Poly Diallyldimethylammonium Chloride Research Articles

Nuclear magnetic resonance enables understanding of polydiallyldimethylammonium chloride composition and N-nitrosodimethylamine formation during chloramination

1H and 13C NMR can inform on the impurities in commercial polyDADMAC solutions and enable mechanistic NDMA formation studies.

Systematic assessment of dredged sludge dewaterability improvement with different organic polymers based on analytic hierarchy process

Organic polymeric flocculants are commonly used in improving dredged sludge dewaterability, but less attention has been paid to residual water quality. In this paper, the effects of cationic etherified starch (CS) and poly-dimethyl diallyl ammonium chloride (PDDA) on dredged sludge dewatering efficiency and residual water quality of Baiyangdian lake were comprehensively investigated and evaluated by analytic hierarchy process (AHP). The results indicated that PDDA had stronger electrical effect and flocculation performance compared with CS, resulting in more efficient dewatering performance. PDDA can reduce the pollutants of discharged residual water, while CS significantly promoted the increase of NH4+-N and NO3–-N in the residual water. The increase of NH4+-N in the residual water of CS was due to the release of dredged sludge, while the increase of NO3–-N was introduced by CS leaching. AHP showed that PDDA performed better in flocculation treatment of dredged sludge than other organic polymers. This work provides a method for optimization of flocculation treatment for dredged sludge dewaterability.

Fabrication of black phosphorus nanosheets/BiOBr visible light photocatalysts via the co-precipitation method

The novel photocatalyst capable of utilizing the full spectrum of solar energy has attracted the attention of researchers. Black phosphorus (BP), as a rising star in an assortment of 2D materials, possesses a broadband absorption due to its tunable direct bandgap, which makes it a candidate photocatalyst. In our work, poly dimethyldiallyl ammonium chloride (PDDA) is used to passivate BP nanosheets (BPNs) to improve its stability. Further, the functionalized BPNs and BiOBr are combined by a one-step co-precipitation method to form nanocomposites. The successful formation of nanocomposites obviously promoted the possibilities for the carrier transporting between BiOBr and BPNs, and effectively hindered the recombination of carriers, which is confirmed by all manner of characterization. Meanwhile, nanocomposites have enhanced light absorption and relatively large specific surface area, which also has a gain in its photocatalytic activity. The as-prepared nanocomposite photocatalysts significantly enhanced the photocatalytic activity with the best degradation effect of 14 and 3.4 times than pure BiOBr towards degradation of methylene orange (MO) and ciprofloxacin (CIP), respectively, under visible light. To get clear proofs of the photocatalytic mechanism, the UV–vis diffuse reflectance spectroscopy, photocurrents, electrochemical impedance spectra and Mott-Schottky measurements et al. were employed and the type-I band alignment was proposed. This finding provides an easily synthesis and effective way of BP/semiconductor photocatalysts and demonstrates a new perspective for designing novel solar light driven photocatalysts.

Highly Efficient Photocatalytic Disinfection of Escherichia coli by Rose Bengal-Functionalized Graphene Oxide Nanosheets.

Rose Bengal (RB) was used as a functional pigment and poly dimethyl diallyl ammonium chloride was used as a coupling agent to modify Graphene Oxide (GO) in order to enhance the light absorption and ROS generation of GO. GO, RB and the obtained RB-PDDA-GO were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, thermogravimetric analysis, Raman spectroscopy, UV-visible spectrophotometry, and X-ray photoelectron spectroscopy. The oxidation of hydroquinone to p-benzoquinone was used to evaluate the oxidation ability. Three kinds of reactive oxygen species (O₂·-, 1O₂ and ·OH) produced by the materials under light irradiation were detected by the ESR method using TEMP (2,2,6,6-tetramethyl-4-piperidine) and DMPO (5,5-dimethyl-1-pyrroline-N-oxide) as capture agents. The results showed that RB-PDDA-GO produced more ROS under light than GO. Antibacterial experiments were carried out with E. coli as the target strain to detect the actual utility of ROS produced by the materials. The results showed that RB-PDDA-GO had a significant sterilization effect.

Poly (dimethyl diallyl ammonium chloride) incorporated multilayer coating on biodegradable AZ31 magnesium alloy with enhanced resistance to chloride corrosion and promoted endothelialization

Controlled corrosion and proper biological response are key demands for biodegradable Mg-alloy based vascular stents. To achieve those properties, herein, a chemical conversion coating was fabricated through layer-by-layer (LBL) assembly via the sequential assembly of poly (dimethyl-diallyl ammonium chloride) (PDDA), epigallocatechin gallate (EGCG) and heparin (Hep). Each component in the coating played a unique role, in which EGCG chelates Mg ions and enhances the stability of the coating by introducing multiple intermolecular interactions, while PDDA effectively enhances the resistance against chloride corrosion, and Hep provides adequate hemocompatibility and promotes endothelialization. Electrochemical assay and immersion test demonstrated that the synergistic combination of PDDA and EGCG effectively suppressed the corrosion rate. A systematic in vitro and ex-vivo evaluation demonstrated an impressive antithrombotic performance, along with a selective promotion of endothelial cells (ECs) proliferation and inhibition of smooth muscle cells (SMCs) growth and macrophages (MAs) activation. More importantly, subcutaneous implantation and implantation in the abdominal aorta wall indicated that the PDDA/EGCG/Hep-modified implants displayed good corrosion resistance and mild tissue response, enhanced endothelialization and suppressed intima hyperplasia. These promising outcomes revealed the clinical potential of the PDDA/EGCG/Hep coating on AZ31 as biodegradable cardiovascular implants.

An efficient floating adsorption-photocatalyst to decarboxylate D-Glu and D-MeAsp of Microcystin-LR via holes direct oxidation

Fates of toxic foundational groups of Microcystin-LR in aqueous have garnered widespread attention because of the difficulty of removal during photocatalytic process. Here, an efficient N, P co-doped TiO2/expanded graphite (NPTEG) floating material (NPTEG) modified by poly dimethyl diallyl ammonium chloride (PDDA) and graphitic carbon nitride (g-C3N4) (x PDDA-g-C3N4-NPTEG) was assembled and used to destroy the toxic foundational groups of MC-LR in water. g-C3N4 can match well with TiO2 to form heterojunction where holes can gather in the valence band of g-C3N4. PDDA is used to passivate the g-C3N4, and performs as holes transport layer during the photocatalytic process to promote the separation of electron-hole pairs. Under the direct interaction of photo-generated holes and free carboxyl groups of MC-LR adsorbed on the surface, the decarboxylation process in the free acid groups on D-glutamic acid (Glu) and methyl-D-aspartic acid (D-MeAsp) of MC-LR occurred which was authenticated by UPLC-ESI-MS/MS. Meanwhile, the conjugated double bond was also removed by hydroxylation, so as to achieve the goal of non-toxic site residues in the degradation process. Furthermore, the degradation byproducts toxicity and photocatalysts stability were explored. The results confirm that x PDDA-g-C3N4-NPTEG exhibits excellent attacking ability of carboxylic acid groups of MC-LR and high recycle ability, which has great promise as a means of effectively treating drinking water.

Antibacterial Effect of Silver Nanoparticles on Klebsiella spp

Silver nanoparticles (AgNP) can be incorporated into medical devices, such as tissues, to circumvent bacterial resistance such as Klebsiella spp, which can lead to skin and mucosal infections. Thus, the aim of the present study was to synthesize silver nanoparticles for later incorporation into cotton fabrics and in vitro tests against Klebsiella spp. The AgNP colloidal solution was synthesized (AgNO3 - 0.1 mM, 100 mM trisodium citrate, polyvinylpyrrolidone - 0.24 g, H2OH2) and then impregnated into the cotton fabric pretreated with poly diallyl dimethylammonium chloride (PDDA) of 100/500 tissue, shaken for 30 minutes). The material produced was analyzed by the FTIR; DLS and reflectance spectroscopy. The tests of the antimicrobial activities were by the microdilution technique against Klebsiella spp, in tubes containing Brain Heart Infusion (BHI), with the solution of silver (1); Tissue containing AgNP - 4 mm (2); Negative control (3) and positive control - ceftriaxone (4). Regarding MIC, the inhibitory activity occurred of the dilutions between 1/2 and 1/16. The AgNP particles had an average size of 24.75 nm. As synthesized AgNPs demonstrate the excellent antimicrobial activity against Klebsiella spp, with special emphasis on applications in nanotechnology and nanomedicine, targeting multiresistant antibiotic bacteria.

In-situ and simultaneous evaluation of optical absorption and deposition for phthalocyanine layer-by-layer thin films using an optical waveguide sensor utilizing surface plasmon resonance

A novel optical waveguide sensor utilizing surface plasmon resonance (SPR) that enables the measurement of optical absorption and the thickness of a thin film was proposed. A BK-7 glass slide was used as a waveguide core, and an Ag/Au film of 5 mm width and transparent polymethyl methacrylate-co-methacrylic acid (PMMA-co-PMAA) were consecutively deposited to develop the sensor. The PMMA-co-PMAA film was used to control the SPR wavelength. This sensor allows us to measure the optical absorption and thickness of the deposited film using the evanescent wave from the waveguide and the SPR phenomena, respectively. In order to demonstrate this, a layer-by-layer deposit of a film of water-soluble phthalocyanine dye (Alcian blue, pyridine variant, AB) and polystyrenesulfonate was observed. Additionally, adsorptions from a mixed solution of AB and polydiallyldimethylammonium chloride were observed.

Synthesis of Diallyl dimethyl ammonium chloride grafted polyvinyl pyrrolidone (PVP-g-DADMAC) and its applications

The search for a sustainable and nontoxic polymeric product has fired an intense research in the field of graft copolymers. This study endeavor to create a polyacrylamide free novel flocculant which showed efficient behavior towards water and wastewater treatment and for mineral ore beneficiation. We synthesized the novel graft copolymer - Poly Diallyl Dimethyl Ammonium Chloride (DADMAC) grafted polyvinyl pyrrolidone (PVP-g-pDADMAC) via graft polymerization route by microwave assisted method. The synthesized novel cationic graft co-polymer has been characterized by elemental analysis, FTIR spectroscopy, intrinsic viscosity measurement, molecular weight determination, and scanning electron micrograph (SEM), taking PVP as reference. The effects of reaction parameters onto the percentage grafting have been studied. The applicability of these grafted polymers as flocculant for the treatment of municipal sewage waste water as well as for mineral ore beneficiation and for suppression of nanopollutant like multi-walled carbon Nano-tubes (MWCNTs) (as nano scavenger) from water systems were also investigated.

Probing surface interactions of underwater oleophobic polyelectrolyte multilayers

In the present work, the interaction mechanism of specific polyelectrolyte multilayers (PEMs), fabricated by layer-by-layer deposition of polydiallyldimethylammonium chloride (PDDA) and poly(sodium 4-styrenesulfonate) (PSS), is studied using atomic force microscopy. The underwater oil-repellency of PSS-capped PEMs was further explored by measuring the interaction forces between tetradecane droplets and PEMs-coated silica substrates under various salinities. The force curves were analyzed following the Stokes–Reynolds–Young–Laplace theoretical model. Desirable consistency was achieved between the experimental and theoretical calculations at low NaCl concentrations (0.1 mM and 1 mM); however, underestimation of the attractive force was found as the NaCl concentration increases to moderate (10 mM) and high (100 mM) levels. Discrepancy analyses and incorporated features toward a reduced surface charge density were considered based on the previous findings of the orientation of anionic benzenesulfonate moieties (Liu et al. in Angew Chem Int Ed 54(16):4851–4856, 2015. https://doi.org/10.1002/anie.201411992). Short-range steric hindrance interactions were further introduced to simulate “brush” effect stemming from nanoscale surface roughness. It is demonstrated in our work that the PSS-capped PEMs remains a stable underwater lipophobicity against high salinity, which renders it potential application in surface wetting modification and anti-fouling.

High performance nanofiltration in BUT-8(A)/PDDA mixed matrix membrane fabricated by spin-assisted layer-by-layer assembly

The membrane fouling is a notorious problem in the practical application of separation membranes. In this study, a mixed matrix membrane based on the MOF BUT-8(A) and the polymer polydiallyldimethylammonium chloride (PDDA) has been prepared on a hydrolyzed polyacrylonitrile (HPAN) substrate by the spin-assisted layer-by-layer assembly (spin-LbL) method. Thanks to the high porosity, high stability, moderate hydrophilicity, and electronegative nature of BUT-8(A), and the good compatibility between BUT-8(A) particles and PDDA polyelectrolytes, the prepared (BUT-8(A)/PDDA)3-HPAN membrane showed high water permeances (over 164 L m−2 h−1 MPa−1) and high rejection rates (over 91.4%) for many dyes in water. Furthermore, the membrane exhibited superior antifouling performance in nanofiltration (NF) with a high flux recovery rate (95.5%) when humic acid (HA) was used as foulant. The high antifouling performance is resulted from tuning hydrophilicity and electronegativity of the membrane surface. These results suggest that the nanofiltration performance of a MOF-based membrane can be well adjusted by a judicious choice of the membrane components and fabrication methods.

Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking

In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ∼400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY@SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY@SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h−1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY@SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.

Ultrasensitive determination of nitrite based on electrochemical platform of AuNPs deposited on PDDA-modified MXene nanosheets

An ultrasensitive and high-performance electrochemical nitrite sensing platform based on gold nanoparticles deposited on poly (dimethyl diallyl ammonium chloride)-decorated MXene (Ti3C2Tx) (AuNPs/Ti3C2Tx-PDDA) was constructed. AuNPs/Ti3C2Tx-PDDA on the surface of electrode displayed synergetic catalytic effect for oxidizing NO2‾ originating from especially catalytic activity of AuNPs, large area and excellent conductivity of Ti3C2Tx, as well as electrostatic interaction of PDDA. The amperometry technique was employed for quantitative determination of nitrite, in which the AuNPs/Ti3C2Tx-PDDA/GCE sensing platform showed outstanding linear relationship in 0.1–2490 μM and 2490–13490 μM for nitrite, meanwhile the detection limit of 0.059 μM. Besides, the prepared sensor possessed high sensitivity of 250 μA mM−1 cm−2 yet excellent selectivity, stability and reproducibility. Furthermore, this platform also exhibited satisfactory feasibility of nitrite sensing in running water and ham sausage sample. This work would broaden a facile approach to construct high sensitivity electrochemical sensing platform via two-dimension materials and its nanocomposites.

Influence of charge density and ionic strength on diallyldimethylammonium chloride (DADMAC)-based polyelectrolyte multilayer membrane formation

Although the layer-by-layer technique to produce nanofiltration membranes has been studied frequently, the influence of ionic strength of the coating solution in relation to the charge density lacks understanding. Here, we investigate the effect of both parameters systematically by comparing two strong polyelectrolyte sets: poly(acrylamide-co-diallyldimethylammoniumchloride) (P(AM-co-DADMAC))/ poly(sodium-4-styrenesulfonate) (PSS) and polydiallyldimethylammoniumchloride (PDADMAC)/PSS, with a polycation charge density of 32 and 100%, respectively. The influence of the charge density and the ionic strength during layer formation (5∙10−5 M – 1 M) has been researched in terms of polyelectrolyte adsorbance, membrane surface charge, and filtration performance. A low charge density is a limiting parameter for polyelectrolyte adsorption and retention, due to limited uptake of two bilayers. Consequently, it is impossible to form NF membranes with solely P(AM-co-DADMAC)/PSS layers. For high charge density polyelectrolytes, increasing the ionic strength is crucial to increase PE adsorption and MgSO4 retention. However, there is an opposite effect of ionic strength and charge density on membrane surface charge and pure water permeability. An increasing ionic strength results in a decreasing surface charge and increasing permeability for P(AM-co-DADMAC)-based membranes, and vice versa for PDADMAC. These opposite trends undoubtedly show the importance of simultaneously taking into account the charge density and ionic strength.

A Pd nanocatalyst supported on a polymer-modified hybrid carbon material for methanol oxidation

A hybrid carbon support is prepared by mixing graphene nanoplates (GNPs) with carbon nanotubes (CNTs) and modifying them with poly dimethyl diallyl ammonium chloride (PDDA). Pd nanoparticles are deposited onto the hybrid support by a microwave-assisted ethylene glycol reduction method. The obtained Pd/GNPs-PDDA-CNTs catalyst exhibits a high catalytic activity toward methanol oxidation in alkaline solution. Scanning electron microscope and transmission electron microscope images show that GNPs and CNTs contact intimately with each other and Pd nanoparticles are uniformly distributed over them. The linear sweeping voltammetry test indicates that Pd/GNPs-PDDA-CNTs has a low onset potential for methanol oxidation, which is attributed to the synergistic interaction between palladium and PDDA, as revealed by the X-ray photoelectron spectroscopy measurement. It is also observed that the poison resistance of the Pd nanocatalyst is improved to some extent due to the modification of the carbon support by the ionic polymer.

Cationization of cotton fiber: an integrated view of cationic agents, processes variables, properties, market and future prospects

Anionic dyes are often used for conventional cotton dyeing. This process, however, has a moderate affinity and it is estimated that less than 70% of the dye interacts with the cotton fiber. Cationization of cellulose is a chemical treatment that modifies the cellulose molecule, making it strongly cationic. This pretreatment increases the affinity between cotton and anionic dyes. Therefore, cationic dyeing reduces water, time, energy and chemical consumption. In this scenario, there is a growing demand to develop new cleaner products, as well as to elucidate the reaction mechanism aiming to create a clean and low-cost process for cotton cationization. In the last decades, more than 800 documents were published, and this number continues to rise. Among the cationic agents, 3-chloro-2-hydroxypropyl trimethylammonium chloride is the most researched and has achieved niche markets. However, poly-diallyldimethylammonium chloride combines effectiveness with a cleaner process. These characteristics make this cationic agent promising for future research. This review reports the state of the art on the techniques used for cationization, with a brief description of the market available for cationic cotton and a critical evaluation of the future perspectives for cationization.

Hybrid Nanotube Assembly and Hierarchical ZSM‐23 Zeolite Synthesized with Cationic Polymer and Enhanced Performance in n‐Heptane Hydroisomerization

AbstractNovel nanotube assembly and hierarchical ZSM‐23 zeolite can be fabricated by using the low‐cost and commercial cationic polymer of polydiallyldimethylammonium chloride (polyDDA) in the synthesis gel. In this facile synthesis, the polyDDA plays roles as the growth inhibitor for nanosized crystals and the secondary porogen. This unique crystal structure shows tubular nanocrystals assembling to form agglomerates. This hierarchical structure combines intercrystalline mesopore and narrow macropore to the micropore of ZSM‐23. Double advantages of nanocrystal and hierarchical structure contribute to higher pore mouths and enhanced diffusion of the reaction molecules. The hierarchical form also benefits for simple crystal recovery of nanozeolite by filtration. The n‐heptane hydroisomerization shows the derived Pt/H‐ZSM‐23 outperforms the conventional Pt/H‐ZSM‐23 with higher isomer yield at higher conversion and less cracked product yield. This could be attributed to higher pore mouths and efficient mass transport because of the shorter diffusion path length by the smaller crystal and hierarchical structure supplementing pore‐to‐pore connection of the molecular transport.

In vitro characterization of osteoblast cells on polyelectrolyte multilayers containing detonation nanodiamonds

Nanoparticle-enhanced coatings of bone implants are a promising method to facilitate sustainable wound healing, leading to an increase in patient well-being. This article describes the in vitro characterization of osteoblast cells interacting with polyelectrolyte multilayers, which contain detonation nanodiamonds (NDs), as a novel class of carbon-based coating material, which presents a unique combination of photoluminescence and drug-binding properties. The cationic polyelectrolyte, namely polydiallyldimethylammonium chloride (PDDA), has been used to immobilize NDs on silica glass. The height of ND-PDDA multilayers varies from a minimum of 10 nm for one bilayer to a maximum of 90 nm for five bilayers of NDs and PDDA. Human fetal osteoblasts (hFOBs) cultured on ND-PDDA multilayers show a large number of focal adhesions, which were studied via quantitative fluorescence imaging analysis. The influence of the surface roughness on the filopodia formation was assessed via scanning electron microscopy and atomic force microscopy. The nano-rough surface of five bilayers constrained the filopodia formation. The hFOBs grown on NDs tend to show not only a similar cell morphology compared to cells cultured on extracellular matrix protein-coated silica glass substrates, but also increased cell viability by about 40%. The high biocompatibility of the ND-PDDA multilayers, indicated via high cell proliferation and sound cell adhesion, shows their potential for biomedical applications such as drug-eluting coatings and biomaterials in general.

Effects of amines on the formation and photodegradation of DCNM under UV/chlorine disinfection

Investigations were conducted to examine the effects of amine type and initial concentration, free chlorine concentration, UV light intensity, pH and tert-butyl alcohol (TBA) on the formation of dichloronitromethane (DCNM) under UV/chlorine. Methylamine (MA), dimethylamine (DMA) and poly-dimethyl diallyl ammonium chloride (PolyDADMAC) were selected as the amine precursors of DCNM. And the reaction products of amines were explored through observing the contents of various nitrogen under UV/chlorine. Experimental results indicated that the higher of the intensity of UV light, the concentration of amines and free chlorine, the greater of the amount of DCNM formation; the amine substance with simple structure is more likely oxidized to form DCNM, so the potential of MA to form DCNM is the largest among three amines; the formation of DCNM decreased with increasing pH from 6.0 to 8.0; due to adding TBA into the reaction solution, halogen and hydroxyl radicals were restrained which resulted the DCNM formation decreased. In the reaction process, the formation of DCNM from amines increased at the beginning, then decreased and almost disappeared due to photodegradation. During the formation and photodegradation of DCNM, the dissolved organic nitrogen could be transformed into the ammonia-nitrogen (NH3-N) and nitrate-nitrogen (NO3−-N).

Synthesis of hierarchical Sn-Beta zeolite and its catalytic performance in glucose conversion

Hierarchical Beta zeolites are successfully synthesized with hydrothermal method in the presence of polydiallyldimethylammonium chloride (PDADMA). Followed a dealumination process, hierarchical Sn-Beta are post-synthesized by the solid-gas reaction of dealuminated Beta zeolite with SnCl4 vapor. All samples are charcterized with XRD, N2 sorption, SEM and TEM. SEM images show that both Beta zeolite and Sn-Beta zeolite exhibit rough spherical-like morphology of about 500−900 nm in diameters, N2 sorptions show the pore size distributions in micropore and mesopore ranges, indicating the formation of mesoporous Beta zeolites. It is proofed that Sn species are doped into the framework in a tetrahedral environment during solid-gas reaction and the introduction of Sn species has negligible impact on the structure of Beta zeolites. Furthermore, the dehydration of glucose into HMF which needs both Brönsted and Lewis acid is selected to evaluate the catalytic performance of hierarchical Sn-Beta. It displays good catalytic activity, the conversion of glucose (99 %) and selectivity to HMF (42 %) are higher than those of the conventional Beta (96 % and 32 %, respectively). This is attributed to the intra-crystalline mesoporous structure and efficient diffusion of reactant/product molecules. Moreover, the catalyst exhibits steady catalytic performance after the fifth repeated run.