Long Molecular Chains Research Articles

On the mechanism of Ca(OH)2 structure modulation by surfactants: Experimental and calculative studies

Surfactants are widely used for structure modulation of calcium-based materials. However, the modification mechanisms underlying the CaO digestion improved by surfactants for Ca(OH)2 production remain unclear. This study employed experiment methods, Density Functional Theory (DFT), and Molecular Dynamics methods (MD) to reveal the mechanism of surfactant modulation at a molecular level. The adsorption energy of Primary Alcohol Ethoxylate (AEO), Sodium Dodecyl Sulfate (SDS), H2O, and Dodecyl Trimethyl Ammonium Bromide (DTAB) on CaO(001) surface were −52.62, −51.98, –23.79, and 3.96 kcal/mol, respectively. The strong chemisorption of AEO and SDS on the surface of CaO improved its structure stability. AEO and SDS weakened the diffusion of H2O to CaO surface, thus causing the reaction between CaO and H2O to be suppressed. After being modulated by SDS and AEO, better crystallinity of Ca(OH)2 and finer crystalline grains were observed with the formation of developed pore structure. AEO has a longer molecular chain, giving better modification performance. On the contrary, DTAB accelerated the diffusion of H2O to CaO surface, leading to more energy released and causing the fast growth of Ca(OH)2 crystals, as evidenced by the much larger particle size compared to that of AEO and SDS. This process led to the creation of a larger pore structure. Desulfurization was used as a performance indicator to evaluate the surfactants modulation efficacy. The sulfur capacity of Ca(OH)2 regulated by 1 % AEO was 100.05 mg/g, being the highest among the used surfactants. For comparison, the sulfur capacity without additives was 49.64 mg/g. This study shows that nonionic surfactants are an ideal choice for regulating the structure of Ca(OH)2, as they can effectively inhibit crystal growth.

Polymerizable Ammonium Salt Interlayer for Efficient and Stable NiOx-Based Perovskite Solar Cells

Although the research of formal perovskite solar cells (PSCs) has achieved great breakthroughs, the use of doped small-molecule organic hole transport layers limits the improvement of stability. PSCs with an inverted form show great potential in a more stable device structure. In this paper, a NiOx/3D perovskite interface in inverted PSCs was modified with a polymerizable amine salt (2-methylallylamine hydroiodide (CTBAI)) interlayer. The double bonds contained in CTBAI thermally induced polymerization of a thin film after heat treatment, resulting in the formation of amine salts with longer molecular chains. The modified layer can improve crystallinity and reduce defects in the film, as well as optimize the interface energy level and reduce interface recombination. The efficiency of NiOx-based inverted PSCs based on the optimized interface increased from 17.0% to 18.2%. After 280 h of MPP testing, the encapsulated device tested in ambient air (RH = 50–60%) demonstrated a robust light stabilization and maintained over 93% efficiency.

Occurrence characteristics and influential factors of movable oil in nano-pores by molecular dynamics simulation

CO2-enhanced oil recovery (CO2-EOR) technology has shown great application potential in the development of tight reservoirs. Since the proportion of nano-pores in tight oil reservoirs exceeds 77%, it is necessary to further study the occurrence state of crude oil in nano-pores. In this paper, the molecular dynamics simulation was applied to study the adsorption and diffusion behaviors of multi-component crude oil in quartz (hydrophilic) nano-pores. Besides, the density discretization method was used to investigate the occurrence characteristics of crude oil, the proportion of movable fluid in nano-pores, and the effects of CO2 and polar molecules (C3H6O) on the adsorption characteristics of crude oil. The simulation results showed that the adsorption state of crude oil in the quartz nano-pores was in the form of 4 adsorption layers with a thickness of 0.45 nm each. In nano-pores, the oil molecules with longer molecular chains were more likely to aggregate and adsorb on the quartz surface. Among them, polar oil molecules have the strongest adsorption capacity on the quartz surface. Moreover, the crude oil potential energy and the self-diffusion coefficient gradually increased from the vicinity of the quartz wall and tended to be stable in the free layer. Meanwhile, the content of movable crude oil gradually augmented with the increasement of nanometer pore width and temperature. Furthermore, the pressure had little effect on the density distribution of crude oil in the pores. In contrast, the temperature had a more significant effect on the density distribution of the adsorption layer. At last, due to the more substantial adsorption capacity of CO2 on the rock surface, the crude oil adsorbed initially on the rock surface would be stripped off by CO2, converting from irreducible oil to moveable oil.

Filling of iron ore tailings into poly(vinyl chloride) based composites: Surface modification effect and performance enhancement

Filler agglomeration and poor compatibility between inorganic filler and organic matrix are key issues to affect the properties of PVC-based composites. Herein, surface treatment of iron ore tailings (IOT) was accomplished by commercially available silane and titanate coupling agents (SCA-K16M and TCA-KTTO), and the modified IOT, named S-IOT and T-IOT, were obtained correspondingly. Chemical modification of IOT by SCA-K16M and TCA-KTTO is successfully confirmed, and modification mechanism is revealed. IOT, T-IOT and S-IOT were subsequently filled into PVC matrix to prepare composites. As T-IOT and S-IOT have better dispersibility and hydrophobicity than IOT, and surface modification with coupling agent improves the inorganic-organic interface compatibility, the properties of S-IOT/PVC and T-IOT/PVC composites are better than those of IOT/PVC. In addition, TCA-KTTO has longer molecular chains and more contact sites on the surface of IOT than SCA-K16M, which makes T-IOT more evenly dispersed and closely adhered in PVC matrix. Hence, T-IOT/PVC composite exhibits the best performance. Its tensile strength, Young's modulus, and flexural strength are increased by 17%, 16%, and 13%, with a remarkable gain of 33% in notched impact strength compared to those of IOT/PVC. The co-extruded hollow floor fabricated by T-IOT/PVC composite meets Chinese standard GB/T 24508-2020.

Sorbitol-modified cellulose hydrogel electrolyte derived from wheat straws towards high-performance environmentally adaptive flexible zinc-ion batteries

Thanks to low manufacturing cost, high safety level, and competitive energy density, flexible aqueous zinc-ion batteries (AZIBs) are very promising for the emerging wearable electronics. However, AZIBs suffer from low zinc stripping/plating reversibility and poor tolerance to sub-zero temperatures. Herein, food-grade sorbitol with abundant hydroxyl groups and longer molecular chain than common cryoprotectants is used to modify cellulose hydrogel electrolyte derived from wheat straws. And concentrated ZnCl2 is utilized in this hydrogel electrolyte to realize “water-in-salt” effect. The obtained hydrogel electrolyte owns superior mechanical properties, strong adhesion, high transparency, good moldability, rich porosity, ultralow freezing point (−101.5 ℃), and large ionic conductivity (35.4 and 19.7 mS cm−1 at 20 and − 40 °C, respectively). Benefiting from excellent anti-freezing ability, tuned solvation sheath, and facilitated desolvation process within this hydrogel electrolyte, high zinc stripping/plating reversibility can be achieved from 20 to − 40 °C. And the assembled flexible Zn–polyaniline (PANI) battery delivers superior electrochemical performances even under extreme conditions. This work offers new opportunities for the development of environmentally adaptive batteries and the efficient utilization of crop straws.

Transformation behavior and fate of chlorine in polychloroprene (PCP) during its pyrolysis

Polychloroprene (PCP) rubber is mostly mixed in industrial solid waste (ISW) as the main source of chlorine element. Whereas, the products formation and chlorine behavior during the pyrolysis are insufficiently illustrated for this typical chlorinated polymer, which is not conducive to the chlorine regulation of ISW pyrolytic products. In order to investigate the chlorine transformation behavior, the PCP pyrolysis under the influence of a wide range of heating rates (3–600 °C/min) was conducted to explore the chlorine distribution properties as well as its migration mechanism in the present study. Importantly, 30–65 wt% chlorine was found to be migrated to gas and tar, respectively. Compared with PVC, the differences of chlorine distribution between PCP and PVC may be attributed to the easier cyclization with a longer molecular chain. Also, the release temperature of HCl acted as main component determines its availability for the subsequent formation of chlorinated hydrocarbons. In details, the conversion pathway from chlorinated limonene to Cl-aromatic hydrocarbons was confirmed and the reaction was found to be enhanced at higher temperature and heating rate. By analyzing the content of tar components (especially at low heating rate), it was found that the major formation pathway of aromatic hydrocarbons was supposed to be the direct Diels-Alder reaction of monomer rather than the dechlorination of intermediate chlorinated limonene. Our findings discussed the effect mechanism of heating rate and temperature on chlorine behavior during PCP pyrolysis, providing guidance for the chlorine regulation of ISW pyrolytic products.

Molecular dynamic study on mechanisms of polyvinylidene fluoride decomposition by using supercritical water

As a thermoplastic fluoropolymer, polyvinylidene fluoride (PVDF) has been widely used as a binder in lithium batteries. However, PVDF is hard to be degraded naturally. Due to the unique properties of supercritical water (SCW), SCW conversion of polymers is considered as a clean and efficient conversion technology. The effects of different reaction parameters on the decomposition of PVDF in SCW were analyzed by the molecular dynamics (MD) method. The results show that higher reaction temperature, longer reaction time, lower raw material concentration, and the addition of oxidant are more conducive to the decomposition of PVDF in SCW. In addition, the molecular structure of products, product yield, and reaction rate of PVDF in SCW under different conditions were analyzed. The decomposition path, HO2 radical formation mechanism, and F element migration path of PVDF in SCW were also studied by using the MD visualization tool. Compared with SCWO, SCWG has a lower reaction rate and the products from SCWG has a longer molecular chain. The main path for HF generation is the direct interaction between the free F atom and H atom in the water molecules.

Effect of nanosilica/metakaolin ratio on the calcium alumina silicate hydrate (C-A-S-H) formed in ternary cement pastes

Supplementary Cementitious Materials (SCM) such as Metakaolin and Nanosilica can be used in blended Portland cements to improve performance of the cement matrix. The use of these materials can also change hydrate formation, altering properties of Calcium Silicate Hydrate (C–S–H) such as chemical composition and molecular structure. The objective of this research was to study the combined effect of these SCM's in different metakaolin/nanosilica ratios forming ternary mixtures with OPC, evaluating properties of both C–S–H and overall paste. Results showed these mixtures had the highest strength values and lowest portlandite content at 28 days. Furthermore, their C-A-S-H was formed in higher content, had higher aluminum inclusion and longer molecular chains. Analyzing the results, a synergistic effect between nanosilica and metakaolin, dependent on their ratio in paste composition, was observed.

Co-Solvent Exfoliation of Hexagonal Boron Nitride: Effect of Raw Bulk Boron Nitride Size and Co-Solvent Composition.

Exfoliation of two-dimensional boron nitride nanosheets (BNNSs) from parent bulk material has been receiving intensive attention because of its fascinating physical properties. Liquid exfoliation is a simple, scalable approach to produce single-layer or few-layer BNNS. In this paper, water/propanol co-solvent exfoliation of bulk boron nitride under the assistance of sonication was investigated in detail. Special attention was paid on the effect of raw bulk boron nitride size and co-solvent composition. The results show that sonication of small-size hexagonal boron nitride tends to generate large nanosheets, due to a predominant solvent wedge effect. In addition, it is found that the composition of water/propanol co-solvent has an important effect on exfoliation efficiency. Interestingly, although two isomers of 1-propanol (NPA) and 2-propanol (IPA) have the same molecular weight and similar surface tension, their aqueous solutions allow the formation of boron nitride nanosheets dispersion with markedly different concentrations. It is proposed that due to their spatial configuration difference, NPA with its longer molecular chain and fewer hydrophobic methyl group tends to form dynamic water-NPA clusters with larger size than water-IPA clusters. The hydrodynamic radius of the co-solvent “clusters” was calculated to be 0.72 nm for water/NPA system and 0.44 nm for water/IPA system at their maximum, respectively. Their size changes, represented by two curves, indicate a strong “cluster size” effect on exfoliation efficiency. Our work provides an insight into co-solvent exfoliation of hexagonal boron nitride and emphasizes the importance of co-solvent cluster size in exfoliation efficiency.

Effect of organic reagents on high temperature rheological characteristics of organic rectorite modified asphalt

The molecular structure of organic reagents has a great effect on properties of organic rectorite (OREC) modified asphalt binder. This paper aims at comparing the influence of molecular chain length and benzyl group on the high temperature rheological characteristics of OREC modified binder. Here, three organic quaternary ammonium salts, including dodecyl trimethyl ammonium chloride (DTAC), dodecyl dimethyl benzyl ammonium chloride (DBAC) and octadecyl trimethyl ammonium chloride (OTAC), were selected as REC modifiers to prepare ORECs. These ORECs were then employed to modify base binder, respectively. The X-ray diffraction (XRD) test and thermogravimetric (TG) test were conducted to study the structure characteristics and thermal behavior of ORECs and corresponding modified binders. The high temperature rheological behavior, rutting and stress susceptibilities of OREC modified binders were evaluated by the temperature and frequency sweep tests, multiple stress creep recovery (MSCR) test. Results indicate that, the organic reagent affects the rheological behavior of OREC modified binder not only by enlarging the basal spacing of REC (specific surface area), but also directly by specific functional groups (e.g. benzyl group). Moreover, the organic reagent with longer molecular chains (18 carbon atoms) or containing benzyl groups is conductive to the improvement in elastic property and stiffness, and reduction in rutting and stress susceptibilities of OREC modified binder. The comparison demonstrates that DBAC containing benzyl groups exhibits better effect. Therefore, organic reagents containing benzyl groups are preferred to obtain OREC modified binder with excellent high temperature property.

Behaviours and mechanisms of nanofiltration membrane fouling by anionic polyacrylamide with different molecular weights in brackish wastewater desalination

The effect of the molecular weight (MW) of anionic polyacrylamide (APAM) on the fouling behaviours of nanofiltration membranes in brackish wastewater desalination was investigated, and its implications were elucidated using the interfacial free energy and intermolecular interactions. The foulant accumulation (mirr) was closely related to the intermolecular maximum adhesion force (Fad, max). For APAM with a larger MW of 5,000,000 Da (500APAM), the longer molecular chains were more susceptible to entanglement and thus caused a larger Fad, max between the APAM chains and membrane, leading to a larger mirr than for APAM with a MW of 500,000 Da (50APAM). In contrast, the irreversible fouling resistance (Rirr) strongly correlated with the interfacial free energy (ΔG). The ΔG for the 500APAM–membrane was higher than that for the 50APAM–membrane, which indicates a more stable thermodynamic system of the membrane surface and 500APAM molecules and thus resulted in a higher Rirr. The higher ΔG and larger Fad, max for 500APAM intensified mirr and Rirr and resulted in more severe flux declines. In addition, the strong coordination between Ca2+, when present, and carboxylates led to the intense attraction between APAM and the membrane, resulting in further flux declines of both APAMs.

A “trampoline” nanocomposite: Tuning the interlayer spacing in graphene oxide/polyurethane to achieve coalesced mechanical and memory properties

Overall high-performance shape memory polymer composites (SMCs) are desired in diverse fields while a stubborn conflict between mechanical and memory properties impedes their development in applications such as bone repair for high load-bearing locations' defects and minimally invasive surgery. For achieving a SMC with coalesced high performances in both shape memory and mechanical properties simultaneously, we here report a novel “trampoline” polyurethane nanocomposite based on the modification sequence of graphene oxide in the composite fabrication process, which can tune interlayer spacing. In this work, an intercalating structure with spring-like support, trampoline model, is proposed and was carefully examined. It is found that with larger interlayer spacing, namely taller spring support, with a longer molecular chain between two-dimensional sheets, the “trampoline” structure can remarkably improve memory and mechanical properties jointly. As desired, both high mechanical and good memory properties, e.g. ∼456.72 MPa of Young's modulus and ∼100% of shape recovery ratio, were attained respectively for the SMC. A minimally invasive bone-repairing example then demonstrated an ideal support performance for bone regeneration through finite element analysis, which showed the highest stress distributed around the implant particularly at the interface, which is essential for effective bone tissue regeneration. This “trampoline” nanocomposite paves a bright way to design and prepare SMCs with advanced performances for broad applications.

Vibration-assisted exciton transfer in molecular aggregates strongly coupled to confined light fields.

We investigate exciton transport through one-dimensional molecular aggregates interacting strongly with a cavity mode. Unlike several prior theoretical studies treating the monomers as simple two-level systems, exciton-vibration coupling is explicitly included in the description of open quantum dynamics of the system. In the framework of the Holstein-Tavis-Cummings model with truncated vibrational space, we investigate the steady-state exciton transfer through both a molecular dimer and longer molecular chains. For a molecular dimer, we find that vibration-assisted exciton transfer occurs at strong exciton-cavity coupling regime where the vacuum Rabi splitting matches the frequency of a single vibrational quantum, whereas for longer molecular chains, vibration-assisted transfer is found to occur at the ultrastrong exciton-cavity coupling limit. In addition, finite relaxation of vibrational modes induced by the continuous phonon bath is found to further facilitate the exciton transport in vibrational enhancement regimes.

Novel approach to determine non-rubber content in Hevea brasiliensis: Influence of clone variation on properties of un-vulcanized natural rubber

The mesostructure and non-rubber content, including proteins and lipids, in natural rubber from three different Hevea brasiliensis clones, namely RRIT408, PB235 and RRIM600, were investigated by a new technique, temperature scanning stress relaxation (TSSR), along with other relevant methods It was found that the significant relaxation spectrum of TSSR was found as broad peaks in the temperature ranges of 58–60 °C which indicated level of interaction for proteins and lipids at the chain terminals. This directly relates to storage hardening phenomenon. Furthermore, we found that the molecular mass distribution is bimodal for RRIM600 clone while it is unimodal for RRIT408 and PB235. Furthermore, the RRIM600 clone contained high aggregates and non-rubber components that enhanced the mechanical and rheological properties and caused strong storage hardening phenomenon. This might be attributed to the high fraction of short chains providing many chain ends, and to the total content of proteins and lipids. However, the unimodal rubber from PB235 clone exhibited poorer mechanical and physical properties and less storage hardening than those from RRIM600 and RRIT408. This might be attributed to lower content of proteins and lipids and longer molecular chains (low number of chain ends), causing less formation of aggregates or lower gel content.

Biosynthesis and characterization of a non-repetitive polypeptide derived from silk fibroin heavy chain

Silk fibroin heavy chain is the major protein component of Bombyx mori silk fibroin and is composed of 12 repetitive and 11 non-repetitive regions, with the non-repetitive domain consisting of a hydrophilic polypeptide chain. In order to determine the biomedical function of the non-repetitive domain or potentially use it to modify hydrophobic biomaterials, high-purity isolation is necessary. Previously, we cloned and extended a gene motif (f(1)) encoding the non-repetitive domain. Here, this motif and its multimers are inserted into a glutathione S-transferase (GST)-tagged fusion-protein expression vector. Motif f(1) and multimers f(4) and f(8) were expressed in Escherichia coli BL21 cells following isopropyl β-D-1-thiogalactopyranoside induction, purified by GST-affinity chromatography, and single bands of purified fusion proteins GST-F(1), GST-F(4), and GST-F(8), were visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Target polypeptides F(1), F(4), and F(8), were cleaved clearly from the GST-fusion tag following thrombin digestion. Mass spectrometry results indicate that the molecular weights associated with fusion proteins GST-F(1), GST-F(4), and GST-F(8) are 31.5, 43.8, and 59.0kDa, respectively, and with the cleaved polypeptides F(1), F(4), and F(8) are 4.8, 16.8, and 32.8kDa, respectively. The F(1), F(4), and F(8) polypeptide chains are negatively charged with isoelectric points (pI) of 3.3, 3.2, and 3.0, respectively. The molecular weight and pI values of the polypeptide chains are consistent with the predicted values and the amino acid compositions similar to predicted sequences. FTIR and CD results show the molecular conformation of F(1) was mainly random coil, and more stable α-helix structure formed in longer molecular chain.

Characteristic of a Novel Composite Inorganic Polymer Coagulant-PAZF Prepared from Industrial Wastes

A new composite coagulant polymeric aluminum zinc ferric (PAZF) was synthesized from industrial wastes. The structure and morphology of the coagulant was characterized by X-ray Diffraction (XRD), Infrared Spectroscopy (IR) and Scanning Electron Microscopy (SEM) and the coagulation performances were evaluated by dyeing-printing wastewater treatment. The results show that new complex compounds are formed in PAZF. Compared with poly aluminum chloride (PAC), the contents of ionic polymerized bonds and the cross-copolymerization among Fe (III), Al (III) and Zn (II) hydroxyl polymerized bonds are increase obviously, and the surface morphology of PAZF presents a net-like structure with the longer molecular chain. Coagulation experiments indicate that PAZF exhibits better coagulation performance in removing turbidity, COD and chromaticity.

Design of magnetic polyplexes taken up efficiently by dendritic cell for enhanced DNA vaccine delivery

Dendritic cells (DC) targeting vaccines require high efficiency for uptake, followed by DC activation and maturation. We used magnetic vectors comprising polyethylenimine (PEI)-coated superparamagnetic iron oxide nanoparticles, with hyaluronic acid (HA) of different molecular weights (<10 and 900 kDa) to reduce cytotoxicity and to facilitate endocytosis of particles into DCs via specific surface receptors. DNA encoding Plasmodium yoelii merozoite surface protein 1-19 and a plasmid encoding yellow fluorescent gene were added to the magnetic complexes with various % charge ratios of HA: PEI. The presence of magnetic fields significantly enhanced DC transfection and maturation. Vectors containing a high-molecular-weight HA with 100% charge ratio of HA: PEI yielded a better transfection efficiency than others. This phenomenon was attributed to their longer molecular chains and higher mucoadhesive properties aiding DNA condensation and stability. Insights gained should improve the design of more effective DNA vaccine delivery systems.

Effect of molecular weight of poly(N-vinyl carbazole) on photorefractive performances

We present here the effect of molecular weight of poly(N-vinyl carbazole) (PVCz) on photorefractive performances. Photorefractive composites with higher molecular weight of PVCz led to higher diffraction efficiency and faster speed of grating buildup. The fastest response time of 18 ms (grating buildup speed of 55.6 s−1) was obtained at 45 V μm−1. Higher diffraction efficiency and faster buildup speed of photorefractive composite with higher molecular weight of PVCz was ascribed to the larger Pockels effect due to larger number density of traps. Dimer cation sites preferentially formed along the longer molecular chain in higher molecular weight of PVCz seem to work as effective traps for hole carriers.

じん性を変えた注型用エポキシ樹脂の耐熱衝撃性評価

Previously the present authors proposed the testing method of thermal shock resistance using a notched disk type specimen of brittle type epoxy resin and its evaluation method based on fracture mechanics. In order to examine their applicability, some practical epoxy resins for casting were tested in this study.For brittle alicyclic epoxy resin, irrespective of the cooling bath temperature, the nondimensional stress intensity factor calculated by the experimental results agreed well with that of theoretical estimation.In the case of mixed resin of bisphenol A epoxy having certain toughness and very brittle alicyclic epoxy, the critical temperature difference ΔTC was clearly recognized for all resin systems with various mixture ratios, and the resin with higher bisphenol A epoxy content showed higher thermal shock resistance. For the bisphenol A type epoxy resin with longer molecular chains (larger number of repeated units) indicated higher resistance. The analysis agreed well with the experiments for these both resin systems.For the epoxy resin modified with a low content of plasticizer, the same evaluation method of thermal shock resistance was found to be applicable. But over 20phr content, plastic flow occurred markedly, and so the critical temperature difference could not be obtained. For such cases, it is still possible to evaluate the thermal shock resistance by using a large size specimen.