Diallydimethylammonium Chloride Research Articles

Chemical specificity in polyzwitterion-polyelectrolyte coacervates: polycations vs polyanions

Aqueous solutions containing polyzwitterions and polyelectrolytes were studied to probe the effects of chemical specificity on the complexation among different types of chains and resulting liquid–liquid phase separation (coacervation). Two kinds of blends were studied. A polyzwitterion, poly(sulfobetaine methacrylate) (PSBMA), was blended with either (1) a polycation, poly(diallydimethylammonium chloride) (PDADMAC), or (2) a polyanion, sodium poly(styrene sulphonate) (NaPSS). Coacervation was observed in both blends after equilibration, while the freshly prepared blend solutions exhibited distinct behavior dependent on the mixing protocols. Mixing solutions of the polyzwitterions and the polycations led to coacervation almost instantaneously. In contrast, the blends containing the same polyzwitterions and the polyanions exhibited no such coacervation by following the same mixing protocol. However, blends prepared after dissolving a solid mixture containing the same polyzwitterions and the polyanions in water exhibited coacervation. Based on the small-angle X-ray scattering (SAXS), cryo-electron microscopy, and rheology measurements, complexation and coacervation in the polyzwitterion-polyelectrolyte blends is rationalized in terms of the entropy change associated with reorganization of solvent (water), which appears to be larger in the polyzwitterion-polycation case in comparison with the polyzwitterion-polyanion blends. These results highlight the importance of chemical specificity and mixing protocols leading to metastable structures in designing a new class of materials based on macromolecular complexation of polyzwitterions.

Perchlorate uptake by poly-(diallydimethylammonium chloride) functionalized montmorillonites

Montmorillonite (Mt) is proposed as a promising adsorbent for removing contaminants from water, yet it is unclear whether and how the layer charge density (LCD) of Mt. affects its hydration properties, especially for the capturing performance of anions by polyelectrolyte modified Mt. Here, the feasibility and performance of perchlorate uptake by poly-(diallydimethylammonium chloride) (PDDA) functionalized Mt. (PDDA-Mtx) with different LCD were investigated. PDDA species were loaded via partial intercalation or adsorption on the surface/end sites of Mt. The CEC of Ca-Mtx increased with increasing LCD, while on the contrary for colloidal valence. The perchlorate uptake by Ca-Mtx can be significantly improved by introducing PDDA species. As expected, the PDDA-Mt0.3 showed superior perchlorate capture of up to 0.80 mmol/g due to the relatively high positive zeta potential and loading of un-ionized PDDA. The perchlorate uptake by PDDA-Mtx still maintained largely despite a slight decrease in the presence of co-competing anions NO-3, SO2–4 and PO3–4. The capture behaviors were well characterized by the pseudo-second-order and Langmuir isotherm models, and the natures of spontaneous and endothermic were demonstrated by thermodynamic analysis. Anion exchange and electrostatic were the dominant ways in which perchlorate was captured onto PDDA-Mtx.

Zwitterionic surfactant as an additive for efficient electrophoretic separation of easily absorbed rhodamine dyes on plastic microchips

Plastic microchips possess the advantages of easy fabrication and low-cost, but their surface properties are frequently incompatible with electrophoretic separation without proper surface modification. Meanwhile, the separation microchannels on typical microchips are usually only a few centimeters long, the pressurized flow may significantly affect the electrophoretic separation if their inner diameters (id) are relatively larger (approximately > 50 μm), viscous separation medium is therefore required for efficient separation. Herein, a zwitterionic surfactant, N-hexadecyl-N,N-dimethyl-3-ammonio-1-propane sulfonate (HDAPS), was used as a multifunctional additive to inhibit the analyte adsorption, improve the surface status, control Joule heating and modulate the resolution on cyclic olefin copolymer microchips with 80 μm id, 5 cm long separation microchannels, eliminating the necessity of viscous polymeric additives. The effectiveness of HDAPS was compared with an ionic polymeric additive, poly(diallydimethylammonium chloride). The streaming potential and electroosmotic flow measurements indicated an effective inhibition of the adsorption of rhodamine B and a stable negative surface charge with zwitterionic HDAPS. Using 15 mmol/L HDAPS, 40% (v/v) methanol, and 10 mmol/L boric acid (pH 3.2) as the running buffer, rapid separation of four rhodamines was achieved within 90 s under a separation electric field of 520 V/cm. The theoretical plate numbers were in a range of 5.0×105–6.9×105/m. The relative standard deviations were no more than 0.9% for retention time and 1.5% for peak area. The proposed system was verified by the determination of rhodamines in eyeshadow and wolfberry, with standard recoveries in a range of 98.2%–101.4%.

Electrical Stimuli-Responsive Decomposition of Layer-by-Layer Films Composed of Polycations and TEMPO-Modified Poly(acrylic acid).

We previously reported that layer-by-layer (LbL) film prepared by a combination of 2,2,6,6-tetramethylpiperidinyl N-oxyl (TEMPO)-modified polyacrylic acid (PAA) and polyethyleneimine (PEI) were decomposed by application of an electric potential. However, there have been no reports yet for other polycationic species. In this study, LbL films were prepared by combining various polycationics (PEI, poly(allylamine hydrochloride) (PAH), poly(diallydimethylammonium chloride) (PDDA), and polyamidoamine (PAMAM) dendrimer) and TEMPO-PAA, and the decomposition of the thin films was evaluated using cyclic voltammetry (CV) and constant potential using an electrochemical quartz crystal microbalance (eQCM). When a potential was applied to an electrode coated on an LbL thin film of polycations and TEMPO-PAA, an oxidation potential peak (Epa) was obtained around +0.6 V vs. Ag/AgCl in CV measurements. EQCM measurements showed the decomposition of the LbL films at voltages near the Epa of the TEMPO residues. Decomposition rate was 82% for the (PEI/TEMPO-PAA)5 film, 52% for the (PAH/TEMPO-PAA)5 film, and 49% for the (PDDA/TEMPO-PAA)5 film. It is considered that the oxoammonium ion has a positive charge, and the LbL films were decomposed due to electrostatic repulsion with the polycations (PEI, PAH, and PDDA). These LbL films may lead to applications in drug release by electrical stimulation. On the other hand, the CV of the (PAMAM/TEMPO-PAA)5 film did not decompose. It is possible that the decomposition of the thin film is not promoted, probably because the amount of TEMPO-PAA absorbed is small.

Synthesis and anticorrosive application of biomimetic dopamine-based cationic polyelectrolytes derived from diallylammonium salts

Dopamine hydrochloride was converted to monomer N,N-diallyldopamine hydrochloride [(3,4-(HO)2C6H4CH2CH2NH+(CH2CHCH2)2 Cl−] (I). Polymerization of monomer diallydimethylammonium chloride (II) gave homocyclopolymer III, while its copolymerization with 5–20 mol% I afforded copolymers IV. Likewise, II/SO2 copolymerization and I/II/SO2 terpolymerization gave respective alternate copolymer V and terpolymers VI. Copolymer IV (containing 20 mol% dopamine motifs) imparted excellent inhibitions of mild steel corrosion in 1 M HCl as well as synergistic inhibition in the presence of iodide ions in 15% HCl at 60 °C. Increasing mol% of dopamine motifs in IV resulted in increasing corrosion protection and demonstrated better efficiency than monomer II and its homopolymer III. Cationic polyelectrolyte IV has been shown to form polyelectrolyte complex/coacervate with three model anionic polyelectrolytes.

Synthesis of Chainlike ZSM-5 with a Polyelectrolyte as a Second Template for Oleic Acid and Ethanol Cracking into Light Olefins.

Chainlike ZSM-5 was synthesized in a tetrapropylammonium hydroxide (TPAOH) and poly(diallydimethylammonium chloride) (PDDA) dual-template system. The synthesis parameters and formation mechanism of chainlike zeolites were investigated. The optimized composition of the synthesis mixture was as follows: the PDDA/SiO2, TPAOH/SiO2, SiO2/Al2O3, and H2O/SiO2 molar ratios are, respectively, 0.16, 0.4, 50, and 40, with tetraethyl orthosilicate and aluminum nitrate as silicon/aluminum sources. The resultant ZSM-5 showed a cross-linked chainlike morphology, mesopore-dominated pore structure, and mild acidity. The formation of the chainlike zeolite was attributed to synergistic actions between PDDA and TPAOH. TPAOH acted as an alkali source and helped to induce nucleation and control the crystal size. PDDA acted as a soft template to promote crystal nucleation, and a hard template to form a three-dimensional mesoporous structure. Light olefin (C2-4 =) selectivities from cracking of ethanol and oleic acid over the present chainlike ZSM-5 at 400 °C reached 90 and 75.7%, respectively, which were much higher than those from commercial ZSM-5 (75 and 52.3%, respectively), demonstrating the excellent hydrothermal stability and catalytic performance of the synthesized chainlike zeolite.

Biocompatible Nanocomposite Coatings Deposited via Layer-by-Layer Assembly for the Mechanical Reinforcement of Highly Porous Interconnected Tissue-Engineered Scaffolds.

Tissue-engineered (TE) scaffolds provide an ‘off-the-shelf’ alternative to autograft procedures and can potentially address their associated complications and limitations. The properties of TE scaffolds do not always match the surrounding bone, often sacrificing porosity for improved compressive strength. Previously, the layer-by-layer (LbL) assembly technique was used to deposit nanoclay containing multilayers capable of improving the mechanical properties of open-cell structures without greatly affecting the porosity. However, the previous coatings studied contained poly(ethylenimine) (PEI), which is known to be cytotoxic due to the presence of amine groups, rendering it unsuitable for use in biomedical applications. In this work, poly(diallydimethylammonium chloride) (PDDA)- and chitosan (CHI)-based polyelectrolyte systems were investigated for the purpose of nanoclay addition as an alternative to PEI-based polyelectrolyte systems. Nanocomposite coatings comprising of PEI, poly(acrylic acid) (PAA), Na+ montmorillonite (NC), PDDA, CHI and sodium alginate (ALG) were fabricated. The coatings were deposited in the following manner: (PEI/PAA/PEI/NC), PEI-(PDDA/PAA/PDDA/NC) and (CHI/ALG/CHI/ALG). Results from scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses demonstrated that the nanoclay was successfully incorporated into each polymer bilayer system, creating a nanocomposite coating. Each coating was successful at tailoring the elastic modulus of the open-cell structures, with polyurethane foams exhibiting an increase from 0.15 ± 0.10 MPa when uncoated to 5.51 ± 0.40 MPa, 6.01 ± 0.36 MPa and 2.61 ± 0.41 MPa when coated with (PEI/PAA/PEI/NC), PEI-(PDDA/PAA/PDDA/NC) and (CHI/ALG/CHI/ALG), respectively. Several biological studies were conducted to determine the cytotoxicity of the coatings, including a resazurin reduction assay, scanning electron microscopy and fluorescent staining of the cell-seeded substrates. In this work, the PDDA-based system exhibited equivalent physical and mechanical properties to the PEI-based system and was significantly more biocompatible, making it a much more suitable alternative for biomaterial applications.

Surface modification of ZnO quantum dots coated polylactic acid knitted fabric for photocatalytic application

AbstractIn this work, ZnO quantum dots (ZnOQD) were synthesized by Sol–gel synthesis and impregnated on polylactic acid (PLA) knitted fabric through self‐assembly of different cycles from layer‐by‐layer (LBL) using cationic agent Poly(diallydimethylammonium chloride) (PDDA). Then, morphological, chemical and photocatalytic properties were studied. The results demonstrate that the synthesis provided 8 nm Wurtzite‐type ZnO nanoparticles. In addition, X‐ray photoelectron spectroscopy (XPS) spectra, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) proved the inclusion of ZnOQD on the surface of PLA matrix, which allowed the evaluation of its photocatalytic properties, therefore, coated PLA with five cycles of ZnOQD obtained the best result for degrading 85% of the dye Rhodamine B (RhB) in 360 min under UV radiation, in addition to its reusability for another five cycles of photocatalytic activity.

Preparation of Pt nanoparticles embedded on ordered mesoporous carbon hybrids for sensitive detection of acetaminophen

In this work, we report a facile microwave-assisted route to rapidly synthesize Pt species embedded on ordered mesoporous carbon (Pt/OMC) hybrids. During synthesis, positively charged poly-(diallydimethylammonium chloride) was used to wrap OMC and attached Pt species via the intermolecular electrostatic attraction. The formation of the electrocatalysts was tested by characterization (e.g., X-ray photoelectron spectroscopy, X-ray diffraction, energy-dispersive X-ray spectra, and TEM). Due to the synergetic effects and special structural, Pt/OMC hybrids can act as an effective and sensitive electrocatalyst for the detection of acetaminophen (AP). It can be anticipated that the successful fabrication of Pt/OMC could provide new opportunities for the preparation of electrochemical sensors for the determination of pharmaceutical products.

Hybrid polymer/ionic liquid electrospun membranes with tunable surface charge for virus capture in aqueous environments

Although electrospun-based membranes may be engineered as efficient platforms for the capture of biomolecules in aqueous environments, the capability of such membranes to selectively capture viruses and proteins is often limited due to poor and constrained surface affinity for molecular bonding. In order to generate more efficient electrospun-based membranes, fine-tuning Van der Waals and ionic interactions is required to control chemical affinities with such contaminants and support advanced remediation solutions. Here, diallydimethylammonium chloride and poly(acrylonitrile) electrospun nanofibres were developed to enhance the adsorption of specific contaminant molecules compared to equivalently shaped pristine poly(acrylonitrile) nanofibre membranes. The results showed that the incorporation of the ionic liquid improved contact with water by forming super-hydrophilic nanofibres with narrow diameters and smaller pore size distributions, while also significantly changing the surface charge of the material and shifting the isoelectric point of the surface from 3 to 4.4. The specific surface area of the membranes was also increased by up to 4 times upon ionic liquid loading, which was found to support efficient coronavirus capture and filtration efficiency. This new strategy represents a promising way to control surface properties of virus filtration membranes towards efficient and targeted remediation solutions.

Ultrafast third order nonlinear optical properties of self-assembled indium phthalocyanine multilayer films

An ultrathin composite films with alternated layers containing anionic lithium tetracarboxyl indium phthalocyanine chloride (ClInPc(COOLi)4) and cationic poly(diallydimethyl ammonium chloride) (PDDA) were prepared using layer-by-layer assembly technique. The resulting films were characterized by Ultraviolet-visible and Fourier transform infrared spectroscopy, showing regularly consecutive adsorption. The ultrafast third-order nonlinear optical properties of the films were investigated via a 4f coherent imaging system with phase object with 190 fs laser pulses at 532nm. The results demonstrate that the ultrathin films exhibited excellent self-focusing effect (n2 ∼ 8.86 × 10−17 m2/W) and reverse saturable absorption properties (β ∼ 5.19 × 10−10 m/W), while the nonlinear optical response of the same composite in aqueous solution were found to be negligible. Our results indicate that the ClInPc(COOLi)4/PDDA film is a promising candidate for future nonlinear optical devices.

Ultrafast third-order nonlinear optical properties of self-assembled poly[[4,4-bis(4-sulphobutyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl]-1,4-phenylene sodium sa multilayer films

An ultrathin multilayer film with well-defined structure containing anionic Poly[[4,4-bis(4-sulphobutyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl]-1,4-phenylene sodium sa (PCPDTPhSO3Na) and cationic poly(diallydimethyl ammonium chloride) (PDDA) was prepared using layer-by-layer assembly technique. The growth of the film was monitored by UV–Vis absorption spectroscopy, showing regularly consecutive adsorption. The ultrafast third-order nonlinear optical (NLO) properties of the multilayer film were investigated via the 4f coherent imaging measurement with phase object with 190 fs laser pulses at both 400 and 532 nm. The results demonstrate that PCPDTPhSO3Na/PDDA film exhibited excellent self-focusing effect (n 2 ∼2.42 × 10−16 m2/W) and reverse saturable absorption properties (β ∼6.34 × 10−10 m/W) at 400 nm. In contrast, self-focusing effect (n 2 ∼1.81 × 10−16 m2/W) and saturable absorption properties (β ∼−8.02 × 10−10 m/W) are observed when the laser wavelength (532 nm) is near-resonant with the absorption peak (470 nm). Our studies indicate that the PCPDTPhSO3Na/PDDA film is a promising candidate for applications in NLO devices.

Evaluation of the flocculation and dewatering performance of dual polymers for treating oil sands tailings

AbstractMature fine tailings produced in the processing of oil sands create serious water‐recovery problems; thus, it is important to characterize them and to improve the applicable dewatering technologies. Existing methods to dewater the tailings are found to be insufficient. Previous research has demonstrated that the addition of dual polymers is more efficient than using a single polymer to flocculate the fine tailings particles. Different from studies that took sophisticated procedures to assess the flocculation and dewatering efficiency of dual polymers, readily available and simple but effective experiments were conducted in this work. Evaluations were conducted with dual polymers comprised of low molecular weight poly(diallydimethylammonium chloride) (polyDADMAC) and high molecular weight cationic or anionic polyacrylamide (PAM). Turbidity and residual solids measurements for dewatered tailings treated with these polymers confirmed that the dual‐polymer approach yield superior performance compared to either polymer functioning alone. Zeta potential and microscopic observations indicated that the dosages of polyDADMAC and PAM that lead to near charge neutralization of the system result in maximal performance. We hypothesize that when dual polymers are added to the tailings, polyDADMAC acts to neutralize the charge and destabilize the fine particles, while high molecular weight PAM, either cationic or anionic, acts to aggregate the destabilized fines by the bridging mechanism. PolyDADMAC forms weak and tiny flocs when mixed with tailings particles. Cationic PAM transforms these small flocs into much larger ones, while anionic PAM connects them into aggregates. Therefore, synergism exists between polyDADMAC and PAM but this synergism is different, based on the charge of the PAM.

Surface-Engineered Cubosomes Serve as a Novel Vaccine Adjuvant to Modulate Innate Immunity and Improve Adaptive Immunity in vivo.

ObjectiveRecent studies have revealed the adjuvant activity of cubosomes and their potential utility as an antigen delivery system. In this study, to further enhance the adjuvant activity of cubosomes, two cationic polymers are modified on the surface of cubosomes.MethodsHere, we exploit the effects of surface chemistry on the adjuvant activity of Ganoderma lucidum polysaccharide cubosomes (GLPC) by placing two kinds of molecules, that is, cetyltrimethylammonium bromide (CTAB) and poly(diallydimethyl ammonium chloride) (PDDAC), on their surface.ResultsCTAB- or PDDAC-modified GLPC were found to significantly promote humoral and cellular immune responses, as well as the proliferation of CD3+ CD4+ or CD3+ CD8+T cells through the powerful activation of dendritic cells (DCs). The enhanced immune responses of PDDAC-modified GLPC might be attributed to the maturation of DCs into draining lymph nodes and the activation of spleen and cytokines in serum.ConclusionPDDAC modification is beneficial for enhancing humoral and cellular immune response, suggesting that PDDAC-GLPC-OVA has the ability to be a potential adjuvant for vaccine.

Sulfate removal using colloid-enhanced ultrafiltration: performance evaluation and adsorption studies.

Colloid-enhanced ultrafiltration (CEUF), i.e., micellar-enhanced ultrafiltration (MEUF) and polymer-enhanced ultrafiltration (PEUF), was investigated to remove sulfate ions from aqueous solution in batch experiments, using cetyltrimethylammonium (CTAB) and poly(diallydimethylammonium chloride) (PDADMAC) as colloids, respectively. Ultrafiltration performance was evaluated under different initial concentrations of sulfate (0-20 mM) and CTAB/PDADMAC (0-100 mM). The highest retention rate (> 99%) was found in dilute sulfate solutions. At high sulfate concentrations (e.g., 10 mM), a dosage of 50 mM CTAB or PDADMAC can retain approximately 90% of sulfate ions. Though concentration polarization behavior was observed, membrane characterization indicated that the fouling was reversible and membranes can be reused. Furthermore, adsorption equilibrium and kinetics studies show that Freundlich isotherm and pseudo-second-order kinetics can describe the sulfate-colloid interaction, indicating that the surface of absorbents are heterogeneous and the rate-controlling step is chemisorption. Both MEUF and PEUF show potential as effective separation techniques in removing sulfate from aqueous solutions. Under the same conditions examined, PEUF shows advantages over MEUF in its higher retention at lower polymer-to-sulfate ratios, cleaner effluent, and higher adsorption capacity, but compromises on severer flux decline and a tendency of membrane fouling. To overcome this disadvantage, membranes with higher molecular weight cut-off can be used.

Synthesis of Grafted Cationic Starch with DMDAAC Using Ammonium Persulfate/Carbamide Initiation System

Using ammonium persulfate (APS)/carbamide initiation system, cationic grafted starch was prepared by the graft copolymerization of starch with diallydimethylammonium chloride (DMDAAC). The synthesized polymer was confirmed by FTIR, NMR, and XRD. And the morphology was characterized by SEM. The optimum conditions of graft copolymerization were determined and the flocculation properties of the cationic grafted starch were investigated using diatomite suspension. The obtained results showed that grafting ratio (G) and grafting efficiency (GE) have an increased trend along with the increase of mass ratio of starch to monomer. G, GE and cationic degree (DC) increased with the rise of mole ratio of AM to DMDAAC. When the total concentration of the monomers in the system is fixed, increasing APS concentration up to 0.33×10-3 M caused a rise for the G, GE and DC. The optimum temperature and the time were 40 °C and 5 h, respectively. The result also showed that the cationic grafted starch has excellent flocculation performance whether in acid, alkaline or neutral conditions.

Preparation of a thiols β-cyclodextrin/gold nanoparticles-coated open tubular column for capillary electrochromatography enantioseparations.

Inspired by the distinct chemical and physical properties of nanoparticles, here a novel open-tubular capillary electrochromatography column was prepared by electrostatic assembly of poly(diallydimethylammonium chloride) onto the inner surface of a fused-silica capillary, followed by self-adsorption of negatively charged SH-β-cyclodextrin/gold nanoparticles. The formation of the SH-β-cyclodextrin/gold nanoparticles coated capillary was confirmed and characterized by scanning electron microscopy and energy dispersive spectrometry. The results of scanning electron microscopy and energy dispersive spectrometry studies indicated that SH-β-cyclodextrin/gold nanoparticles were successfully coated on the inner wall of the capillary column. The performance of the SH-β-cyclodextrin/gold nanoparticles coated capillary was validated by the analysis of six pairs of chiral drugs, namely zopiclone, carvedilol, salbutamol, terbutaline sulfate, phenoxybenzamine hydrochloride, and ibuprofen. Satisfactory enantioseparation results were achieved, confirming the use of gold nanoparticles as the support could enhance the phase ratio of the open-tubular capillary column. Additionally, the stability and reproducibility of the SH-β-cyclodextrin/gold nanoparticles coated capillary column were also investigated. Then, this proposed method was well validated with good linearity (≥0.999), recovery (90.0-93.5%) and repeatability, and was successfully used for enantioseparation of ibuprofen in spiked plasma samples, which indicated the new column's potential usage in biological analysis.

Transparent conductive film based on silver nanowires and single-wall carbon nanotubes for transparent heating films

In this paper, hybrid transparent conductive films (TCFs) are designed by combining silver nanowires with the single-wall carbon nanotubes (SWCNTs) and the transparent heating films (THFs) based on the TCFs are evaluated for possible vehicle applications. By comparing the properties, including the transmittance, sheet resistance, microstructure and heating curves, we found that the SWCNTs/AgNWs are considerably suitable for making THFs. The after-treatment methods, such as physical method (hot roll pressing) and chemical method (nitric acid and Poly (diallydimethylammonium chloride) solution, (PDAC)) were researched in detail to optimize the sheet resistance and transparency to fit the THF requirements. A careful study of the different after-treatment methods revealed that hot roll pressing can quickly and efficiently improve the properties, while the nitric acid is more helpful than PDAC for the long-term stability. The results showed that a small amount of SWCNTs addition can promote the endurable maximum electric current by spreading the heat fast and efficiently, and the maximum current flow can be as high as 4 A. The thermal stability of the THFs and the de-frog performance were tested, indicating that the hybrid film had an advantage in resisting current shock and good thermal efficiency was obtained. The fabricated TCFs of stable thermal properties are qualified as a windshield-glass heater.

Poly(diallydimethylammonium chloride)-Induced Dispersion and Exfoliation of Tungsten Disulfide for the Sensing of Glutathione and Catalytic Hydrogenation of p-Nitrophenol

Poly(diallydimethylammonium chloride) (PDDA) has been demonstrated to be valuable in diverse fields, such as layer-by-layer assembly and material surface modification. Herein, we report a novel application of PDDA for exfoliating bulk tungsten disulfide (WS2) into few-layer WS2 nanosheets (FL-WS2-NSs) under ultrasonication treatment. Cationic PDDA molecules were capable of firmly binding to the WS2 surface to expose quaternary ammonium moieties in water, thereby creating electrostatic repulsion between each FL-WS2-NS. The formation of FL-WS2-NSs was proven by absorption spectroscopy, high-resolution transmission electron microscopy, and atomic force microscopy. Additionally, PDDA molecules enable FL-WS2-NSs to be stable in 200 mM NaCl for more than six months without thermal-triggered nanosheet aggregation. Given that PDDA-stabilized FL-WS2-NSs (PDDA-FL-WS2-NSs) exhibit sulfur vacancy sites, thiolated boron–dipyrromethene (BODIPY) molecules were self-assembled onto the surface of PDDA-FL-WS2-NSs. As a res...

Adsorption Characteristics of Carboxymethylated Lignin on Rigid and Soft Surfaces Probed by Quartz Crystal Microbalance.

Limited information is available on the interaction of anionically charged lignin and cationic particles, despite the promising use of anionic lignin as a coagulant and dispersant for suspension systems. The main objective of this study was to discover the fate of lignin on its interaction with rigid and soft surfaces. In this work, carboxymethylated lignin (CML) with two different charge densities were produced, and their adsorption performance on gold and poly(diallydimethylammonium chloride) (PDADMAC)-coated gold surfaces was comprehensively studied. The viscoelastic properties of adsorbed CML on the gold surface were investigated by means of quartz crystal microbalance with dissipation. A higher adsorbed amount and compact layer were observed for the adsorption of CML with a lower charge density of -1.16 meq/g (CML1). CML with a higher charge density (-2.92 meq/g), CML2, yielded a lower surface excess density of 2.31 × 10-6 mol/m2 and a higher occupied area per molecule (71.84 Å2) at the interface of water and gold sensor. Below and at equilibrium, CML2 generated a bulkier adsorption layer than did CML1 on the gold sensor and on the PDADMAC-coated sensor. Studies on the layer-by-layer (LBL) assembly of CML and PDADMAC revealed that CML1 adsorbed more greatly than CML2 on PDADMAC, and it generated a thicker but less viscoelastic layer. In this system, the greater loss to storage modulus ( G″/ G') value was achieved for CML2, indicating its looser structure in the LBL system. Studies on the LBL assembly of carboxymethylated xylan/PDADMAC and CML/PDADMAC provided concrete evidence for the fate of three-dimensional structure of CML on its adsorption performance.