Yakimanskii, Nazarova, Melenevskaya, Dmitrieva, Belyaev, Litvinova, Lavrenko.     

A non‐volatile,bistable, and rewritable memory device fabricated with poly(nitroxide radical) and silver salt layers

A non‐volatile, bistable, and rewritable organic memory device was successfully fabricated with the layers of poly(2,2,6,6‐tetramethylpiperidine‐1‐oxyl methacrylate) (PTMA) and poly(methyl methacrylate) (PMMA) containing silver salt. The PTMA layer was employed as a p‐dopable material, while the silver salt‐dispersed PMMA layer acted as an n‐dopable material. The ON–OFF ratio between low‐conductivity and high‐conductivity states amounted to more than four orders of magnitude, and the retention time was longer than 10³ sec. The device was characterized by excellent rewritability. Copyright © 2007 John Wiley & Sons, Ltd.     

Polymer solid electrolytes from the PEG-PMMA-LiCF3SO3 system

Highly conductive solid polymeric electrolytes based upon low molecular weight poly(ethylene glycol) and ethylene oxide/propylene oxide copolymers blended with up to 50% by volume of poly(methyl methacrylate) have been synthesized using LiCF₃SO₃ (25:1 ether oxygen to cation ratio). Room-temperature ionic conductivities were measured to be in the range 10^?4 to 10^?5 S/cm for poly(methyl methacrylate) concentrations up to 30% by volume. In some cases, the addition of the poly(methyl methacrylate) enhanced the conductivity. All of the electrolytes studied were either amorphous or crystallized below 0°C. The variation of conductivity with temperature and polymer composition was measured and the results were analyzed in terms of effective medium theory and semiempirical considerations. Ionic transport is coupled to the structural relaxation of the polymer segments. At lower temperatures activated processes were required. Both charge carrier mobility and charge concentration were found to contribute to conduction. The effective medium theory quantitatively describes conductivities of amorphous heterogenous systems of limited miscibility (microphase separation) quite well. For miscible or partially crystalline systems other effects not incorporated in this theory play an important role, and conductivities are measured to be higher than theoretically predicted. © 1994 John Wiley & Sons, Inc.     

Preparation of P(AN–MMA) microporous membrane for Li-ion batteries by phase inversion

A novel process was proposed for preparation of microporous poly(acrylonitrile–methyl methacrylate) (P(AN–MMA)) membranes by phase inversion techniques using ultrasonic humidifier. Being prepared by dissolving the polymer (PAN–MMA) in the N,N-dimethylformamide (DMF) solution with mechanical stirring, the homogenous casting solution was cast onto a clean glass plate. Successively, the glass plate was exposed to the water vapor produced by ultrasonic humidifier, inducing the phase inversion. It is found the pore size is much more uniform across the cross-section of the membrane than that of the porous membrane prepared by conventional water bath coagulation technique. The microporous membranes were directly obtained after the washing and drying. It had about 1–5 μm of pores and presented an ionic conductivity of 2.52 × 10⁻³ S/cm at room temperature when gelled with 1 M LiPF₆/EC-DMC (1:1 vol.%) electrolyte solution. The test cells with the gel electrolytes prepared from as-prepared microporous membranes showed stable cycling capacities, indicating that the microporous membrane, which was prepared from cheap starting materials acrylonitrile and methyl methacrylate, can be used for the gel electrolyte of lithium batteries.