Polymerization Of N-butyl Acrylate Research Articles

Interfacial and ion-pairing catalysis for oxygen-tolerant large-scale ATRP in ab initio emulsion

A cooperative interfacial and ion-pairing catalysis, coupled with a molecular oxygen reduction reaction (ORR), to scale up an Atom Transfer Radical Polymerization of n-butyl acrylate (BA) from 20 mL to 10 L (scale-up factor = 500) in ab initio emulsion conditions is introduced. The polymerization is driven by the regeneration of [CuIL]+ through CuII/Cu0 comproportionation. [CuIL]+ simultaneously converts O2 to H2O2 (which is then degraded by sodium pyruvate) and drives the polymerization of butyl acrylate. The anionic surfactant sodium dodecyl sulfate (SDS) facilitates catalyst transport inside and outside the micelles by ion-pairing catalysis. n-Butyl acrylate polymerizations are investigated on a small scale with Cu0 wire and on a larger scale with Cu0 powder. On a 10 L scale, the polymerization yielded controlled PBA-Br (Mn = 32.3 × 103; Ð = 1.39, ∼1.64 kg) after 9 h. Chain extension of PBA-Br macroinitiators proved their livingness. An on-line electrochemical monitoring was also introduced to determine the instantaneous CuI and CuII concentrations at the Cu0 wire surface during the polymerization.

Double polymer networks comprising covalent and hydrogen-bonded cross-links

We report the investigation of rubbery double networks that are based on poly(n-butyl acrylate) (BA) backbones and feature either non-covalent or covalent cross-links. The polymers for the supramolecular network were prepared by reversible addition−fragmentation chain-transfer polymerization of n-butyl acrylate and up to 10 mol% of the self-complementary hydrogen bonding motif 2-ureido-4[1H]pyrimidinone (UPy), which dimerizes into supramolecular cross-links. The covalent polymer network was synthesized by UV-initiated free-radical polymerization of BA and up to 5 mol% of the difunctional cross-linker 1,4-butanediol diacrylate, either separately, or after imbibing films of the supramolecular network with the reaction mixture for the covalent network. The combination of the two network types affords materials that show features of both single networks. The co-existence of a static and a dynamic network affords materials that owe their high thermal stability and creep resistance to the covalent network, and their high extensibility and healability to the supramolecular network.

Computational and Experimental Confirmation of the Diradical Character of para-Quinonedimethide.

The ground-state structure of the parent para-quinonedimethide (p-QDM) molecule is generally represented in its closed shell form, i.e., as a cyclic, nonaromatic, through-conjugated/cross-conjugated hybrid comprising four C═C bonds. Nonetheless, p-QDM has been theorized to contain a contribution from its open-shell aromatic singlet diradical form. VBSCF calculations identify an open-shell contribution of 29% to the structure, while CASPT2(16,16)/def2-TZVP and ωB97XD/aug-cc-pVTZ calculations predict that dimerization proceeds along an open-shell singlet diradical pathway with a low (77 kJ/mol) barrier toward dimerization, which occurs by way of C-C bond formation between the exocyclic methylene carbons. A similar low (98 kJ/mol) barrier exists toward the reaction between a p-QDM molecule and the radical trap TEMPO. These predictions are verified experimentally through the isolation of bis-TEMPO-trapped p-QDM, its C-C coupled dimer, and by demonstrating that a mixture of p-QDM and TEMPO can initiate the radical polymerization of n-butyl acrylate at ambient temperature. In contrast to p-QDM, tetracyanoquinone (TCNQ) neither dimerizes nor reacts with TEMPO, despite having a similar diradical character to p-QDM. This lack of reactivity is consistent with both a higher kinetic barrier and a thermodynamically unfavorable process, which is ascribed to destabilizing steric clashes and polar effects.

How phase transfer increases the number of kinetic regimes from three to seven in nitroxide mediated polymerization of n-butyl acrylate in aqueous miniemulsion

One of the challenges in reversible deactivation radical polymerization (RDRP) in miniemulsion is identifying the optimal average particle size (dp), offering both high reaction rates and excellent control over chain length, branching level and functionality. In this work, a deterministic multi-dimensional Smith-Ewart model is combined with a method of moments model for nitroxide (N-(2-methyl-2-propyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-N-oxyl; SG1) mediated polymerization (NMP) of n-butyl acrylate in miniemulsion. This model accounts for reaction and phase transfer, to showcase for the first time seven instead of three kinetic regimes in a broad dp range from 5 to 300 nm. The reliability of the model prediction is high because of (i) successful model validation under miniemulsion conditions at 385 K; (ii) unique consideration of β-scission, allowing realistic prediction of the livingness; (iii) a validated temperature dependent SG1 partitioning coefficient; and (iv) many kinetic model parameters sourced from independent experimental validation under bulk/solution conditions. Pseudo-bulk kinetics (kinetic regime 1) and a dominance of the segregation effect (kinetic regime 2) are predicted at the highest dp. For decreasing dp, a novel regime 3 emerges in which exit of NMP initiator radicals is dominant. For even lower dp, dominance of free SG1 exit (kinetic regime 4), then dominance of the confined space effect first for NMP initiator radicals (kinetic regime 5), then the same but for free SG1 (kinetic regime 6), and rapid exit-entry dynamics with negligible termination (kinetic regime 7) are obtained. This work demonstrates that advanced population balance models for sustainable multiphase reactive processes can bridge experiment and simulation for improved functional material design.

Deterministic modeling of non-adiabatic solution radical polymerization of n-butyl acrylate in light of runaway prevention

Acrylate polymerizations with high exothermicity exhibit strongly non-isothermal characteristics. The presence of side reactions involved in the polymerization mechanisms makes process safety as well as polymer properties more sensitive to operation parameters. In this study, a deterministic moment-based modeling approach combining with the divergence criterion was developed to investigate the non-isothermality of acrylate polymerization process. In silico design of non-adiabatic processes was achieved by the modeling approach involving reaction mechanism, energy balance, and mass balance. The safe and unsafe states of the reactor under a wide range of process operating conditions were identified by a divergence criterion. From the perspective of process intensification, optimization of operating parameters was carried out. Afterwards, the pseudo-isothermal operation was mimicked by using stepwise jacket temperature profiles to investigate the effects of temperature and monomer content on molecular properties. The simulation results provide a safe operating window for the polymerization reactor under the given feed schemes and process conditions. Additionally, a pseudo-isothermal process is more suitable to tune the molecular properties of the resulting polymers during polymerization. The current work puts forward deterministic simulations in terms of both process safety and molecular properties control compared to the previous works.

New thermal-latent titanium metal catalyst using dual curing reaction for electroactive polymers

New thermal-latent metal catalyst (LPTi) was designed and synthesized based on a lauroyl peroxide and titanium. The synthetic method has facile one step reaction. LPTi structure was confirmed by FT-IR analysis. Molecular design was based on radical preparation from lauroyl peroxide moiety under the constant increased temperature as well as titanium metal catalyst property for urethane polymerization, meaning dual curing method. n-Butyl acrylate polymerization with LPTi had an exothermic peak at about 113 °C in DSC, and the crosslinking conversion was 75%. Also, in the reaction of polyol and isocyanate, the storage modulus value was 3.87 × 103 Pa in case of catalyst-free and the storage modulus value was 1.12 × 105 Pa when LPTi was added. Therefore, storage modulus increased about 30 times by the catalytic effect of LPTi.

Coupling Kinetic Modelling with SAOS and LAOS Rheology of Poly(n-butyl acrylate).

A kinetic model based on fundamentals of radical polymerization and literature known rate parameters for the polymerization of n-butyl acrylate is validated against molecular analysis and rheological data. The model is used to predict conversion, molar mass distribution, and branching densities in form of short and long chain branching. Rheological measurements of synthesized model polymers are evaluated along the Carreau-Yasuda and Van Gurp-Palmen presentations, allowing to detect small differences in the degree of long chain branching. Contributions of anharmonics to viscoelastic response in large amplitude oscillations are small and differences between the products are dominated by the differences in molar mass.

Photoinduced organometallic mediating radical polymerization of acrylates mediated by CoII complexes of non-symmetrical tetradentate Schiff-base ligands

Three new cobalt(II) complexes with non-symmetrically-substituted N2O2 tetradentate Schiff-base ligands, prepared from the 1:1:1 condensation of 3-etoxy-salicylaldehyde, salicylaldehyde and ethylenediamine (H2Etsal − 1), o-phenylenediamine (H2Phsal − 2) or 1,2-cis,trans-cyclohexyldiamine (H2Cysal − 3), were synthesized. The complexes 1–3 were characterized by UV–Vis, FTIR, and MALDI-TOF spectroscopy, elemental analysis, molar conductance, cyclic voltammetry, and computational methods. The CoII-Schiff-base complexes (1–3) were used as controlling agents for the polymerization of n-butyl acrylate (BA) photoinitiated by diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), according to an organometallic-mediated radical polymerization (OMRP) mechanism. Although, all complexes have presented good control ability, the polymerization mediated by complex 1 showed the best control over molecular weight (Mn matching with Mn,th) and dispersity (Ð < 1.50). Kinetic results and computational investigations support the activation/deactivation equilibrium, exerted by complexes 1–3, occurring by one face of the complexes via reversible termination (RT) mechanism.minim.

Synthesis of poly (n-butyl acrylate) with tempo by nitroxide mediated polymerization method

It has been observed that acrylate monomers are very difficult to polymerize with the low cost nitroxide catalyst 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO). Therefore, costly acyclic nitroxides such as N-tert-butyl-N-(1-diethylphosphono-2,2-dimethyl)-N-oxyl, (SG1), 2,2,5-Trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) and TIPNO derivatives have to be used for the polymerization of the acrylic acid derivatives. There are very few reports on the use of TEMPO-derivatives toward the polymerization of n-butyl acrylate. Generally different reducing agents viz. glucose, ascorbic acid, hydroxyacetone etc. have been used to destroy excess TEMPO during the polymerization reaction. The acrylate polymerizations fail in the presence of TEMPO due to the strong C–O bond formed between the acrylate chain end and nitroxide. To the best of our knowledge, no literature report is available on the use of TEMPO without reducing agent or high temperature initiators, toward the polymerization of n-butyl acrylate. The present study has been carried out with a view to re-examine the application of low cost nitroxide TEMPO, so that it can be utilized towards the polymerization of acrylate monomers (e.g. n-butyl acrylate). We have been able to polymerize n-butyl acrylate using the nitroxide TEMPO as initiator (via a macroinitiator). In this synthesis, a polystyrene macroinitiator was synthesized in the first step from TEMPO, after this TEMPO end-capped styrene macroinitiator (PSt-TEMPO) is used to polymerize n-butyl acrylate monomer. The amount of macroinitiator taken was varied from 0.05% to 50% by weight of n-butyl acrylate monomer. The polymerization was carried out at 120°C by bulk polymerization method. The experimental findings showed a gradual increase in molecular weight of the polymer formed and decrease in the polydispersity index (PDI) with increase in amount of PSt-TEMPO macroinitiator taken. In all experiments conversion was more than 80%. These results indicate that the polymerization takes place through controlled polymerization process. Effect of different solvents on polymerization has also been investigated. In the following experiments TEMPO capped styrene has been used as macroinitiator leading to the successful synthesis of poly n-Butyl acrylate. It has been found that styrene macroinitiator is highly efficient for the nitroxide mediated polymerization, even in very small concentration for the synthesis of poly n-butyl acrylate. High concentration of macroinitiator results in the formation of block copolymers of polystyrene and poly ( n-butyl acrylate) viz. polystyrene-block-poly-( n-butyl acrylate). The use of TEMPO toward controlled polymerization is of much importance, because it is the nitroxide commercially available at the lowest cost.

Optimization of a 3D-printed tubular reactor for free radical polymerization by CFD

A flow reactor for the complex reaction network of the free radical solution polymerization of n-butyl acrylate was optimized by a combination of kinetic modeling, computational fluid dynamics (CFD) and additive manufacturing. CFD was used to model a flow reactor with SMX mixing elements. An optimized geometry was 3D-printed from polypropylene. The modeled residence time behavior was compared to relevant experiments, giving a validation for the flow behavior of the reactor. A kinetic model for the free radical solution polymerization of n-butyl acrylate (BA) was in addition implemented into the CFD model. It was used to predict the polymerization behavior in the flow reactor and the resulting product properties. The experimental and computational results were in acceptable agreement.Graphical abstract

Impact of side reactions on molar mass distribution, unsaturation level and branching density in solution free radical polymerization of n-butyl acrylate under well-defined lab-scale reactor conditions

The paper describes the influence of side reactions in isothermal solution free-radical polymerization of n-butyl acrylate accounting for chain-length dependent diffusional limitations on termination.

Jacket temperature regulation allowing well-defined non-adiabatic lab-scale solution free radical polymerization of acrylates

Conventional batch solution free radical polymerization of n-butyl acrylate with thermal initiators such as AIBN is known to be strongly exothermic and influenced by highly activated side reactions such as backbiting and β-scission.

Oblique angle initiated chemical vapor deposition for patterning film growth

Initiated chemical vapor deposition (iCVD) can be used to deposit thin polymer films on a variety of substrates. In this work, the monomer precursor was introduced at an oblique angle to the substrate using an inlet extension, and the pattern of the resulting polymer film was studied as a function of deposition time, substrate temperature, monomer flow rate, reactor pressure, and vapor flow angle. The polymerizations of n-butyl acrylate, methacrylic acid, and 2-hydroxyethyl methacrylate were examined to determine the generality of the trends across several monomers. It was found that the monomer flow rate significantly affected the pattern of the deposited polymer by shifting the location of the thickest point in the films. Increasing the deposition time, decreasing the substrate temperature, and increasing the reactor pressure all increased the polymer deposition rate consistent with conventional iCVD; however, the pattern of the deposited polymer did not vary with these parameters. Computational analysis was used to determine how the inlet extension affects the pressure and velocity profiles within the reactor. The data demonstrate that the introduction of a monomer precursor at an oblique angle can be used to pattern polymer films during iCVD.

Synthesis of Block Copolymers of Acrylic Acid and N-Butyl Acrylate under Reversible Chain-Transfer Conditions in a Water-Alcohol Medium

The laws of dispersion polymerization of n-butyl acrylate in an aqueous-alcoholic medium in the presence of a hydrophilic reversible addition-fragmentation chain-transfer poly(acrylic acid)-based polymeric agent with a trithiocarbonate group within the chain are investigated. It is shown that the portioned introduction of the monomer into the synthesis makes it possible to achieve higher maximum conversions. The resulting block copolymers are characterized by a relatively narrow molecular weight distribution and their number-average molecular weight increases linearly with increasing monomer concentration. The obtained dispersions of triblock copolymer poly(acrylic acid)–block-poly(n-butyl acrylate)–block-poly(acrylic acid) have a unimodal particle size distribution that persists after dialysis against water. It is shown that the synthesized dispersions may be used as a polymer matrix for immobilizing zinc oxide nanoparticles and as a polymer precursor in the process of the seeded polymerization of styrene.

Dispersion polymerization of n-butylacrylate under the action of acrylic acid and N-isopropylacrylamide copolymers

The regularities of dispersion radical polymerization of n-butylacrylate in water-alcohol medium under the action of polymer tritiocarbonates based on copolymers of acrylic acid and N-isopropylacrylamide have been investigated. The conditions for the formation of a block copolymer with controlled molecular weight and high yield have been found. The conditions of formation of stable suspensions of block copolymers with unimodal particle size distribution have been determined.

Cu(0)-mediated reversible-deactivation radical polymerization of n-butyl acrylate in suspension

Cu(0)-mediated reversible-deactivation radical polymerization of n-butyl acrylate was performed in suspension without the use of an organic solvent. In all cases, a 5 v% organic phase (monomer, initiator, and ligand) was used with respect to 95 v% aqueous phase. Polyvinyl alcohol (PVA) as a suspension stabilizer has been shown to be able to control the polymerization for the degree of polymerizations of 222 and higher. The polymerization reaction showed linear first-order kinetics for a PVA concentration range of 1–10 wt%, leading to polymers with dispersities from 1.22 to 1.43. Conversions as high as 96% were obtained in 55 min. Scanning electron microscopy analysis of the suspensions confirmed the formation of micron-sized polymer particles dispersed in aqueous media, and that the size of the particles decreased with increasing PVA concentration. Rheometry measurements of the aqueous phase containing PVA before and after polymerization demonstrated the increase in the viscosity of the reaction mixture after polymerization. The difference between the viscosity of the PVA solution in water and the same solution after polymerization decreased as the PVA decreased, which indicates smaller particle sizes formed with increasing PVA content. All suspensions were stable over a period of three months storage at room temperature without any precipitation or sedimentation. The maximum copper species concentration in the reaction medium and water can be as low as 7 ppm. This Cu(0)-mediated reversible-deactivation radical polymerization in suspension has the potential for industrial use, especially for paint and adhesives.

Synthesis of Film-Forming Photoactive Latex Particles by Emulsion Polymerization-Induced Self-Assembly to Produce Singlet Oxygen.

The design of photoactive polymer substrates producing singlet oxygen under visible light irradiation has great technological potential. Aqueous dispersion of novel photoactive core-shell particles was synthesized by surfactant-free reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of n-butyl acrylate. The surface of the nanoparticles is directly decorated thanks to the polymerization-induced self-assembly process using a hydrophilic macromolecular chain transfer agent (macro-CTA) functionalized with the organic photosensitizer. The macro-CTA was synthesized by statistical copolymerization of acrylic acid and 2-Rose Bengal ethyl acrylate (RBEA) at 80 °C mediated with 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid. Monitoring polymerization kinetics of RAFT polymerization highlights that increasing amount of RBEA induces retardation, still more pronounced when using the vinylbenzyl Rose Bengal comonomer. The present work provides insight into the quantum yield of singlet oxygen production in water (ΦΔ = 0.2-0.6) for the three types of synthesized polymers (hydrophilic polymer, latex particles, and polymer film). The photoactive core-shell latex particles enabled the easy preparation of photoactive polymer film by simple casting.

Mid-Chain Radical Migration in the Radical Polymerization of n-Butyl Acrylate.

The occurrence of intramolecular transfer to polymer in the radical polymerization of acrylic monomers has been extensively documented in the literature. Whilst it has been largely assumed that intramolecular transfer to polymer leads to short chain branches, there has been some speculation over whether the mid-chain radical can migrate. Herein, by the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) of poly(n-butyl acrylate) synthesized by solution polymerization under a range of conditions, it is shown that this mid-chain radical migration does occur in the radical polymerization of acrylates conducted at high temperatures, as is evident from the shape of the molecular weight distribution. Using a mathematical model, an initial approximation of the rate at which migration occurs is made and the distribution of branching lengths formed in this scenario is explored. It is shown that the polymerizations carried out under a low monomer concentration and at high temperatures are particularly prone to radical migration reactions, which may affect the rheological properties of the polymer.

On the Thermal Self-Initiation Reaction of n-Butyl Acrylate in Free-Radical Polymerization

This experimental and theoretical study deals with the thermal spontaneous polymerization of n-butyl acrylate (n-BA). The polymerization was carried out in solution (n-heptane as the solvent) at 200 and 220 °C without adding any conventional initiators. It was studied with the five different n-BA/n-heptane volume ratios: 50/50, 70/30, 80/20, 90/10, and 100/0. Extensive experimental data presented here show significant monomer conversion at all temperatures and concentrations confirming the occurrence of the thermal self-initiation of the monomer. The order, frequency factor, and activation energy of the thermal self-initiation reaction of n-BA were estimated from n-BA conversion, using a macroscopic mechanistic model. The estimated reaction order agrees well with the order obtained via our quantum chemical calculations. Furthermore, the frequency factor and activation energy estimates agree well with the corresponding values that we already reported for bulk polymerization of n-BA.

Supramolecular H-bonded three-arm star polymers by efficient combination of RAFT polymerization and thio-bromo “click” reaction

Efficient and versatile “click”-based post-polymerization tools for the straightforward modification of especially polymers with sophisticated architectures play a significant role in polymer chemistry. We here report on the synthesis of supramolecular three-arm star polymers by a combination of RAFT polymerization and the thio-bromo “click” reaction, consequently exploring the potential of this particular thiol-halogen “click” reactions as post-polymerization tool. Therefore, two new trivalent chain transfer agents (CTAs) bearing either trithiocarbonate or dithiobenzoate groups were designed and investigated for the RAFT polymerization of n-butyl acrylate (nBA) and styrene. Kinetic investigations of CTA/monomer combinations were performed to obtain star-shaped poly(n-butyl acrylate)s (PnBA) and poly(styrene)s (PS) with adjustable molecular weights and well controllable polydispersities in the range of 1.13–1.30. The capped thiol-groups were released by aminolysis and quantitatively converted into barbiturate or imidazolium end-groups, allowing to prepare functionalized supramolecular star polymers via this particular thio-bromo “click” reaction. Thereby, the best results for aminolysis were not obtained in a one-pot reaction as expected but in a two step process, while acetonitrile has been shown to be essential for the success of the reaction in contrast to the pKa-value of the investigated bases. As proven via NMR spectroscopy and mass spectrometry all desired supramolecular star polymers were obtained with an exceptional high extend of end-group functionality (>95%) underscoring the potential of this specific “click”-based post-polymerization modification tool in combination with RAFT polymerization.