Free Radical Polymerization Process Research Articles

Fast synthesis of an inorganic–organic block copolymer in a droplet-based microreactor

In this report, we used a non-lithographic embedded template method to fabricate a polyvinyl silane (Kion) microfluidic device. The device possesses a good solvent resistance, thermal stability and air-impermeability. The device was used for the synthesis of an inorganic–organic block copolymer through the generation and merging of reactant droplets. The SP-b-PMMA block copolymer was synthesized successfully by the atom transfer free radical polymerization (ATRP) process with a high conversion and narrow polydispersity in a very short reaction time, about ten minutes. The results obtained using the droplet-based microreactor were much better than those obtained with a macroscale batch reactor. Moreover, the as-synthesized SP-b-PMMA block copolymer was used to generate a highly ordered self-assembled ceramic pattern hence demonstrating the high quality of the block copolymer with superior molecular weight distribution control.

Fabrication of Thermoresponsive Glycopolymers Fibers for Lectin Recognition

A thermoresponsive glycopolymer poly-(N-isopropylacrylamide-co-6-O-vinylsebacoyl D-glucose) (poly-NIPAM-co-VSEG; PNE) has been prepared by free radical polymerization process, and subsequently processed into nanofibers with poly-L-lactide-co-ε-caprolactone (PLCL) using electrospinning. The thermoresponsive glycopolymer materials have been characterized by Fourier transform infrared (FTIR) spectroscopy, 1H NMR, and scanning electron microscopy (SEM). And the lower critical solution temperature (LCST) of these thermoresponsive materials was also measured. The nanofibers containing PNE can greatly selective recognize with lectin Concanavalin A (Con A), and the adsorbed Con A can be easily eluted by 1 M glucose solution. These results indicate that PNE can separate and purify proteins, and also the temperature sensitive characteristic has the potential to achieve the intelligent control.

Lyotropic Liquid Crystal of Polyacrylonitrile-Grafted Graphene Oxide and Its Assembled Continuous Strong Nacre-Mimetic Fibers

Liquid crystals (LCs) of pristine graphene oxide (GO), a kind of novel two-dimensional (2D) macromolecule, have been discovered recently, opening an avenue to high performance neat graphene fibers. Here, we report for the first time LC of polymer-grafted GO and its macroscopic assembled nacre-mimetic composite. Polyacrylonitrile (PAN) chains were covalently and uniformly grafted onto GO surfaces via a simple free radical polymerization process. The PAN-grafted GO (GO-g-PAN) sheets were well dispersed in polar organic solvents such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), forming nematic and lamellar LCs upon increasing concentration. A strong signal was found in the circular dichroism spectra of the LCs, indicating the formation of helical lamellar structures for the GO-g-PAN LCs. Macroscopic assembled fibers were continuously spun from the GO-g-PAN LCs via the industrially viable wet-spinning technology. The fibers held strict layered structures of GO and PAN, resembling the classic “brick-and-mortar” microstructure observed in nacre. The nacre-mimetic composite showed excellent mechanical property with tensile strength of 452 MPa, Young’s modulus of 8.31 GPa, and breakage elongation of 5.44%. This offers a new approach for the fabrication of continuous, ultrastrong, and tough biomimic composites.

Kinetics of Free-Radical Cross-Linking Polymerization: Comparative Experimental and Numerical Study

Modeling free radical polymerization processes in the presence of cross-linkers is a challenging problem that has been addressed using numerous techniques for over more than half a century. However, a model providing a comprehensive description of the phenomenon has not been proposed yet. In this work, we implement a simple free-radical polymerization scheme of a monovinyl (difunctional) monomer and a divinyl (tetrafunctional) cross-linker in a Monte Carlo (MC) scheme, which describes polymer dynamics using a bond-fluctuation model. MC simulations allow us to follow the entire polymerization kinetics and the formation of a percolating network (gel phase) by realistically taking into account diffusion limitations, to extract scaling information at the percolation threshold and to recover the distribution of number of monomer units between two successive fully cross-linked units, from which the extent of swelling can be computed. The predictions of MC simulations are also successfully compared to a kinetic model based on numerical fractionation, with kinetic constants used as fitting parameters. MC data and kinetic simulations are compared to some experimental data on the swelling behavior of polyacrylamide hydrogels and of poly(methyl methacrylate) (PMMA) gels, exhibiting good agreement. We conclude that the proposed MC simulation scheme represents a powerful tool from which precious and experimentally inaccessible information on polymerization processes in the presence of cross-linkers can be extracted.

Benzotriazinyl-mediated controlled radical polymerization of styrene

The stable free radical polymerization (SFRP) process based on (1,3-diphenyl-1,4-dihydro-1,2,4-benzotriazin-4-yl), the so-called ‘Blatter radical’, and several C-7 substituted derivatives is introduced for the first time for the polymerization of styrene. Polystyrenes characterized by polydispersity indices in the 1.05 − 1.27 range were obtained in the presence of the Blatter radical and its derivatives containing CF3, Ph, Fur-2-yl and 4-PhC6H4 substituents, while polymerization proceeded either in a non-controlled manner or in very low polymerization yields in the presence of derivatives containing halogen (Cl, Br, I) substituents. This preliminary investigation, demonstrating the potential use of the Blatter radical and its derivatives in mediated SFRP, creates new opportunities to design and develop radicals to optimize performance in such polymerization processes. © 2013 Society of Chemical Industry

Dynamic simulation of high-pressure tubular reactor for low-density polyethylene production

Low-density polyethylene, one of the most important polymer products, is commonly produced in high-pressure free radical polymerization processes. A dynamic model of the high-pressure polymerization of ethylene initiated by oxygen in tubular reactor is introduced, and a dynamic optimization problem is formulated for process start-up strategies. The present study proposes a kinetic model based on an assumed reaction mechanism. The model describes the rates of oxygen decomposition and propagation of free radical ethylene polymerization. The mass and heat balance equations in an adiabatic tubular reactor operated at a constant pressure of 2.4 kbars and a temperature range of 110–300°C are presented. Simulations of polymerization process predict temperature of the reaction mixture, response time for cooling water, and also conversion along the reactor length. Response time was obtained using different inputs of controlled variables. Values obtained from these simulations are compared with real data from the process unit ( Polietilen, Dioki®, Zagreb, Croatia) and a model validation is confirmed. Improvement in reactor productivity and better understanding of few different start-up procedures is achieved.

Cross-linkable urethane acrylate oligomers as binders for lithium-ion battery

Cross-linked polymers generated from low molecular weight oligomers were investigated for the first time as electrode binders in lithium-ion batteries. With urethane acrylate-based binder precursors, electrode laminates of LiNi1/3Mn1/3Co1/3O2 (NMC) with good physical properties were prepared via a thermally initiated free-radical polymerization process. The cured NMC electrode was evaluated in both NMC/Li and NMC/MCMB cells and showed excellent cycling performance and C-rate capability.

α‐Bis and α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polymers by atom transfer radical polymerization using 1,1‐bis[(4‐dimethylamino)phenyl]ethylene as tertiary diamine initiator precursor and functionalizing agent

The quantitative syntheses of α-bis and α,ω-tetrakis tertiary diamine functionalized polymers by atom transfer radical polymerization (ATRP) methods are described. A tertiary diamine functionalized 1,1-diphenylethylene derivative, 1,1-bis[(4-dimethylamino)phenyl]ethylene (1), was evaluated as a unimolecular tertiary diamine functionalized initiator precursor as well as a functionalizing agent in ATRP reactions. The ATRP of styrene, initiated by a new tertiary diamine functionalized initiator adduct (2), affords the corresponding α-bis(4-dimethylaminophenyl) functionalized polystyrene (3). The tertiary diamine functionalized initiator adduct (2) was prepared in situ by the reaction of (1-bromoethyl)benzene with 1,1-bis[(4-dimethylamino)phenyl]ethylene (1) in the presence of a copper (I) bromide/2,2′-bipyridyl catalyst system. The ATRP of styrene proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding α-bis(4-dimethylaminophenyl) functionalized polystyrene derivative (3) with predictable number-average molecular weight (Mn) and narrow molecular weight distribution (Mw/Mn) in a high initiator efficiency reaction. The polymerization process was monitored by gas chromatography analysis. Quantitative yields of α,ω-tetrakis(4-dimethylaminophenyl) functionalized polystyrene (4) were obtained by a new post ATRP chain end modification reaction of α-bis(4-dimethylaminophenyl) functionalized polystyrene (3) with excess 1,1-bis[(4-dimethylamino)phenyl]ethylene (1). The tertiary diamine functionalized initiator precursor 1,1-bis[(4-dimethylamino)phenyl]ethylene (1) and the different tertiary amine functionalized polymers were characterized by chromatography, spectroscopy and non-aqueous titration measurements. Copyright © 2012 Society of Chemical Industry

Conceptual Design of Large Surface Area Porous Polymeric Hybrid Media Based on Polyhedral Oligomeric Silsesquioxane Precursors: Preparation, Tailoring of Porous Properties, and Internal Surface Functionalization

We report on the preparation of hybrid, organic–inorganic porous materials derived from polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) via a single-step molding process. The monolithic, large surface area materials are studied with a particular focus on morphology and porous properties. Radical vinyl polymerization of the nanometer-sized POSS building blocks is therefore utilized via a thermally initiated route and in porogenic diluents such as tetrahydrofuran and polyethylene glycols of varying composition. Careful choice of these porogenic solvents and proper choice of initiator concentration lead to highly porous monolithic building entities which show a rigid, 3D-adhered, porous structure, macroscopically adapting the shape of a given mold. The described materials reflect Brunauer–Emmett–Teller (BET) surface areas of 700 m2/g or more and maximum tunable mesopore volumes of up to 2 cm3/g. Experimental investigations demonstrate the option to tailor nanoporosity and macroporosity in the single-step free-radical polymerization process. While studies on the influence of the used porogenic solvents reveal tuneability of pore sizes due to the unique pore formation process, tailored existence of residual vinyl groups allows facile postpolymerization modification of the highly porous, large surface area hybrid materials exploited via thiol–ene “click” chemistry. Our developed, simply realizable preparation process explores a new route to derive porous organic–inorganic hybrid adsorbents for a wide variety of applications such as extraction, separation science, and catalysis.

Synthesis and photo-curing behaviors of silicon-containing (vinyl ether)-(allyl ether) hybrid monomers

A series of silicon-containing (vinyl ether)–(allyl ether) hybrid monomers used in nano-imprint lithography resists were synthesized and subjected to photo-initiated polymerization. The surface energies of the monomers and the resulting polymer films were then investigated. The surface energies of the monomers were very low at less than 15 mJ m–2. The photo-curing behaviors of the five hybrid monomers were investigated using real-time Fourier transform infrared spectroscopy. The monomers were sequentially initiated with cationic (PAG201) and mixed (cationic initiator PAG201, radical initiator ITX or TPO) initiators. The vinyl ether double bond polymerized both rapidly and completely, whereas the allyl ether double bond remained when PAG201 was used as the photo-initiator and polymerized completely with mixed initiators. The different double bonds of the silicon-containing (vinyl ether)–(allyl ether) hybrid monomer increased the efficiency of the polymerization and overcame the intrinsic limitations of the free radical and cationic polymerization processes, including strong oxygen inhibition, large volume shrinkage and high humidity sensitivity. The five monomers with low viscosity, low surface energy, good thermal stability and good photo-polymerization properties were suitable for nano-imprint photoresists. © 2013 Society of Chemical Industry

Synthesis of polysulfone-b-polystyrene block copolymers by mechanistic transformation from condensation polymerization to free radical polymerization

Synthesis of polysulfone-b-polystyrene (PSU-b-PS) block copolymers by a combination of condensation polymerization and free radical polymerization processes are described. First, a new macroazoinitiator (MAI) containing polysulfone (PSU) units was prepared by direct esterification of 4,4-azobis(4-cyanopentanoic acid) with α,ω-hydroxyl PSU telechelics at ambient conditions. The macroinitiator was then used in conventional free radical polymerization of styrene leading to the formation of desired block copolymers. In this process, initiating macroradicals were generated by thermal cleavage of the azo group present in the macroazoinitiator structure. The precursor polysulfone macroazoinitiator (PSU-MAI) and resulting block copolymers were characterized by spectral analysis using FT-IR, 1H-NMR, GPC, TGA, and DSC.

Parallel calculation methods for molecular weight distribution of batch free radical polymerization

The molecular weight distribution (MWD) is at the core of establishing key quality indices for free radical polymerization processes. Due to large-scale features of the rigorous model, consisting of a very large number of differential and algebraic equations, dynamic simulation of MWD is always challenging. A sequential variable decoupling method (SVD) has been proposed to calculate the MWD for any reasonably large chain-length number. In the current paper, parallel computing methods were developed to accelerate the MWD simulation. Both coarse-grained and fine-grained parallelism methods have been proposed. A theoretical analysis of the proposed methods was conducted to demonstrate its high efficiency in parallel computing. Both Intel multi-core-processor-based and NVIDIA graphics-processing-unit-based parallel computing platforms were implemented, achieving significant speedups in computation for MWD simulation.

Phototriggered In‐Situ Generation of Triethylborane for Polymer Synthesis Under Air

AbstractUpon demand, 1,3‐diamino‐propane‐triethylborane (DAPTB) is photolyzed in the presence of an acid generator such as a diphenyliodonium salt. Interestingly, triethylborane is released. In the presence of oxygen, ethyl radicals are generated and initiate an acrylate polymerization. This is the first example of a phototriggered production of a triethylborane usable in the photoinitiation of acrylate polymerizations. This approach is also worthwhile to overcome the oxygen inhibition for free‐radical polymerization processes.

α‐Bis and α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polymers by atom transfer radical polymerization using 1,1‐bis[(4‐dimethylamino)phenyl]ethylene as tertiary diamine initiator precursor and functionalizing agent

AbstractThe quantitative syntheses of α‐bis and α,ω‐tetrakis tertiary diamine functionalized polymers by atom transfer radical polymerization (ATRP) methods are described. A tertiary diamine functionalized 1,1‐diphenylethylene derivative, 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1), was evaluated as a unimolecular tertiary diamine functionalized initiator precursor as well as a functionalizing agent in ATRP reactions. The ATRP of styrene, initiated by a new tertiary diamine functionalized initiator adduct (2), affords the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3). The tertiary diamine functionalized initiator adduct (2) was prepared in situ by the reaction of (1‐bromoethyl)benzene with 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) in the presence of a copper (I) bromide/2,2′‐bipyridyl catalyst system. The ATRP of styrene proceeded via a controlled free radical polymerization process to afford quantitative yields of the corresponding α‐bis(4‐dimethylaminophenyl) functionalized polystyrene derivative (3) with predictable number‐average molecular weight (Mn) and narrow molecular weight distribution (Mw/Mn) in a high initiator efficiency reaction. The polymerization process was monitored by gas chromatography analysis. Quantitative yields of α,ω‐tetrakis(4‐dimethylaminophenyl) functionalized polystyrene (4) were obtained by a new post ATRP chain end modification reaction of α‐bis(4‐dimethylaminophenyl) functionalized polystyrene (3) with excess 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1). The tertiary diamine functionalized initiator precursor 1,1‐bis[(4‐dimethylamino)phenyl]ethylene (1) and the different tertiary amine functionalized polymers were characterized by chromatography, spectroscopy and non‐aqueous titration measurements. Copyright © 2012 Society of Chemical Industry

Synthesis and Characterization of PMMA/MMT Nanocomposites

PMMA/MMT nanocomposites has been prepared by using methyl methacrylate (MMA), montmorillonite (MMT) and ethanolamine as the raw materials via an in-situ free radical polymerization process. The as-prepared nanocomposites were characterized by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results show that the poly(methyl methacrylate) and inorganic montmorillonite have been effectively combined. The structure and thermal stability of the as-prepared nanocomposites are different from the content of MMT in the nanacomposites.

Synthesis of Crosslinked Networks of Gum ghatti with Different Vinyl Monomer Mixtures and Effect of Ionic Strength of Various Cations on its Swelling Behavior

A series of pH, temperature, and electrical stimulus sensitive novel hydrogels of Gum ghatti (Gg) with vinyl monomer mixtures of acrylamide (AAm) with acrylic acid (AA), acrylonitrile (AN), and methacrylic acid (MAA) using potassium persulphate-ascorbic acid redox pair as an initiator and N,N’-methylene-bis-acrylamide (MBA) as a crosslinker was synthesized using a free radical polymerization process. Initially, different reaction parameters for the graft copolymerization and crosslinking of Gum ghatti with AAm and MBA were optimized. Afterwards, optimization of AA, AN, and MAA in combination with preoptimized AAm was carried out. Synthesized products were characterized by FT-IR, SEM, XRD, and TGA/DTA/DTG. Swelling behavior of hydrogels was investigated in deionized water as a function of time, temperature, and pH of swelling medium. Moreover, hydrogels have been found to exhibit cationic charge-dependent swelling in different salt solutions of Na+, Ba2+, Fe3+, and Sn4+. The order of swelling was found to be Na+>Ba2+>Fe3+>Sn4+.

Controllable Preparation of Poly(butyl acrylate) by Suspension Polymerization in a Coaxial Capillary Microreactor

In this work, a new controllable and continuous free radical polymerization process was developed and characterized in a coaxial capillary microreactor. In this process, the monomer solution was first dispersed into monodispersed droplets followed by thermal-initiated polymerization in the following capillary immersed in an oil bath. Poly(butyl acrylate) prepared in this microreactor possessed a much higher average molecular weight (Mn) and far lower polydispersity index (PDI) than that produced in a typical stirred vessel. The microreactor method possesses two unique advantages which allow for the optimization of the free radical polymerization process. First, the use of highly monodispersed droplets as polymerization units ensures that the polymerization process occurs uniformly in each individual droplet. Second, the small droplet size, on the order of several hundred micrometers, greatly enhances heat transfer efficiency with no heat accumulation within the droplets during polymerization. A simplified...

Synthesis of aromatic oxazolyl- and carboxyl-functionalized polymers: Atom transfer radical polymerization of styrene initiated by 2-[(4-bromomethyl)phenyl]-4,5-dihydro-4,4-dimethyloxazole

The synthesis of a new compound, 2-[(4-bromomethyl)phenyl]-4,5-dihydro-4,4-dimethyloxazole (1), and its utility in the synthesis of oxazoline-functionalized polystyrene by atom transfer radical polymerization (ATRP) methods are described. Aromatic oxazolyl-functionalized polymers were prepared by the ATRP of styrene, initiated by (1) in the presence of copper(I) bromide/2,2′-bipyridyl catalyst system, to afford the corresponding α-oxazolyl-functionalized polystyrene (2). The polymerization proceeded via a controlled free radical polymerization process to produce the corresponding α-oxazolyl-functionalized polymers with predictable number-average molecular weights, narrow molecular weight distributions in high-initiator efficiency reactions. Post-ATRP chain end modification of α-oxazolyl-functionalized polystyrene (2) to form the corresponding α-carboxyl-functionalized polystyrene (3) was achieved by successive acid-catalyzed hydrolysis and saponification reactions. The polymerization processes were monitored by gas chromatography analyses. The unimolecular-functionalized initiator and functionalized polymers were characterized by thin layer chromatography, spectroscopy, size exclusion chromatography, and nonaqueous titration analysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

Vapor-Phase Free Radical Polymerization in the Presence of an Ionic Liquid

An ionic liquid (IL) was introduced into a vapor-phase free radical polymerization process for the first time. The deposition of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) was studied in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) droplets. The polymerization occurred either at the vapor−IL interface or within the IL depending on reaction conditions such as the duration of deposition, the stage temperature, and the monomer solubility. A variety of polymeric architectures such as polymer skins that completely encapsulated the droplet, free-standing polymer, and polymer films that float freely on the surface of the IL were formed. The results from this study will facilitate the design of new polymer−IL composite materials for use in fuel cell and battery applications.

Scaling-up of poly(vinyl chloride) prepared by single electron transfer degenerative chain transfer mediated living radical polymerization in water media: 1) Low molecular weight. Kinetic analysis

This paper reports the kinetic study of the scale-up for the production of PVC by using a single electron transfer degenerative chain transfer mediated living radical polymerization in water media in a 150 L reactor. It presents the study of several parameters that have an important role in the reaction kinetics (initiators, suspending agents, catalysts and temperature). The thermal stability of the materials was also assessed using a standard discoloration test employed by the PVC industry. The results show the possibility of scaling-up this new and promising technology using the same facilities as the conventional free radical polymerization process with results closely matching those obtained in 50 mL glass reactors.