RESEARCH ON CATIONIC POLYMER WATER BASE DRILLING FLUIDS

Cationic polymer drilling fluid (CPDF) is a new water base drilling fluid in which high molecular weight (HMW) cationic polymer (CPAM) is an encapsulating and flocculating agent and organic quaternary ammonium compound (NW-1) acts as shale inhibitor. This paper describes the experimental results of cuttings recovery, particle size distribution layer spacing and Zeta potential, and discusses the inhibition of CPDF system and its major additives. The advantages of CPDF will be proved by its application in well LX-2.

Nanoparticle-induced drag reduction for polyacrylamide in turbulent flow with high Reynolds numbers

Although having been increasingly studied, there is still controversy as to when the addition of nanoparticles could improve the drag reduction performance of polymer drag reducer and particularly what is the underlying mechanism from the fluid dynamics viewpoint. The drag reduction effects of adding SiO_(2) nanoparticles to various polymer polyacrylamide(PAM) solutions were examined in this work.The optimal combination of SiO_(2) nanoparticles with cationic polyacrylamide was confirmed.Interestingly,the addition of SiO_(2) nanoparticles to cationic polyacrylamide solution was shown to be quite efficient for reducing drag, but only at higher flow rates with Reynolds numbers more than 6000, below which the nanoparticle addition is even negative. The addition of SiO_(2) nanoparticles to the PAM solution is supposed to play a dual role. The first is an increase in flow resistance caused by the Brownian motion of nanoparticles, while the second is a decrease in flow resistance caused by acting as nodes to protect the polymer chain from shear-induced breaking under high shear action. At optimal nanoparticle concentration and under higher Reynolds numbers, the later effect is dominant, which could improve the drag reduction performance of polymer drag reducers. Our work should serve as a guide for the application of natural gas fracturing, where the flow rate is frequently very high.

Assembling structurally customizable synthetic carriers of si RNA through thermodynamically self-regulated process

This study demonstrates that our previously reported polywraplex, a synthetic siRNA carrier consisting of a uni-molecular polyplex core of customizable size and a self-assembled triblock copolymer envelop, may be constructed using dendrimers as the crosslinking junctions. Replacing the branched low molecular weight PEI with polyamidoamine(PAMAM) dendrimer in the zeta potential regulated polymerization resulted in the similar network structured cationic polymer with electron microscopically visible crosslinking junctions. This visibility may offer a convenient way to characterize the molecular structure of the rationally designed networked siRNA-packing cationic polymer without altering its chemical properties and biologic functions. A series of physical-chemical characterizations and biological assays, comprising size, zeta potential, pre-phagocytic siRNA leaking and degradation, and silencing of functional genes, confirmed that the advanced properties of polywraplexes remained with the dendrimer junctions. Although sixth generation PAMAM dendrimer was used as the crosslinking junctions in the size-customizable polymerization for electron microscopic observation, lower generation dendrimer should also work in case more practical and structurally defined cationic polymer is needed.

Removal of total cyanide in coking wastewater during a coagulation process: Significance of organic polymers

Whether a cationic organic polymer can remove more total cyanide （TCN） than a non-ionic organic polymer during the same flocculation system has not been reported previously. In this study, the effects of organic polymers with different charge density on the removal mechanisms of TCN in coking wastewater are investigated by polyferric sulfate （PFS） with a cationic organic polymer （PFS-C） or a non-ionic polymer （PFS-N）. The coagulation experiments results show that residual concentrations of TCN （Fe（CN）6^3-） after PFS-C flocculation （TCN 〈 0.2 mg/L） are much lower than that after PFS-N precipitation. This can be attributed to the different TCN removal mechanisms of the individual organic polymers. To investigate the roles of organic polymers, physical and structural characteristics of the floes are analyzed by FT-IR, XPS, TEM and XRD. Owing to the presence of N＋ in PFS-C, Fe（CN）3- and negative flocs （Fe（CN）63- adsorbed on ferric hydroxides） can be removed via charge neutralization and electrostatic patch flocculation by the cationic organic polymer. However, non-ionic N in PFS-N barely reacts with cyanides through sweeping or bridging, which indicates that the non-ionic polymer has little influence on TCN removal.

Synthesis and characterization of PEGylated comb-like cationic polymer by polycondensation and ATRP

PEGylated poly（2-（dimethylamino）ethyl methacrylate） with comb-like architecture was synthesized by two-step polymerization. First,poly（oligo（ethylene glycol） malicate）（POEGMA） bearing pendant hydroxyl groups was prepared by direct polycondensation of oligo（ethylene glycol） and malic acid in the presence of scandium triflate as chemoselective catalyst.Then the poly（2- （dimethylamino）ethyl methacrylate） side chains were grafted from the POEGMA backbone by atom transfer radical polymerization （ATRP） after the hydroxyl groups were modified into bromo-ester form,resulting in a PEGylated cationic copolymer with branched architecture.

Rational design of a cationic polymer network towards record high uptake of ^(99)TcO_(4)^(-)in nuclear waste

^(99)Tc is a long-lived radionuclide present in large amounts as TcO_(4)^(-)-anion in used nuclear fuel.Its removal from the waste stream is highly desirable because of its interference capability with actinide separation and its volatile nature during the nuclear waste vitrification process.Despite the progress achieved in the past few years,the design of anion-exchange materials with optimized Tc uptake property and improved stability under the extreme condition is still a research goal beneficial for reducing the volume of secondary radioactive solid waste generated during the waste partitioning process.However,their design philosophy remains elusive,with challenges coming from charge repulsion,steric hindrance,and insufficient reactive sites within the materials.Herein,we present a design philosophy of cationic polymer network materials for TcO_(4)^(-)separation by systematic precursor screening and structure prediction.This affords an optimized material,SCU-CPN-2(SCU=Soochow University),with extremely high positive charge density while maintaining high radiation resistance.SCU-CPN-2 exhibits a record high adsorption capacity1,467 mg/g towards the surrogate ReO_(4)^(-)compared to all anion-exchange materials reported up to date.In addition to ultrafast adsorption kinetics,SCU-CPN-2 has remarkable selectivity over nitrate and sulfate,and facile recyclability.

Synthesis of a cationic poly(p-phenylenevinylene) derivative for Iysosome-specific and long-term imaging

The development of long-term imaging agents and subcellular imaging materials is of great importance in the research of cancer cell behaviors. In this work, a cationic poly（p-phenylenevinylene） derivative（PPV） is designed and synthesized to link quaternized N-methyl-imidazole groups as pendants which endow the polymer to bear positive charges. Absorption and fluorescence emission spectra of PPV display a large Stokes shift of 102 nm which is much larger than the commercial cell dyes. Positively charged polymer could adsorb onto the surface of cells via electrostatic interactions followed by cell endocytosis process to enter cells. Importantly, PPV barely has influence on the cell viability through cytotoxicity analysis. The colocalization data demonstrates that PPV and commercial lysosome-specific dye are highly colocalized in the same region, indicating that the green fluorescent PPV mainly distributes in the lysosomes. Moreover, the continuous imaging investigation shows that PPV could stay in cells for more than seven days while the commercial Lyso-Tracker would be extruded by cells after three days. PPV exhibits superior capabilities including strong fluorescence, large Stokes shift, good biocompatibility and high photostablity, which has great potential in the applications of cellular process monitoring.

Hollow click-based porous organic polymers for heterogenization of [Ru（bpy）3]2＋ through electrostatic interactions

A facile approach for the heterogenization of transition metal catalysts using non-covalent interactions in hollow click-based porous organic polymers （H-CPPs） is presented. A catalytically active cationic species, [Ru（bpy）3]〉 （bpy = 2,2＇-bipyridyl）, was immobilized in H-CPPs via electrostatic interactions. The intrinsic properties of [Ru（bpy）3]〉 were well retained. The resulting Ru- containing hollow polymers exhibited excellent catalytic activity, enhanced stability, and good recyclability when used for the oxidative hydroxylation of 4-methoxyphenylboronic acid to 4-methoxyphenol under visible-light irradiation. The attractive catalytic performance mainly resulted from efficient mass transfer and the maintenance of the chemical properties of the cationic Ru complex in the H-CPPs.

Metal-free multicomponent polymerization toward cationic polyamidines

Cationic polymers,also known as polycations,are considered to be the most potential non-viral gene carriers due to their unique advantages such as the ability to bind the negative charge of nucleic acid molecules.Multicomponent polymerization(MCP)is a one-step,tandem strategy to construct complex structures based on multicomponent reactions.Herein,we developed a metal-free MCP method based on three monomers of p-dinitrovinylbenzene(p-DNVB),1,1-dimethylethyl N,N-dibromocarbamate(BocNBr_(2)),and bis-secondary-amines with a ratio of 1:2:1,to access a library of Boc-substituted polyamidines with well-defined structures and suitable molecular weights(M w ranging from 4400Da to 11,000Da)in high yields(up to 85%)under mild conditions.Upon the removal of Boc groups,a series of water-soluble polymers with cationic property were prepared and their gene binding capability was further evaluated.

WHAT CAN WE LEARN FROM VIRUS IN DESIGNING NONVIRAL GENE VECTORS

Gene therapy has emerged as a potential new approach to treat genetic disorders by delivering therapeutic genes to target diseased tissues. However, its clinical use has been impeded by gene delivery systems. The viral vectors are very efficient in delivering and expressing their carried genes, but they have safety issues in clinical use. While nonviral vectors are much safer with very low risks after careful material design, but their gene transcription efficiency is too low to be clinically used. Thus, rational design of nonviral vectors mimicking the viral vectors would be a way to break this bottleneck. This review compares side-by-side how viral/nonviral gene vectors transcend these biological barriers in terms of blood circulation, cellular uptake, endosome escape, nucleus import and gene transcription.

Rapid inactivation of multidrug-resistant bacteria and enhancement of osteoinduction via titania nanotubes grafted with polyguanidines

The rapid in situ inhibition of bacterial contamination and subsequent infection without inducing drug resistance is highly vital for the successful implantation and long-term service of titanium(Ti)-based orthopedic implants.However,the instability and potential cytotoxicity of current coatings have deterred their clinical practice.In this study,anodic oxidized titania nanotubes(TNT)were modified with antibacterial polyhexamethylene guanidine(PG)with the assistance of 3,4-dihydroxyphenylacetic acid.Interestingly,the prepared TNT-PG coating exhibited superior in vitro antibacterial activity than flat Ti-PG coating and effectively killed typical pathogens such as Escherichia coli and superbug methicillinresistant Staphylococcus aureus with above 4-log reduction(>99.99%killed)in only 5 min.TNT-PG coating also exerted excellent hemocompatibility with red blood cells and nontoxicity toward mouse pre-osteoblasts(MC3 T3-E1)in 1 week of coculture.In addition,the efficient in vivo anti-infective property of this coating was observed in a rat subcutaneous infection model.More importantly,TNT-PG coating improved the expression of alkaline phosphatase and enhanced the extracellular matrix mineralization of pre-osteoblasts,denoting its osteoinductive capacity.This versatile TNT-PG coating with excellent antibacterial activity and biocompatibility could be a promising candidate for advanced orthopedic implant applications.

Synthesis and in vitro Property Study of Polyaspartamides

Cationic polyaspartamides including poly-α,β-[N＇-（2-aminoethyl）-L-aspartamide] （PAEA）, poly-α,β-[N＇-（4- aminobutyl）-L-aspartamide] （PABA）, poly-α,β-[N＇-（6-aminohexyl）-L-aspartamide] （PAHA）, poly-α,β-[N＇-（5-amino- 3-azapentyl）-L-aspartamide] （PAAPA） and poly-α,β-[N＇-（8-amino-3,6-diazaoctyl）-L-aspartamide] （PADAOA） were synthesized from polysuccinimide. Their properties were evaluated by ^1H NMR, IR, GPC, fluorescence measurement and in vitro cytotoxicity assays. The molecular weights per primary amine charge group of PAEA（1） （Mn= 2229）, PAAPA and PADAOA are 212, 279, and 226. Polyaspartamides including PAEA（1）, PAAPA, PADAOA and low molecular weight PAHA are markedly less toxic than poly（ethyleneimine） and poly（L-lysine）, however, PABA and higher molecular weight PAHA are slightly less toxic than poly（L-lysine）. Cell cytotoxicity of PAHA was seen to decrease with increasing molecular weight of PAHA, due to water solubility reduction. The negatively charged plasmid DNA has been found to be completely neutralized and complexed by the cationic polyaspartamides at an N/P ratio of 5 ： 1 to 10 ： 1, forming self-assembled polyplexes via ionic interactions. These polyaspartamide/DNA complexes possess stable zeta potentials and mean particle diameters of about 180 nm for PAEA （1）/DNA and PAAPA/DNA complexes and 280 nm for PADAOA/DNA complexes.

Polymer-capped gold nanoparticles and ZnO nanorods form binary photocatalyst on cotton fabrics: Catalytic breakdown of dye

This work reports the immobilization of zinc oxide(ZnO)nanostructures and gold nanoparticles(AuNPs)on cotton fabrics(CFs).The ZnO and AuNPs containing CF composite materials demonstrated excellent photocatalytic activity towards degradation of the model organic dye molecule.A two-step method was used to first create zinc oxide nanorods(ZnONRs)on the CF fibers.Subsequently,these ZnONRs were decorated with cationic polymer-capped AuNPs to yield the composite materials.A one-pot synthetic route was developed to synthesize polymer-capped AuNPs.The water-soluble cationic polymers used here are polyguanidino oxanorbornenes(PGONs)at 20 kDa and polyamino oxanorbornenes(PAONs)at 20 kDa.UV-vis was utilized to monitor the composite materials’photocatalytic activity in degrading model organic dye molecules.All the materials were characterized by FTIR,UV-visible DRS,SEM,EDX,and XRD.The composite materials exhibited excellent photocatalytic activity and recyclability in the presence of UV light.

Antimicrobial peptide-inspired antibacterial polymeric materials for biosafety

The emergence of antimicrobial resistance attributed to the overuse and abuse of antibiotics severely endangers global biosafety.Antimicrobial peptides(AMPs)produced by various living organisms exhibit broad-spectrum antimicrobial properties with a low propensity to the resistance.However,the application of AMPs has been greatly limited owing to their poor stability,high manufacturing cost,and high cytotoxicity.Thus,AMP-mimetic antimicrobial cationic polymers with cationic and amphiphilic moieties have attracted considerable attention as antimicrobial agents.These polymers typically exhibit broad-spectrum antimicrobial activities,negligible antimicrobial resistance,and rapid bactericidal effect.These polymers exhibit low hemolysis and cytotoxicity by optimizing their chemical structures.In this study,we summarize the design principles and current findings of antimicrobial cationic polymers and identify potential candidates for developing innovative polymeric antimicrobials.