Monomer Concentration Research Articles

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.

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

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.

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.

Formation of monodispersed anatase TiO2 spheres from TiOSO4 for enhanced hydrogen evolution of TiO2/g-C3N4 photocatalysts

Monodispersed anatase TiO2 spheres were synthesized from TiOSO4 solution made from Ti-bearing blast furnace slags (TBFS) via the hydrothermal hydrolysis-calcination route. By simply increasing the solution acidity before the hydrolysis, 2–4 μm TiO2 aggregates formed by 30–50 nm primary particles convert to 200–400 nm monodispersed spheres. The key to dispersion is investigated: As the acidity rises, SO42- in solution is converted to HSO4-, which changes the SO42-/HSO4- species adsorbed on the primary particle surface. DFT calculations show that Ti-SO4-Ti bridges between the primary particles are more easily broken than Ti-HSO4-Ti, allowing for the dispersion of the primary particles. The reasons for the narrow size distribution were investigated: The high acidity and hydrothermal treatment enhance the dissolution-deposition of TiO2. The small primary particles dissolve quickly and increase the monomer concentration, which promotes the growth of monodispersed TiO2 spheres following the "size focusing" mode, leading to a narrow size distribution. Finally, TiO2/g-C3N4 photocatalysts were prepared based on the aggregated TiO2 and monodispersed TiO2 spheres. Due to the more surface oxygen vacancies and higher dispersion, the photocatalyst made from the monodispersed TiO2 spheres shows enhanced hydrogen evolution than the aggregated TiO2. The present results may provide insights into TiO2 sphere synthesis and TBFS recycling.

Microcrystal Growth Pathways Investigated with Machine Learning Segmentation and Classification in Scanning Electron Microscopy.

Advances in electron microscopy have revolutionized material characterization on the nano- and microscales, providing important insights into local ordering, structure, and size and quality distributions. While shape and size can be rigorously quantified through microscopy, it is often limited to local structure analysis and fails to describe bulk sample quality. Herein, a flexible machine learning (ML) tool is described that can segment and classify faceted crystals in scanning electron microscopy (SEM) micrographs to determine sample quality through the crystal size and product distribution. As a case study, this tool was applied to investigate crystal growth pathways (classical nucleation and growth compared to nonclassical growth) in DNA-mediated nanoparticle assembly through size and product (single crystal, fused crystal, or noncrystal) distribution of samples containing over 13000 colloidal crystal products. Strong DNA bond strengths (controlled by DNA sequence) lead to fast nucleation that exhausts the monomer concentration, resulting in smaller colloidal crystals. Alternatively, increased thermal energy and crystallization time lead to nonclassical crystallization pathways (coalescence) that result in larger colloidal crystals. This tool is useful since experimental conditions can now be deliberately identified to control colloidal crystal size and size distribution, important considerations for researchers interested in designing and synthesizing colloidal crystal metamaterials.

Phenylpropanoid pathway mediated the defense response of ‘Korla’ fragrant pear against Alternaria alternata infection

Alternaria alternata has been found to be the dominating pathogenic fungus of harvested ‘Korla’ fragrant pear, and the resulting blackhead disease is a significant factor affecting the storage quality of pears. The present study explored the specific mechanisms by which the phenylpropanoid pathway mediates the defense response to A. alternata infection in pear fruit. In the A. alternata-inoculated group, the fruit exhibited increased activity and gene expression levels of key enzymes (PAL, C4H, and 4CL) as well as higher content of phenolic acids (trans-cinnamic acid, ferulic acid, caffeic acid, p-coumaric acid, and sinapic acid) and total phenol in the general phenylpropanoid pathway. In the mid-to-late storage period, the activity and gene expression levels of key enzymes in the lignin biosynthetic pathway (CCR and CAD) were suppressed, and the content of lignin monomers (sinapyl alcohol, coniferyl alcohol, and p-coumaryl alcohol) and lignin was reduced. Notably, the activity and gene expression levels of flavonoid biosynthetic pathway-related enzymes (CHS and CHI) as well as the content of various flavonoids (naringenin, apigenin, rutin, quercetin, and epicatechin) and total flavonoids continuously increased in response to A. alternata infection in the early to middle stages of storage but declined in the late storage period. In summary, the initial infection of A. alternata infection activated the stress response of pear fruit, particularly the phenylpropanoid–flavonoid branch pathway, to enhance the fruit’s defense against pathogens, but with the prolongation of the infestation time, the fruit could not continuously resist the invasion of pathogens, ultimately leading to the outbreak of disease. The present findings furnish a theoretical foundation further elucidating the interaction between ‘Korla’ fragrant pear and A. alternata and for developing an effective strategy to control the blackhead disease.

Optimization of continuous spin-freeze-drying: The role of spin-freezing on quality attributes and drying efficiency of a model peptide formulation

Continuous spin-freeze-drying is an innovative pharmaceutical manufacturing approach offering real-time monitoring and control at the individual vial level, unlike conventional batch lyophilization. A central feature of this technology is spin-freezing, which involves rapidly spinning liquid-filled vials under a precisely controlled cold gas flow, resulting in a thin, uniform frozen product layer. Using a model peptide formulation, we investigated the impact of different cooling and crystallization rates on quality attributes (QA) and primary drying duration. Key QAs included monomer content, peptide assay, moisture content, and pore structure. The monomer content, peptide content, and primary drying duration remained consistent across all spin-freezing conditions. However, scanning electron microscopy (SEM) and Karl Fischer titration revealed that freezing parameters significantly influenced pore structure and residual moisture content. Samples with smaller pores displayed lower residual moisture, as larger surface areas facilitate moisture desorption. Variations in freezing parameters also significantly impacted desorption kinetics during secondary drying. Slower crystallization rates led to more cracks and less shrinkage in the cake structure, while faster rates resulted in more uniform, stable cakes. Although specific to the product under study, these findings highlight the crucial role of spin-freezing in enhancing freeze-drying efficiency and product quality of biopharmaceuticals.

A Simple Preparation of Crosslinked, Highly Alkaline Diallyldimethylammonium Hydroxide Hydrogel Particles via Inverse Static Anion Exchange.

Highly alkaline hydrogels are gaining increasing attention in building materials research. Specifically, cationic alkaline hydrogels based on diallyldimethylammonium hydroxide (DADMAOH) as the monomer have been effectively used to seal water-bearing cracks or serve as coupling media for electrochemical chloride extraction. However, the residual halogen content and challenges in scaling up monomer production have hindered broader application. Attempts to use a commercially available cation-selective membrane for ion exchange achieved up to 90% chloride-to-hydroxide switch, but the approach proved ineffective due to significant monomer decomposition during the process. By contrast, neutral gels and gel particles can be readily prepared from diallyldimethylammonium chloride (DADMAC) in large quantities and with a wide range of compositions. It is demonstrated here that these neutral gel particles undergo inverse static anion exchange when suspended in NaOH solution, generating DADMAOH particles with residual halide contents of <0.3%, without the need for ion-selective or dialysis membranes. This corresponds to an up to 100-fold reduction in residual chloride content compared to particles produced directly from alkaline monomer solutions, thereby significantly enhancing the efficiency of hydroxide ion release. The swelling behaviour of the particles is primarily influenced by the initial monomer concentration, while conductivity remains largely unaffected, indicating that charge transport occurs mainly along the particle surface. Despite the pronounced increase in swelling with decreasing particle radii, the specific conductivity of 2.8 Ω-1 m-1 is still sufficient for their use as coupling media in concrete applications. In summary, the alkaline particles prepared via inverse static anion exchange meet all necessary requirements for building materials applications, offering a broader range of tuneable properties and greater ease of production compared to gels or particles derived from DADMAOH.

Aqueous Dispersion Polymerization for the Development of Lamivudine-Polyacrylonitrile Nanoparticles through Quality by Design Approach.

The development of polymeric nanoparticles (NPs) from preformed polymers usually requires the use of organic solvents and is more expensive. Hence, in this work, the development of polymeric nanoparticles by in situ aqueous dispersion polymerization from the monomers was set as an objective. Acrylonitrile monomer based polymeric NPs comprising Lamivudine (LMV) as a model drug were prepared using the aqueous dispersion polymerization technique. A quality by design approach was applied to optimise various formulation and process factors viz. monomer concentration, initiator concentration, stabilizer concentration and polymerization temperature. Polymerization time (PT), entrapment efficiency (EE), particle size (PS), and drug release rate constant (k) were taken as the responses to define the quality of the prepared NPs. Design of experiments analysis followed by optimization was performed to identify the optimized combination of the factors. Later, the optimized formulation was studied for the physical state of the LMV in the nanoparticles, surface morphology of the NPs and cytotoxicity studies. The optimized formulation was found to have 91.7 min. of PT, 81.4% of EE, 253 nm of PS and a k value of 0.262 h-1 (18 h to release 99%). The cytotoxicity studies indicated that the NPs were highly safe to use. These results altogether inferred that LMV contained NPs were developed effectively from the acrylonitrile monomer by the aqueous dispersion polymerization method.

Antimicrobial Activity of Copolymer Structures from Bio-Based Monomers.

The urgent need for new antimicrobial compounds has led scientists to explore antimicrobial peptides (AMPs) and antimicrobial polymers as solutions for multidrug resistance. In this study, we synthesized copolymers with cationic and hydrophobic moieties by free-radical polymerization (FRP) using a chain transfer agent to control molecular weights. The potential of natural products as part of the hydrophobic moiety was evaluated, along with variations in their monomer content (13-25%) and the molecular weight (MW) of the copolymer (5000-20,000 g·mol-1). Hydrophobicity was evaluated using the theoretical Log Poct values and surface areas (SAs). Biological assays included antimicrobial activity against Escherichia coli and Staphylococcus aureus standard strains, hemolytic activity in red blood cells (RBC), and cytotoxicity tests against HEK293T cells. Keys findings indicate that copolymers with tropolone moieties, lower MWs, and an optimal balance between hydrophobic and cationic moieties show a promising basis for future generations of antimicrobials.

Effect of smectic polymers on cholesteric liquid crystals.

Composite materials made of polymers and liquid crystals have been widely employed in smart windows, optical filters, and bistable displays. However, it is often difficult to decipher the role of the polymer network architecture on the alignment and the texture of liquid crystals. In this study, we use a simple model system where a small amount of polymerizable liquid crystalline monomer is mixed in a liquid crystal that exhibits both a smectic phase and a cholesteric phase with a large helical pitch. By cross-linking the monomer in the smectic phase, the liquid crystal textures become significantly altered. The existence of a polymer network not only creates resistance to form a helix and therefore hinders the formation of cholesteric fingerprints but also modifies the structure of the cholesteric texture. We investigate the effects of changing the concentration of chiral dopant and monomer on the formation and growth of the cholesteric fingerprint texture during the phase transition and on the width of the fingerprints. We find that, within a certain parameter range, the cholesteric fingerprints do not depend on the concentration of the chiral dopant. We explain this phenomenon by hypothesizing that the polymer network acts as a bulk alignment field.

Effects of Deficit Irrigation on Spring Wheat Lignification Process, Yield Productivity and Stalk Strength

Moderate deficit irrigation can improve lignin metabolism, thereby increasing wheat yield and lodging resistance. The moisture-sensitive variety Xinchun 22 (XC22) and drought-resistant variety Xinchun 6 (XC6) were used as experimental materials. We set mild drought (T1, J1 and 60–65% FC, where FC is the field capacity) and moderate drought (T2, J2 and 45–50% FC) during the tillering stage (T) and the jointing stage (J). We used conventional drip irrigation as a control (CK and 75–80% FC). The results show that the activity of lignin synthesis-related enzymes decreased with the growth process, while the accumulation and monomer content of lignin increased under different water treatments. The lignin metabolism and morphological characteristics of XC6 were higher than those of XC22. Under the same processing conditions, the indicators of XC22 showed more significant changes and were more sensitive to changes in the moisture content. Compared with other treatments, the stem thickness and wall thickness of the J1 treatment increased by 0.86–23.49% and 1.72–23.58%. The yield of the T1 treatment was the highest, increasing by 3.05–44.06% compared to other treatments. In addition, by improving PAL, H-type lignin monomers, S-type lignin monomers, stem thickness and lignin metabolism, grain yield can be increased. After mild drought during the jointing stage, J1 significantly improved the lignin metabolism capacity of the stem, increased stem thickness and wall thickness, and was beneficial for improving lodging resistance. The T1 treatment favored the improvement of the production capacity of assimilates, thus promoting a high yield of spring wheat.

A Novel method of controlling the molecular weight of PAN-lignin copolymer—Synthesis and characterization

Polyacrylonitrile-lignin copolymer (PLC) has been successfully prepared via solution polymerization technique by a three step synthesis procedure. The main aim of this research is to control the molecular weight of the PLC by varying the initiator, monomer or solvent concentration in the reaction. The loading of lignin was kept constant which is 20 wt % in the PLC. The Polyacrylonitrile (PAN) homopolymer synthesized in the first step and the final copolymer PLC were characterized by various techniques such as FTIR, NMR, DSC, UV etc. The chemical bonding of lignin with the PAN backbone has been ascertained by these characterisation methods. This study explores a promising way to control the molecular weight of PLC copolymer which can be further used in the production of precursor fibre for carbon fibre.

Graphene Oxide-Enhanced Nucleation and Growth of Calcium-Silicate-Hydrate Gel at Nanoscale: A Molecular Dynamics Study.

Graphene oxide (GO) enhances the performance of cement-based materials by optimizing the microstructure of calcium-silicate-hydrate (C-S-H). However, the influence of GO on the nucleation and growth of C-S-H gel at nanoscale is unexplored. This study investigates this mechanism by molecular dynamics simulation at nano scale. Results show that GO can reduce the activation energy during the polymerization reaction of silicon oxide tetrahedra during the reaction process, and can increase the content of polymer Q3 and Q4. The influence of GO with epoxy (-O-), hydroxyl (-OH) and carboxyl (-COOH) groups on the radial distribution function (RDF), mean square displacement (MSD), and atomic spatial distribution of monomers are studied. Results show that GO-OH exhibits excellent performance, with the highest number of bridging oxygen atoms (about 0.6), the lowest Q0 monomer content (just 26.8%), the highest RDF (27.18), and the highest MSD (calcium and silicon content around 20,000 Å2). This paper elucidates the nucleation and growth mechanism of C-S-H influenced by GO to develop high performance cement.

Uniform Polymer Microspheres by Photoinduced Metal-Free Atom Transfer Radical Precipitation Polymerization.

Herein, a photoinduced method is introduced for the synthesis of highly cross-linked and uniform polymer microspheres by atom transfer radical polymerization (ATRP) at room temperature and in the absence of stabilizers or surfactants. Uniform particles are obtained at monomer concentrations as high as 10% (by volume), with polymers being exempt from contamination by residual transition metal catalysts, thereby overcoming the two major longstanding problems associated with thermally initiated ATRP-mediated precipitation polymerization. Moreover, the obtained particles have also immobilized ATRP initiators on their surface, which directly enables the controlled growth of densely grafted polymer layers with adjustable thickness and a well-defined chemical composition. The method is then employed successfully for the synthesis of molecularly imprinted polymer microspheres.

L-Cysteine-Bonded Polymeric Monolithic Stationary Phase for Enantioseparation of Dansyl Amino Acids in Capillary Liquid Chromatography.

A chiral monolith stationary phase was fabricated by modifying the monolith surface using L-cysteine through a thiol-epoxy click reaction. L-cysteine-bonded polymer monolith was characterized by scanning electron microscopy/energy-dispersive X-ray and attenuated total reflectance Fourier-transformed infrared. The monomer content and modification temperature were carefully optimized to create a polymer monolith with excellent mechanical stability and permeability. Our findings revealed that the column morphology depended significantly on the porogen concentration and modification temperature for its morphology and efficiency. Adequate pores and binding sites were formed with the optimal porogen content, while a higher modification temperature improved the modification yield, enhancing peak shapes and increasing separation efficiency. The column demonstrated its capability for enantioseparation of dansyl glutamic acid, dansyl aspartic acid, dansyl methionine, and dansyl phenylalanine using a 60mM ammonium acetate buffer solution and acetonitrile in a 20:80 v/v ratio. It maintained good mechanical stability and repeatability with no relative standard deviation exceeding 7%. These results indicated that the L-cysteine-bonded polymer monolith has excellent potential as a chiral stationary phase.