Molecular Weight Distribution Research Articles

Synthesis of well-defined poly(p-alkoxystyrene) by anionic polymerization in the presence of di-n-butylmagnesium

This study demonstrates the necessity of introducing di-n-butylmagnesium (n-Bu2Mg) additives to synthesize precisely controlled polymers through anionic polymerization of p-alkoxystyrene monomers at -40°C. Without additives, 4-tert-butoxystyrene (BSt) and 4-(1-ethoxy ethoxy)styrene (EESt) are polymerized using sec-butyllithium (s-BuLi) in tetrahydrofuran (THF) solvent, yielding a molecular weight distribution (MWD) of 1.36. However, the MWD is strictly controlled to 1.05–1.06 after adding n-Bu2Mg in more than 30 times the amount of s-BuLi, resulting in an accurately designed molecular weight. Therefore, n-Bu2Mg effectively suppresses side reactions that could occur at the polymerization temperature of -40°C in the Schlenk reactor. Interestingly, the polymerization reaction of styrene monomer proceeds when n-Bu2Mg is mixed in THF solvent at -40°C for an extended period, even without s-BuLi. This result suggests that, despite being a weak anionic initiator, n-Bu2Mg can initiate polymerization due to the lower electron density of the styrene double bond compared to BSt or EESt. Based on these results, a precise copolymer with a narrow molecular weight distribution can be synthesized by initiating polymerization with s-BuLi within 20 seconds of adding n-Bu2Mg to the mixed monomers of styrene and EESt.

Comparison of the characteristics of small intestinal fluid from white-feathered and yellow-feathered broilers

The objective of this study was to compare the properties of small intestinal fluid (SIF) from white- and yellow-feathered broilers fed variable dietary CP to test the hypothesis that digestive enzymes sourced from the SIF of yellow-feathered broilers could serve as a viable alternative for preparing in vitro SIF specifically for white-feathered broilers. Ten Arbor Acres Plus broilers (32 days of age) and 20 Chinese yellow chickens (51 days of age) were fitted with jejunal cannulas and assigned to dietary treatments as follows: 1) white-feathered broilers (BW of 4.08 ± 0.39 kg) fed diet 1 with CP of 19.88 %, 2) yellow-feathered broilers (BW of 2.89 ± 0.27 kg) fed diet 1, and 3) yellow-feathered broilers (BW of 2.84 ± 0.20 kg) fed diet 2 with CP of 16.32 %. Each treatment contained 10 replicates with 1 broiler in each replicate. Digestive enzyme activities, ion concentrations, pH, 16 amino acid (AA, excluding Tyr and Trp) contents, molecular weight distribution (MWD) of protein, hydrolysis rates on wheat starch, corn starch, casein, and soybean protein concentrate, and in vitro digestible energy of corn, soybean meal, and corn gluten meal were evaluated for SIF. Activities of chymotrypsin and amylase, pH, concentrations (mg/mL) of total amino acid (TAA) and 13 AA (excluding Pro, Cys, and Glu), and hydrolysis rates in casein or soybean protein concentrate were greater (P < 0.05), whereas MWD of protein from 19 to 23 kDa was lower (P < 0.05) in the SIF of yellow compared to white-feathered broilers fed diet 1. Furthermore, activities of chymotrypsin and amylase, concentrations of Na+, and Cl−, MWD of protein from 15 to 18 kDa were greater, while concentrations of K+ were lower in the SIF of yellow-feathered broilers fed diet 2 compared to white feathered broilers fed diet 1. Activities of chymotrypsin and amylase, K+ concentration, pH, TAA and 13 AA (excluding Pro, Cys, and Glu), hydrolysis rates in casein or soybean protein concentrate increased (P < 0.05), while concentrations of Na+ and Cl− (P < 0.05) decreased with dietary CP in SIF from yellow-feathered broilers. This experiment demonstrated diet composition and breed modulate digestive enzyme activities, ions (Na+, K+, Cl−), pH, and AA concentrations in the SIF. Our findings revealed no substantial difference in the hydrolytic characteristics of SIF from white-feathered broilers fed diet 1 and yellow-feathered broilers fed diet 2. Consequently, it is feasible to use digestive enzymes extracted from the SIF of yellow-feathered broilers to prepare simulated SIF for in vitro digestion of white-feathered broilers.

Effects of cooking and market classes on nutritional and antioxidant properties of dry bean flours and soluble dietary fiber-rich fractions

Dry beans are a rich source of proteins, starch, dietary fiber, and phenolic compounds, thus exhibiting potential health benefits. Fractionating dry beans, especially soluble dietary fiber (SDF), could be considered a valuable functional food ingredient. This study investigated the effects of pinto and black dry bean market classes and atmospheric pressure cooking on the physicochemical attributes of dry bean flours and the extraction and characterization of SDF-rich fractions. Cooking significantly (p < 0.05) increased the dietary fiber content, altering the macronutrient profile. Raw flours exhibited higher levels of extractable phenols and antioxidant capacity, while cooked flours had more hydrolyzable phenols and associated antioxidant activities. Pinto beans were found to have higher levels of slowly digestible starch (23.76%) and resistant starch (5.24%) compared to black beans (20.63% and 3.22%, respectively). The SDF-rich fraction from cooked flours showed a reduced residual protein content and included pectic polysaccharides, hemicelluloses, and raffinose family oligosaccharides (RFOs), with cooking affecting their molecular weight distribution. These fractions demonstrated shear-thinning behavior and temperature-dependent viscosity. The study highlights the significant influence of market class and cooking process on the nutritional and antioxidant properties of dry beans, suggesting their potential contributions to dietary health.

Effect of ultrasound and enzymatic pre-treatments on the profile of bioactive peptides of beef liver hydrolysates

The use of meat by-products as a potential source of protein hydrolysates rich in bioactive peptides is of growing interest to valorise these products and improve their sustainable use. This study aimed to evaluate the effect of different pre-treatments (hydrolysis with pepsin, ultrasounds, and ultrasounds-assisted pepsin hydrolysis) on the peptide profile and bioactivity of beef liver hydrolysed with flavourzyme. The pre-treatments with pepsin increased the degree of hydrolysis and generation of free amino acids in the liver hydrolysates, whereas the subsequent hydrolysis with flavourzyme influenced the molecular weight distribution of the peptides. Samples pre-treated with pepsin and ultrasounds-assisted pepsin hydrolysates showed the highest values of antioxidant and inhibitory activity of ACE-I, ECE-I, DPP-IV, and neprilysin enzymes, and therefore these hydrolysates were characterised to obtain the bioactive peptide profiles. A total of 995 peptides were identified by tandem mass spectrometry in the most active fractions separated by reversed-phase liquid chromatography, and 20 of them were predicted as potentially responsible for the observed bioactivities and subsequently characterised by in silico tools. These results evidenced the potential of hydrolysis pre-treatments with pepsin and ultrasounds-assisted pepsin to obtain beef liver hydrolysates rich in bioactive peptides that could exert multifunctional bioactivities such as antioxidant, antihypertensive, and antidiabetic, while giving added value to this meat by-product.

Synthesis of grafted copolymers of cod collagen and acrylamides in the presence of alkylborane – p-quinone system

The graft polymerization of acrylamide and N-isopropylacrylamide onto collagen in the presence of triethylborohexamethylenediamine complex and a number of p-quinones, including benzoquinone, naphthoquinone, 2,5-di-tretbutyl-p-benzoquinone, and duroquinone, was studied. In all cases, p-quinones act as polymerization retarders, reducing monomer conversion. An exception is the graft polymerization of acrylamide onto collagen in the presence of benzoquinone, which acts as a polymerization inhibitor. The proportion of the synthetic fragment in the obtained copolymers is determined by the structure of the monomer and p-quinone. The molecular weight distribution curves contain modes related to unreacted collagen, which differ significantly from those of the initial collagen in terms of intensity. This is related to the formation of a grafted copolymer of cross-linked structure, which cannot be analyzed by gel permeation chromatography. The degradation of copolymers under the action of enzymes was controlled by gel permeation chromatography. Enzymatic hydrolysis of copolymers proceeds slower than that of collagen, which confirms the formation of a copolymer. Following three hours after the onset of hydrolysis, the molecular weight distribution curves contain low-molecular weight modes of collagen and low-intensity modes related to polyacrylamide. The morphology of copolymers differs from that of collagen and polyacrylamides. Cytotoxicity evaluation of copolymers is an important research stage, determining their prospects as the basis of materials for regenerative medicine. An analysis of extracts obtained from the copolymers using culture medium by MTT assay showed a high rank of their toxicity, which can be reduced by dilution of collagen and N-isopropylacrylamide copolymer extracts with aqueous solutions. For the copolymers of collagen and acrylamide, the toxicity is maintained due to the high toxicity of the monomer. Their toxicity can be reduced by extraction of unreacted acrylamide with chloroform.

Biochemical composition of biological substances extracted from red deer antlers

We aim to study biologically active agents in biological substances obtained from different parts of red deer antlers. Frozen red deer antlers were separated into skin and antler base, crushed, and subjected to ultrasonic enzymatic hydrolysis. The press cake from the extraction of antler base was dried in a vacuum unit. The content of protein, fat, ash, and moisture in the obtained biological substances was studied. In addition, the amino acid, fatty acid, and mineral compositions were analyzed, as well as the molecular weight distribution of peptide fractions. The concentrates from the skin and base of red deer antlers were found to contain the maximum of proteins (73.68–74.41%). The mineral biological substances comprise the maximum of macroand microelements (84.17%), in particular, a high level of 136,000 mg /kg of phosphorus, 29,230 mg /kg of sodium, and 5,140 mg /kg of calcium. All biological substances are characterized by a low-fat content in the range from 0.3 to 1.76%. Similar to the protein content, the total amount of amino acids prevails in concentrates from the skin and base of red deer antlers, equaling 40.90 and 43.66 g /100 g, respectively. Moreover, in both samples, the amount of essential amino acids is higher than that of non-essential ones. The amount of vitamins is low, being represented by B1, B2, B6 water-soluble vitamins. The fatty acid composition is most balanced in the concentrate from the red deer antler base, containing omega-3 and omega-6. The ratio of unsaturated to saturated fatty acids is equal to 0.96. In the concentrate from antler skin, the maximum content (54.7%) of peptides with a low molecular weight of less than 2.9 kDa and up to 6.4 kDa was found using the molecular-weight distribution of peptide fractions.

Exploring the potential of taro (Colocasia esculenta) starch: Recent developments in modification, health benefits, and food industry applications

AbstractTaro is a tropical plant and an underutilized root crop that has a good source of carbohydrate. Taro tuber contains 70%–80% of starch on dry basis. This review highlights the extraction of taro starch, latest advancements in the modification such as physical, chemical and enzymatic modification of taro starch. Furthermore, after modification of taro starch, molecular weight and amylopectin branch chain length distribution, granular shape, percentage crystallinity, swelling and solubilization, pasting and thermal properties and in vitro digestibility of taro starch were significantly affected. Additionally, researchers have explored novel methods to modify the physicochemical characteristics of taro starch, enhancing its functionality as a thickening, gelling, and stabilizing agent in various food formulations. However, fabrication of nanoparticles from taro starch was also studies. Various health benefits of taro starch have been reported in this study. One significant health benefit of taro starch is its potential to improve blood sugar management. Furthermore, the versatility of taro starch in food applications has expanded, ranging from traditional staples to modern convenience foods. Its gluten‐free nature makes it an attractive option for individuals with gluten sensitivity or celiac disease. Taro starch is increasingly incorporated into bakery products, snacks, noodles, and as a thickening agent in soups and sauces. The unique sensory attributes and nutritional profile of taro starch contribute to the development of novel, health‐conscious food products that cater to evolving consumer preferences.

Multiscale modeling and experimental study of molecular weight distribution and monomeric ratio in PHA production

While plastics have brought considerable convenience to our daily lives, most of them are still made up of petroleum-based materials. The plastic production industry accounts for a substantial portion of greenhouse gas emissions, and these products cause serious environmental pollution due to their poor degradability. Hence, bio-derived polymers have gained much research interest to substitute the existing plastic materials. Among them, polyhydroxyalkanoates (PHAs) are regarded as the most promising candidate owing to their biocompatible and biodegradable nature. In particular, poly(3-hydroxybutyrate-co-4-hydroxybutyrate), P(3HB-co-4HB) is now in the limelight for its unique mechanical properties. However, understanding the sophisticated mechanism and structure is quite challenging, posing obstacles to its successful commercialization. In response to this difficulty, we devised a multiscale model using the kinetic Monte Carlo (kMC) algorithm to enable capturing the extensive characteristics of PHA, including molecular weight distribution and monomeric ratio. Considering the different time and length scales of the overall process, the model is developed with two layers for the fermentation and polymerization reactions, and they are successfully integrated. The results not only validate the experimental results but also showcase a wide range of PHA information that cannot be measured through instrumental analyses.

Biodegradation mechanism of asphalt by microbial consortia in asphalt pavement of forest area road

To study the degradation behaviors of asphalt by microorganisms and reveal biodegradation mechanism of asphalt, 16S rRNA full-length sequencing was utilized to analyze the collected samples from three forest areas. Five strains, namely Sphingomonas polyaromaticivorans, Pseudomonas putida, Pseudomonas fluorescens, Bacillus cereus, and Bacillus subtilis, were selected for compounding microbial consortium to study its degradation effects on asphalt. The micromorphology, elemental chemical states, micromechanical properties, molecular weight distribution, and functional groups of degraded asphalt were studied using environmental scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, gel permeation chromatography, and Fourier transform infrared spectroscopy. The results show that the biodegradation of asphalt by microbial consortium increases the surface roughness of asphalt and reduces surface adhesion. Asphalt is used as the sole carbon source by microbial consortium, resulting in a continuous decrease in the contents of C and N elements, while the content of O element is continuously increased. Simultaneously, under the action of microbial enzymes, C-C/C-H bonds which are combined with molecular oxygen in asphalt are continuously broken and converted to C-O-C/C-O-H bonds. The continuous reductions in methylene index and butadiene index of asphalt, as well as the production of carbonyl functional groups confirm the oxidative degradation of asphalt by microbial consortium. Additionally, with the extension of degradation time, the large molecular substances in asphalt are gradually degraded by microbial consortium, leading to a more concentrated molecular weight distribution. This study is of great importance to understand biodegradation mechanism of asphalt.

HUMIC ACIDS: PROPERTIES, STRUCTURE, AND APPLICATION

Humic substances (HSs) are a diverse class of natural compounds with no fixed chemical composition, formed from plant and microbial residues through the action of environmental factors and living organisms over many years. Despite extensive research spanning two centuries, the complex and variable nature of HSs' structure remains a subject of scientific inquiry. These substances, notably humic acids, fulvic acids, and humin, play crucial roles in ecological and environmental processes due to their abundant functional groups and resilience to biodegradation. This review explores the intricate structure and properties of HSs, their classification, and their occurrence in nature. It highlights the different models proposed to describe the structural fragments of humic acids, emphasizing their aromatic cores and diverse functional groups. The variability in the molecular weight distribution of HSs, attributed to their polydisperse nature, is also discussed, along with methods used for their determination, such as exclusion chromatography. Furthermore, the elemental and functional compositions of humic acids are examined, detailing their acid-base properties and capacity for heavy metal complexation. The synthesis of HSs from natural sources, such as soil, peat, coal, and artificial processes, is covered, showcasing methods like alkaline extraction and hydrothermal treatment. Recent advancements in artificial humification, including oxidative ammonolysis and Fenton reagent-based oxidation, are reviewed for their potential in producing environmentally friendly humic materials from lignin and waste biomass. The study concludes by underscoring the environmental significance and practical applications of HSs, particularly in agriculture, soil conditioning, and environmental remediation. The diverse properties and synthesis methods of HSs make them promising candidates for sustainable material production and environmental management. Humic acids are versatile compounds beneficial for human health due to their potent antioxidant properties, immune-modulating effects, and support for gastrointestinal health and detoxification. Structurally diverse, they feature groups like carboxyl, phenolic hydroxyl, quinones, ketonic carbonyls, amino, and sulfhydryl, contributing to their stability and amphiphilic nature. In pharmaceutical applications, they show promise for drug delivery, antioxidant therapies, wound healing, antimicrobial actions, and biofilm disruption, underlining their biocompatibility and safety. Key words:

Recent Advances in Propylene-Based Elastomers Polymerized by Homogeneous Catalysts.

Propylene-based elastomers (PBEs) have received widespread attention and research in recent years due to their structural diversity and excellent properties, and are also an important area for leading chemical companies to compete for layout, but efficient synthesis of PBEs remains challenging. In this paper, we review the development of PBEs and categorize them into three types, grounded in their unique chain structures, including homopolymer propylene-based elastomers (hPBEs), random copolymer propylene-based elastomers (rPBEs), and block copolymer propylene-based elastomers (bPBEs). The successful synthesis of these diverse PBEs is largely credited to the relentless innovative advancements in homogeneous catalysts (metallocene catalysts, constrained geometry catalysts, and non-metallocene catalysts). Consequently, we summarize the catalytic performance of various homogeneous catalysts employed in PBE synthesis and delve into their effect on molecular weight, molecular weight distribution, and chain structures of the resulting PBEs. In the end, based on the current academic research and industrialization status of PBEs, an outlook on potential future research directions for PBEs is provided.

Hofmeister ion effects induced by different acidifiers and alkalizers improve the techno-functional properties of complex rapeseed protein during pH-driven self-assembly

pH-driven method is an effective strategy to prepare complex protein. This study provides guidance on how to select acidifiers and alkalizers from view of Hofmeister ion effects. Cations and anions regulated the molecular structure (particle size, surface charge, protein folding/unfolding, structural orderliness) of complex rapeseed proteins (CRPs) mainly via electrostatic and hydrogen bond. No evident changes were found in the molecular weight distribution, but their distribution on oil/air-water interface varied greatly. Various techno-functional properties of CRPs were synergistically improved: Citrate3− and Na+ increased the emulsifying activity index of CRPs from 80 to 102.21 m2/g; Citrate3−, K+ and Na+ made the foaming stability of CRPs close to 80 % after 60 min of storage. Moreover, the oil/water-holding and gel properties of CRPs were regulated effectively. These findings demonstrate the key role of Hofmeister ion effects in improving CRPs properties, contributing to develop, select, and apply novel acidifiers and alkalizers during pH-driven treatment.

Faster and greater moisture curing ethylene‐silane copolymers with good shelf stabilities

AbstractVinyltrimethoxysilane (VTMS) functionalized ethylenic polymers, in the form of reactor‐made ethylene‐silane copolymers as well as post‐reactor made silane‐grafted ethylene polymers, were evaluated for the purpose of moisture‐induced crosslinking through hydrolysis and condensation reactions. The copolymers were of 1.6 wt% or 4.2 wt% VTMS contents, and the silane‐grafted resins ranged in VTMS contents from 1.1 to 3.7 wt%. The silane‐grafted materials were very reactive under humid conditions at room temperature, resulting in very poor shelf stabilities manifested in sharp drops in their melt indices over time (changes that in the early stages were dominated mostly by resin molecular weight distribution and/or branching, and in the later stages much more by silane content). In sharp contrast, the ethylene‐silane copolymers exhibited outstanding shelf stabilities over time even at relatively high silane content, indicating desirably low reactivities in the absence of moisture‐cure catalyst. When formulated with catalyst, and exposed to humid conditions, the cure characteristics of the silane functionalized ethylene polymers varied significantly, with the fastest and greatest crosslinking observed using the ethylene‐silane copolymer of 4.2 wt% VTMS content and remarkably excellent shelf stability. Analyses of reaction rates revealed very interesting trends, depending on type of catalyst (tin or sulfonic acid) and resin.Highlights Ethylene‐silane copolymers and silane‐grafted ethylene polymers were studied. Copolymers exhibited vastly superior shelf stabilities than grafted materials. Catalyst type and loading affected moisture‐induced crosslinkability. Increased silane content in copolymer led to faster and greater crosslinking. Best balance of crosslinkability and shelf stability obtained with copolymers.

Optimizing alginate extraction using Box-Behnken design: Improving yield and antioxidant properties through ultrasound-assisted citric acid extraction

The Box-Behnken Design was employed to optimize the extraction of alginate (ALG) from Sargassum cymosum C. Agardh using ultrasound-assisted treatment and substituting hydrochloric acid with citric acid during the acidic step. The study aimed to maximize yield and enhance the functional properties of the polysaccharide. The effects of pH of the citric acid (CA) solution, ultrasound power, and treatment time were evaluated in terms of yield, viscosity-average molecular weight (Mw), dynamic viscosity (µdyn), and antioxidant capacity (AC) of the ALG. The optimized conditions (176 W, 15 min, pH 1) resulted in a yield of 54.20 %, Mw of 202.56 kDa, µdyn of 10.43 mPa•s, and AC of 80.81 µM Trolox g-1. The lowest pH was found to be optimal for enhancing alginate extraction efficiency and improving its properties (viscosity and antioxidant capacity). Under optimized conditions, the CA solution resulted in a higher ALG yield with minimal changes in Mw and µdyn, while also retaining the main functional groups and chemical bonds, and doubling the AC compared to hydrochloric acid. The results indicate that ultrasound-assisted extraction is a promising method for extracting alginate from brown algae and that CA can satisfactorily replace the conventional solvent used in the acidic treatment.

Storage-induced changes in β-strand interactions within bovine lactoferrin powder analyzed through X-ray diffraction

Bovine lactoferrin (bLF) is a multifunctional protein used in the food and pharmaceutical industries. Various commercially available bLF powders (bLFPs) have different ratios of protein monomers to aggregates, which affects the aggregation rate. However, the changes in molecular structure and interactions during aggregation are unclear. This study investigated changes in the structure and interactions of stored bLFPs during aggregation. Five commercially available bLFPs with different molecular weight distributions were analyzed before and after storage using size-exclusion chromatography and X-ray diffraction (XRD) to monitor aggregation and β-strand interaction, respectively. These bLFPs were stored for four weeks under high temperature and humidity conditions as a stress test. The XRD results revealed changes in peak II (around 2θ = 20°), corresponding to β-strand interactions. The peak II change rate suggested that the aggregation occurs due to partial structural fluctuations and interaction changes. Furthermore, time-course analysis of peak II and correlations with the pre-storage monomer ratio and aggregation phase index demonstrated that β-strand interactions decreased during the transformation of monomers to low-molecular-weight (LMW) aggregates, while it increased during the LMW-to-high-molecular-weight aggregate phase. These results provide novel insights into the conformational changes and molecular interactions of bLFPs during aggregation.

Extraction and characterisation of gelatine from yellowfin tuna skin pretreated with a eutectic solvent

The accumulation and management of waste generated during the processing of seafood products is one of the major current challenges in the fishery industry. Among these residues, fish skin stands out for its high collagen content, from which high-quality gelatine can be obtained. However, conventional methods for gelatine extraction are time-consuming and complex processes that involve the use of strong acidic and alkaline solutions, leading to serious environmental concerns. This research studied the use of a eutectic solvent, formed by two safe and environmentally friendly compounds such as sodium acetate trihydrate and urea, to pretreat the skin of yellowfin tuna before the extraction of gelatine. Two different times of pretreatment were tested, and the subsequent extraction was carried out in warm water, resulting in much higher yields of gelatine (0.3 g/g wet fish skin) than previous studies. Additionally, using FT-IR analysis and amino acid profiling, it was observed that the pretreatment time did not significantly affect the structure or composition of the gelatine. However, some variation was found in its molecular weight distribution and therefore in its rheological properties: with an increase in the pretreatment time, both the molecular weight and the storage modulus of the gel also increased, as well as the gelation and melting temperatures. This contribution offers a simplified process that reduces environmental impact and provides the opportunity to tailor the final product.

Miktoarm Star-polypept(o)ide-Based Polyion Complex Micelles for the Delivery of Large Nucleic Acids.

Miktoarm star polymers exhibit a captivating range of physicochemical properties, setting them apart from their linear counterparts. This study devised a synthetic pathway to synthesize cationic miktoarm stars utilizing polypept(o)ides (PeptoMiktoStars), comprising 3 or 6 polysarcosine (pSar) arms (AB3×100, AB6×50, overall 300) for shielding and a cross-linkable poly(S-ethylsulfonyl-l-homocysteine) (pHcy(SO2Et)20) block and a poly(l-lysine) ((pLys)20) block for nucleic acid complexation. Precise control over the DPn and narrow molecular weight distributions (D̵ ≈ 1.2) were achieved for both structures. Both PeptoMiktoStars efficiently complexed mRNA and pDNA into polyion complex micelles (PICMs). AB6-PICMs provided modest (mRNA) to high (pDNA) stability against glutathione and heparin sulfate (HS), while even cross-linked AB3-PICMs were susceptible to HS. All PICMs delivered pDNA and mRNA into D1 cells (over 80%) and Jurkat T cells (over 50%) in vitro. Despite payload- and cell-dependency, AB3 showed overall higher transfection efficiency, while AB6 demonstrated better shielding and enhanced stability.

Silver-Mediated ARGET-ATRP of Reactive Acrylates Using TPMANMe2 Ligand: A Universal Strategy for Controlled Copolymerization.

A controlled polymerization using activated acrylate monomers via ARGET-ATRP is developed with a tris[(4-dimethylamino pyridyl)methyl]amine ligand to address issues with weaker ligands and monomers that can undergo postpolymerization functionalization. This catalyst system enables the polymerization of N-acryloxy succinimide, fluorinated monomers, and isocyanato ethyl acrylate under controlled homogeneous conditions, ensuring linear molecular-weight growth and low polydispersity. Two block copolymerization strategies produce amphiphilic copolymers with narrow molecular-weight distributions and customizable compositions, allowing for various postpolymerization functionalizations.

Living anionic copolymerization of 1,3-pentadiene isomers with alpha-methylstyrene in the presence of 2,2-di(2-tetrahydrofuryl)propane

The synthesis of statistical copolymers of alpha-methylstyrene (AMS) and 1,3-pentadiene (PD) isomers in the presence of 2,2-di(2-tetrahydrofuryl)propane (DTHFP) by living carbanionic polymerization was investigated in this paper. To the best of our knowledge, either AMS or PD monomer was rather difficult to homopolymerize in non-polar solvents without the help of polar additives even at high temperature due to its low ceiling temperature or relatively high electron cloud density of the conjugated CC double bond. However, the combination of RLi initiator and DTHFP regulator (0.1<DTHFP/Li < 0.5) allowed the rapid synthesis of the well-defined poly(AMS-stat-PD) with controlled molar masses (up to 32.5 kDa) and relatively narrow molecular weight distributions (1.10 < ĐMs < 1.52). Calculation of reactivity ratios by the Kelen–Tüdos method suggested that AMS copolymerized much more readily to with (Z)-1,3-pentadiene (ZP) than with (E)-1,3-pentadiene (EP) under the same conditions, whereas the EP/AMS copolymer exhibited much lower dispersity. 1H NMR results indicated that the polymer chain was found to be a mixture of 1,2-addition and 1,4-addition units, in the absence of 3,4-units. Kinetic experiments also showed that the apparent activation energy of EP/AMS copolymerization was slightly higher than that of the ZP/AMS case. To ensure complete conversion of the monomer, the feed ratio of AMS (fAMS) must be controlled to be within 0.3. In addition, the incorporation rate of AMS into the polymer chain increased with the increase in the feed ratio of AMS monomer. DSC curves showed that the Tg of the resulting copolymers increased gradually and could reach up to 25 °C (FAMS = 47). Based on the observation of the anionic statistical copolymerization behavior, an interpretation of the formation mechanism is presented here.

Removal of refractory humic acid-like components from UF filtrate of landfill leachate through pH adjustment and coupled electrochemical process

Mature landfill leachate contains large quantities of a wide range of hazardous and refractory pollutants, especially humic acid-like (HA) and fulvic acid-like (FA) substances. These have poor biodegradability and a considerable ultraviolet-light quenching capacity, severely inhibiting the performance of wastewater treatment and post ultraviolet-light disinfection, but this aspect has attracted little previous research. The Fenton reaction has proved to be a feasible method for removing ultraviolet-quenching substances (UVQSs) but in conventional systems it is unable to completely mineralize organic contaminants. In this study, a novel electro-oxidation process was developed consisting of a flow-through reactor with a Cu2O cathode to catalyze Fenton-type reactions, and oxidation at a RuO2 anode. The combination of pH adjustment and electro-oxidation was evaluated for the treatment of real ultrafiltration (UF) filtrate of mature landfill leachate. A series of analytical techniques were used to determine the performance for the removal of HA and FA. Under optimal conditions, the elimination of fluorescence characteristics of HA and FA reached 100 % and 99.3 %, respectively, according to PARAFAC results based on EEM spectra. TOC was removed by 25.5 %∼30.4 % during the pH adjustment step and 51 % by electrochemical oxidation. Changes in the molecular weight distribution and fluorescence content showed that pH adjustment played an important and significant role in removing UVQSs, and the remaining TOC after electrochemical oxidation was attributed to bioavailable amino acid-like substances. Overall, the results have demonstrated the successful development of an effective method of treating the UF filtrate from mature landfill leachate, with particular respect to the removal of the problematic HA and FA content.