Effect Of Polymerization Conditions Research Articles

Features of Methyl Methacrylate Polymerization Mediated by Methylene Blue and Ethyl 2-Bromoisobutyrate under Photoirradiation Conditions

Using methyl methacrylate polymerization as an example, the features of polymer synthesis in the presence of the catalytic system [methylene blue + ethyl 2-bromoisobutyrate] at room temperature under visible light irradiation are investigated. The effect of polymerization conditions, including the light irradiation wavelength and various structure activators, on the monomer conversion and molecular weight characteristics of polymers is estimated. It is shown that polymerization can proceed in the controlled mode under mild temperature conditions according to the atom transfer mechanism (Metal Free Atom Transfer Radical Polymerization) to high conversions at low photocatalyst concentrations.

Synthesis of Acrylate Dual-Tone Resists and the Effect of Their Molecular Weight on Lithography Performance and Mechanism: An Investigation.

Acrylate photoresists have gained considerable attention in recent years owing to their high resolution, high sensitivity, and versality. In this work, a series of thermally stable copolymers are synthesized by introducing an isobornyl group, and well characterized using Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectra (1H-NMR). The effects of polymerization conditions on the molecular weight and their further influence on lithography are explored. By analyzing the thermal properties, film-forming capabilities, and the patterning behavior of these copolymers, a direct correlation between lithography performance and polymerization conditions is established via the molecular weight. In addition, the baking temperature of lithography is also optimized by atomic force microscopy (AFM), after which a line resolution of 0.1 μm is observed under the exposure of a 248 nm UV light and electron beam. Notably, our synthesized photoresist displays dual-tone resist characteristics when different developers are applied, and the reaction mechanism of acid-catalyzed hydrolysis is finally proposed by comparing the structural changes before and after exposure.

Modeling Low‐Density Polyethylene (LDPE) Production in Tubular Reactors: Connecting Polymerization Conditions with Polymer Microstructure and Rheological Behavior

AbstractThe production of low‐density polyethylene (LDPE) in high‐pressure tubular reactors is widely studied due to its extensive use worldwide. Reaction conditions have a crucial impact on the polymer molecular architecture, which, in turn, influences the rheological behavior of the polymer in the molten state, a very important variable during subsequent processing. Up to now, the relationships between reactor polymerization conditions, polymer microstructure, and final rheological properties are not completely established, although they could be a very useful tool for rapid process control and optimization. This work presents an integrated model of the high‐pressure polymerization of ethylene in tubular reactors, consisting of the combination of a deterministic model of the tubular reactor that calculates molecular properties of the polymer and an empirical rheological model for branched molecules. The integrated model predicts conversion, temperature, and average molecular properties, as well as the bivariate molecular weight‐long chain branching distribution, the branching index, and the shear viscosity flow curve for LDPE under different operating conditions. Results compare well with experimental data of an actual industrial reactor. Additionally, the effect of polymerization conditions on molecular and rheological properties is analyzed.

Bisphenol A Release from Dental Composites and Resin-Modified Glass Ionomers under Two Polymerization Conditions.

Bisphenol A (BPA)-based monomers are commonly contained in dental resin-based materials. As BPA is an endocrine disruptor, its long-term release from restorative composites and resin-modified glass ionomers (RM-GICs) under two polymerization conditions was measured in this study. Specimens of two conventional composites containing BPA-based monomers, two “BPA-free” composites, and two RM-GICs were polymerized from one side for 20 s at 1300 mW/cm2 or for 5 s at 3000 mW/cm2. The amounts of BPA released in artificial saliva and methanol after 1, 4, 9, 16, 35, 65, 130, and 260 days were measured using liquid chromatography–tandem mass spectrometry. The highest amounts of BPA were released from conventional composites, followed by RM-GICs, while the least was released from “BPA-free” composites. Amounts of released BPA were significantly higher in methanol and decreased gradually after the first day. Fast polymerization (5 s at 3000 mW/cm2) resulted in a significantly higher release of BPA after 1 day, but the effect of polymerization conditions was not significant overall. In conclusion, fast polymerization increased the initial release of BPA, but the released amounts were significantly lower than the current tolerable daily intake (4 μg/kg body weight/day) even in methanol, representing the worst-case scenario of BPA release.

Effect of polymerization conditions on the physicochemical and electrochemical properties of SnO2/polypyrrole composites for supercapacitor applications

A stable and unique porous SnO2/polypyrrole composite has been successfully manufactured using various SnO2 loadings (5, 8, 10, 15 and 20 wt%) by applying a direct polymerization approach and employing a cheap oxidizing agent (FeCl3). The physicochemical properties of the new composites were investigated using X-ray Diffractometer (XRD), Fourier Transform Infra-Red spectrometer (FTIR), Field Emission Scanning Electron Microscope (FESEM) and UV-Visible spectrometer. The estimated band gap energy (Eg) for SnO2/PPy composite revealed lower value ∼ 1.1 eV than pure PPy suggesting good electronic conductivity. Optimization of the polymerization parameters indicated that the prepared SnO2/PPy composite at 0°C with mass ratio 0.1 exhibited the highest specific capacitance ∼ 450 F.g−1 at 20 mV.S−1 with a significant improvement ∼ 56% with respect to the pure PPy. The optimized SnO2/PPy electrode material revealed an excellent cyclability with constant loss in the capacitance retention ∼ 5% from 500 to 1100 charge/discharge cycles till reach 94% capacitance retention after 1500 cycles. On the other hand, pure PPy displayed a continuous decrease in the capacitance retention approaching 75% after1500 cycles.

Polymerization‐induced self‐assembly of amino‐acid‐based nano‐objects by reversible addition–fragmentation chain‐transfer dispersion polymerization

AbstractA series of amino‐acid‐based amphiphilic diblock copolymer nano‐objects having different morphologies were developed by reversible addition–fragmentation chain‐transfer (RAFT) dispersion polymerization of styrene (St) in methanol. This was mediated by six different hydrophilic poly(N‐acryloyl amino acid) macro‐chain transfer agents (CTAs), including three carboxylic‐acid‐containing ones, poly(N‐acryloyl‐l‐proline) (PAProOH), poly(N‐acryloyl‐4‐trans‐hydroxy‐l‐proline) (PAHypOH), and poly(N‐acryloyl‐l‐threonine) (PAThrOH) prepared by RAFT polymerization, and their methyl ester forms, PAProOMe, PAHypOMe, and PAThrOMe. The effects of polymerization conditions on RAFT dispersion polymerization of St using a dithiocarbamate‐terminated PAProOH was investigated. A systematic study of the effects of monomer conversion and concentration afforded the formation of various morphologies (i.e., spheres, worms, and vesicles). The effects of hydrogen‐bonding and ionic interactions of the macro‐CTAs on the assembled structures of the nano‐objects were evaluated using six different macro‐CTAs. Transforming the products from methanol to water via dialysis produced amino‐acid‐based block copolymer nano‐objects, exhibiting pH‐responsive morphological change, in aqueous solution.

Continuous-flow RAFT copolymerization of styrene and maleic anhydride: acceleration of reaction and effect of polymerization conditions on reaction kinetics

Continuous-flow RAFT copolymerization of styrene and maleic anhydride: acceleration of reaction and effect of polymerization conditions on reaction kinetics

Effect of polymerization conditions on physicochemical properties of gold-like lustrous films of organic solvent soluble 3-methoxythiophene oligomers

Solution-cast films of ClO4−-doped oligo(3-methoxythiophene) exhibit a luster similar to that of metallic gold; however, the effects of synthetic conditions on the physicochemical properties of the above oligomer and its films remain underexplored. To bridge this gap, this study examines how these properties are affected by (i) the time required to add the oxidant solution to the monomer solution (ta) and (ii) the polymerization time (tp) for oligomer synthesis, revealing that oligomer molecular weight, film conductivity, and the amount of edge-on lamellar crystallites increase with decreasing ta and/or increasing tp. Given that the crystallinity of edge-on lamellar structures, together with film surface roughness, strongly influences film specular reflectance, the obtained results are expected to facilitate the fabrication of conductive oligo(3-methoxythiophene) films with tunable color and metal-like luster for diverse applications. The oxidant addition time and polymerization time were varied during the synthesis of oligo(3-methoxythiophene), and the effect of such polymerization conditions on the physicochemical properties of the oligomer and its cast films was investigated. The polymerization conditions changed the oligomer molecular weight and the amount of edge-on lamellar crystallites in the films and, in turn, affected the color and gloss of the films. The obtained results are expected to facilitate the fabrication of conductive oligo(3-methoxythiophene) films with tunable color and metal-like luster for diverse applications.

Sulfone-functionalized poly(p-phenylene terephthalamide) copolymer fibers with improved interfacial adhesion to epoxy matrices

The poor interfacial adhesion of aramid fiber and matrix limits the application of the final composites. In this study, a series of the sulfone-functionalized poly( p-phenylene terephthalamide) (SPPTA) copolymers were satisfactorily synthesized and the effects of polymerization conditions (contents of the additional monomer and the cosolvent LiCl, molar concentration and ratio of the monomer, reaction temperature and time) on the molecular weight of the copolymer were discussed. The introduction of the sulfone group in aromatic polyamides not only increased the polarity of poly( p-phenylene terephthalamide) (PPTA) but destroyed the regular arrangement of the molecular chains, which greatly improved the surface free energy and the solubility of the polymers in organic solvents. The polymer maintained excellent thermal and interfacial properties. Compared with the PPTA fiber/epoxy composites, the interfacial shear strength (IFSS) of SPPTA fiber-reinforced epoxy composites reached 43.5 MPa, with a significantly enhancement of 20.8%, implying that the study provided an effective method to achieve highly interfacial adhesion of aramid fiber-reinforced composites.

One-pot synthesis of cross-linked nonspherical polystyrene particles via dispersion polymerization: the effect of polymerization conditions on the morphology of the particles

Herein we report the fabrication of cross-linked polystyrene particle with a variety of nonspherical morphologies such as red blood cell-like, cap-like, apple-like and so forth through two-stage dispersion polymerization in polar media. Furthermore, we examine the effect of different polymerization conditions including monomer and cross-linker concentration, and the type of initiator, monomer, stabilizer and cross-linker on the shape of the obtained particles. The acquired results reveal that the particles morphology can be altered from spherical to nonspherical with a decrease in the content of cross-linker and monomer, and using more reactive initiators and cross-linkers. Furthermore, particles shape can be changed through the addition of a different second-stage monomer type. Finally, the possible formation mechanism of the discussed nonspherical particles is illustrated.

Design of Graft Architectures via Simultaneous Kinetic Control of Cationic Vinyl-Addition Polymerization of Vinyl Ethers, Coordination Ring-Opening Polymerization of Cyclic Esters, and Merging at the Propagating Chain End

Versatile graft architectures were synthesized in one shot via simultaneous controlled cationic vinyl-addition polymerization of vinyl ethers (VEs) and coordination ring-opening polymerization of cyclic esters (CEs). Graft copolymers were generated via independent propagation reactions and transient incorporation of a poly(CE) chain into the side chain of the poly(VE) propagating end via the exchange of alkoxy groups. In this mechanism, the grafting density and grafting length of a copolymer were designable by tuning the rates of each propagation reaction and the exchange reaction. As a result of a systematic investigation, the effects of polymerization conditions, such as the kinds and concentrations of monomers and catalysts, on the rate of each reaction were revealed and a design principle of various graft architectures was established. Notably, a copolymer with a remarkably high grafting density was obtained [max. 88% of poly(VE) side chains were substituted with poly(CE) chains] when a VE with an ethylenedioxy side chain was used with a titanium catalyst. The specific interaction of an ethylenedioxy unit and a titanium catalyst was key to the high grafting density.

Formation of Ziegler‐type catalytic systems on the surface of multi‐walled carbon nanotubes for the production of composite materials by in situ polymerization

ABSTRACTThe peculiarity of formation of Ziegler‐type catalytic systems prepared using organoaluminum (AlR3) and organomagnesium (MgR2) on the surface of multi‐walled carbon nanotubes (MWCNTs) was revealed. We have found first AlR3 and MgR2 interact with different sites on MWCNT surface. It was demonstrated by IR spectroscopy that organoaluminum compounds were immobilized on the hydroxyl‐containing groups on MWCNT surface. Organomagnesium compounds were immobilized on the topological structural defects of MWCNTs; hydroxyl‐containing groups were not required for their immobilization. Further interaction between TiCl4 and organomagnesium compound immobilized on the MWCNT surface yielded a catalyst containing titanium and magnesium chlorides (an analogue of the known titanium–magnesium catalysts), which exhibits an enhanced activity in ethylene polymerization. The effect of polymerization conditions on molecular weight characteristics of polyethylene in the MWCNT/PE composite material produced by in situ polymerization over the catalyst immobilized on the MWCNT surface was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48212.

Effect of Polymerization Conditions on Polypropylene Synthesis in Liquid Monomer

The effect of polymerization conditions (temperature, polymerization time, monomer and hydrogen concentrations) on propylene polymerization in the liquid monomer in the presence of a TiCl4/DBP/MgCl2 + TEA/cyclohexylmethyldimethoxysilane catalyst system is studied . It is shown that the variation of the propylene polymerization conditions in the studied ranges leads to a change in the characteristics of the resulting polypropylene. The kinetic parameters of propylene polymerization in the liquid monomer for the studied catalyst system are determined. Polymerization conditions providing the formation of polypropylene with high polymer yield, isotacticity, and bulk density values are found. The process parameters that make it possible to effectively control the molecular and rheological characteristics of polypropylene are identified.

Synthesis of an Acrylamide Copolymer Containing Nano-SiO2 by Ex Situ Cu(0)-Mediated SET-LRP

We report herein the synthesis of a novel star-shaped copolymer containing nano-SiO2 by single-electron transfer living radical polymerization (SET-LRP) in aqueous solution. The effects of polymerization conditions, such as the total amounts and molar ratios of the monomer, initiator, catalyst, ligand, and modified nano-SiO2, have been investigated through a series of experiments. The prepared acrylamide copolymers have been characterized by FTIR spectroscopy and 1H NMR spectrometry. The properties of the copolymers have been assessed by viscometry and rheometry. The results confirmed that the nano-SiO2 functional monomer was successfully combined in the SET-LRP. The optimum polymerization conditions were established through orthogonal experiments as a ratio of [AM] : [DMAEMA] : [I] : [CuBr] : [Me6TREN] of 674.4 : 35.5 : 1 : 1 : 2 at a total concentration of [AM] + [DMAEMA] of 2.5 mol/L. The appropriate concentration of the nano-SiO2 functional monomer (NSFM) was 0.5 wt% with respect to AM + DMAEMA. The rheology of the star-shaped copolymer exhibited a shear-thickening property when the shear rate exceeded a critical value (100 s−1). The AM/DMAEMA/NSFM copolymer displayed a higher viscosity than AM/DMAEMA at the same concentration. It was found that AM/DMAEMA/NSFM exhibited better salt and temperature tolerances.

Stereoselective ring-opening polymerization of rac-lactide by bulky chiral and achiral N-heterocyclic carbenes

Despite the extraordinary success has been achieved in metal catalyst-promoted stereoselective ring-opening polymerization (ROP) of rac-lactide (rac-LA), well-controlled stereoselective rac-LA ROP by organic catalyst still remains a scientific challenge. Here we report our investigations into organocatalytic stereoselective ROP of rac-LA by utilizing novel bulky chiral and achiral N-heterocyclic carbenes (NHC), 1,3-bis-(1′-naphthylethyl)imidazolin-2-ylidene. The effect of polymerization conditions (e.g. solvent, temperature, alcohol initiator) on ROP behavior by these bulky NHCs has been fully studied, leading to the formation of isotactic-rich stereoblock polylactide (Pi = 0.81) under optimized conditions with high activity (Conv. = 98% in 30 min) and narrow molecular weight dispersity (Ɖ = 1.05).

Peculiarities of Ethylene Polymerization Kinetics with an Imido-Vanadium/Silyl-Chromate Bimetallic Catalyst: Effect of Polymerization Conditions

The effects of various polymerization conditions such as cocatalyst concentration, pressure, temperature, and reaction time on ethylene homopolymerization over a SiO2-supported imido-vanadium/silyl-chromate (Cr-iV) bimetallic catalyst were systematically investigated. The monometallic silyl-chromate (S-2) and imido-vanadium (iV) catalyst were also employed for comparison. It was found that the S-2 catalyst produced a polymer with relatively low molecular weight, while the iV catalyst produced ultrahigh-molecular-weight polyethylene (UHMWPE). The bimetallic catalyst was capable of producing reactor blends, with bimodal molecular weight distribution (MWD) and a considerable amount of UHMWPE. Increasing cocatalyst concentration and decreasing polymerization temperature both enhanced the high molecular weight part of the bimodal MWD while the position of the two peaks remained unchanged. The polymerization rates all showed first-order dependences with respect to ethylene pressure for the three catalysts. Ethy...

Композиционные полимерные суспензии со сложной морфологией частиц

The review is dedicated to the synthesis of composite polymer suspensions with complex particle morphology. Authors attempted to summarize effects of polymerization conditions on particle morphology. The significance of further investigations in the field of composite polymer suspensions synthesis was shown. The main aspects of different monomers emulsion homopolymerization, affecting the polymer particle morphology, such as polymerization topochemistry, free energy of particle formation, the kind of monomer and others were discussed. The determination methods of polymer particles phase structure may be shown to be classified as direct and indirect. The most frequently used investigation methods of suspension particles morphology viz electron microscopy, soap titration technique and film forming were described. General techniques of composite polymer particle synthesis, such as emulsion copolymerization and seed polymerization, were given and considered in detail. Advantages and disadvantages of each method were listed. Determination of particle morphology, using thermodynamic approach, was discussed. Obtained composite polymer particles were found to be classified into two large groups: non-uniform composite gradient particles and heterophase particles.

Mechanisms for the effects of fluorine and α-diimine backbone structure on the catalyst behavior and catalyst deactivation in ethylene polymerization by Ni catalysts

Ethylene polymerizations were carried out via three fluorinated late transition metal (LTM) catalysts activated by methylaluminoxane (MAO) as a co catalyst. The effects of polymerization conditions, the fluorine of ligand and the α-diimine backbone structure on the catalysts performance and polymer properties were studied. Modification of the α-diimine ligand had a notable effect on the catalysts behavior. The catalyst [bis(N,N/-2-fluorophenylimino)acenaphthene] nickel (ΙΙ) dibromide (catalyst 1) showed the highest activity compared to other catalysts used in this study. Moreover, the catalyst 1 produced a polymer with the highest molecular weight, while the catalyst [bis(N,N/-2-fluorophenylimino)ethan] nickel (II) dibromide (catalyst 2) produced a polymer with the lowest molecular weight. A mechanism was proposed for the effects of fluorine and α-diimine backbone structure on the catalysts behavior, catalyst deactivation and molecular weight of the polymers obtained. Our mechanistic hypothesis was strongly verified by computational approaches, we used to describe the system. The probable reactive electronic interactions of fluorine substitution were accurately distinguished to explain the influence of the ligand backbone on the molecular weight of the obtained polymer.

Self‐driven graft polymerization of vinyl monomers on poultry chicken feathers in the absence of initiator/catalyst

ABSTRACTAn efficient and simple method for graft copolymerization of powdered chicken feather (CF) with vinyl monomers without any free radical initiator is reported. Various vinyl monomers such as glycidyl methacrylate (GMA), styrene (S), and methyl methacrylate (MMA); (20–60 wt % with respect to CF) were successfully grafted to chicken feather (CF) by using sodium dodecyl sulfate (SDS, 0.086–0.5 mmol) in the absence of any catalyst or initiator. Most likely, the hydrophilicity, hydrophobicity, and complex forming properties of chicken feather keratin with surfactant molecules were responsible for efficient grafting of polymers on CF surface. The effect of polymerization conditions, such as monomer concentration, temperature, and time of reaction, on the grafting parameters such as monomer conversion, grafting efficiency, and molar grafting ratio were studied. The described method showed a good potential of using low cost, easily accessible poultry chicken feathers as grafting material and self catalyzing agent for graft copolymerization with vinyl monomers to produce low cost commodity plastic for various end uses. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44645.

Radical mediated thiol-ene/yne dispersion polymerizations

Abstract We report the synthesis of polymeric particles using radical mediated step-growth thiol-ene and thiol-yne ‘click’ dispersion polymerizations in alcoholic solvents. Various alkene, alkyne and thiol monomers were used, and thermal, photo- or redox initiation methods were all shown to be effective means to initiate polymerization. Polymer particles typically were formed with diameters in the range of several hundred nanometers, with narrow size distributions though broader than typical free-radical chain-growth dispersion polymerizations. Photoinitiation yielded the smallest sizes due to the rapid nucleation of particles as compared to redox and thermal initiation methods. Reaction kinetics were monitored by FT-IR spectroscopy for aliquot samples taken at various reaction durations. The reaction achieved full conversion in photoinitiated systems within five minutes, while it took three hours for both thermal and redox initiation to be completed. The effects of polymerization conditions on particle size particularly the impact of monomer, stabilizer, and initiator concentrations were studied. Generally, average particle size increased with higher monomer concentration and decreased with additional stabilizer or initiator. Combinations of monomers with varying number of functional groups were investigated to form particles of various mechanical and physical behavior, including both linear and crosslinked systems.