Chain Molecular Weight Research Articles

End-To-End FRET Enabling Direct Measurement of Oligomer Chain Conformations and Molecular Weight in Reaction Solutions.

Förster resonance energy transfer (FRET) is an established tool for measuring distances between two molecules (donor and acceptor) on the nanometer scale. In the field of polymer science, the use of FRET to measure polymer end-to-end distances (Ree) often requires complex synthetic steps to label the chain ends with the FRET pair. This work reports an anthracene-functionalized chain-transfer agent for reversible addition-fragmentation chain-transfer (RAFT) polymerization, enabling the synthesized chains to be directly end-labeled with a donor and acceptor without the need for any post-polymerization functionalization. Noteworthily, this FRET method allows for chain conformation measurements of low molecular weight oligomers in situ, without any work-up steps. Using FRET to directly measure the average Ree of the oligomer chains during polymerization, the chain growth of methyl methacrylate, styrene, and methyl acrylate is investigated as a function of reaction time, including determining their degree of polymerization (DP). It is found that DP results from FRET are consistent with other established measurement methods, such as nuclear magnetic resonance (NMR) spectroscopy. Altogether, this work presents a broadly applicable and straightforward method to in situ characterize Ree of low molecular weight oligomers and their DP during reaction.

Polymer-siRNA nanovectors for treating lung inflammation.

Uncontrolled inflammation is the driver of numerous lung diseases. Current treatments, including corticosteroids and bronchodilators, can be effective. However, they often come with notable side effects. siRNA is a promising therapeutic modality for immune regulation. However, effective delivery of siRNA is challenged by issues related to cellular uptake and localization within tissues. This study investigates a series of guanidinium-functionalized polymers (Cn-Guan) designed to explore the effects of amphiphilicity on siRNA complexation and efficiency in vitro and in vivo. Nine polymers with varying side chain lengths (C3, C5, C7) and molecular weights (17 kDa, 30 kDa, 65 kDa) were synthesized, forming polyplexes with siRNA. Characterization revealed that C7-Guan/si_scr polymers exhibited the smallest polyplex sizes and the tightest complexation with siRNA. In vitro studies showed that 65 kDa polymers had the highest gene knockdown efficiency, with C3 and C5-Guan/si_TNF-α achieving ~70 % knockdown, while C7-Guan/si_TNF-α achieved ~30 %. In vivo, C7-Guan/Cy5-siRNA demonstrated the highest lung accumulation, and all polymers showed ~70 % TNF-α knockdown with a low siRNA dosage (0.14 mg/kg) in a murine lung inflammation model. C7-Guan polymers, despite lower in vitro efficiency, were quite effective in vivo, potentially due to enhanced serum stability. These findings demonstrate that Cn-Guan/siRNA polyplexes are effective and safe for attenuating pulmonary inflammation and provide important insights for the development of future siRNA delivery vectors for lung disease treatment.

Effect of KOH Concentration on Viscoelastic and Conformational Changes of Xanthan Gum-Based Hydrogel Electrolytes

Introduction Lithium-ion batteries (LIBs) are currently the most practical rechargeable batteries, but their energy density is insufficient for applications such as electric vehicles and power storage. Moreover, the safety issues for LIBs have not yet been completely resolved. Therefore, research on the development of next-generation batteries with high safety and high energy density is being promoted. Recently, aqueous rechargeable batteries using zinc as the negative electrode has attracted considerable attention because zinc has many attractive features: low standard potential (−0.76 V vs. SHE), high hydrogen overpotential, high gravimetric and volumetric theoretical capacities (820 mAh g-1, 5855 mAh cm-3), and low cost. However, for the implementation of aqueous rechargeable zinc batteries, there are some serious issues such as zinc dendrite formation, shape change and side reactions (hydrogen evolution, corrosion, passivation, etc.) at the negative electrode. We have demonstrated the effectiveness of crosslinked polyacrylate-based hydrogel electrolytes (HEs) as an alternative to aqueous alkaline solutions to improve these issues (1). We have recently become interested in physical gels in which the host polymer is cross-linked by intermolecular interactions such as hydrogen and ionic bonding, and prepared new HEs by mixing xanthan gum (XG), one of polysaccharides, as host polymer and aqueous KOH solutions. The XG-based HEs showed ionic conductivity comparable to the corresponding alkaline aqueous solutions. However, the details of the influence of the gel structure on the diffusion of zincate in the gel and the deposition and dissolution of zinc at the electrode/hydrogel electrolyte interface remain unclear. In this study, the viscoelasticity of XG-based HEs with different KOH concentrations and XG contents were evaluated to investigate how the gel structure, and in particular the conformation of XG, changes with different KOH concentrations and XG contents. Experimental HEs were prepared by mixing various concentrations of aqueous KOH solutions and XG powders with stirring. A rheometer was used to measure the viscoelasticity of the prepared HEs. In addition, structural changes in XG in the HEs were investigated by Infra-red (IR) spectroscopy and gel permeation chromatography (GPC). Results and Discussion Change in viscosity, which was measured with a rheometer, with the concentration of KOH for the HEs with 0.05, 0.1 and 0.3 g mL-1 XG is shown in Fig. 1. The XG structure consists of a β-glucan main chain with long side chains (molecular weight about 600) consisting of three molecules of monosaccharide attached in an orderly fashion. In water, XG molecules exist in a state where the individual main chains are elongated due to electrostatic repulsion between COO- groups in the side chains. In aqueous KOH solutions, as the KOH concentration increases, the negative charges of COO- groups on the side chains are shielded by the interaction with K+, reducing the electrostatic repulsion. As a result, the XG molecules become entangled, increasing viscosity. In Fig. 1, as expected, viscosity increased as KOH concentration increased up to 1 M. However, it decreased significantly above 1 M and was a minimum at 4 M. For the HE prepared by using 4 M KOH solution, GPC analysis suggested that some of the side chains were cleaved. This may cause the decrease in viscosity. When the KOH concentration was higher than 4 M, the viscosity increased again, as can be seen from Fig. 1. The analysis of IR spectra for HEs exhibited that the structure of XG molecules scarcely changed as the KOH concentration increased from 4 M to 7 M. Therefore, the increase in viscosity at KOH concentrations above 4 M is probably due to the salting out.This work is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Reference C. Iwakura, H. Murakami, S. Nohara, N. Furukawa, H. Inoue, J. Power Sources, 152, 291 (2005). Figure 1

Highly accelerated kinetic Monte Carlo models for depolymerisation systems

Kinetic Monte Carlo (kMC) models are a well-established modelling framework for the simulation of complex free-radical kinetic systems. kMC models offer the advantage of discretely monitoring every chain sequence in the system, providing full accounting of the chain molecular weight distribution. These models are marred by the necessity to simulate a minimum number of molecules, which confers significant computational burden. This paper adapts and creates a highly generalizable methodology for scaling dilute radical populations in discrete stochastic models, such as Gillespie's Stochastic Simulation Algorithm (SSA). The methodology is then applied to a kMC simulation of polystyrene (PS) pyrolysis, using a modelling framework adapted from literature. The results show that the required number of simulated molecules can be successfully reduced by up to three orders of magnitude with minimal loss of convergent behaviour, corresponding to a wall-clock simulation speed reduction of between 95.2 to 99.6 % at common pyrolysis temperatures.

Effect of high-molecular-weight glutenin subunit deletion on gluten functionality and Chinese southern-type steamed bread quality

High-molecular-weight glutenin subunit (HMW-GS) is key factor in gluten strength and end-use quality. However, the contribution of individual HMW-GS on dough strength and Chinese southern-type steamed bread (CSTSB) quality remained unknown. In this study, we investigated the effects of individual HMW-GS deletion on CSTSB quality. The HMW-GS deletion led to significant reductions in glutenin/gliadin ratios, disulfide bond content, and SDS-unextractable polymeric protein formation. Additionally, HMW-GS deletion resulted in decreased gluten protein chain length, molecular weight, and particle size, contributing to increased thermal instability and reduced crosslinking. The HMW-GS deletion weakened dough strength but improved CSTSB performance, particularly in Dx2d and Dy12d. In-silico analysis further revealed strong interactions between Bx7 and Dx2, primarily driven by desolvation energy, highlighting their crucial role in stabilizing gluten protein interactions.

Utilization of mycelial polysaccharide from Schizophyllum commune for the formation of highly stable o/w emulsion

This study investigated the emulsifying properties of a hot water extracted polysaccharide (SCMP) derived from liquid fermentation mycelium of Schizophyllum commune in stabilizing oil-in-water (o/w) emulsions. SCMP demonstrated the ability to stabilize o/w emulsions (referred to as SCMPe) for extended periods (>21 days) even at low concentrations (2 g/L) and increased the viscosity and elasticity of the emulsion system. Through confocal laser-scanning microscope visualization, it was observed that SCMP created a physical barrier on the surface of the oil droplets, contributing to emulsion stability. Furthermore, SCMPe demonstrated excellent tolerance to varying concentrations of Na+ (0.1–0.5 mol/L) and Ca2+ (0.01–0.05 mol/L) as well as a wide pH range (3.0–9.0). Moreover, increasing SCMP concentration effectively inhibited lipid oxidation and improved the stability of β-carotene and curcumin in the emulsion during storage. A detailed analysis of SCMP's composition and structure was done to better understand its emulsifier properties, revealing SCMP to be composed of two β-glucans with a rigid chain and high molecular weight. These results suggest that SCMP holds great potential an efficient stabilizer in the food industry, particularly in enhancing emulsion stability.

Detection of coconut oil adulteration with palm oil through NMR spectroscopic method

Coconut oil is a costly commodity in the food and traditional medicinal sectors and its adulteration with cheap palm oil is a serious issue. The present study evaluates the application of 1H NMR spectroscopy to authenticate coconut oil, and to monitor its adulteration with the cheap palm oil substitute. Various parameters such as average chain length (14.25), saponification index (244.66 mg KOH/100 g), molecular weight (652.12), iodine value (8.27 mg/100 g), peroxide value (0.02 meqO2/kg) and percentage of unsaturation (7.81%) were calculated through the NMR technique, and were found to be in concurrence with the values obtained from wet lab experiments. The extent of palm oil adulteration can be detected through NMR by evaluating the chemical shift values for olefinic protons. The findings have a significant impact on both the food and traditional medicine sectors, as NMR spectroscopy can replace the conventional wet lab methods as a reliable and precise method for analysis.

A recombinant amylomaltase from Thermus thermophilus STB20 can tailor the macromolecular characteristics of tapioca starch through its transglycosylation activity

Amylomaltase (AM) is a transglucosylase known for producing glucans exclusively with α-1,4 linkages, which is widely used in the industries for modification of starch. In this paper, a study was conducted to investigate both the characteristics of recombinant amylomaltase from Thermus thermophilus STB20 (TtAM) and its impact on the fine structure of tapioca starch. The TtAM showed an excellent thermostability and a high affinity for larger molecular substrates. Changes in the molecular characteristics of tapioca starch were discussed in terms of chain length distribution (CLD) and molecular weight distribution (Mw) under different enzyme dosages and reaction times. The TtAM degraded amylose, which was transferred to short side chains (DP 11-26) of amylopectin, thereby extending short side chains into longer chains (DP >26). The Mw of TtAM-treated starches initially increased and then decreased. With increasing enzyme dosage and reaction time, the TtAM facilitated hydrolysis activities, reducing the proportion of long side chains, which led to increase the dextrose equivalent (DE) value. Cycloamylose (DP 8 - 33) was generated during the modification process, reflecting a diversified range of the enzyme products, and resulting in a polymodal distribution profile in the Mw. These findings potentially broaden the utilization of TtAM in the production of starch conversion products, indicating that novel starch-based derivatives with tailor-made structures can be obtained by controlling the enzyme dosages and reaction times.

Crystallization-Induced Self-Assembly of Poly(ethylene glycol) Side Chains in Dithiol-yne-Based Comb Polymers: Side Chain Spacing and Molecular Weight Effects.

The chain architecture and topology of macromolecules impact their physical properties and final performance, including their crystallization process. In this work, comb polymers constituted by poly(ethylene glycol), PEG, side chains, and a dithiol-yne-based ring polymer backbone have been studied, focusing on the micro- and nanostructures of the system, thermal behavior, and crystallization kinetics. The designed comb system allows us to investigate the role of a ring backbone, the impact of varying the distance between two neighboring side chains, and the effect of the molecular weight of the side chain. The results reflect that the governing factor in the crystalline properties is the molar mass of the side chains and that the tethering of PEG chains to the ring backbone brings important constraints to the crystallization process, reducing the crystallinity degree and slowing down the crystallization kinetics in comparison to analogue PEG homopolymers. We demonstrate that the effect of spatial hindrance in the comb-like PEG polymers drives the morphology toward highly ordered, self-assembled, semicrystalline superstructures with either extended interdigitated chain crystals or novel (for comb polymers) interdigitated folded chain lamellar crystals. These structures depend on PEG molecular weight, the distance between neighboring tethered PEG chains, and the crystallization conditions (nonisothermal versus isothermal). This work sheds light on the role of chain architecture and topology in the structure of comb-like semicrystalline polymers.

Mechanism of the green coagulation processes on the construction of raw rubber network structure

AbstractAcid coagulation is the most traditional latex coagulation technology, but this coagulation process leads to delayed vulcanization, corrosiveness, and environmental pollution. Different coagulation processes significantly impact the raw rubber network structure, leading to differences in the properties of both raw rubber and rubber vulcanizates. Raw rubber was prepared by three acid‐free coagulation processes: freeze, microwave, and flash drying. The network density, molecular chain flexibility, molecular weight, processing fluidity, and plasticity retention of the raw rubber were characterized, and the vulcanization characteristics, viscoelasticity, mechanical properties, and dynamic mechanical properties of the cured rubber composites were investigated. Raw rubbers prepared by microwave drying and flash drying had higher crosslink density, more flexible molecular chains, larger molecular weight, and wider molecular weight distribution, thereby increasing the crosslink density of rubber vulcanizates. The crosslink density of the raw rubber prepared by microwave drying versus the acid coagulated raw rubber increased by 51% to 105.71 mol/m3, the tensile strength increased by 16% to reach 28.12 MPa, and the elastic modulus and rolling resistance under dynamic stress increased. This paper provides a new idea for analyzing the relationship between the raw rubber network structure and the properties of vulcanized rubber.Highlights Acid‐free raw rubbers are prepared by freeze, microwave, and flash drying. Coagulation processes significantly impact the raw rubber network structures. Effects of raw rubber network structures on properties are investigated. Crosslink density, plasticity retention, and tensile strength are improved.

Investigating the effects of the local environment on bottlebrush conformations using super-resolution microscopy.

The single-chain physics of bottlebrush polymers plays a key role in their macroscopic properties. Although efforts have been made to understand the behavior of single isolated bottlebrushes, studies on their behavior in crowded, application-relevant environments have been insufficient due to limitations in characterization techniques. Here, we use single-molecule localization microscopy (SMLM) to study the conformations of individual bottlebrush polymers by direct imaging. Our previous work focused on bottlebrushes in a matrix of linear polymers, where our observations suggested that their behavior was largely influenced by an entropic incompatibility between the bottlebrush side chains and the linear matrix. Instead, here we focus on systems where this effect is reduced: in solvent-swollen polymer materials and in systems entirely composed of bottlebrushes. We measure chain conformations and rigidity using persistence length (lp) as side chain molecular weight (Msc) is varied. Compared to a system of linear polymers, we observe greater flexibility of the backbone in both systems. For bottlebrushes in bottlebrush matrices, we additionally observed a scaling relationship between lp and Msc that more closely follows theoretical predictions. For the more flexible chains in both systems, we reach the edge of our resolution limit and cannot visualize the entire contour of every chain. We bypass this limitation by discussing the aspect ratios of the features within the super-resolution images.

Poly(glycidyl methacrylate) modified cellulose nanocrystals and their PBAT-based nanocomposites

Melt processing of cellulose nanocrystals (CNCs) reinforced nanocomposites is still a serious challenge due to the hydrophilic nature of CNCs and their severe agglomeration tendency within the polymer melt. In this study, chemical modification of CNC through grafting poly(glycidyl methacrylate) (PGMA) with various degrees was implemented. Wettability of the modified CNCs (mCNCs) were controlled and their structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), optical microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The nanocomposites of polybutylene adipate terephthalate (PBAT) with 3 wt% CNC and mCNC were prepared using an internal melt mixer. To differentiate the effects of CNC and PGMA molecules on the final properties of nanocomposites, PBAT/PGMA compounds were separately prepared. To confirm the chain characterization and molecular weight of the synthesized PGMAs, 1H NMR and gel permeation chromatography (GPC) analysis were conducted. Melt rheological analysis, dynamic mechanical analysis (DMA), DSC, and atomic force microscopy (AFM) were used to monitor the mCNC dispersion quality and the effect of PGMA modification in PBAT compounds. The results revealed that grafting CNC with longer PGMA considerably improved the CNCs' dispersion quality within PBAT. Such dispersion enhancement of long-chain mCNCs and interfacial interaction of PGMA and PBAT resulted in a noticeable increase in storage modulus and complex viscosity of the final nanocomposites.

Structure and microbial-modulating evaluation of a sulfhydryl-modified pectin

In this study, we synthesized a modified form of pectin know as sulfhydryl group (-SH) modified pectin (PSH) by linking cysteine's amino groups and pectin's carboxyl group through amide bonds. The -SH amounts varied from 517 μmol/g to 732 μmol/g. Pectin (PEC) modified with -SH groups showed no significant alteration in chain structure, monosaccharide composition and molecular weight. Compared to PEC, PSH had a stronger interaction with mucus, and the strength of this interaction increased with the -SH amounts. In vitro fermentation indicated that PSH was fermentable by human fecal microbiota, and the -SH modified can prolong the overall fermentation time of PEC from 48 h to 72 h, as evidenced by the variations in pH values, total sugar, molecular weight, monosaccharide consumption and short-chain fatty acids production. Furthermore, microbial analysis revealed that PSH significantly increased the abundance of Faecalibacterium and Bifidobacterium while decreasing the abundance of Klebsiella and Collinsella. These results provided a solid foundation for the potential use of -SH modified PEC as a mucoadhesive material for delivering active substances and regulating the effect of PEC on gut microbiota.

Classification of dissolution modes of partially protected poly(4-hydroxystyrene) in tetraalkylammonium hydroxide aqueous solutions

The development of high-numerical aperture exposure tools for EUV lithography is in progress. The development process (the dissolution of resist films) is the key to fine patterning. The dissolution dynamics of acidic polymers (the backbone polymers of chemically amplified resists) depend on various parameters related to molecular structures. In this study, the dissolution dynamics in tetraalkylammonium hydroxide (TAAH) aqueous solutions were classified into six classes on the basis of the frequency and impedance changes observed during the development process by a quartz crystal microbalance method. The relationship between class and physical parameters of materials was analyzed by decision tree and support vector machine methods. The feature values used were the alkyl chain length, molecular weight, and concentration of TAAH; the viscosity of the developer; and the protection ratio, molecular weight, contact angle, surface free energies of polymers, and film thickness. The classification accuracy was 0.80 for the validation data.

High-temperature creep behaviors of polybutene-1 with different chain microstructure and molecular weight

The creep resistance of polymer determines the dimensional stability of product under stress. The isotactic polybutene-1 (iPB) with outstanding high-temperature creep resistance and stress-crack resistance is applied widely in the field of hot-water pipes. Although the chain information including weight-average molecular weight (Mw) and aggregate structures of isotactic polybutene-1 (iPB) influence the creep resistance, the crucial factor affecting the creep behavior greatly is unclear. In this work, a series PB samples with varied Mw, isotacticity and configurational sequence were synthesized and characterized based on Gel Permeation Chromatography (GPC), solvent fractionation and Nuclear Magnetic Resonance Spectroscopy (NMR). The Differential Scanning Calorimetry (DSC), Wide-angle X-ray diffraction (WAXD) and Small angle X-ray scattering (SAXS) were used to characterize the aggregation structures of PB samples. The stress-strain behaviors and 95 °C creep deformation of these PB samples were testes by tensile test and Dynamic Mechanical Analysis (DMA), respectively. It was found that these PB samples showed different chain microstructures like 88–99 wt% high isotactic PB (HiPB) fractions, 90–97.6 mol% tetra-meso placements (mmmm) in HiPB fraction, and 50 × 104-160 × 104Mw. Increasing the molecular weight, isotacticity or configurational sequence mmmm enhanced the creep resistance of PB, while mmmm configurational sequence played more important role in creep resistance of PB through adjusting the aggregation structure (crystalline domains) of the final product greatly. Exploring the influencing factors of creep resistance provided guidance for the synthesis of high-performance PB for high-temperature pipe application.

Removal of per- and polyfluoroalkyl substances by nanofiltration: Effect of molecular structure and coexisting natural organic matter

This study investigates the removal efficiency of anionic, cationic, and zwitterionic per- and polyfluoroalkyl substances (PFAS) by nanofiltration (NF) in the presence of three representative natural organic matter (NOM) types: bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA). In particular, effects of PFAS molecular structure and coexisting NOM on the transmission and adsorption efficiency of PFAS during NF treatment were analyzed. The results indicate that NOM types dominate membrane fouling behavior despite the coexistence of PFAS. SA exhibits the most significant fouling propensity, resulting in maximum water flux decline. NF effectively removed both ether and precursor PFAS. The effects of the three typical NOM on the membrane-passing behavior of PFAS were consistent for all PFAS investigated. Generally, PFAS transmission decreased in the order of SA-fouled > pristine > HA-fouled > BSA-fouled, indicating that the presence of HA and BSA enhanced PFAS removal while SA declined. Furthermore, reduced PFAS transmission was observed with increased perfluorocarbon chain length or molecular weight (MW), regardless of the presence or type of the NOM. The impacts of NOM on PFAS filtration diminished when the PFAS van der Waals radius was > 4.0 Å, MW > 500 Da, polarization > 20 Å, or LogKow > 3. These findings suggest that both steric repulsion and hydrophobic interactions, especially the former, play important roles in PFAS rejection by NF. This study provides insights into the specific applicability and performance of membrane-based processes for eliminating PFAS during drinking and wastewater treatments, and highlighting the importance of coexisting NOM.

Flowability, Strength, and Water Absorption of Mortars Containing Fly Ash and WRA Having Varying Main Chain Lengths

Within the scope of this study, the effect of the main chain length of polycarboxylate-based water-reducing admixture (WRA) on the fresh properties, compressive strength, and water absorption of mortar mixtures containing fly ash was investigated. Three WRAs with the same structure but different main chain lengths and resultantly different molecular weights were used. Effects of the admixtures on the properties of cementitious systems with 0, 15, 30, and 45 wt.% fly ash were investigated. Irrespective of the fly ash substitution level, the fluidity of the mixtures was improved when the admixture main chain length was increased up to a certain level. Possibly beyond a certain main chain length, the entanglement of too large main chains of the polymer to each other reduced the electrostatic effect of the polymer. Thus, the flow properties of the mixtures were affected negatively. The side chain molecular weight (length) of the admixtures was fixed (2,400 g/mol). However, the molecular weight of the admixtures was adjusted as 24, 48, and 71 kg/mol by changing the main chain length of the polymer. The admixture with 48 kg/mol molecular weight showed the best performance in terms of mortar fresh properties. However, the change in the length of the main chain of admixture did not have a considerable effect on the compressive strength and water absorption of the mortar. In addition, apart from the WRA admixture property, time-dependent flow and permeation properties of the mixtures were affected negatively by the increase in fly ash substitution level.

Simulating Stress-Strain Behavior by Using Individual Chains: Uniaxial Deformation of Amorphous Cis- and Trans-1,4-Polybutadiene.

This work develops a probability-based numerical method for quantifying mechanical properties of non-Gaussian chains subject to uniaxial deformation, with the intention of being able to incorporate polymer-polymer and polymer-filler interactions. The numerical method arises from a probabilistic approach for evaluating the elastic free energy change of chain end-to-end vectors under deformation. The elastic free energy change, force, and stress computed by applying the numerical method to uniaxial deformation of an ensemble of Gaussian chains were in excellent agreement with analytical solutions that were obtained with a Gaussian chain model. Next, the method was applied to configurations of cis- and trans-1,4-polybutadiene chains of various molecular weights that were generated under unperturbed conditions over a range of temperatures with a Rotational Isomeric State (RIS) approach in previous work (Polymer2015, 62, 129-138). Forces and stresses increased with deformation, and further dependences on chain molecular weight and temperature were confirmed. Compression forces normal to the imposed deformation were much larger than tension forces on chains. Smaller molecular weight chains represent the equivalent of a much more tightly cross-linked network, resulting in greater moduli than larger chains. Young's moduli computed from the coarse-grained numerical model were in good agreement with experimental results.

Compatibilized PC/ABS blends from solvent recycled PC and ABS polymers from electronic equipment waste

This study encompasses the development of high-performance PC/ABS blends utilizing recycled PC (r-PC) and recycled ABS (r-ABS) polymers from waste electric and electronic equipment (WEEE) fractions heavily contaminated by flame retardants (FRs). Upgrading of mechanical properties was facilitated by addition of virgin ABS and additives. In total three different WEEE fractions -containing high concentrations of bromine, chloride and phosphorous were purified from polymers other than PC and decontaminated from halogenated contaminants by dissolution-precipitation CreaSolv® Process. In two studied cases the WEEE fractions were optically pre-sorted for PC before purification and decontamination. Gas chromatography (GC-ECD) and X-ray fluorescence (XRF) analyses were performed to validate efficient removal of contaminants from r-PC.The targeted mechanical properties of polymers to upgrade are notched impact strength and elastic moduli. Upgrading was achieved by using the suitable compatibilizers, and, optionally by a chain extender. First, small-scale laboratory screening test series were conducted for three compatibilizers and different ABS polymers based on micro-compounding experiments. Upscaling test series based on the pre-screening data was then organized on a conventional bench scale twin-screw extruder.SEM microstructural characterizations of the blend morphology and fractured surfaces are done to correlate structure to the mechanical properties.Dynamic mechanical analysis (DMA) and Rheological Dynamic Analysis (RDA) and Gel permeation chromatography (GPC) provided some insight to the chain branching and molecular weight distribution of r-PC, respectively. Moreover, melt rheology and solid-state mechanical properties of the compatibilized r-PC/ABS blend were thoroughly investigated.Addition of virgin ABS polymer and a suitable compatibilizer enhance the properties of the recycled PC/ABS 60/40 blends towards virgin-like, allowing easily >55% r-PC content, or in favourable cases much higher than 75% recycled polymer content when applying significant concentration of recycled ABS from CreaSolv® together with some virgin ABS.

Rheological properties of wheat dough mediated by low-sodium salt

To clarify the correlations between dough rheology and gluten aggregation, the rheological properties of low-sodium salt dough, the molecular chain morphology, molecular weight, subunit distribution and molecular conformation of dough gluten were investigated in this paper, and these results were compared with those of NaCl and KCl alone. Results showed that hardness, extensibility and compression resistance of low-sodium salt dough were enhanced, and the doughs were more like viscoelastic solid material. Atomic force microscopy images showed that low-sodium salt induced the combination of gluten peaks to form the larger protein clusters. Size exclusion/reversed phase-high performance liquid chromatography profiles suggested that low-sodium salt increased the content of B/C-low molecular weight glutenin subunits and high molecular weight glutenin subunits by reducing the content of α- and γ-gliadin, and mediated gluten aggregation to a certain degree. Besides, fluorescence spectra demonstrated low-sodium salt changed the conformation of gluten molecules. In summary, the improvement of rheological properties of low-sodium salt dough could be caused by the aggregation of low-sodium salt and dough gluten. Correlation analysis revealed that rheological properties of low-sodium salt doughs were highly related to the content of gliadin and glutenin fractions. NaCl and KCl also presented similar effects. Among the three salts, NaCl had the most prominent effect, followed by low-sodium salt. This study provides new insights and more comprehensive theoretical basis for sodium reduction.