Reversible Chain Transfer Catalyzed Polymerization Research Articles

Impact of Interfacial Halogen Bonding with a Surfactant on Miniemulsion Reversible Chain Transfer-Catalyzed Polymerization

Impact of Interfacial Halogen Bonding with a Surfactant on Miniemulsion Reversible Chain Transfer-Catalyzed Polymerization

Facilely Control Grafting Density and Side Chain Composition of Bottlebrush Polymer.

Control over polymer architecture and composition is essential for disclosing structure-property relationships and developing high-performance materials. Herein, a new method is successfully developed to synthesize bottlebrush polymer (BP) with controllable graft density and side chain composition by "grafting-from" strategy using in situ halogen exchange and reversible chain transfer catalyzed polymerization (RTCP). The main chain of the BP is first synthesized by the polymerization of methacrylates containing alkyl bromide as a side group. Then, the alkyl bromine is quantitatively converted to alkyl iodide with sodium iodide (NaI) via in situ halogen exchange to efficiently initiate the RTCP of methacrylates. By adjusting the input amount of NaI and monomers in sequence, BP named PBPEMA-g-PMMA/PBzMA/PPEGMEMA which contains three different kinds of polymer side chains including hydrophilic PPEGMEMA, hydrophobic PMMA, and PBzMA is synthesized with narrow molecular weight distribution (Mw /Mn ≤1.36). The grafting density and the chain length of each polymer side chain are well controlled by the addition of NaI in batches and following RTCP. Moreover, the obtained BP self-assembled into spherical vesicles in aqueous with hydrophilic coronal structure, core region, and the hydrophobic wall between the former two, which enables to wrap hydrophobic pyrene and hydrophilic Rhodamine 6G separately or simultaneously.

Reversible chain transfer catalyzed polymerization in miniemulsion systems with tetraiodomethane as a catalyst

Tetraiodomethane (CI4) is an effective catalyst in reversible chain transfer catalyzed polymerization (RTCP) of methacrylate monomers in miniemulsion polymerization systems (miniemulsion RTCP).

Reversible Chain Transfer Catalyzed Polymerization with Alkyl Iodides Generated from Alkyl Bromides by in Situ Halogen Exchange

Reversible chain transfer catalyzed polymerization (RTCP) is a practical and efficient process for the precise synthesis of polymers with special architecture by using simple phenols (2,4,6-trimethylphenol, TMP) or hydrocarbons (xanthene, XT) as efficient organocatalysts. Herein, alkyl iodide (R-I) which was generated from in situ bromine-iodine transformation of alkyl bromide (R-Br) with sodium iodide (NaI), was served as initiator to mediate RTCP with TMP or XT. MMA and other functional methacrylates, including GMA, DEAM, DMAEMA and BzMA, were successfully initiated by combining organocatalysts and azo initiators to yield polymers with low-polydispersity (Mw/Mn=1.1-1.5) and ideal monomer conversions (50-90%) at moderate temperature. Moreover, 3-arm star polymers were also obtained by this method. The high chain-end fidelity of the obtained poly(methyl methacrylate) with iodine as chain-end group (PMMA-I)was confirmed by chain-extension reaction. The environmentally friendly initiators and organocatalysts exhibit powerful polymerization properties toward RTCP, providing a significant method to synthesize functional polymers.

Surface molecularly-imprinted magnetic nanoparticles coupled with SERS sensing platform for selective detection of malachite green

Herein, a novel analytical method was reported for sensitive and selective quantification of malachite green (MG) in tap water and carp samples based on a combination of surface-enhanced Raman spectroscopy (SERS) and molecular imprinting technology. For this purpose, surface molecularly-imprinted magnetic nanoparticles (MIP@Fe3O4 NPs) were synthesized through recently developed living/controlled radical polymerization mechanism referred to as reversible chain transfer catalyzed polymerization (RTCP). Surface characterization of MIP@Fe3O4 NPs was carried out in detail by using the combination of several analytical techniques and the results showed the presence of a thin polymer layer on the nanoparticles. Rebinding properties, selectivity and reusability of the nanoparticles were investigated and the obtained results indicated the prepared nanoparticles had excellent selectivity, high adsorption capacity, fast adsorption kinetics and multiple-uses with an imprinting factor of 3.86. Then, silver dendrites (Ag NPs) were deposited on silicon wafers and used as SERS sensing platform. Moreover, surface properties of the SERS substrate were also investigated in detail in terms of stability, reusability and homogeneity. After that, the eluted MG from the imprinted nanoparticles was dropped on the sensing platform and SERS analysis was carried out. Under optimized conditions, limit of detection and limit of quantification were determined to be 1.50 pM and 4.96 pM for tap water, respectively and 1.62 pM and 5.38 pM for carp samples, respectively within acceptable recovery rates and standard deviations. The overall results indicated that the proposed method can be effectively used for the quantification of trace amounts of MG in tap water and carp samples. Moreover, the proposed method is promising for development of new ways to prepare MIPs via surface-initiated RTCP.

Partitioning effect of nitrogen catalyst into polymerizing particles on dispersion reversible chain transfer catalyzed polymerization (dispersionRTCP) of methyl methacrylate in supercritical carbon dioxide and organic solvents

Reversible chain transfer catalyzed polymerization (RTCP) in dispersion polymerization system (dispersion RTCP) of methyl methacrylate (MMA) was performed with N-iodosuccimide (NIS) as a nitrogen catalyst in supercritical carbon dioxide (scCO2). The solubility of NIS in scCO2 can be controlled by tuning the pressure, and this led to promote NIS partitioning into polymerizing particles. As a result, the molecular weight distribution control was successfully improved by decreasing the NIS solubility in the medium by tuning the scCO2 at a low pressure of 20 MPa. On the other hand, at the same NIS concentration, a solution RTCP of MMA in toluene as a homogeneous polymerization system did not proceed with a controlled/living manner. The importance of NIS partitioning into the polymerizing particles was also confirmed in hexane as well as scCO2 medium. From these results, it was clarified that the NIS catalyst partitioning into the polymerizing particles as main polymerization loci is a key factor to control the molecular weight distribution in the dispersion RTCP of MMA in scCO2. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 613–620

Stereospecific reversible deactivation radical polymerization of biomass‐based acrylates for precise control of tacticity and molecular weight

ABSTRACTReversible deactivation radical polymerization (RDRP) of biomass‐based acrylates, (S)‐ and (R)‐2‐isopropyl‐5‐methylene‐1,3‐dioxolan‐4‐ones (S‐MiPDO and R‐MiPDO), was successfully performed to produce a well‐defined polymer with simultaneously controlled tacticity and molecular weight, and low dispersity (Đ < 1.3). In particular, meso triad (mm) of the polymer was continuously controlled as designed from 28.1% to about 100% by changing the molar ratio of S‐MiPDO/R‐MiPDO in feed. In kinetic studies, the rate of RDRP was strongly influenced by the stereostructures of the propagating radical, and it was much lower in isospecific RDRP than atactic one in reversible chain transfer catalyzed polymerization (RTCP) in contrast to atom transfer radical polymerization (ATRP) where the rate would not change regardless of the tacticity. Increase of molecular weight and low Đ of the polymer were also observed in reversible addition‐fragmentation chain transfer (RAFT) polymerization of MiPDO. In addition, block copolymers including stereoblock copolymers were feasibly synthesized by RTCP of styrene and methyl methacrylate using poly(MiPDO) prepolymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 445–456

Living radical polymerization of diisopropyl fumarate to obtain block copolymers containing rigid poly(substituted methylene) and flexible polyacrylate segments

ABSTRACTLiving radical polymerizations of diisopropyl fumarate (DiPF) are carried out to synthesize poly(diisopropyl fumarate) (PDiPF) as a rigid poly(substituted methylene) and its block copolymers combined with a flexible polyacrylate segment. Reversible addition‐fragmentation chain transfer (RAFT) polymerization is suitable to obtain a high‐molecular‐weight PDiPF with well‐controlled molecular weight, molecular weight distribution, and chain‐end structures, while organotellurium‐mediated living radical polymerization (TERP) and reversible chain transfer catalyzed polymerization (RTCP) give PDiPF with controlled chain structures under limited polymerization conditions. In contrast, controlled polymerization for the production of high‐molecular‐weight and well‐defined PDiPF is not achieved by atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMP). The block copolymers consisting of rigid poly(substituted methylene) and flexible polyacrylate segments are synthesized by the RAFT polymerization. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2136–2147

Reversible chain transfer catalyzed polymerization (RTCP) in nitrogen-based solvents without additional catalysts

N,N-Dimethylformamide (DMF) andN-methyl-2-pyrrolidone (NMP) as typical nitrogen-based solvents were used as the catalyst for RTCP without additional catalyst, which could also be carried out in the presence of a limited amount of air.

Modeling of Reversible Chain Transfer Catalyzed Polymerization by Moment Equations Method

A moment equations method was performed to study the Reversible chain Transfer Catalyzed Polymerization (RTCP) of styrene in 80°C. To do this, a kinetic scheme containing conventional free radical polymerization reactions and equilibrium reactions of RTCP was assumed. After obtaining mass balance equations, three moment equations were defined for free and dormant radicals and dead chains. Monomer conversion, catalyst and cocatalyst concentrations, molecular weights and polydispersity index profiles were achieved for two different systems and compared with the simulation results of Goto et al. and also with the experimental results of this work. These systems have had different reaction rate constants for equilibrium reactions of RTCP. The results showed the pseudo-linear increase of conversion and molecular weight versus time while a small PDI values were obtained for system 1 while the final PDI value of system 2 was high. Calculating average error of results compared to experimental and simulation results of Goto et al. showed a good agreement of modeling results with others and confirm the accuracy of results obtained in this work.

Direct synthesis of polymer-grafted inorganic hybrids via reversible chain transfer catalyzed polymerization

In this work, a new simple and robust method for preparation of polymer-grafted inorganic hybrids through “grafting to” reaction is presented. Polymer chains were synthesized by reversible chain transfer catalyzed polymerization (RTCP) are capped with iodine according to the RTCP mechanism. The obtained iodine-capped polymer chains can react irreversibly with the hydroxyl groups available on the surface of inorganic materials through a nucleophilic substitution (SN) reaction. In this method, there is no need to modify the surface of inorganic materials or to functionalize polymer chains prior to the “grafting to” reaction. RTCP produced polystyrenes with different molecular weights, e.g., 4,000, 6,000, and 8,000 g/mol, and silica nanoparticles were employed as the polymer and inorganic materials, respectively. The resulting hybrids were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, and transmission electron microscopy techniques. According to the results, graft density decreased by increasing the polystyrene molecular weight. Additionally, the rheological studies of prepared polystyrene nanocomposites containing 2 wt % of the produced hybrids confirmed the better dispersion of the modified hybrids in the polystyrene matrix. The glass transition temperature (T g) of the polystyrene nanocomposites was driven by differential scanning calorimeter technique. Analysis of nanocomposites’ T g results revealed that increment of the grafted polymer molecular weight of hybrids increased the glass transition temperature of the prepared nanocomposites due to improvement of the dispersion level.

Triphenylphosphine as phosphorus catalyst for reversible chain-transfer catalyzed polymerization (RTCP)

Triphenylphosphine (TPP) was used as the catalyst for reversible chain-transfer catalyzed polymerizations (RTCPs) of styrene and methyl methacrylate for the first time. The polymerizations showed the typical features of “living”/controlled radical polymerization, and well-defined polymers with designable molecular weights and narrow molecular weight distributions (Mw/Mn < 1.35) were obtained. In addition, RTCP of styrene using TPP as a novel catalyst not only could be conducted in the presence of a limited amount of air but also did not destroy the controllability over polymerizations.

Simulation of reversible chain transfer catalyzed polymerization (RTCP): effect of different iodide based catalysts

Monte Carlo kinetic simulation method was performed to study the reversible chain transfer catalyzed polymerization (RTCP) of styrene in 80°C. The effect of different iodide based catalysts (AI) was investigated on RTCP systems by simulating the chain length distribution, the depletion rate of polymerization ingredients, average molecular weights and the monomer conversion. In RTCP systems a narrow distribution was obtained compared to iodide-mediated polymerization. Superior reversible chain transfer reaction constants (ka and kda) led to a more uniform chain length distribution and a faster PDI decrement. In each RTCP system kda/ka ratio, designates the concentration of A* by dictating the dominant side of exchange equilibriums which specifies the number of cross-termination reactions. Addition of cross-termination reactions to the iodide-mediated polymerization system decreases the number of combination reactions leading to lower average molecular weights. Higher kda/ka ratios also consequences in faster catalyst depletions and lessen monomer conversions. On the other hand, PhE-I was found to deplete rapidly in RTCP systems, changing the nonlinear increase of the number average molecular weight to a linear pattern. The Monte Carlo simulation results were in a fine agreement with experimental data which were obtained from different RTCP systems.

Iodine Transfer Polymerization (ITP with CHI3) and Reversible Chain Transfer Catalyzed Polymerization (RTCP with Nitrogen Catalyst) of Methyl Methacrylate in Aqueous Microsuspension Systems: Comparison with Bulk System

Iodine transfer polymerization (ITP) with CHI3 as transfer agent and reversible chain transfer catalyzed polymerization (RTCP) with N-iodosuccinimide (NIS) as catalyst of methyl methacrylate (MMA) were successfully applied to aqueous microsuspension systems (respectively, microsuspension ITP and microsuspension RTCP). Both microsuspension ITP and RTCP proceeded smoothly without induction period and with a controlled/living manner. Polydispersity index (PDI, Mw/Mn) of the microsuspension RTCP was smaller than that of the microsuspension ITP, and it was larger than RTCP in a bulk system (bulk RTCP). The difference seems to be based on that NIS would partly react with water dissolved in the MMA phase, and formed succinimide, which is a low controllable catalyst in comparison with NIS. With decreasing particle (monomer droplet) size, the polymerization rate increased, and a reasonable control was maintained throughout the polymerization based on the segregation effect.

Preparation of block copolymer particles by two-step, reversible chain transfer catalyzed polymerization (RTCP) with nitrogen catalyst in miniemulsion systems

We demonstrated a successful preparation of poly(methyl methacrylate) (PMMA)-b-poly(benzyl methacrylate) (PBzMA) particles in aqueous media by two-step reversible chain transfer catalyzed polymerization (RTCP) with N-iodosuccinimide as a catalyst at 70 °C. The polymerization smoothly proceeded, and the number-average molecular weight (Mn) increased linearly with conversion, which agreed with the theoretical molecular weight (Mn,th). The molecular weight distribution at each conversion was narrow (polydispersity index ≈ 1.4). Approximately 88% PMMA chains became PMMA-b-PBzMA at 64% conversion, which was a relatively high value.

H‐Phosphonic Acid Derivatives as Catalysts for Reversible Chain Transfer Catalyzed Polymerization (RTCP) at Ambient and High Pressure

AbstractSeveral H‐phosphonic acid derivatives (PADs) were analyzed regarding their ability to perform as effective catalysts in reversible chain transfer catalyzed polymerization (RTCP), a relatively new type of controlled radical polymerization. Therefore, bulk polymerizations of styrene at 100 °C using different PADs were studied in detail. The obtained number‐average molar masses and polydispersities of the polymeric products showed that a cyclic PAD derived from pinacol was found to be a very well suited catalyst for RTCP under the chosen conditions. In addition, RTCPs at high pressure up to 2000 bar were conducted indicating poor molar mass control compared to the systems at ambient pressure. magnified image

Reversible Chain Transfer Catalyzed Polymerization (RTCP) of Methyl Methacrylate with Nitrogen Catalyst in an Aqueous Microsuspension System

Reversible Chain Transfer Catalyzed Polymerization (RTCP) of Methyl Methacrylate with Nitrogen Catalyst in an Aqueous Microsuspension System

Use of Alcohol as Initiator for Reversible Chain Transfer Catalyzed Polymerization

AbstractA novel initiation system, using a hydroxyl group as an initiating moiety, was developed for reversible chain transfer catalyzed polymerization (RTCP), a living radical polymerization. The hydroxyl (alcohol) group was reacted with an iodinating agent and a monomer (M), giving a dormant species RO–M–I (I = iodine). It was prepared in the polymerization medium (monomer) and used in the polymerization without the purification, leading to a one‐pot RTCP from a hydroxyl group (an alcohol).magnified image

Kinetic Simulations of Reversible Chain Transfer Catalyzed Polymerization (RTCP): Guidelines to Optimum Molecular Weight Control

AbstractKinetic simulations of reversible chain transfer catalyzed polymerization (RTCP) were performed using the program package Predici. Mimicking the RTCP of styrene in bulk at 80 °C, the full molecular weight distributions, the polydispersities of resulting polymer and the time evolutions of monomer conversion and participating species were simulated. The influence of the kinetic coefficients governing the RTCP equilibrium – specifically, the rate coefficients of activation, ka, and deactivation, kda – on the controlled polymerization behavior was probed in detail by varying their respective simulation input values over five orders of magnitude. It was found that optimum results for molecular weight control are obtained for K = ka/kda in the range 1 to 10 and with ka and kda being of the order of 106 L · mol−1 · s−1 or above. The influence of degenerative chain transfer on the process was found to be significant only in poorly controlled systems, but is small in well‐controlled RTCP. Based on the finding that the catalyst is depleting during the polymerization due to cross‐termination, guidelines for obtaining high molecular weight material via repeated addition of catalyst were developed.magnified image

Reversible Chain Transfer Catalyzed Polymerization of Methyl Methacrylate with In-Situ Formed Alkyl Iodide Initiator

A method utilizing generation of an alkyl iodide (low-mass dormant species) in situ formed in polymerization was adopted to reversible chain transfer catalyzed polymerizations (RTCP) (living radical polymerizations) with several nitrogen and phosphorus catalysts. The polymerization of methyl methacrylate afforded low-polydispersity polymers (Mw/Mn ~1.2–1.4), with Mn values predicted to high conversions; where Mn and Mw are the number- and weight-average molecular weights respectively. This method is robust and would enhance the utility of RTCP.