Copolymerization Research Papers - Academia.edu (original) (raw)

Ethylene was copolymerized with 10undecen-1-ol and 5-hexen-1-ol using stereorigid [rac-ethylene(Ind) 2 ZrCl 2 ], [rac-ethylene(H 4 Ind) 2 ZrCl 2 ], and the new catalyst systems [rac-norbornane(Ind) 2 TiCl 2 ] and [mesonorbornane(Ind) 2 TiCl 2 ], activated with methylaluminoxane. The characterization of the copolymers by 13 C NMR spectroscopy revealed that the polymerization products were copolymers and that the conversion of the polar comonomer was strongly favored in the case of the zirconocene precursors. Very high catalytic activity values, nearly independent on the amount of comonomer in the feed, and comonomer incorporations up to 25.4%weight have been found for 10-undencen-1-ol comonomer.

- by
- •
- Engineering, CHEMICAL SCIENCES, Journal of Applied Polymer Science, Copolymerization

Nickel ion-imprinted membrane was synthesized using PVDF microfiltration membrane as support. In the current study, thermodynamic and kinetic of Ni(II) and Co(II) ions adsorption onto the membrane was investigated. Classical adsorption isotherms including Langmuir, Freundlich, Redlich-Peterson and Langmuir-Freundlich (Sips) were employed to describe the adsorption equilibria. The Sips equilibrium model could superiorly represent the equilibrium adsorption of the ions. Calculation of principle thermodynamic parameters such as free energy, enthalpy and entropy change revealed exothermic and spontaneous adsorption on the basis of the negative H • and G • values, respectively. Meanwhile, adsorption of Co(II) ions on the imprinted membrane was less favorable than that of Ni(II) ions. Moreover, negative values of S • demonstrated randomness reduction at the solid-liquid interface. Pseudo-firstorder, pseudo-second-order and intra-particle diffusion models were utilized to describe the adsorption kinetic. Ion diffusivity through the membrane was also examined versus time and initial concentration. The kinetic results indicated superior adsorption-permeation rate of Ni(II) compared with Co(II) ions. In addition, a novel mathematical model was developed for prediction of the ions adsorption-transport behavior. Well fitted to the experimental data, the model provided a new insight into the phenomena involved in ion adsorption on imprinted membranes.

- by hamid rajabi
- •
- Engineering, Technology, Membrane Science, Adsorption

High intensity ultrasound has been used to prepare homopolymers and copolymers of styrene, methyl methacrylate and n-butyl methacrylate. High molecular weight homopolymers are formed rapidly during sonication and are then subjected to a degradation process. The copolymers prepared by this method have similar structure and properties to those prepared using AIBN as an initiator.

- by Gareth Price
- •
- Materials Engineering, Chemical Engineering, Analytical Chemistry, Ultrasound

Ethyl-(ECA) and butyl-2-cyanoacrylate (BCA) monomers of high purity and acidic stabilization were synthesized and anionically polymerized to homo-and copolymers in two different ways: by piperidine-catalyzed bulk polymerization leading to transparent, brittle films (method A) and by polymerization in aqueous medium in the presence of sodium bicarbonate to obtain white powders (Method B). The molecular structure of the synthesized monomers, homopolymers and copolymers were corroborated by spectral methods. The polymers were studied further by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and proton nuclear magnetic resonance ( 1 H NMR). Controlling the composition of the monomer feed and the way the polymerization was performed, it was possible to obtain phase separated or homogeneous cyanoacrylate copolymers with glass transitions varying between the T g of polyECA and that of polyBCA. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5142-5156, 2008

- by Albena Lederer and +1
- •
- Materials Engineering, DSC, Sec, Anionic Polymerization

The true monomer reactivity ratios for the vinyl acetate/butyl acrylate system were determined with experimental data from the cumulative copolymer composition at low, intermediate, and high conversions and with the monomer partitioning among the aqueous, microemulsion droplet, and polymer particle phases taken into account. A mixture of sodium dodecyl sulfate and poly(ethylene oxide) (23) dodecyl ether (Brij-35; 3 : 1 w/w) was used as a stabilizer. Potassium persulfate was used as an initiator. The true values of the monomer reactivity ratios were 0.028 AE 3.2 Â 10 À3 for vinyl acetate and 6.219 AE 3.1 Â 10 À1 for butyl acrylate, and these were

- by René Peralta
- •
- Engineering, Microstructure, Kinetics, Modeling

A precise data set describing the kinetics of the free radical copolymerization of acrylamide/acrylic acid (AM/AA) in the range of low total monomer concentration as a function of the pH, total monomer concentration, initiator concentration, and comonomer ratio is presented. Strong impact on the reactivity ratios has been identified for the pH and total monomer concentration. Specifically, at constant total monomer concentration of 0.4 mol/l and TZ313 K the reactivity ratio of AM increases from 0.54 at pH 1.8 to 3.04 at pH 12. Contrarily, the reactivity ratio of AA decreases from 1.48 to 0.32. The crossover occurs at pHz4.2. Electrostatic effects due to the variation of the degree of ionization of AA are primarily suggested to influence the kinetics. When the total monomer concentration increases from 0.2 to 0.6 mol/l at constant pHZ12, the reactivity ratios of AM and AA decrease from 4.01 to 2.13 and increase from 0.25 to 0.47, respectively. Reduction of electrostatic repulsion between the ionized monomer AA and partially charged growing polymer chain ends due to higher ionic strength at higher total monomer concentration serves as explanation of the effect. The precise data set is the prerequisite for a novel approach to calculate copolymer compositions in case of variable monomer reactivity. q

- by Christine Wandrey
- •
- Engineering, Kinetics, Free Radical, Polymer

(FS) was prepared and copolymerized with chloromethylstyrene (CMS). Conventional radical copolymerization of both these aromatic monomers led to poly(CMS-co-FS) random copolymers for which CMS was shown to be more reactive than the fluorinated comonomer. Their controlled radical copolymerization based on degenerative transfer, namely iodine transfer polymerization (ITP), led to various poly(CMS)-b-poly(FS) block copolymers. Molecular weights of poly(CMS-co-FS) copolymers reached 33,000 g mol À1 while those of poly(CMS)-bpoly(FS) block copolymers were 22,000 g mol À1. Their composition ranged from 18 to 61 mol.% in FS. These copolymers were modified via a cationization step, aiming at replacing the

The synthesis and characterization of amphiphilic polymers bearing gluconolactone moieties has been described. In a first step, an unprotected glycomonomer 2- butyl]amino}carbonyl)oxy]ethyl acrylate, HEAG, has been synthesized. Posterior, this glycomonomer has been copolymerized with methyl methacrylate at different compositions and the kinetic behavior has been also studied calculating the monomer reactivity ratios by Kelen-Tüdös extended equation. In addition, the long side-chain crystalline behavior of these carbohydrate-based copolymers with high composition of glycomonomer has been examined by using conventional and modulated differential scanning calorimetry and X-ray diffraction measurements. At the same time, the phase separation behavior of carbohydrate-based copolymers with lower HEAG content has been determined by their glass transition temperature measurements. Finally, the thermal stability of all these amphiphilic copolymers has been evaluated by thermogravimetric analysis.

- by Marta Fernandez-garcia and +2
- •
- Organic Chemistry, Differential scanning calorimetry, X ray diffraction, Food Sciences
- by Suresh Kothapalli
- •
- Engineering, Film, Activation Energy, CHEMICAL SCIENCES
- by Marta Fernandez-garcia and +1
- •
- Materials Engineering, Molecular Recognition, Degradation, Glass Transition

Natural fiber–biopolymer composites have been prepared using flax and poly(3-hydroxylbutyrate) bipolyesters (PHB). The biopolyesters consist of the homopolyester PHB and its copolymers with 5 and 12% 3-hydroxyvalerate (PHV). These biopolymer–natural fiber composites provide structures totally composed of biodegradable and renewable resources. The adhesion between the fibers and the polyesters was better than for analogous polypropylene composites. Wetting of the fibers by the polyesters was observed using scanning electron microscopy. The composites were limited by the properties of the polyesters. PHB is a brittle polymer though flexibility is improved in its copolymers with PHV, but at the expense of crystallization rate. Nucleation was increased by the fibers and silane coupling agent used as adhesion promoter. The melting temperature was influenced by the promoted adhesion and copolymerization. The bending modulus was increased in the composites and dynamic mechanical analysis provided storage modulus of as much as 4 GPa at 25°C with a smaller component as the loss modulus. The maximum in the loss modulus curve was taken as the glass transition temperature, and this increased in the composites. The influence of silane coupling agent was found beneficial for the material properties of the biopolyester–flax composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2114–2121, 2004

- by Alma Hodzic
- •
- Engineering, Adhesion, Composite, Composite Material

. The characteristic features of hydrophobically-modified polyacrylamides HMPAM prepared by a micellar polymerization technique are reviewed. This method of synthesis leads to copolymers in which the hydrophobic units are randomly distributed as small blocks in the acrylamide backbone. Special emphasis is put on the improvement of the technique so that well characterized and homogeneous samples are synthesized. The effect of the various parameters controlling the rheological behavior of HMPAM is thoroughly analyzed. In particular, it is shown that a determining factor for a good thickening ability is the copolymer microstructure, i.e. the hydrophobe distribution. Some recent advances are presented towards a better understanding of the association structure, thus allowing the design of tailored materials with good controllable rheological properties. ᮊ

- by Joseph SELB
- •
- Engineering, Hydrophobic Interactions, Chemical Analysis, CHEMICAL SCIENCES

Copolymers of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) were prepared and their cloud points in aqueous solution were studied as a function of comonomer ratio, solution pH, and presence of hydrophobic comonomers. Under acidic conditions, the cloud point falls below 0 8C for copolymers with between 25% to 60% ether content, because of the formation of hydrophobic H-bonded ether-acid complexes. The cloud point also decreases with solution pH. For equivalent ether to acid ratios, the cloud point decreases with decreasing PEG chain length, because of the presence of a larger number of hydrophobic methyl and methacrylate groups. Similarly, the cloud point decreases upon incorporation of hydrophobic comonomers such as butyl, lauryl, or glycidyl methacrylates. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6095-6104, 2005

- by Nicholas Burke and +1
- •
- Materials Engineering, Chemistry, Polymer, Ph
- by Edvaldo Rossini
- •
- Management, Packaging, Recycling, Polymerization
- by Roger Ruan
- •
- Tissue Engineering, Drug Delivery System, Surface modification, Plasma Treatment

A new cellulose-based superabsorbent polymer, carboxymethyl cellulose-graft-poly(acrylic acid-co-acrylamide), was prepared by the free-radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto carboxymethyl cellulose (CMC) in the presence of N,N 0 -methylenebisacrylamide as a crosslinker with a redox couple of potassium persulfate and sodium metabisulfite as an initiator. The influences of reaction variables such as the initiator content, crosslinker content, bath temperature, molar ratio of AA to AM, and weight ratio of the monomers to CMC on the water absorbency of the carboxymethylcellulose-graft-poly(acrylic acid-co-acrylamide) copolymer were investigated. The copolymer's structures were characterized with Fourier transform infrared spectroscopy. The optimum reaction conditions were obtained as follows: the bath temperature was 508C; the molar ratio of AA to AM was 3 : 1; the mass ratio of the monomers to CMC was 4 : 1; and the weight percentages of the crosslinker and initiator with respect to the monomers were 0.75 and 1%, respectively. The maximum water absorbency of the optimized product was 920 g/ g for distilled water and 85 g/g for a 0.9 wt % aqueous NaCl solution. In addition, the superabsorbent possessed good water retention and salt resistance.

- by andria setyorini
- •
- Engineering, Optimization, Grafting, Crosslinking

Methylalumoxane (MAO) is an active pre-catalyst for the polymerization of isobutylene and the copolymerization of isobutylene with isoprene at ambient temperature. The absence of any proton-containing substances suggests that the solvent dichloromethane reacts with the MAO forming the active cationic species. In the presence of toluene, as the solvent, the reaction rate is extremely low. The increase of the MAO concentration in the reaction mixture causes a large increase in the isobutylene conversion, although the molecular weight of the polymers sharply decreases. The use of CD 2 Cl 2 as a solvent induces a large kinetic isotope effect (KIE 0/7). In the copolymerization of isobutylene with large amounts of isoprene a cross-linkage copolymer is formed. The polymerization and copolymerization reactions were also studied in the presence of a mixture of MAO with the complex (acac) 2 TiCl 2 (acac 0/ acetylacetonate). # (M.S. Eisen).

- by Victoria Volkis
- •
- Inorganic Chemistry, Polymerization, Kinetic Isotope Effect, Ambient Temperature

A novel composite hydrogel was prepared via UV irradiation copolymerization of acrylic acid and maize bran (MB) in the presence of composite initiator (2,2-dimethoxy-2-phenylacetophenone and ammonium persulfate) and cross-linker (N,N′-methylenebis(acrylamide)). Under the optimized conditions, maize bran−poly(acrylic acid) was obtained (2507 g g −1 in distilled water and 658 g g −1 in 0.9 wt % NaCl solution). Effects of granularity, salt concentration, and various cations and anions on water absorbency were investigated. It was found that swelling was extremely sensitive to the ionic strength and cation and anion type. Swelling kinetics and water diffusion mechanism in distilled water were also discussed. Moreover, the product showed excellent water retention capability under the condition of high temperature or high pressure. The salt sensitivity, good water absorbency, and excellent water retention capability of the hydrogels give this intelligentized polymer wide potential applications.

- by ALI Pourjavadi
- •
- Engineering, Materials Engineering, Mechanical Engineering, Chemical Engineering

Hydrosoluble copolymers containing sulfonic acid groups incorporated into a macromolecule were synthesized. The group of polymers studied was obtained by free radical solution polymerization, using potassium persulfate as an initiator. The copolymerization of the monomers 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and acrylamide (AA) was carried out at different pH values of the reaction medium of the monomer mix. The copolymers were characterized by proton nuclear magnetic resonance spectroscopy ( 1 H NMR) and Fourier transform infrared spectroscopy (FTIR). The viscosity behavior of the co-polymers in NaCl solution showed a dependency on the pH of the reaction medium, with higher pH leading to lower viscosities. The acidic conditions of this medium affect the initiator decomposition rate, which is a probable cause of the viscosity variation, and the extent of decomposition increases with increasing pH.

- by Miguel Casquilho
- •
- Engineering, Spectroscopy, FTIR, Viscosity

A novel amphiphilic photochromic copolymer P1-o consisting of a hydrophilic poly(N-isopropylacrylamide) backbone and thermally irreversible photochromic and hydrophobic 1,2-dithienylethene derivative pendants was designed, synthesized and used to fabricate self-assembled copolymer nanoparticles in an aqueous condition. The hydrodynamic diameters of the multifunctional copolymer P1-o nanoparticles reversibly switched between two stable states with two stimuli: light and temperature in an aqueous suspension.Graphical abstract:

- by Dennis Hsiao
- •
- Chemical Engineering, Photochemistry, Self Assembly, Nanoparticles

The radical terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and 4,5,5-trifluoro-4-penten-1-ol (FA3) for the synthesis of fluorinated polymers bearing hydroxy side groups is presented. The polymerization was carried out in emulsion and in a batch operation, initiated by a redox system containing tert-butylperoxybenzoate. The reaction proceeded without any induction period and in a stationary state at low conversion (up to 12%). The presence of the trifluorovinyl hydroxy monomer in the ternary system sharply decreased the polymerization rate, in contrast to that of the TFE/P binary one. The order of the reaction about FA3 was 1.25. The terpolymer compositions were determined by elemental analysis by 1 H-and 19 F-NMR spectroscopy. An almost equimolar ratio of TFE and P base units in the terpolymer was found, while the FA3 was inserted between TFE/P blocks. The presence of P increased the polymerization rate and lowered the chain transfer coming from FA3 when compared to the TFE/FA3 binary system. Thermal properties were assessed. The glass transition temperatures (T g ) slightly decreased with the FA3 content. The decomposition temperatures were also affected, showing two steps of decomposition related to the amount of FA3 in the copolymer, and is discussed.

- by petya petrova
- •
- Engineering, Materials Engineering, Inorganic Chemistry, Organic Chemistry

A strategy of the fine-tuning of the degree of intrachain charge transfer and aromaticity of polymer backbone was adopted to design and synthesize new polymers applicable in photovoltaics. Three conjugated polymers P1, P2, and P3 were synthesized by alternating the electron-donating dithieno[3,2-b:2 0 3 0 -d]pyrrole (D) and three different electronaccepting (A) segments (P1: N-(2-ethylhexyl)phthalimide; P2: 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole; and P3: thiophene-3-hexyl formate) in the polymer main chain. Among the three polymers, P2 possessed the broadest absorption band ranging from 300 to 760 nm, the lowest bandgap (1.63 eV), and enough low HOMO energy level (À5.27 eV) because of the strong intrachain charge transfer from D to A units and the appropriate extent of quinoid state in the main chain of P2, which was convinced by the theoretical simulation of molecular geometry and front orbits. Photovoltaic study of solar cells based on the blends of P1-P3 and [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) demonstrated that P2:PCBM exhibited the best performance: a power conversion efficiency of 1.22% with a high open-circuit voltage (V OC ) of 0.70 V and a large short-circuit current (I SC ) of 5.02 mA/cm 2 were achieved.

- by Dan Deng
- •
- Materials Engineering, Organic solar cells, Polymer Solar Cells, Energy Levels

Atactic polystyrene (PS) was chemically modified with maleic (MAH), succinic (SAH), and phtalic (PhAH) anhydrides. Styrene was copolymerized with acrylic (AA) and methacrylic acids (MA). Amount of carboxyl groups (%) bound to polymers was determined in the range of 6.9–25.9. Different modified polystyrenes (MPS) and styrene copolymers were used in the experiments to study Cu(II) and Zn(II) ions adsorption probability and their comparison. Sorption capacity of the polymers for the metal ions were investigated in aqueous media containing different amounts of these ions (5–40 mg/L) and at different pH values (2.0–6.0). Adsorption behavior of heavy metal ions could be modeled using both the Langmuir and Freundlich isotherms. It was found that the adsorption capacity is highest at pH value of 6, whereas it decreases as the pH value decreases at temperature 25°C ± 1°C for 240 min. The results obtained from the adsorption capacity experiments for Cu(II) and Zn(II) ions were 3.47–5.45 and 5.42–6.85 mg/g, respectively. The affinity order of polymers for both metal ions was observed as follows: SMAC > SAAC > MPS with MAH > MPS with SAH > MPS with PhAH. The maximum adsorption capacities of SMAC were 6.85mg/g for Zn(II) and 5.45 mg/g for Cu(II). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

- by Mustafa Ersoz
- •
- Engineering, Adsorption, Functionalization, Applied

A series of starch/methacrylic acid (MAAc) copolymer hydrogels of different compositions were synthesized
using c-rays induced polymerization and crosslinking. The effects of the preparation conditions such as the feed solution concentration, feed solution composition and irradiation dose on the gelation process of the synthesized copolymer were investigated. The swelling behavior of the starch/methacrylic
acid (MAAc) copolymer hydrogels was characterized by studying the effect of the hydrogel composition on the time- and pH-dependent swelling. Swelling kinetics showed that the synthesized hydrogels possessed Fickian diffusion behavior at pH 1 and non-Fickian diffusion at pH 7 which recommend them as good candidate for colon specific drug delivery systems. The synthesized hydrogels were loaded with
ketoprofen as a model drug to investigate the release behavior of the synthesized hydrogels. The results showed the ability of the hydrogels to keep the loaded drug at pH 1 and release it at pH 7. The data also showed that the release rate can be controlled by controlling the preparation conditions such as comonomer concentration and composition and irradiation dose.

This paper describes a modeling and simulation study for the polyurethane synthesis by bulk copolymerization of dicyclohexylmethane 4,4diisocyanate with a mixture of a polyether diol and 1,4-butane diol, in a co-rotating twin-screw extruder. The process model is based on linear chain growth theory, a kinetic expression previously published in literature and the axial dispersion model, in both the hypothesis of non-segregated and totally segregated fluid structures. The numerical simulations evidenced that the effect of segregation phenomenon appears to be significant, particularly in the evaluation of the product polydispersity. Also, the polymerization process features an important sensitivity of the polymer molecular weight in respect to the inlet monomer molar ratio.

- by Philippe Cassagnau
- •
- Chemical Engineering, Kinetics, Modeling, Modeling and Simulation

The kinetics of free-radical emulsion polymerization of c-methyl-a-methylene-c-butyrolactone (MeMBL), a renewable monomer related to methyl methacrylate, are presented in detail for the first time, and stable polymer latices are prepared. The effects of different reaction parameters on free-radical emulsion polymerization of MeMBL are presented. Homogeneous nucleation is asserted to be the dominant path for particle formation. Miniemulsion copolymerization of MeMBL and styrene is also reported. In this case, the homogeneous nucleation process appears limited when using an oil soluble initiator. Both the RAFT miniemulsion polymerizations and RAFT bulk polymerizations are well controlled and narrow polydispersity copolymers are produced. Rate retardation is observed in the RAFT miniemulsion polymerizations compared with the free-radical polymerization and RAFT bulk polymerizations and the possible causes of the retardation are discussed. The reactivity ratios of MeMBL and styrene in RAFT bulk copolymerization are also determined. V

- by F. Joseph Schork
- •
- Materials Engineering, Biomass, Emulsion polymerization, Polymer

Octa(maleimido phenyl) silsesquioxane (OMPS) was prepared from octa(aminophenyl) silsesquioxane (OAPS) and maleic anhydride. Initially, octaphenyl silsesquioxane was prepared, and it was nitrated to obtain octa(nitrophenyl) silsesquioxane; subsequently, reduction was carried out to obtain OAPS. These compounds were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and wide-angle X-ray diffraction. Differential scanning calorimetry scans of OMPS showed an exotherm above 100 8C, and it was attributed to the curing. The peak maximum temperature depended on the heating rate. Both Ozawa's and Kissinger's methods were used to determine the activation energy for the curing reaction, which was approximately 29 kcal/mol. OMPS was copolymerized with various molar percentages of (1) N,N 0 -p-phenylenedimaleimide (PPMI) and (2) urethane methacrylate (UMA) by thermal and free-radical polymerization, respectively. The copolymers were characterized with differential scanning calorimetry, dielectric analysis, thermogravimetric analysis, and wide-angle X-ray diffraction. In the PPMI and UMA copolymer series, the glass-transition temperature increased with an increase in the OMPS concentration. The permittivity of the UMA copolymers decreased and tan increased with an increase in the OMPS concentration. In air and nitrogen atmospheres, the thermal stability of the PPMI and UMA copolymers increased with an increase in the OMPS concentration. C 2005 Wiley Periodicals, Inc. J Polym Sci Part

- by P S G KRISHNAN
- •
- Materials Engineering, Copolymerization
- by Marcos Dias
- •
- Materials Engineering, Chemical Engineering, Biocompatible, Copolymerization

Poly(methacrylic acid) brushes have been prepared utilizing the “grafting from” technique and a living radical synthesis route using a two stage process. Firstly a poly(1-ethoxyethyl methacrylate) brush was synthesized by atom transfer radical polymerization and then thermally decomposed to poly(methacrylic acid). The swelling behaviour of the weak polyacid brush was investigated as a function of pH and salt concentration in

- by Jonathan Howse
- •
- Engineering, Materials Engineering, Mechanical Engineering, Aerospace Engineering

The copolymerization behaviour of the adduct of N',N'-dimethylaminopropyl methacrylamide and epichlorohydrin (DMAPMA-Epi) and methyl methacrylate (MMA) was investigated. The reactivity ratios for the MMA (I)/DMAPMA-Epi (2) couple in solution, using various regression methods based on the Mayo-Lewis model, are r 1 ---1.73 and r2 =0.03. The Q and e values for DMAPMA-Epi are estimated to be 0.23 and -1.32 respectively. On the basis of the reactivity ratios, theoretical curves for the instantaneous copolymer composition throughout conversion have been calculated.

- by Liam P Devlin
- •
- Engineering, Polymer, CHEMICAL SCIENCES, Copolymerization
- by Márcio Nele
- •
- Kinetics, Modeling, Polymer Blends, Parameter estimation
- by Kadir Onder
- •
- Engineering, Materials Engineering, Physics, Condensed Matter Physics

Syndiotactic polystyrene (sPS) is a promising material that has been commercialized and widely studied by the academic community. Several drawbacks can however restrict its practical use: its brittleness, in areas where mechanical properties are important, the lack of polar groups, for adhesion and compatibility with other polymers, and the need to process sPS at high temperatures. These drawbacks can be overcome by the introduction of relevant functional groups into sPS. We present in this review the various strategies reported for the functionalization of syndiotactic polystyrene: statistical and sequential block copolymerization, chain transfer and chain end functionalization, polymerization of substituted styrenic monomers and chemical modification of sPS.

- by Philippe Zinck
- •
- Engineering, Catalysis, Grafting, Functionalization

Borohydrido-halflanthanidocene / dialkylmagnesium combinations are found to be powerful catalytic systems for the chain transfer polymerization of isoprene and its copolymerization with styrene. A behavior close to a lanthanide catalyzed polyisoprene chain growth on magnesium is reported. Transmetalation is further shown to occur in the course of the statistical copolymerization of isoprene and styrene. For the same monomer feed, the amount of styrene inserted in the copolymer can be increased by a factor 3 using 10 eq. dialkylmagnesium vs. 1 in the range of our experimental conditions. Chain transfer in the course of a metal catalyzed statistical copolymerization may thus be viewed as a new and original way for the control of the composition of a copolymer.

- by Philippe Zinck
- •
- Engineering, Microstructure, Catalysis, CHEMICAL SCIENCES

Electrochemical copolymerization of 3-octyloxy-4-methylthiophene (OOT) and 1-[6-[(4-methyl-3thienyl) oxy] hexyl]-4-cyanopyridinium bromide (HOT-CNP) was carried out using tetrabutylammonium hexafluorophosphate and acetonitrile (TBAPF 6 /ACN) as electrolyte. The cyanopyridine functionalized HOT-CNP undergoes further electrochemical reductive coupling to viologen. Both polymer (POOT) and copolymer P(OOT-co-HOT-CNP) were characterized by cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and in situ UV-vis spectroscopy. The effect of the monomer concentration ratio and the scan rate on the electrochemical properties of the copolymer was studied by the CV technique. The electrochemical redox response of the copolymer together with FTIR analysis further confirms the formation of viologen. The surface morphology was studied using SEM analysis. The polymer POOT revealed color changes between violet and bright blue, whereas the copolymer showed the most vivid change of color between purple and greenish blue in its fully reduced and oxidized states respectively. The results showed that copolymerization is a valuable approach in order to achieve desired electrochromic and redox properties.

- by Bhushan Gadgil
- •
- Physical Chemistry, Electrochemistry, Conducting Polymers, Organic Electronics

In this article, we describe electrically conductive nanoblends containing poly(aniline-co-3aminobenzoic acid) (PANABA), poly(styrene-alt-maleic acid) (PSMAC), and polystyrene. PANABA copolymers on a nanoscale were prepared under ultrasonic irradiation by the oxidative copolymerization of aniline and 3-aminobenzoic acid at different molar ratios. PSMAC was also prepared in our laboratory. The obtained conductive nanoblends formed films with good homogeneity and flexibility. The conductivity of the obtained nanoblends was measured with a four-probe method.

- by Asanga Ranasinghe
- •
- Engineering, Materials Engineering, Condensed Matter Physics, Inkjet printing
- by Lorenzo Mognon and +2
- •
- CHEMICAL SCIENCES, Oxidation, Desulfurization, Copolymerization

Long chain branches (LCBs) can be very advantageous for certain applications of polyolefins. The main feature of LCBs is that, contrary to short chain branches, they improve polymer viscoelastic properties and processability without compromising mechanical properties of the polymer. Before the advent of metallocene catalysts, low-density polyethylene (LDPE) was the only LCB-polyolefin industrially available from a one-step synthesis. LDPE is produced through high-temperature, high-pressure, peroxide-initiated polymerization processes. Polypropylene containing LCBs could only be prepared by controlled degradation of polyolefins with peroxides, laser beams, or heat in post-polymerization processes. Beside the production of linear polyolefins with improved mechanical properties, metallocene catalysts provide a convenient route to produce branched polyolefins under mild polymerization conditions. The LCBs are believed to be generated through re-incorporation of macromonomers, generated in situ by b-hydride elimination, into the growing polymer chain. In this way, LCB formation with these catalysts is analogous to copolymerization with very long a-olefins. These branched chains improve the processability of the polymer, solving one of the most significant technological drawbacks of metallocene-catalyzed polyolefins.

- by Jose Pinto
- •
- Modeling, Molecular weight, Copolymerization, Olefin

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

- by Jacob Kleiman
- •
- Solar Cell, Erosion, Silica, Atomic Oxygen

A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (M n ) in the range of 3.85À5.13 Â 10 4 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300À750 nm with optical bandgaps of 1.80À1.93 eV. Both the HOMO energy level (À5.38 to À5.47 eV) and LUMO energy level (À3.47 to À3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm 2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) or [6,6]-phenyl-C 71butyric acid methyl ester (PC 71 BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC 71 BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (V oc ) value of 0.75 V, a short-circuit current (J sc ) value of 4.60 mA/cm 2 , and a fill factor (FF) value of 35.0% were achieved. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4823][4824][4825][4826][4827][4828][4829][4830][4831][4832][4833][4834] 2010

The living/controlled copolymerization of methyl acrylate with 1-alkenes and norbornene derivatives through several radical polymerization techniques has been achieved. These techniques include atom transfer radical polymerization, reversible addition–fragmentation transfer polymerization, nitroxide-mediated polymerization, and degenerative transfer polymerization. These systems display many of the characteristics of a living polymerization process: the molecular weight increases linearly with the overall conversion, but the polydispersity remains low. Novel block copolymers have been synthesized through the sequential addition of monomers or chain extension. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6175–6192, 2004

Here, we present the first example of application of single-electron transfer living radical polymerization (SET-LRP) process to a controlled grafting of cellulose esters, cellulose diacetate (CDA), and cellulose acetate butyrate (CAB). The cellulose ester macroinitiators with various functionality densities have been prepared by acylation of the backbones with 2-bromoisobutyryl (BrIB) and dichloroacetyl (DCA) groups, respectively. Methacrylate monomers were polymerized using DCA-functionalized macroinitiators in the presence of pentamethyldiethylene triamine as a ligand. At 30 C, the reaction is rather slow, reaching about 10% conversion after 3 to 6 h of polymerization, whereas the higher temperature (60 C) perceptibly speeds up the polymerization so that methyl methacrylate (MMA) conversion is $30% after 5 h. Graft copolymers with random-type and diblock-type grafts having amphiphilic character were also synthesized. For acrylate grafting (BuA and t-BuA), BrIB-functionalized macroinitiators are more convenient in a combination with a low concentration of Cu(0) and Me 6 TREN as a ligand and polymerization is detectably faster even at the lower temperature than that of MMA. Kinetic studies show ''living'' character of both the graftings. Important advantages of SET-LRP, compared with classic ATRP, are (i) higher polymerization rate, (ii) lower extent of recombination of the growing grafts and (iii) negligible coloration of the products with catalytic residua, so that the prepared polymers do not require additional careful purification.

Copolymers of aniline and 2-ethylaniline can be easily formed by electrochemical or chemical oxidation in acidic medium, but the composition of the polymeric chain differs from the composition of the synthesis solution. Copolymers formed from precursor solutions containing less than 30% (in moles) of 2-ethylaniline show intermediate properties between those of the homopolymers, and these properties vary gradually with the amount of 2-ethylaniline units in the copolymeric chain. The properties of those copolymers have been studied by UV Á/Vis and resonance Raman spectroscopies, cyclic voltammetry, two-probe conductivity and solubility measurements. Results obtained by these techniques corroborate the formation of a block copolymeric material. #

- by Luiz L Faria
- •
- Chemistry, Organic Chemistry, Physical Chemistry, Electrochemistry

This report results from a contract tasking Institute of Physiologically Active Compounds as follows: The contractor will investigate and develop new methods for introduction of pentafluorothio groups (SF5) into various unsaturated heterocyclic and aromatic molecular systems and will synthesize new materials containing SF5-groups. The majority of synthesized materials (or composition) will be subjected to a broad spectrum of physics-chemical tests. Expected results include: a) synthesis and study of reactions homo- and copolymerization for new types of unsaturated compounds with pentafuorosulfanyl (SF5) groupings: b) new methods of introduction pentafluorothio groups (SF5) into various unsaturated heterncyclic and aromatic molecular systems will be developed; c) study of reaction fluorination of ethers with pentafluorothio groups (SF5) nitro (NO2) groups and related compounds having electron-withdrawing groups.

- by Valery Brel
- •
- Organic Chemistry, Copolymerization, Molecular Structure

The propensity of a half-sandwich (η5-tetramethylcyclopentadienyl) dimethylsilylamido Ti IV -based catalyst bearing an auxiliary diethylboryl-protected pyridyl moiety (Ti-8), activated by methylaluminoxane (MAO) to homopolymerize α-olefins such as ethylene, 1-hexene and styrene as well as to copolymerize styrene with 1,3-cyclohexadiene is described. The reactivity of Ti-8 was investigated in comparison to a 6-(2-(diethylboryl)phenyl)pyrid-2-yl-free analogue (Ti-3).

- by Ulrich Decker
- •
- Organic Chemistry, Catalysis, Titanium, Polymers

The co-polymerization of CO2 with the non-polar monomer ethylene, though highly desirable, still presents a challenge whereas the palladium-catalyzed CO/C2H4 co-polymerization is well understood. Building on this analogy, the goal of this study was to elucidate the feasibility of developing suitable catalysts for co-polymerizing CO2 with ethylene to polyethylene esters. Computational methods based on density functional theory were hereby employed. In the search for new catalyst lead structures, a closed catalytic cycle was identified for the palladium-catalyzed CO2/C2H4 co-polymerization reaction. The computational study on palladium complexes with a substituted anionic 2-[bis(2,4-dimethoxyphenyl)-phosphine]-benzene- 2-hydroxo ligand revealed key aspects that need to be considered when designing ligand sets for potential catalysts for the non-alternating co-polymerization of CO2 and ethylene.

- by Thomas E Müller
- •
- Polymer Engineering, Polymer Chemistry, Catalysis, DFT calculation
- by Mohamed Mekewi
- •
- Engineering, CHEMICAL SCIENCES, Thermal Stability, Schiff Base

Summary: The incorporation of comonomer molecules in the backbone of a homopolymer can influence the final properties of the material, decreasing its crystallinity and the melting and glass transition temperatures, and increasing its impact resistance and transparency. In the present work, ten ethylene/propylene copolymers have been synthesized using a supported metallocene catalytic system covering the whole composition range. Any desired composition was obtained by controlling the feed composition during the reaction. These synthesized copolymers have been characterized by different techniques in order to study the effect of the comonomer incorporation onto their final properties. When the comonomer content is low, the behaviour of the copolymer is similar to that of the corresponding homopolymer. Nevertheless, if the comonomer content increases, the copolymer becomes more amorphous (low crystallization temperature and soft XRD signals) and easily deformable, reaching a behaviour close to that corresponding to an elastomeric material. In order to corroborate these results the samples have been characterized by TREF and GPC-MALS. TREF analysis showed that copolymers containing less than 10% and more than 80% of ethylene are semicrystalline, with elution temperatures typical of this kind of polymers. Molecular weights are higher for homopolymers and they decrease as the comonomer concentration increases, whereas the polydispersity index keeps almost constant at the expected value for this kind of samples.

- by Rafael van Grieken
- •
- Materials Engineering, Microstructure, Catalysts, Morphology