Monomer Concentration Research Articles

Emulsion Polymerization of Styrene to Polystyrene Nanoparticles with Self-Emulsifying Nanodroplets as Nucleus.

The mechanism of the emulsion polymerization of styrene to polystyrene nanoparticles (PSNPs) remains a subject of debate. Herein, a series of reaction parameters with different surfactant concentrations, monomer contents, temperatures, and equilibration times were investigated to understand the formation mechanism of PSNPs, which demonstrate a correlation between the properties of PSNPs and the mesostructure of the premix. Cooling the model systems with self-emulsifying nanodroplets (SENDs) in the early reaction stages resulted in the hollow polystyrene spheres (H-PSSs), ruptured PSNPs, and dandelion-like PSNPs, further indicating that the oil nanodroplets are the key sites for the formation of PSNPs. Therefore, the oligomer radicals generated in the medium at the early polymerization stages are preferentially captured by the oil-H2O interface, and once in the oil droplets, the oligomeric radical continues to grow until colliding with another radical or monomers run out. The self-emulsifying oil nanodroplets with a particle size of 100-300 nm are formed under high temperature and low surfactant concentration conditions and serve as nucleation sites. This study not only contributes to a profound understanding of the correlation between the mesostructure and nucleation pathways but also paves the way for the flexible regulation of the monodispersity and morphology of PSNPs.

Synthesis of Poly(Itaconate)s With High Monomer Conversion Applying Emulsion Polymerization

ABSTRACTItaconic acid and its derivatives can be obtained from renewable feedstocks. However, there are only very limited applications of polymers containing itaconic acid so far. One limitation of the application of this polymer is that commonly utilized polymerization techniques lead to very low conversions of the corresponding monomers. Consequently, itaconic acid and its derivatives are generally considered difficult or poorly polymerizable monomers. The current study presents the improvement of the polymerization by applying an emulsion polymerization of itaconic acid esters, leading to very high monomer conversions with a residual monomer content of less than 1%.

Depolymerisation of poly(lactide) under continuous flow conditions.

Poly(l-lactic acid) (PLLA) is commercially successful bio-based plastic, where end-of-life materials can undergo industrial composting. To create a circular economy, a desirable alternative to composting is chemical recycling to monomer (CRM), where direct depolymerisation to l-lactide can be achieved. CRM of PLLA is typically impeded by thermal decomposition and side reactions, due to the high ceiling temperate (T c) of PLLA in bulk (>600 °C), which preclude implementation on a large scale, and has led to the development of catalytic strategies, under vacuum or high dilution in high boiling point solvents conditions. In this study, a commercially available Sn(ii) catalyst and low boiling point solvents, at a range of temperatures and concentrations, were explored for the CRM of PLLA in a continuous flow process. The solvent THF was found to produce the best results, where up to 92% conversion of lactide could be achieved, with 92-97% selectivity for l-lactide formation at temperatures 150-170 °C. Further, inline monitoring of monomer and polymer concentrations in flow were used to determine the depolymerisation rate coefficient k depo and the activation energy of k depo was determined to be 129.4 kJ mol-1.

Radical polymerization of itaconic acid in dipolar aprotic solvents − The effect of high monomer concentration

Radical polymerization of itaconic acid in dipolar aprotic solvents − The effect of high monomer concentration

Transcriptomic Insights into Higher Anthocyanin Accumulation in 'Summer Black' Table Grapes in Winter Crop Under Double-Cropping Viticulture System.

Anthocyanins are responsible for grape (Vitis vinifera L.) skin color. To obtain a more detailed understanding of the anthocyanin regulatory networks across' the summer and winter seasons in grapes under a double-cropping viticulture system, the transcriptomes of 'Summer Black' grapes were analyzed using RNA sequencing. The average daily temperature during the harvest stage in the summer crop, ranging from 26.18 °C to 32.98 °C, was higher than that in the winter crop, ranging from 11.03 °C to 23.90 °C. Grapes from the winter crop accumulated a greater content of anthocyanins than those from the summer crop, peaking in the harvest stage (E-L38) with 207.51 mg·100 g-1. Among them, malvidin-3-O-glucoside (Mv-3-G) had the highest monomer content, accounting for 32%. The content of Cy-3-G during winter increased by 55% compared to summer. KEGG analysis indicated that the flavonoid biosynthesis and circadian rhythm-plant pathways are involved in the regulation of anthocyanin biosynthesis during fruit development. Pearson's coefficient showed significant positive correlations between anthocyanin content and the VvDFR, VvUFGT, VvOMT, VvMYB, and VvbHLH genes in the winter crop; at full veraison stage, their expressions were 1.34, 1.98, 1.28, 1.17, and 1.34 times greater than in summer, respectively. The higher expression of VvUFGT and VvOMT led to higher contents of Cy-3-G and Mv-3-G in the winter berries, respectively.

Integrating Hydrogels and Biomedical Plastics via In Situ Physical Entanglements and Covalent Bonding.

Both rigid plastics and soft hydrogels find ample applications in engineering and medicine but bear their own disadvantages that limit their broader applications. Bonding these mechanically dissimilar materials may resolve these limitations, preserve their advantages, and offer new opportunities as biointerfaces. Here, a robust adhesion strategy is proposed to integrate highly entangled tough hydrogels and diverse plastics with high interfacial adhesion energy and strength. Systemic investigations on the effects of hydrogel monomer content and crosslink fraction revealed the significant contributions of both polymer physical entanglements and interfacial covalent bonding. This hybrid engineering strategy also enables the plastic-hydrogel composite to attenuate foreign body response caused by pristine rigid plastics in vivo in mice. This versatile materials engineering approach may be broadly applicable to other polymer-based devices commonly used in regenerative medicine and surgical robotics.

Прививочная полимеризация метакриловой и акриловой кислот на облученную пленку полиэтилена и оценка прочностных характеристик привитых сополимеров

Membranes on the basis of synthetic and modified natural polymeric substrates are widely used in separation and filtration processes and as conductive or isolating media. Grafting acrylic monomers onto polymeric substrates is an effective method of their production. Polyethylene, a synthetic polymer, has high strength properties, thermal and chemical resistance, which makes it a good substrate for various products. The objective of this work was producing ion exchange grafted films on the basis of preirradiated polyethylene grafted with methacrylic and acrylic acids, and regulation of their properties during synthesis. Methacrylic and acrylic acids have been grafted onto preirradiated polyethylene film (thickness 30±5 μm) in concentrated solutions with a monomer content up to 45 wt.% in the presence of iron (II) ions at temperatures within 90–97 °C. The concentration of the monomers, initiators, additives of modifiers and the reaction temperature have been varied. The kinetics of grafting polymerization, grafting degree and the degree of swelling in an electrolyte have been studied by a gravimetric method. The influence of the nature of grafted monomers, the concentration of components and modifiers on the above quantities and mechanical properties of the grafted films have been established. Our modified films have been characterized by FTIR spectroscopy, chemical elemental analysis, scanning electron microscopy (the relief and surface morphology), and their mechanical properties have been assessed by the uniaxial tensile method. The study of the resulting ion exchange composites for the purpose of further application in the technology of treating waste and industrial waters from polyvalent metals and as ion conducting media will be carried out in the future.

NIPAm Microgels Synthesised in Water: Tailored Control of Particles' Size and Thermoresponsive Properties.

Microgels, combining the properties of hydrogels and microparticles, are emerging as versatile materials for varied applications such as drug delivery and sensing, although the precise control of particle size remains a challenge. Advances in synthetic methodologies have provided new tools for tailoring of properties, however costs and scalability of the processes remains a limitation. We report here the water-based synthesis of a library of N-isopropylacrylamide-based microgels covalently crosslinked with varying contents of N,N'-methylenebisacrylamide. The results highlight the versatility of water as a synthetic medium, which yields large and monodisperse microgels, with excellent control over size. Dynamic light scattering data demonstrate that by increasing the total monomer concentration from 1 to 3 wt%, the particle size is increased by up to 4.9-fold. Crosslinker content allows fine-tuning of microgel size, with greater relevance for functionalised microgels. Functional co-monomers such as N-(3-aminopropyl)methacrylamide hydrochloride and N-(hydroxymethyl)acrylamide are shown to influence size and thermoresponsive behaviour, with hydrogen-bonding monomers reducing particle size and increasing the volume phase transition temperature by 2 °C. Positively charged monomers show a size reduction upon heating but provide colloidal stability at temperatures up to 60 °C. These findings emphasize the importance of tailoring synthetic conditions and formulations to optimize microgel properties for specific applications.

Taguchi method optimisation for synthesising a novel Fe3O4@Sodium alginate-g-copolymer for enhanced methylene blue adsorption: optimisation, kinetics, and isotherm analyses

ABSTRACT This research paper includes a novel hydrogel as an adsorbent prepared via free radical polymerisation of sodium alginate-grafting-poly (N-isopropylacrylamide-co-hydroxy ethyl acrylamide-co-2-Acrylamido-2-methylpropane sulphonic acid) (HGs). Employing the Taguchi method, optimal concentrations of monomers, sodium alginate, initiator, and crosslinking agent were determined to achieve maximum swelling ratio for the incorporation of Fe2+ and Fe3+ ions to produce Fe3O4/HGS magnetic hydrogel nanocomposites (MGHs) as shown in Scheme 1. HGS and MGHs were characterised using various techniques, including the infrared absorption spectrum (FTIR), the field emission scanning electron microscope (FESEM), the atomic force microscope (AFM), the transmission electron microscope (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), the Brunauer–Emmett–Teller (BET), Vibrating‑Sample Magnetometer (VSM). The study compared swelling behaviours at different pH values for both adsorbents. The point zero charge PZC was studied to understand adsorption behaviour, which was equal to 5.44 for the adsorbent. Adsorption kinetics exhibited pseudo-second-order behaviour after determining the adsorbent’s effective weight, which is 0.002 g, and the equilibrium time, which was 60 min. The adsorption isotherm showed good agreement with both Langmuir and Dubinin–Radushkevich models. Thermodynamic parameters were calculated at different temperatures (5–35 °C), indicating physisorption. While the removal percent of Mb dye was equal to 95% and Qe = 474.7 mg/g, adsorption conditions were studied using the Response Surface Methodology (RSM) and analysed through Analysis of Variance (ANOVA). Results demonstrated that adsorption increases with increasing pH and temperature, confirming the endothermic nature of the process. The study also investigated adsorbent Reusability, which exhibited high efficiency after five cycles.

Fabrication of Polyurethane-Polyacrylate Hybrid Latexes with High Organosilicon Content via Phase Inversion Emulsion Polymerization.

Waterborne polyurethane, with a mechanical strength comparable to solvent-based types, is eco-friendly and safe, using water as a dispersion medium. Polyacrylate excels in film formation and weather resistance but suffers from "hot stickiness and cold brittleness". Merging polyurethane and polyacrylate creates advanced hybrids, while organosilicon enhances properties but is restricted due to hydrolytic crosslinking. In this paper, a series of polyurethane-polyacrylate hybrid latexes with high organosilicon content were prepared using phase inversion emulsion polymerization technology. Even when the monomer content of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) was increased to 10%, the polymerization process was stable, without the formation of a gel precipitate. The resulting latexes could remain stable for at least 6 months without significant changes in the properties of their films. The effects of MPS content on the mechanical and thermal properties of latex films were systematically researched. The study showed that with an increase in MPS dosage, the hardness and elastic modulus of the latex films increased, while the elongation at break and water absorption decreased, together with the increased glass transition temperature and surface hydrophilicity. This work aims to provide new theoretical guidance for the preparation of silicone-modified hybrid latexes, enabling their safe and stable production and storage.

Markov State Model Approach to Simulate Self-Assembly

Computational modeling of assembly is challenging for many systems, because their timescales can vastly exceed those accessible to simulations. This article describes the multiMSM, which is a general framework that uses Markov state models (MSMs) to enable simulating self-assembly and self-organization of finite-sized structures on timescales that are orders of magnitude longer than those accessible to brute-force dynamics simulations. As with traditional MSM approaches, the method efficiently overcomes free energy barriers and other dynamical bottlenecks. In contrast to previous MSM approaches to simulating assembly, the framework describes simultaneous assembly of many clusters and the consequent depletion of free subunits or other small oligomers. The algorithm accounts for changes in transition rates as concentrations of monomers and intermediates evolve over the course of the reaction. Using two model systems, we show that the multiMSM accurately predicts the concentrations of the full ensemble of intermediates on timescales required to reach equilibrium. Importantly, after constructing a multiMSM for one system concentration, yields at other concentrations can be approximately calculated without any further sampling. This capability allows for orders of magnitude additional speedup. In addition, the method enables highly efficient calculation of quantities such as free energy profiles, nucleation timescales, flux along the ensemble of assembly pathways, and entropy production rates. Identifying contributions of individual transitions to entropy production rates reveals sources of kinetic traps. The method is broadly applicable to systems with equilibrium or nonequilibrium dynamics and is trivially parallelizable and, thus, highly scalable. Published by the American Physical Society 2024

Synthesis and Optimization of Polypyrrole-Grafted Graphene Oxide Nanohybrids

Herein, we have synthesized polypyrrole grafted graphene oxide (GO-g-PPy) nanohybrids by a free radical emulsion graft polymerization method. GO was used as the substrate for pyrrole grafting. The parameters of the graft polymerization reaction were optimized. The optimum concentrations of surfactant, monomer and initiator were 0.25 wt. %, 3 vol.%, and 7 wt.%, respectively. The maximum grafting percentage was 989.6% at these optimal reaction parameters. The formation of the grafted nanohybrids was confirmed by Fourier transform infrared spectroscopy (FTIR) and thermal stability studies were carried out by thermogravimetric analysis (TGA). GO-g-PPy naohybrids can be used as functional additives or conductive materials for EMI shielding applications.

Synthesis of sodium alginate grafted and silver nanoparticles filled anionic copolymer polyelectrolytes for adsorption and photocatalytic degradation of a cationic dye from water

Sodium alginate (SA) was grafted to poly (acrylonitrile-co‑sodium acrylate-co-acrylic acid). The grafted copolymer was crosslinked with N. N, methylene bis acrylamide (MBA). Silver nanoparticles (AgNPs) were generated in situ within the growing polymer network by reducing 0.1 mM silver nitrate with 0.05 mM ascorbic acid (ASA). The effect of initiator concentration, total monomer concentration, SA weight%, MBA weight% and acrylonitrile (AN):sodium acrylate (NaAA)/ acrylic acid (AA) molar ratios on the grafting were studied. The nanocomposite was characterized and used for adsorption of methylene blue (MB) dye from water. The composite was also used for photocatalytic degradation of the dye in the presence of sun light. The Box-Behnken design (BBD) of response surface methodology (RSM) with different compositions resulted in an optimized composition of 5:1 M ratio of AN:NaAA/AA, 1 wt% MBA and 2 wt% SA. The nanocomposite (SACP5Ag) prepared with the optimized composition showed an equilibrium batch adsorption(qe, mg/g)/removal(R)% of 245/98 from 50 mg/L MB dye in water and a qe /R% of 18.87/31.4 in a fixed bed adsorption at a feed inlet concentration(mgL−1)/inflow rate (mLmin−1)/bed height (mm) of 100/20/25. The composite showed a photocatalytic degradation efficiency of 98 % in sunlight for 80 min and a 1st order rate constant of 0.02 min−1.

Effect of Styrene Concentration on Tensile Properties of Styrene-Acrylate Films

Abstract Due to an increasing awareness of environmental protection, waterborne coatings have replaced solvent-borne ones. The waterborne styrene-acrylate dispersion was successfully synthesized using emulsion polymerization. In this work, the emulsion was composed of Butyl Acrylate (BA) and Styrene (Sty) at different ratios. FTIR spectra confirmed the successful copolymerization of BA and Sty. Additionally, it was observed that all emulsions exhibited a consistent hydrodynamic diameter (120 nm to 140 nm), polydispersity index (between 0.030 and 0.050), and zeta potential (-40 mV to -60 mV). Thus, the BA/St ratio did not impact particle growth during emulsion polymerization. Furthermore, an increase in Sty concentration raised the glass transition temperature (Tg) of the films from 10.8 °C to 30.8 °C. This is attributed to Sty being a high Tg polymer, contributing to a rigid monomer that could enhance rigidity and restrict the movement of polymer chains. Additionally, the tensile strength of the dispersion films increased with the increase in Sty concentration, from 3.01 MPa to 5.88 MPa. Interestingly, the elongation at break did not significantly change as the St concentration increased, dropping by 15%. The investigation to aid in establishing relationships between the monomer concentration and mechanical properties of styrene-acrylate films.

Hierarchical Arrangement of P(VDF-TrFE) Copolymer Crystals: A SAXS and AFM Study

P(VDF-TrFE) copolymers are materials with high relevance in printed organic electronics. These copolymers easily crystallize into the ferroelectric phase without resorting to post-deposition treatments (thermal annealing, poling, or mechanical stretching). The detection of a morphotropic phase boundary further increased the interest in this copolymer system by demonstrating relaxor behavior for higher TrFE content. This prompted an in-depth analysis of the P(VDF-TrFE) chiral chain structure responsible for the relaxor properties. Nevertheless, the efficient application of these materials also depends heavily on the quality and morphology of the crystalline domains. In this work, we combine SAXS and AFM imaging to analyze the structure of the crystalline domains as a function of the TrFE content. The detection of different structural distributions revealed the presence of hierarchical arrangements within the crystalline domains. Furthermore, these hierarchical arrangements were observed to change with the TrFE monomer content, presenting distinct morphologies for low and high TrFE contents, in line with previous works on the morphotropic phase boundary in these systems.

Antimicrobial and antioxidant properties of water-soluble lignin extracts obtained from ozonation of Miscanthus giganteus and Vitis vinifera in a pilot-scale reactor

Lignin is a potential source of polyphenols with different biological activities which might be affected by the extraction or isolation process. This study investigated the effect of ozonation on the bioactive properties of water-soluble lignin extracts from Miscanthus giganteus (grass-type biomass) and Vitis vinifera (wood-type biomass). Total polyphenolic content, antioxidant activities (ABTS, DPPH and β-carotene bleaching assays), and antimicrobial properties were evaluated. Although ozonation did not improve the antioxidant activity per gram of lignin extract with any of the methods employed, it significantly enhanced extraction of antioxidants. All lignin extracts displayed significant antioxidant potential, DPPH IC50 values ranging from 7.6 to 29.0 µg/mL and ABTS ranging 64.1–154.6 mg Trolox/g extract. Miscanthus lignin extracts achieved 70.6 % β-carotene bleaching inhibition, compared with 96.2 % inhibition by BHT. Miscanthus lignin extracts exhibited better yield and antioxidant activity compared with vine shoots, likely due to their lower molecular weight and higher content of phenolic monomers. Antibacterial analysis revealed that Miscanthus lignin extracts had superior activity against Staphylococcus aureus and Escherichia coli, which was enhanced by ozonation and linked to zeta potential and compositional aspects. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for Miscanthus extracts were 3 mg/mL and 6 mg/mL, respectively. Miscanthus extracts from 160 min ozonation demonstrated better antifungal activity than vine shoots, particularly against Penicillium digitatum (MIC:12 mg/mL) compared with Botrytis cinerea (MIC:25 mg/mL). The bioactive properties of water-soluble lignin extracts from ozonated Miscanthus open up new possibilities for their potential use in food and food packaging applications.

Degradation and/or Dissociation of Neurodegenerative Disease-Related Factor Amyloid-β by a Suspension Containing Calcium Hydrogen Carbonate Mesoscopic Crystals.

Amyloid-β (Aβ) aggregates accumulate in the brains of individuals with Alzheimer's disease and are thought to potentially act as prions, promoting further aggregation. Consequently, the biochemistry of Aβ has emerged as a promising target for Alzheimer's disease. CAC-717, a suspension of calcium bicarbonate mesoscopic structures derived from natural sources, has been shown to inactivate various pathogens, including prions. This study examined the effects of CAC-717 on both the formation and degradation/dissociation of Aβ aggregates using thioflavin T fluorescence and enzyme-linked immunosorbent assays. Aggregates of Aβ(1-42) peptide were generated by incubation at 37 °C for 24 h, and the effect of introducing CAC-717 on the aggregates was evaluated after further incubation at 25 °C for 30 min. Moreover, CAC-717 was also tested for its ability to inhibit the initial aggregation of Aβ. The results showed that CAC-717 significantly degraded and/or dissociated Aβ aggregates in a concentration-dependent manner. Specifically, CAC-717 treatment for 5 min disrupted Aβ aggregates to give Aβ monomer and oligomer concentrations as high as 130 nM compared to ~10 nM for the water control. In addition, CAC-717 degraded and/or dissociated aggregates within 10 s at 37 °C, and pre-treatment with CAC-717 significantly inhibited aggregation. These results suggest that CAC-717 not only degrades and/or dissociates Aβ aggregates but also inhibits their formation, highlighting its potential as a disinfectant for Alzheimer's disease.

Design of Emulsion Polymerization Reactors for Monomer‐Transport Limited Emulsion Polymerization

AbstractDamkohler Number (Da) analysis can identify monomers and emulsion polymerization operating regimes where the polymerization may be monomer‐transport, rather than reaction‐limited. In these cases, the expected monomer concentration in the growing polymer particles will be reduced due to the transport limitation. This will reduce the expected rate of polymerization, and require the design of a larger polymerization reactor for a given production rate. In heterogenous catalysis, an effectiveness factor is used to quantify the reduction in reaction rate and necessarily increase reactor size to compensate. This paper will show that it is possible to use Da (functionally equivalent to the Thiele Modulus in heterogeneous catalysis) to estimate an effectiveness factor for emulsion polymerization. Also shown is a procedure for calculating the monomer feed ratio during binary copolymerization when one must not only take into account the reactivity ratios but also the possibility that one of the monomers is monomer‐transport limited. The method provides the monomer feed ratio during the semibatch phase of a binary copolymerization. This alternative to starved‐feed polymerization shall result in much faster polymerization and higher polymerization kettle utility.

Polymerization of acrylonitrile in dimethyl carbonate: A kinetic and mechanistic study

For the first time, a new polymerization medium, dimethyl carbonate (DMC), was used for the polymerization of acrylonitrile (AN), and polyacrylonitrile (PAN) powder was obtained successfully. The effects of polymerization factors, including monomer concentrations, temperature and initiator concentrations on the structures and properties of PAN powders were investigated by nuclear magnetic resonance spectroscopy (NMR), total internal reflectance Fourier transform infrared spectrometer (FTIR), wide-angle X-ray diffractometer (WXRD) and thermal gravimetric analyzer (TGA). The polymerization kinetic and mechanistic study of PAN with DMC as the polymerization medium were discussed in details. There are three key achievements in this paper. First, the kinetic equation of PAN polymerization with DMC as a medium was established: Rp = K[ABVN]0.92[AN]6.78. This result shows that the Rp is highly dependent on the AN concentrations. Second, the chain transfer constant of DMC was measured to be 4.57 × 10−4 at 60 °C, and the chain transfer constant increases with polymerization temperature. Lastly, the structures and properties of PAN powders prepared with H2O, tetrahydrofuran (THF) and DMC as media were compared. The results showed that the PAN prepared with DMC as a medium by free radical polymerization had a higher conversion, molecular weight and better crystalline property compared to THF. These findings indicate that DMC is a promising medium for manufacturing high quality PAN powder by free radical polymerization.

A Facile Strategy for In Situ Fabrication of Covalent Triazine Framework Aerogel with Thermal Insulation Property.

Covalent triazine frameworks (CTFs) have attracted tremendous attention with respect to their rich nitrogen content, functional triazine units, and high porosity. However, efficient and simple preparation of CTF monoliths is still a challenge. Here, we propose a novel and facile approach for the in situ preparation of CTF aerogels. Trifluoromethanesulfonic acid was used as the solvent and catalyst, which could not only promote the polymerization reaction to form a gel but also protonate the CTFs. By virtue of the simplicity and efficiency of the strategy, a series of macroscopic CTF aerogels with tunable density were obtained by adjusting the monomer concentration. Due to the porous and partially crystalline structure, the as-produced macroscopic CTF aerogels behaved with good mechanical and thermal insulation performances. This finding thus offers an effective and easily scalable approach toward fabricating macroscopic CTF aerogels and broadens the applications of CTFs in a variety of domains.