Monomer Solvent Research Articles

Computational approach and ultrasound Probe–Assisted synthesis of magnetic molecularly imprinted polymer for the electrochemical detection of bisphenol A

A new theoretical approach based on density functional theory was developed to find the most suitable monomer and porogen solvent to design a specific molecularly imprinted polymer (MIP) for bisphenol-A (BPA). Various theoretical investigations were carried out including HOMO and LUMO calculation, molecular electrostatic potential of the BPA-monomer interactions, and selection of the optimal monomer and porogen solvent using binding energies of BPA-monomer. Besides, counterpoise correction was used to avoid the problem of basis set superposition error. The theoretical results demonstrated that among virtual monomers, methacrylic acid and acrylamide showed good affinity towards BPA. The optimization of solvents was done using the polarizable continuum model and it was found that acetone was the most appropriate solvent. According to the obtained theoretical approach results, magnetic MIP (magMIP) was prepared using a high-power ultrasound probe. Scanning/transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction were used to characterize the as-prepared magMIP. Adsorption behavior was explained by Sips and pseudo-second-order models for isotherm and kinetic studies, respectively. Furthermore, magMIP showed favorable adsorption selectivity for BPA over other phenolic compounds. Finally, the developed magMIP was successfully used as a sorbent in solid-phase extraction combined with an electrochemical sensor for the detection of BPA. The obtained limit of detection was 66 nM and the recovery values in tap water sample were 104 and 105.5% for 2 and 10 µM, respectively, with RSD values lower than 5 % (n = 3).

Real-Time Zeta Potential Analysis of Microchannel Surfaces during Aminosilane Deposition and Exposure Using Current Monitoring.

Surface coatings are extensively used in capillary electrophoresis to increase separation efficiency and resolution. The stability of these coatings across a wide pH range is desirable to achieve repeatable migration times; therefore, a comprehensive understanding of coating degradation timescales is needed. We present a novel platform for automated zeta potential analysis based upon current monitoring that delivers improved time resolution over the existing methods. Using our platform, we measure the zeta potential continuously during aminosilane coating reactions and infer changes in the surface composition. We found that the change in the zeta potential after coating depended on the monomer type and solvent, while its stability was influenced by the coating solvent and exposure pH. Our versatile platform provides an elegant approach for evaluating the molecular composition, reactivity, and stability of surfaces in real time.

L‐glutamic acid as a versatile platform for rapid synthesis of functional polyesters via facile Passerini multicomponent polymerization

AbstractIn this work, a series of polyesters with different functional side groups were successfully prepared by Passerini three‐component polymerization (P‐3CP) in “one‐pot” from biorenewable l‐glutamic acid (l‐GA)‐based monomers. First, the polymerization conditions including monomer feed ratios, solvents and comonomer were systematically studied using Boc‐protected l‐GA with adipaldehyde and tert‐butyl isocyanide. Under the optimal polymerization conditions, a variety of N‐substituted l‐GA‐based monomers as well as functional isocyanides were attempted in the P‐3CP to produce polyesters with different functionalities. Moreover, it was found that after removal of pendant protecting groups, the obtained l‐GA‐based polyester degraded spontaneously into small molecules via 1,5‐intramolecular cyclization between the pendant amine groups and the ester groups in polymer backbone. The structures and thermal properties of obtained polymers were determined by 1H NMR, IR, SEC, MALDI‐ToF‐MS, DSC, and TGA measurements. Starting from biorenewable l‐GA, this approach will provide a facile and straightforward route to produce functional and biodegradable polyesters, thus effectively expanding the range of biodegradable polymers.

Rapid Fabrication of Patterned Gels via Microchannel-Conformal Frontal Polymerization.

From the perspective of both fundamental and applied science, it is extremely advisable to develop a facile and feasible strategy for fabricating gels with defined structures. Herein, the authors report the rapid synthesis of patterned gels by conducting frontal polymerization (FP) at millimeter-scale (2mm), where a series of microchannels, including linear-, parallel-, divergent-, snakelike-, circular- and concentric circular channels, were used. They have investigated the effect of various factors (monomer mass ratio, channel size, initiator concentration, and solvent content) on FP at millimeter-scale, along with the propagating rule of the front during FP in these microchannels. In addition, we developed a new microfluidic-assisted FP (MFP) strategy by combining the FP and microfluidic technique. Interestingly, the MFP can realize the production of hollow-structured gel in a rapid and continuous fashion, which have never been reported. Our work not only offers an effective pathway towards patterned gels by the microchannel-conformal FP, but also gives new insight into the continuous production of hollow-structured materials. Such a method will be beneficial for fabricating vessel and scaffold materials in a flexible, easy-to-perform, time and energy saving way.

Tunable Multiple Morphological Transformation of Supramolecular Hyperbranched Polymers Based on an A2B6-type POSS Monomer

The growing demands of supramolecular hyperbranched polymers integrating noncovalent interaction and unique topological structure merits had received considerable interests in the fabrication of novel materials for advanced applications. Herein, we prepared A2B6-type POSS-containing supramolecular hyperbranched polymers with multiple morphologies including lamellar-like, branched, hollow, core-shell and porous spherical structures through regulating self-assembling monomer concentrations and solvent polarities. The incorporation of appropriate emulative guest molecules would further trigger morphological transformations (such as vesicles and spherical micelles) by synergistic effects of unique POSS aggregation ability, supramolecular complexations and hydrophilic-hydrophobic interactions. Thus, this facile and universal strategy may enable a modular nanofabrication of supramolecular hyperbranched polymers with diversiform topological structure and sophisticated multifunctionality for their potential applications.

Modeling structural interconversion in Alzheimers’ amyloid beta peptide with classical and intrinsically disordered protein force fields

A comprehensive understanding of the aggregation mechanism in amyloid beta 42 (Aβ42) peptide is imperative for developing therapeutic drugs to prevent or treat Alzheimer’s disease. Because of the high flexibility and lack of native tertiary structures of Aβ42, molecular dynamics (MD) simulations may help elucidate the peptide’s dynamics with atomic details and collectively improve ensembles not seen in experiments. We applied microsecond-timescale MD simulations to investigate the dynamics and conformational changes of Aβ42 by using a newly developed Amber force field (ff14IDPSFF). We compared the ff14IDPSFF and the regular ff14SB force field by examining the conformational changes of two distinct Aβ42 monomers in explicit solvent. Conformational ensembles obtained by simulations depend on the force field and initial structure, Aβ42α-helix or Aβ42β-strand. The ff14IDPSFF sampled a high ratio of disordered structures and diverse β-strand secondary structures; in contrast, ff14SB favored helicity during the Aβ42α-helix simulations. The conformations obtained from Aβ42β-strand simulations maintained a balanced content in the disordered and helical structures when simulated by ff14SB, but the conformers clearly favored disordered and β-sheet structures simulated by ff14IDPSFF. The results obtained with ff14IDPSFF qualitatively reproduced the NMR chemical shifts well. In-depth peptide and cluster analysis revealed some characteristic features that may be linked to early onset of the fibril-like structure. The C-terminal region (mainly M35-V40) featured in-registered anti-parallel β-strand (β-hairpin) conformations with tested systems. Our work should expand the knowledge of force field and structure dependency in MD simulations and reveals the underlying structural mechanism–function relationship in Aβ42 peptides. Communicated by Ramaswamy H. Sarma

Radiation induced graft polymerization of fluorinated methacrylate onto polypropylene spunbond nonwoven fabric.

Radiation-induced grafting technique is one of the most promising methods to improve functional properties of textile materials. This work reports the grafting of 2,2,2-trifluoroethyl methacrylate (TFEM) onto polypropylene (PP) spunbond nonwoven fabric via gamma irradiation to improve its hydrophobicity. The effects of monomer concentration, solvent type, atmospheric condition, and irradiation dose on the degree of grafting were investigated. As characterized by SEM, FTIR, and NMR, the appearance and chemical characteristic of grafted fabric were completely altered compared to the original fabric. The grafted fabrics illustrated impressively high water contact angle of 125 degree. Moreover, the grafted fabrics maintained great hydrophobicity after the tests of chemical, thermal, UV, mechanical, and washing durability. These results suggested that grafting of 2,2,2-trifluoroethyl methacrylate onto PP spunbond offered a potential method to generate reusable hydrophobic fabrics.

Accounting for Cooperativity in the Thermotropic Volume Phase Transition of Smart Microgels.

A full quantitative description of the swelling of smart microgels is still problematic in many cases. The original approach of Flory and Huggins for the monomer–solvent interaction parameter cannot be applied to some microgels. The reason for this obviously is that the cross-linking enhances the cooperativity of the volume phase transitions, since all meshes of the network are mechanically coupled. This was ignored in previous approaches, arguing with distinct transition temperatures for different meshes to describe the continuous character of the transition of microgels. Here, we adjust the swelling curves of a series of smart microgels using the Flory–Rehner description, where the polymer–solvent interaction parameter is modeled by a Hill-like equation for a cooperative thermotropic transition. This leads to a very good description of all measured microgel swelling curves and yields the physically meaningful Hill parameter . A linear decrease of is found with increasing concentration of the cross-linker N,N-methylenebisacrylamide in the microgel particles p(NIPAM), p(NNPAM), and p(NIPMAM). The linearity suggests that the Hill parameter corresponds to the number of water molecules per network chain that cooperatively leave the chain at the volume phase transition. Driven by entropy, water molecules of the solvate become cooperatively “free” and leave the polymer network.

Theoretical investigation of fluorescence changes caused by methanol bridge based on ESIPT reaction* *Project supported by the National Basic Research Program of China (Grant No. 2019YFA0307701), the National Natural Science Foundation of China (Grant No. 11874180), the Young and Middle-aged Scientific and Technological Innovation Leaders and Team Projects in Jilin Province (Grant No. 20200301020RQ).

The different fluorescence behavior caused by the excited state proton transfer in 3-hydroxy-4-pyridylisoquinoline (2a) compound has been theoretically investigated. Our calculation results illustrate that the 2a monomer in tetrahydrofuran solvent would not occur proton transfer spontaneously, while the 2a complex in methanol (MeOH) solvent can undergo an asynchronous excited state intramolecular proton transfer (ESIPT) process. The result was confirmed by analyzing the related structural parameters, infrared vibration spectrum and reduced density gradient isosurfaces. Moreover, the potential curves revealed that with the bridging of single MeOH molecular the energy barrier of ESIPT was modulated effectively. It was distinctly reduced to 4.80 kcal/mol in 2a-MeOH complex from 25.01 kcal/mol in 2a monomer. Accordingly, the ESIPT process induced a fluorochromic phenomenon with the assistant of proton-bridge. The elucidation of the mechanism of solvent discoloration will contribute to the design and synthesis of fluorogenic dyes as environment-sensitive probes.

Self-Assembled 2,3-Dicyanopyrazino Phenanthrene Aggregates as a Visible-Light Photocatalyst.

In this study, 2,3-dicyanopyrazino phenanthrene (DCPP), a commodity chemical that can be prepared at an industrial scale, was used as a photocatalyst in lieu of Ru or Ir complexes in C-X (X = C, N, and O) bond-forming reactions under visible-light irradiation. In these reactions, [DCPP]n aggregates were formed in situ through physical π-π stacking of DCPP monomers in organic solvents. These aggregates exhibited excellent photo- and electrochemical properties, including a visible light response (430 nm), long excited-state lifetime (19.3 μs), high excited-state reduction potential (Ered([DCPP]n*/[DCPP]n·-) = +2.10 V vs SCE), and good reduction stability. The applications of [DCPP]n aggregates as a versatile visible-light photocatalyst were demonstrated in decarboxylative C-C cross-coupling, amidation, and esterification reactions.

Quantum Chemical Simulation of the Qy Absorption Spectrum of Zn Chlorin Aggregates for Artificial Photosynthesis.

Zn chlorin (Znchl) is easy to synthesize and has similar optical properties to those of bacteriochlorophyll c in the nature, which is expected to be used as a light-harvesting antenna system in artificial photosynthesis. In order to further explore the optical characteristics of Znchl, various sizes of a parallel layered Znchl-aggregate model and the THF-Znchl explicit solvent monomer model were constructed in this study, and their excited state properties were simulated by using time-dependent density functional theory (TDDFT) and exciton theory. For the Znchl monomer, with a combination of the explicit solvent model and the implicit solvation model based on density (SMD), the calculated excitation energy agreed very well with the experimental one. The Znchl aggregates may be simplified to a Zn36 model to reproduce the experimental absorption spectrum by the Förster coupling theory. The proposed Znchl aggregate model provides a good foundation for the future exploration of other properties of Znchl and simulations of artificial light-harvesting antennas. The results also indicate that J-aggregrates along z-direction, due to intermolecular coordination bonds, are the dominant factor in extending the band of Znchl into the near infrared region.

Modeling short-chain branched polyethylenes in dilute solution under variable solvent quality conditions: Basic configurational properties

We perform molecular dynamics (MD) simulations of a coarse-grained model of linear low-density polyethylenes (LLDPEs) having short-chain branching in an implicit solvent and calculate basic configurational properties (radius of gyration Rg, hydrodynamic radius Rh, and intrinsic viscosity [η]) using the path-integration program ZENO. Solvent quality effects in our model are accounted for through the introduction of an attractive polymer-polymer interaction potential with solvent quality “strength” λ that is tuned from a “good” solvent limit, where the inter-polymer interactions are purely repulsive, to a “very poor” solvent regime, where the polymers collapse due to their self-attractive intermolecular interactions. We also identify a compensation condition or “θ point” in our model between these limits, where the polymers are “ideal” in the sense in which attractive interactions effectively nullify inter-polymer repulsions so that the chains behave akin to Gaussian polymer chains in their average conformational properties. In order to compare with experiments performed under variable solvent conditions, we define a dimensionless measure of excluded volume interaction parameter δ in terms of the mass scaling exponent ν for Rg or νh for Rh, which can be determined from both experiment and simulation. We illustrate our variable solvent approach to estimate polymer solution properties in the case of polyethylenes (PEs) and evaluate the δ value that corresponds to the experimental solvent conditions. Our combined use of MD and ZENO allows for the numerical estimation of polymer solution properties for polymers having general monomer structures and solvent qualities in a computationally tractable fashion and should be useful as a general computational tool for polymer structural characterization.

Long-Range Surface-Directed Polymerization-Induced Phase Separation: A Computational Study.

The presence of a surface preferably attracting one component of a polymer mixture by the long-range van der Waals surface potential while the mixture undergoes phase separation by spinodal decomposition is called long-range surface-directed spinodal decomposition (SDSD). The morphology achieved under SDSD is an enrichment layer(s) close to the wall surface and a droplet-type structure in the bulk. In the current study of the long-range surface-directed polymerization-induced phase separation, the surface-directed spinodal decomposition of a monomer–solvent mixture undergoing self-condensation polymerization was theoretically simulated. The nonlinear Cahn–Hilliard and Flory–Huggins free energy theories were applied to investigate the phase separation phenomenon. The long-range surface potential led to the formation of a wetting layer on the surface. The thickness of the wetting layer was found proportional to time t*1/5 and surface potential parameter h11/5. A larger diffusion coefficient led to the formation of smaller droplets in the bulk and a thinner depletion layer, while it did not affect the thickness of the enrichment layer close to the wall. A temperature gradient imposed in the same direction of long-range surface potential led to the formation of a stripe morphology near the wall, while imposing it in the opposite direction of surface potential led to the formation of large particles at the high-temperature side, the opposite side of the interacting wall.

The influences of monomer structure and solvent on the radical copolymerization of tertiary amine and PEGylated methacrylates

This work presents a meticulous and rigorous investigation of reactivity ratios of commonly used monomers (PEGMA, DEAEMA, and DMAEMA) with high importance for stimuli-responsive materials; a copolymerization mini-library with 9 systems is reported.

Preparation of thermoresponsive hydrogels via polymerizable deep eutectic monomer solvents

We report the preparation of thermoresponsive hydrogels via free-radical polymerization and crosslinking of NIPAM based deep eutectic monomer solvents (DEMs).

Peculiar effect of acylamino and cyan groups on thermal behavior of 2-(1-cyano-1-methylethyl)azocarboxamide

2-(1-Cyano-1-methylethyl)azocarboxamide (CABN) is a representative of new-type azo initiator in the radical polymerization industry. The peculiar water and oil soluble characters make it a versatile rising star for the industry to initiate the polymerization of monomers in either polar or nonpolar solvents based continuous phases. This paper decodes the effect of acylamino and cyan groups on thermal stability and hazards of CABN via advanced thermokinetic analysis and numerical simulation. Initially, simultaneous thermogravimetric analyzer was employed to evaluate the thermal stability of CABN and its two structurally similar azo compounds (azos), azobisisobutyronitrile (AIBN) and azodicarbonamide (AC). Followed with calorimetric experiments by differential scanning calorimetry, the effect of two functional groups on thermal behavior parameters, such as decomposition temperature, melting point, and heat of decomposition was estimated. The results indicated that the acylamino group can improve the thermal stability of CABN but with bulkier heat release. Ultimately, through the medium of thermokinetic analysis, the thermal hazard of AIBN, CABN, and AC was simulated based on auto-ignition and thermal explosion theory. The research results would provide references for the synthesis of new-type azo initiators and process safety parameters to the polymerization industry.

Rational Design of an Ion-Imprinted Polymer for Aqueous Methylmercury Sorption.

Methylmercury (MeHg+) is a mercury species that is very toxic for humans, and its monitoring and sorption from environmental samples of water are a public health concern. In this work, a combination of theory and experiment was used to rationally synthesize an ion-imprinted polymer (IIP) with the aim of the extraction of MeHg+ from samples of water. Interactions among MeHg+ and possible reaction components in the pre-polymerization stage were studied by computational simulation using density functional theory. Accordingly, 2-mercaptobenzimidazole (MBI) and 2-mercaptobenzothiazole (MBT), acrylic acid (AA) and ethanol were predicted as excellent sulfhydryl ligands, a functional monomer and porogenic solvent, respectively. Characterization studies by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) revealed the obtention of porous materials with specific surface areas of 11 m2 g−1 (IIP–MBI–AA) and 5.3 m2 g−1 (IIP–MBT–AA). Under optimized conditions, the maximum adsorption capacities were 157 µg g−1 (for IIP–MBI–AA) and 457 µg g−1 (for IIP–MBT–AA). The IIP–MBT–AA was selected for further experiments and application, and the selectivity coefficients were MeHg+/Hg2+ (0.86), MeHg+/Cd2+ (260), MeHg+/Pb2+ (288) and MeHg+/Zn2+ (1510), highlighting the material’s high affinity for MeHg+. The IIP was successfully applied to the sorption of MeHg+ in river and tap water samples at environmentally relevant concentrations.

Optimization aspects of electrodeposition of photoluminescent conductive polymer layer onto neural microelectrode arrays

In neuroscience the use of a microelectrode array allows the detection of neuroelectric signals with high temporal resolution in a confined space within the tissue, while two-photon laser scanning microscopy provides high spatial resolution in a wide region of interest. The combination of these two techniques promises better understanding of the operation of neural pathways. To facilitate this connection, we studied the direct electrochemical deposition of the conductive polymer poly-2,3-ethylenedioxy-thiophene onto different Pt and Pt/Ir electrode surfaces from non-aqueous solvents, such as ionic liquid and propylene carbonate. We show the effects of electrochemical deposition technique (pulsed or continuous), monomer concentration range and solvent electrolyte type on the formation of photoluminescent - conductive films. For these variables we determined the optimal deposition parameters given as 0.025–0.050 M EDOT monomer concentration in BMIMBF4 ionic liquid and the use of pulsed deposition process to form an adherent, uniform functional electrode coating.

Charge affinity and solvent effects in numerical simulations of ionic microgels

Ionic microgel particles are intriguing systems in which the properties of thermo-responsive polymeric colloids are enriched by the presence of charged groups. In order to rationalize their properties and predict the behaviour of microgel suspensions, it is necessary to develop a coarse-graining strategy that starts from the accurate modelling of single particles. Here, we provide a numerical advancement of a recently-introduced model for charged co-polymerized microgels by improving the treatment of ionic groups in the polymer network. We investigate the thermoresponsive properties of the particles, in particular their swelling behaviour and structure, finding that, when charged groups are considered to be hydrophilic at all temperatures, highly charged microgels do not achieve a fully collapsed state, in favorable comparison to experiments. In addition, we explicitly include the solvent in the description and put forward a mapping between the solvophobic potential in the absence of the solvent and the monomer–solvent interactions in its presence, which is found to work very accurately for any charge fraction of the microgel. Our work paves the way for comparing single-particle properties and swelling behaviour of ionic microgels to experiments and to tackle the study of these charged soft particles at a liquid–liquid interface.

Mechanistic study on radiation‐induced grafting into fluorinated polymer solid films using a swelling‐induced detachment of grafted polymers

AbstractThe radiation‐induced graft polymerization (RGP) of styrene into poly(ethylene‐co‐tetrafluoroethylene) films was performed at various monomer concentrations and solvents at 60 °C. The grafted polystyrene (g‐PS) was isolated using the swelling‐induced detachment phenomenon, and the number‐averaged molecular weight (Mn) and the number of g‐PS (Np) were determined using gel permeation chromatography. The Mn increased consistently with an increase in the grafting time up to 2–3 hours, indicating very low termination rates, which was a result of the “gel effect”. This is the first direct evidence of the gradual Mn increase over time using RGP in thermally and chemically stable polymer films such as fluorinated polymers. When the Mn and Np were plotted as a function of the degree of grafting (DOG), sudden Np drops along with rapid Mn increases were observed in the DOG region of 80–90%, indicating negligible initiation and propagation; however, a recombination termination between two propagating g‐PS radicals dominated the later part of the grafting process. Further increases in both Mn and Np were observed subsequently, implying that reinitiation and propagation events were triggered by morphological changes, as observed by small‐ and ultrasmall‐angle X‐ray scattering experiments, which liberated the dormant radicals from the lamellar crystals.