Search

The quantification of dispersity is an indispensable part of characterizing polymers. In this work, general dispersity equations for “living” polymers obtained by nitroxide-mediated polymerization ...

The kinetics of the ultraviolet light-induced solution atom transfer radical polymerization (ATRP) of methyl acrylate using titanium oxide (TiO2) was investigated through experiments and modeling b...

An electrochemically mediated atom transfer radical polymerization (eATRP) of methyl acrylate (MA) in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) ionic liquid (IL) was reported. Remarkably, the kinetic results revealed an extremely fast and well controlled polymerization in the presence of tris(2-(dimethylamino)ethyl)amine (Me6TREN). The monomer conversion reached more than 90% within a period of 300 s. Computational and simulation results indicated that the IL induced acceleration of polymerization can be attributed to the increased value of k t / k p 2 compared to the associated literature value. Additionally, polymerizations under different conditions, including ligand types, monomer/IL ratios, catalyst loadings, and targeted degrees of polymerization were explored. All the kinetic plots suggested superfast polymerization rates with good control over molecular weight and dispersity. Furthermore, the livingness of MA polymerization was confirmed by chain extension experiment. This work provides a new insight into eATRP in IL through experimentation and simulation and thus enriches the knowledge of reaction features of eATRP.

A water-soluble organic photoredox catalyst, 3,7-methoxypolyethylene glycol 1-naphthalene-10-phenoxazine (Naph-PXZ-PEG), that can catalyze aqueous organocatalyzed atom transfer radical polymerization (ATRP) via oxidative quenching cycle has been reported for the first time. Comparative studies of Naph-PXZ-PEG and EosinY involved aqueous organocatalyzed ATRP systems have been done via polymerization experiment and kinetic modeling approach. Results showed that the polymerization via oxidative quenching cycle in Naph-PXZ-PEG system proceeded much faster and higher initiator efficiency than the polymerization via reductive quenching cycle in Eosin Y system under same conditions. Detailed information of the Naph-PXZ-PEG was presented by experiments and density functional theory (DFT) simulation. A series of kinetics experiments under different catalyst loadings, initiator concentrations, “on-off” switch of light and chain extension have been conducted and confirmed the good controllability of the current system and high end-group fidelity. This work provides a systematic study on developing an effective water soluble organic catalyst for the preparation of the well-defined polymers by a “green” and sustainable ATRP.

A thermo-responsive copolymer with a gas-switchable LCST-type phase transition was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) and glycidyl methacrylate (GMA), followed by post-polymerization functionalization with sodium 3-amino-1,2,4-triazole (ATANa). Incorporating ionic moieties provides an elevated cloud point of 61 °C. Importantly, both CO2 and SO2 cause a reduction in the cloud point of the polymer solution. The CO2-triggered system can be easily and fully recovered to its initial state by introducing an inert gas (e.g. N2), whereas the SO2-triggered system shows only partial recovery. The pH-dependent phase transition behaviors confirm that the gas bubbling-induced pH changes contribute to the gas-switchable cloud point of P(NIPAM-co-(GMA-ATANa)). In addition, P(NIPAM-co-(GMA-ATA)) (ATA: 3-amino-1,2,4-triazole), a counterpart of P(NIPAM-co-(GMA-ATANa)), was prepared and the relevant solution phase transition behavior was studied. Its cloud point shift in response to gas bubbling and pH adjustment is opposite to that of P(NIPAM-co-(GMA-ATANa)), indicating that the latter does not result from the protonation of amidine groups. Alternatively, a reversible H+-induced decrease in hydrophilicity was thus proposed. This contribution enriches the family of thermo-responsive polymers by introducing gas-sensitive polyelectrolytes and also broadens the scope of gas-responsive smart materials.

A well-controlled atom transfer radicfal polymerization of methyl acrylate (MA) was realized by mechanical mediation (mechanoATRP) in dimethyl sulfoxide (DMSO, 50% v/v). High conversions of typically over 90% were achieved. The resulting polymers had well-controlled molecular weights and very low dispersities (Đ = 1.03–1.09). No polymerization of MA was observed under various conditions from bulk up to 33.3% DMSO (v/v) solution. It was found that adding an equivalent volume of DMSO with respect to MA activated the polymerization. This finding suggested that DMSO played a crucial role in the mechanoATRP of MA. DMSO not only improved the solubility of CuBr2 complex but also facilitated an electron transfer process in the mechanical reduction of CuBr2. For a proof of the concept, a DMSO analogue acrylate, 2-(methylsulfinyl)ethyl acrylate (MSEA), was also polymerized. In addition, the high chain-end functionality of the polymers collected at ∼95% conversion was confirmed by 1H NMR, MALDI-ToF-MS, and in-situ c...

A challenge for the design of nonlinear polymerization is the full appreciation of the impact of side reactions, demanding the development of modeling techniques to determine the associated kinetic parameters while using the most important experimental responses. Here the combination of computationally inexpensive method of moments (MoM) kinetic simulations and dedicated principal component analysis (PCA) is put forward as a promising strategy to be successful in this respect. Focus is on (radical) vinyl grafting of chains containing unsaturations, selecting styrene (St) as monomer and polybutadiene (PB) as backbone, and low St conversions accounting for diffusional limitations on termination. It is highlighted that the less studied macropropagation cannot be directly ignored and a combined set of experimental responses related to free polystyrene and grafted copolymer (GC) average product properties is recommended for kinetic parameter estimation. This is supported by regression analysis considering in silico generated experimental data compensated for random noise and considering a validated end-chain approximation.

The past decades have witnessed an increasing interest in developing advanced polymerization techniques subjected to external fields. Various physical modulations, such as temperature, light, electricity, magnetic field, ultrasound, and microwave irradiation, are noninvasive means, having superb but distinct abilities to regulate polymerizations in terms of process intensification and spatial and temporal controls. Gas as an emerging regulator plays a distinctive role in controlling polymerization and resembles a physical regulator in some cases. This review provides a systematic overview of seven types of external-field-regulated polymerizations, ranging from chain-growth to step-growth polymerization. A detailed account of the relevant mechanism and kinetics is provided to better understand the role of each external field in polymerization. In addition, given the crucial role of modeling and simulation in mechanisms and kinetics investigation, an overview of model construction and typical numerical methods used in this field as well as highlights of the interaction between experiment and simulation toward kinetics in the existing systems are given. At the end, limitations and future perspectives for this field are critically discussed. This state-of-the-art research progress not only provides the fundamental principles underlying external-field-regulated polymerizations but also stimulates new development of advanced polymerization methods.

Metal-free atom transfer radical polymerization (ATRP) was successfully achieved in aqueous media for the first time. Polymerization of poly(ethylene oxide) methyl ether acrylate (PEGA480) was well controlled (Đ < 1.40) under visible light irradiation using tetrabromofluorescein (Eosin Y) as catalyst and pentamethyldiethylenetriamine (PMDETA) as electron donor. A validated kinetic model was developed to investigate the process of photoredox catalytic cycle via reductive quenching pathway. Experimental and simulation results showed that electron donor not only had an important influence on the ATRP activation, but also participated in the ATRP deactivation. Furthermore, the effects of water content, catalyst concentration, and degree of polymerization on the polymerization were studied thoroughly by a series of experiments. Good controllability of the polymerization regulated by light on and off confirmed the high degree of temporal control. The livingness of the chains was proved by a successful chain ext...

Thermoresponsive random copolymers consisting of poly(N-isopropylacrylamide) (PNIPAM) and polymerized ionic liquid (IL) poly(1,1,3,3-tetramethylguanidine acrylate) (PTMGA) were synthesized via reversible addition–fragmentation chain transfer radical polymerization (RAFT). The reactivity ratios of NIPAM (rNIPAM = 2.11) and TMGA (rTMGA = 0.56) were determined by the extended Kelen–Todus method. Glass transition temperatures (Tg) of the copolymers were analyzed, which followed the Fox equation very well. The phase transition behaviors of the copolymers in aqueous solution were studied through UV–vis transmission measurements. Their lower critical solution temperature (LCST) ranged from 30.5 to 73.2 °C, depending on the hydrophilic IL content. The apparent pKa related to LCST was determined, and thus the protonation degree was calculated. The hydrophilicity of the copolymers could be regulated by gas treatments. Bubbling CO2 led to lowering the transition temperature while bubbling N2 resulted in its recovery...

Kinetic insight into photoinduced Fe-based atom transfer radical polymerization (ATRP) involving monomer-mediated photoreduction was performed by modeling approach for the first time. Preliminary numerical analysis of number-average molar mass (Mn) derivation in this specific system was given. Simulation results provided a full picture of reactant concentration and reaction rate throughout the entire polymerization. Methyl 2,3-dibromoisobutyrate (MibBr2) generated from methyl methacrylate (MMA)-mediated photoreduction as the leading factor for the deviation of Mn from theoretical value was confirmed by reaction contributions in α-bromophenylacetate (EBPA) containing system. Reasonable predictions were made with respect to the polymerizations under a variety of initial conditions. Results show that increasing light intensity will shorten transition period and increase steady state polymerization rate; decreasing catalyst loading will cause the decrease in polymerization rate and Mn deviation; varying initiation activity will slightly increase the time to attain steady state of dispersity (Mw/Mn) evolution and enormously change the fraction of reaction contributions; increasing targeted chain length will extend transition period, decrease steady state polymerization rate, increase Mn deviation degree with same reaction contributions, and decrease the time to attain the steady state of Mw/Mn. The numerical analysis presented in this work clearly demonstrates the unique ability of our modeling approach in describing the kinetics of photoinduced Fe-based ATRP of MMA. © 2017 American Institute of Chemical Engineers AIChE J, 2017

A low-ppm-level iron (Fe)-based photoinduced atom-transfer-radical polymerization (ATRP) under visible-light irradiation was developed. Various ligands, tris(4-methoxyphenyl)phosphine (TMPP), 4,4′-dinonyl-2,2′-dipyridyl (dNbpy), and tris[2-(dimethylamino)ethyl]amine (Me6TREN), were used to enhance the catalytic activity of Fe complexes. Activator FeII complexes were formed by the reduction of FeIII complexes with a monomer under visible-light irradiation. Linear semilogarithmic plots and low polydispersities (Mw/Mn dNbpy > Me6TREN. Additionally, this polymerization could be ceased and restarted, responding to light off and light on. Retention of the chain-end functionality was anal...

Photoinduced atom transfer radical polymerization with an Fe catalyst was successfully performed in aqueous media for the first time. Three water-soluble ligands [i.e., tetrabutylammonium bromide (TBABr), tris[2-(2-methoxyethoxy)ethyl]amine (TDA), and triphenylphosphine-3,3′,3′′-trisulfonic acid trisodium (TPPSA)] were screened for polymerization in aqueous media. Linear semilogarithmic plots, increasing molecular weights (Mn) with conversion, and low dispersity (Đ < 1.40) were achieved by using a new water-soluble phosphine ligand TPPSA, indicating a well-controlled polymerization. Subsequently, the polymerization kinetics of different catalyst concentrations and the targeted degree of polymerizations were investigated. The applicability of this system to the polymerization of different water-soluble monomers was examined. Furthermore, the polymerization can be regulated by switching the light on and off, which further confirmed its controlled and “living” nature. A successful experiment of chain extension suggested the retention of chain-end functionality. A study of the mechanism showed that the activator (FeIIX2/L) and the additional initiator were generated by the photochemical reduction of FeIIIX3/L in the presence of a monomer. This work provides an environmentally benign ATRP to synthesize well-defined water-soluble materials.

A novel water-soluble hyperbranched polymer (AA/AM/SMNS) consisting of functionalized Nano-SiO2 as the core was synthesized by free-radical polymerization for low-moderate permeability reservoirs. The AA/AM/SMNS was carefully characterized by spectroscopic and electronic technologies. It was found that the microscopic structures of AA/AM/SMNS was denser and more regular in comparison to the linear polymer HPAM. The hydrodynamic radius of AA/AM/SMNS was 197 nm, less than the HPAM radius of 244 nm with similar molecular weight, so that the AA/AM/SMNS had a good matching relationship with pore throat in midpermeability reservoirs (100–500 mD). Besides, the introduction of Nano-SiO2 endowed the AA/AM/SMNS remarkable thermal stability, shear resistance and viscoelasticity. Based on core flooding experiments, the AA/AM/SMNS could build high resistance factor and residual resistance factor in the corresponding porous medium. Furthermore, the sheared AA/AM/SMNS solution of 1500 mg L–1 performed excellent oil recovery of 15.47% in the 300 mD porous medium, which suggested the hyperbranched polymer based on modified Nano-SiO2 have a valuable prospect for enhancing oil recovery in low-moderate permeability reservoirs.

In this work, a photoinduced iron(III)-based atom transfer radical polymerization (ATRP) without any reducing agents and additional initiators was suggested. In addition, detailed kinetic studies, including the effects of ligand and catalyst concentrations on polymerization kinetics, and the polymerization behaviors using various solvents and monomer types were evaluated for this new polymerization technique. Results showed that photoinduced iron(III)-mediated ATRP using 5000 ppm catalyst loading with 1 equiv of ligand in N,N-dimethylformamide (DMF) produced poly(methyl methacrylate) with low molecular weight distribution (Mw/Mn < 1.45) and that the evolution of molecular weight (Mn) was linearly related to monomer conversion. 1H NMR analysis confirmed that the resulting polymer prepared through photoinduced ATRP in the present work was initiated by methyl 2,3-dichloroisobutyrate. Facile temporal control and the successful chain extension highlighted the good chain-end functionality of the resulting polym...

An iron- and methyl methacrylate (MMA)-based electrochemically mediated atom transfer radical polymerization (eATRP) system was developed for the first time. Kinetic behaviors, including the effect of applied potential and catalyst loading, were systematically investigated. Results indicated that with more negative electrode potential, the polymerization rate increased until the mass transport limitation was reached. However, reduction of the catalyst loading had adverse effects on polymerization behaviors, such as decreased polymerization rate and increased molecular weight distributions (Mw/Mn). In addition, a kinetic model based on the method of moments was also constructed to explain the mismatch in Mn and Mn,theo. Simulation results showed that slow initiation significantly influenced on the kinetic behaviors in this system. Iron(II) bromide-catalyzed normal ATRP, iron(III) bromide-catalyzed eATRP, and copper(II) bromide-catalyzed eATRP were conducted to compare and elucidate their respective polymer...

Reversible-deactivation radical polymerization (RDRP) techniques have received lots of interest for the past 20 years, not only owing to their simple, mild reaction conditions and broad applicability, but also their accessibility to produce polymeric materials with well-defined structures. Modeling is widely applied to optimize the polymerization conditions and processes. In addition, there are numerous literatures on the kinetic and reactor models for RDRP processes, which show the accessibility on polymerization kinetics insight, process optimization, and controlling over chain microstructure with predetermined molecular weight and low dispersity, copolymer composition distribution, and sequence distribution. This review highlights the facility of the method of moments in the modeling field and presents a summary of the present state-of-the-art and future perspectives focusing on the model-based RDRP processes based on the method of moments. Summary on the current status and challenges is discussed briefly.

A detailed kinetic model was constructed using the method of moments to elucidate the electrochemically mediated atom transfer radical polymerization (eATRP). Combined with electrochemical theory, the reducing rate coefficient relevant to the overpotential in eATRP was coupled into the kinetic model. The rate coefficients for eATRP equilibrium and the reducing rate coefficient were fitted to match the experimental data. The effects of catalyst loading, overpotential, and application of programmable electrolysis on the eATRP behavior were investigated based on the tested kinetic model. Results showed that the apparent polymerization rate exhibited a square root dependence on catalyst loading. In addition, a more negative potential accelerated the polymerization rate before the mass transport limitation was reached. This phenomenon indicated that the polymerization rate could be artificially controlled by the designed program (i.e., stepwise and intermittent electrolysis programs). What is more, the normal ATRP, photo-ATRP, and eATRP were compared to obtain a deeper understanding of these ATRP systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4347–4357, 2015

Preparation of two-component materials having morphologies with bicontinuous minor and major components is challenging. An innovative method has been developed to synthesize bicontinuous polymeric monoliths based on high internal phase emulsion (HIPE) templating. This work demonstrated a protocol of dual-hydrophobic bicontinuous material of glassy polystyrene (PS) and elastic poly(butyl acrylate) (PBA). The PS scaffold was prepared through polymerizing styrene (St) as the external phase of HIPE with an aqueous free radical initiator, in the presence of divinylbenzene (DVB) as a crosslinker. The resulting PS scaffolds were then employed as templates to absorb butyl acrylate (BA) mixed with ethylene glycol dimethylacrylate (EGDMA). Results suggested that the polymeric monoliths possessed a bicontinuous structure and good compatibility in the bulk state. This work provides a new approach for the synthesis of bicontinuous two-component materials.

The low ionic conductivity and poor interfacial contact are the main obstacles restricting the practical application of all-solid-state polymer electrolyte in lithium metal batteries. Herein, four-armed and imidazolium cation-tethered polymeric ionic liquid (IMFPIL) is prepared through atom transfer radical polymerization of hydroxyethyl acrylate and subsequent functionalization. The branching architecture of the organic scaffold endows IMFPIL with high thermal stability, low glass transition temperature and loosely packed polymer backbones. The derived more free paths and volumes for Li-ion migration confer much enhanced ion conductivity on the as-prepared all-solid-state polymer electrolyte (IMFSPE), which is 22 times that of the linear counterpart with the same composition. High-temperature thermal integration of IMFSPE into the lithium metal battery effectively eliminates the gaps between the electrolyte and the two electrodes, rendering excellent interfacial contact and stability. The volume variation of the electrodes during the charge-discharge can be effectively mediated. As a result, in sharp contrast to the battery failure of the linear counterpart, such an integrated LiFePO4/IMFSPE/Li all-solid-state battery presents a high discharge capacity of 153 mAh g−1 at 0.2 C with 99% of coulombic efficiency, and the capacity retention ratio reaches 73% after 150 cycles. Compared with IMLSPE, IMFSPE-2 efficiently weakens the formation of dendritic lithium. The branching design combining with the thermal integration strategy and superior electrochemical features of imidazole make IMFSPE behave as an all-solid-state polymer electrolyte, which paves a new way for developing PILs as ideal SPEs in energy storage device.

With the idea of “an old method for a new mechanism,” a detailed kinetic insight into photochemically mediated atom-transfer radical polymerization (photo ATRP) was presented through a validated comprehensive model. The simulation mimics the experimental results of the model system using optimized photochemically mediated radical generation rate coefficients. The activator and radical (re)generated from the photo mediated reactions endow the photo ATRP with unique features, such as rapid ATRP equilibrium and quick consumption of initiator with a small amount of residual. The effect of the reaction parameters on ATRP behaviors was also investigated. Results showed that the acceleration of polymerization rate follows the square root law in the following three cases: the overall photochemically mediated radical generation rate coefficients (kr), the free ligand concentration, and the initiator concentration. However, the independence of the apparent propagation rate coefficient ( kpapp) on the square root of catalyst concentration might be attributed to the result of the synergy between the activators regenerated by electron-transfer ATRP and the initiators for continuous activator regeneration ATRP mechanism. The photo ATRP is able to design and prepare various polymers by carefully tuning the conditions using the model-based optimization approach. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1947–1958, 2015

Poly(methyl methacrylate)-block-poly(4-vinylpyridine), polystyrene-block-poly(4-vinyl pyridine), and poly(ethylene glycol)-block-poly(4-vinylpyridine) block copolymers are synthesized by successive atom transfer radical polymerization (ATRP), single-electron-transfer nitroxide-radical-coupling (SET-NRC) and nitroxide-mediated polymerization (NMP). This paper demonstrates that this new approach offers an efficient method for the preparation of 4-vinylpyridine-containing copolymers.

A comprehensive kinetic model based on the mechanism of supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) was developed to better understand the kinetics of copper(0)-mediated reversible-deactivation radical polymerization [Cu(0)-mediated RDRP]. Simulation results show that diffusional limitation on termination significantly affects on polymerization. A comprehensive description of the variation trend of soluble species and reaction rates during polymerization was illustrated by simulation. The effects on kinetics of four key rate constants (i.e., ka0, kdisp, ka1, kcomp) involved in Cu(0)-mediated RDRP were investigated in detail, which contributed to greater insight into the differences between the SET-LRP and SARA ATRP mechanisms. Finally, Cu(0)-mediated RDRPs of methyl methacrylate (MMA) and butyl methacrylate (BMA) were conducted to study the polymerization kinetics at 25 °C. Results of simulations and experiments performed under polymerization conditions show ...

A kinetic model was developed for the atom transfer radical copolymerization (ATRcoP) of methyl methacrylate (MMA) and 2-(trimethylsilyl) ethyl methacrylate (HEMA-TMS) in tank reactors under three typical feeding modes, namely, batch, semibatch, and continuous feeding. The kinetic parameters for ATRcoP equilibrium were estimated from the model using the experiment data obtained under the batch mode. The simulation results were validated using the experimental data for the semibatch process. An excellent agreement between experiment and simulation data suggests that the model is suitable for simulating the copolymerization. The effects of different operating modes on the ATRcoP characteristics were investigated. The results demonstrated that each reactor possesses its own advantages and disadvantages. Furthermore, this study offers thorough polymerization characteristics comparison with the use of a constant ATRcoP system, and the results show a promising design in determining the optimal operating conditi...

We study the use of post-self-assembly cross-linking to combine molecular nanofibers of hydrogelators with copolymers to generate oscillatory materials using the Belousov-Zhabotinsky reaction. The formation of nanofibers from designed hydrogelators provides multiple polymerizable sites for copolymerizing with N-isopropylacrylamide and for attaching a catalytic ruthenium bipyridine complex on the copolymer. The combination of supramolecular self-assembly with copolymerization offers a versatile and facile approach for generating soft materials that have large pores in the gel network and robust mechanical integrity. These larger pores facilitate the diffusion of the reactants and accelerate the chemical oscillation by about a factor of 4 relative to a poly(NIPAAm-Ru) gel that contains no molecular nanofibers.