Grafting Density Research Articles

Magnetic graphene oxide grafted boronic acid-decorated metal-organic frameworks for selective enrichment of cis-diol-containing nucleosides

In this study, a novel magnetic graphene oxide grafted boronic acid-decorated metal-organic frameworks (Fe3O4@GO@BA-MOF) composite was developed for the selective enrichment of cis-diol-containing nucleosides. It is noteworthy that the amino-functionalized Fe3O4 was prepared by polyethyleneimine (PEI) as modifier, resulting in excellent durability and stability of magnetic nanoparticles under different environment, as well as introducing rich active functional groups for post-modification. GO with large surface area and abundant multi-active group was covalently bonded on amino-rich Fe3O4 as interlayer to facilitate the growth of BA-MOF with high boronic acid grafting density for selective capture of nucleosides. Due to the multi-interactions, especially the boronate affinity as well as the synergistic effect, the Fe3O4@GO@BA-MOF composite exhibited superior selectivity and adsorption capacity to nucleosides. Under the optimal conditions, an efficient magnetic solid-phase extraction-high-performance liquid chromatography technique was established using Fe3O4@GO@BA-MOF composite for the purpose of extracting and detecting nucleosides in urine, with recoveries ranging from 90.69 % to 110.36 %, relative standard deviations below 8.5 % and detection limits ranging from 0.004 to 0.010 μg mL−1. This study offers a new approach for preparation of high grafting density of boronic acid-decorated magnetic MOF, which is promising in selective enrichment of cis-diol-containing compounds in biological analysis.

Increased stearic acid grafting density on silica nanoparticles via alumina-activation

Stearic acid (SA) has a low grafting density on silica nanoparticle (NP) surfaces. However, alumina coating on the particle surface effectively increases the surface reactivity with SA, significantly increasing the grafting density of SA. When the alumina coating amount reaches 15 %, the grafting density of SA increases by 350 % compared to that of the reference sample, while the water contact angle reaches 124°. The coated alumina is chemically bonded to the surfaces of the SiO2 particles. After alumina coating, the particle surface is loaded with electron acceptor sites with strong electron-receiving ability, allowing SA to undergo Lewis acid–base reactions with the particle surface.

Effect of Grafting Density on the Crystallization Behavior of Molecular Bottlebrushes.

A unique case of sterically constrained crystallization arises in bottlebrush polymers bearing semicrystalline side chains. Bottlebrushes with grafted side chains can form crystalline structures governed by the complex interplay between side chain packing and backbone confinement. The confinement effect can be readily tuned by varying the side chain grafting density, thus affording control over the crystallization behavior of these systems. In this work, the grafting density effect on the crystallization behavior of molecular bottlebrushes comprising poly(ethylene oxide) (PEO) side chains grafted to a methacrylate backbone was systematically studied. Thermal analysis using differential scanning calorimetry showed that the bottlebrush polymers displayed suppressed crystallization temperatures, lower melting temperatures, and reduced crystallinities compared to linear homopolymer PEO. The crystalline morphology was investigated using polarized light, atomic force, and scanning electron microscopy. Isothermal crystallization experiments revealed a nonmonotonous dependence of the nucleation density on the side chain grafting density. The grafting density effect was also investigated using self-seeding experiments, revealing an increased clearing temperature and memory retention at higher grafting densities. This work highlights how grafting density influences the crystallization behavior of semicrystalline bottlebrushes, providing information for the processing and application of these unique polymers.

Rewritable Surface-Grafted Polymer Brushes with Dynamic Covalent Linkages.

Surface grafting of polymer brushes drastically modifies surface properties, including wettability, compatibility, responsiveness, etc. A broad variety of functionalities can be introduced to the surface via different types of polymers. Bringing together properties of two or more types of polymer brushes to one surface opens up even more possibilities in brush-modified materials. However, while it is generally feasible to introduce several chemical compositions along the brushes via copolymerization, it is challenging to vary the types of polymer brushes along a surface. Although previous studies have demonstrated binary brushes via orthogonal polymerization techniques or partial deactivation/regrafting, they commonly limit the number of polymer types to two. Here, we propose a strategy to introduce dynamic covalent diketoenamine linkages at the root of polymer brushes. The grafting density could be precisely tuned during surface functionalization. The surface-anchored polymer brushes were cleaved by the addition of small molecule amines. New polymer brushes can be regrafted from the surface following refunctionalization of exposed sites. The maneuverability allows tuning of the types and densities of the polymer brushes, pointing the way to the preparation of a new generation of well-defined brush-modified materials with mixed grafts, with potential applications in the design of smart materials and surfaces.

Interference Effects in Micro-Raman Spectroscopy Enable Mapping of Chemical Gradients on an Elastomer Surface.

Chemically modified elastomer surfaces are important to many applications, including microfluidics and soft sensors. Sensitive characterization of the interfacial chemistry of soft materials has been a persistent challenge, given their structural and chemical complexity. This article reports a method to probe local chemical states of elastomer surfaces that leverages the interference effects observed in micro-Raman spectroscopy. Unexpectedly, systematic variations of Raman scattering intensity were observed across a chemical wettability gradient grafted to the surface of a poly(dimethylsiloxane) (PDMS) film. Specifically, hydrophobic surface regions with a high graft density of long-chain hydrocarbon molecules showed suppressed Raman intensity. An optical interference model that accounts for molecular filling and swelling of an interfacial glassy layer during chemical modifications of the PDMS surface quantitatively reproduces experimental observations. This work establishes the spectroscopic signatures of interfacial chemical modifications on elastomer surfaces and enables a noncontact optical probe of local chemical states at the micro- and nanoscale compatible with the complex interfaces of soft materials.

Super-hydrophobic ceramic membrane with dense and robust silane grafting for efficient water-in-oil emulsion separation

Separate water from water-in-oil (W/O) emulsions is essential in oil resources recycling and wastewater treatment. Hydrophobic ceramic membranes (HCM) have shown great potential in the dehydration of W/O emulsions but developing high-performance HCM is still a challenge due to the difficulty in hydrophobic modification of ceramic membranes. In this study, an HCM with high grafting density and robust structure was prepared by the grafting silane coupling agent onto an attapulgite (ATP) ceramic membrane. The hexadecyltrimethoxysilane (HDTMS) was chosen for membrane surface modification considering its reaction activity and stability based on molecular dynamic simulation. The effect of the HDTMS contents in the grafting solution and reaction time on the membrane properties were examined. The ATP membrane grafted by HDTMS solution with a content of 9600 ppm for 24 h had a water contact angle of 161° and oil permeability larger than 2207.5 L·m−2·h−1·bar−1 (LMHB). When dealing with W/O emulsions with a water content of 10000 ppm, the steady permeability, permeability recovery ratio, and water rejection of ATP-based HCM was 362 LMHB, 97 %, and 99 %, respectively. Ascribe to the –OH-rich nature of ATP, the performance of HCM in this work is superior to most membranes including Al2O3, ZrO2, and SiC. Hydrophobic-modified ATP provides a new idea for the development of high-performance HCM based on natural mineral ceramics.

Comparative Molecular Dynamics Simulation of Wetting on Liquid-like Surfaces.

We utilize molecular dynamics simulations to comparably investigate the wetting and motion behavior of droplets on liquid-like surfaces (LLS) with varying grafting conditions. Polydimethylsiloxane (PDMS) and perfluoropolyether (PFPE) have been considered to be flexible molecules versus rigid molecules of trichloro(octadecyl) silane (OTS) and trichloro(1H,1H,2H,2H-perfluorooctyl) silane (PFOS), respectively. Our findings reveal that droplets on surfaces tethered with either PDMS or PFPE brushes can generate indentations and wetting ridges, providing microscopic evidence of their liquid-like nature. The grafting density of mobile chains exerts a dominant influence on the wetting properties compared to the molecular weight. A parameter map is created to pinpoint the precise range of grafting densities essential for the optimal construction of LLS at predetermined molecular weights. Furthermore, the investigation of droplet motion dynamics on LLS demonstrates that droplets consistently exhibit a rolling state, regardless of the intensity of the applied lateral force. The movement pattern of the droplet shifts only under conditions where the grafting density is significantly reduced and the substrate exhibits hydrophilic tendencies. These findings and the developed model are anticipated to offer valuable guidelines for optimal designs of LLS.

Surface Orthogonal Patterning and Bidirectional Self-Assembly of Nanoparticles Tethered by V-Shaped Diblock Copolymers.

We investigated the surface orthogonal patterning and bidirectional self-assembly of binary hairy nanoparticles (NPs) constructed by uniformly tethering a single NP with multiple V-shaped AB diblock copolymers using Brownian dynamics simulations in a poor solvent. At low concentration, the chain collapse and microphase separation of binary polymer brushes can lead to the patterning of the NP surface into A- and B-type orthogonal patches with various numbers of domains (valency), n = 1-6, that adopt spherical, linear, triangular, tetrahedral, square pyramidal, and pentagonal pyramidal configurations. There is a linear relationship between the valency and the average ratio of NP diameter to the polymers' unperturbed root-mean-square end-to-end distance for the corresponding valency. The linear slope depends on the grafting density and is independent of the interaction parameters between polymers. At high concentration, the orthogonal patch NPs serve as building blocks and exhibit directional attractions by overlapping the same type of domains, resulting in self-assembly into a series of fascinating architectures depending on the valency and polymer length. Notably, the 2-valent orthogonal patch NPs have the bidirectional bonding ability to form the two-dimensional (2D) square NP arrays by two distinct pathways. Simultaneously patching A and B blocks enables the one-step formation of 2D square arrays via bidirectional growth, whereas step-by-step patching causes the directional formation of 1D chains followed by 2D square arrays. Moreover, the gap between NPs in the 2D square arrays is related to the polymer length but independent of the NP diameter. These 2D square NP arrays are of significant value in practical applications such as integrated circuit manufacturing and nanotechnology.

Rational development of functional hydrophilic polymer to characterize site-specific glycan differences between bovine milk and colostrum

As vastly modified on secreted proteins, N-glycosylation is found on milk proteins and undergo dynamic changes during lactation, characterizing milk protein glycosylation would benefit the elucidation of glycosylation pattern differences between samples. However, their low abundance required specific enrichment. Herein, through rational design and controllable synthesis, we developed a novel multi-functional polymer for the isolation of protein glycosylation. It efficiently separated glycopeptides from complex background inferences with mutual efforts of hydrophilic interaction chromatography (HILIC), metal ion affinity and ion exchange. By fine-tuning Ca2+ as regulators of aldehyde hyaluronic acid (HA) conformation, the grafting density of HA was remarkably improved. Moreover, grafting Ti4+ further enhanced the enrichment performance. Application of this material to characterize bovine milk and colostrum proteins yields 479 and 611 intact glycopeptides, respectively. Comparative analysis unraveled the distinct glycosylation pattern as well the different distribution of glycoprotein abundances between the two samples, offering insights for functional food development.

Amidoxime‐based Star Polymer Adsorbent with Ultra‐High Uranyl Affinity for Extremely Fast Uranium Extraction from Natural Seawater

AbstractPolymer adsorbents functionalized with amidoxime groups are widely considered to have the most industrial potential for uranium extraction from seawater. However, the entanglement upon the collapse of polymer chain in seawater greatly reduces the utilization ratio of amidoxime ligands. Herein, a novel star‐shaped molecular brush adsorbent (β‐CD‐g‐PAO) is obtained by densely grafting polyamidoxime (PAO) chains from β‐cyclodextrin (β‐CD). Experimental and theoretical results reveal that, in contrast to conventional linear polymer adsorbents, the star polymer adsorbent with a high grafting density of PAO side chains enables strong steric repulsion between the polymer chains, leading to increased persistence length and disentanglement of side chains. As a result, the star polymer adsorbent shows higher accessibility of the adsorption ligands with lower adsorption energy, achieving an adsorption capacity of up to 944.75 mg g−1 in uranium‐spiked seawater, surpassing that of conventional linear PAO by 3.2 times. Remarkably, this star polymer adsorbent demonstrates an extraordinarily adsorption capacity of 10.9 mg−1 g−1 in only 1 day in natural seawater, coupled with excellent affinity for uranyl ions (K = 0.31 pM). The unique topological structure design provides a new approach to solving the problem of low utilization ratio of functional ligands in polymer adsorbents.

Growth phase-dependent changes in conformational and physicochemical properties of bacterial surface biopolymers lead to changes in bacterial adhesion strength at nanoscale and macroscale

This study presents a detailed investigation into conformational, physicochemical and adhesive characteristics of biopolymers on the surfaces of Escherichia coli and potential probiotic Bacillus subtilis harvested from middle-exponential phase (mid-EP), late-exponential phase (late-EP) and early-stationary phase (early-SP) of growth. The lengths to which bacterial surface biopolymers extend (biopolymer brush lengths), densities of grafted bacterial surface biopolymers indicating the amounts of molecules covering the bacterial surfaces (biopolymer grafting densities), adhesion forces of bacterial surface biopolymers to the model inert surfaces of silicon nitride (Si3N4), and the pull-off distances of biopolymers from Si3N4 were measured in water by atomic force microscopy (AFM). The Weibull analysis of AFM adhesion data showed that as the culture aged, the adhesive bonds between Si3N4 AFM tips and surface molecules of E. coli harvested from the culture were broken with a higher applied force. However, the highest applied force to break the bonds was required for B. subtilis in late-EP, followed by those required for cells in early-SP and mid-EP, respectively. The results of a steric model fitting to AFM approach force-distance (FD) curves and analysis of the pull-off distances in the AFM retraction FD curves showed higher biopolymer grafting density for E. coli in early-SP and longer biopolymer brush layer for B. subtilis in late-EP, which were associated with stronger adhesion to Si3N4 in water. The results of thermodynamic adhesion energy calculations based on the Wu model showed that polar interaction energy dominated the bacterial adhesion at the macroscale, the strength of which varied as a function of the growth phase for both E. coli and B. subtilis. The growth phase-dependent variation in polar components of thermodynamic adhesion energies between the bacteria and Si3N4 in water was consistent with the growth phase-dependent variation in the bond strengths between the bacteria and Si3N4 in water as revealed by the Weibull analysis of AFM adhesion data. Therefore, information obtained by Weibull analysis of nanoscale AFM bacterial adhesion data can be used to predict macroscale bacterial adhesion to the model inert Si3N4 surface in water.

Temperature-Sensitive Sensors Modified with Poly(N-isopropylacrylamide): Enhancing Performance through Tailored Thermoresponsiveness.

The development of temperature-sensitive sensors upgraded by poly(N-isopropylacrylamide) (PNIPAM) represents a significant stride in enhancing performance and tailoring thermoresponsiveness. In this study, an array of temperature-responsive electrochemical sensors modified with different PNIPAM-based copolymer films were fabricated via a "coating and grafting" two-step film-forming technique on screen-printed platinum electrodes (SPPEs). Chemical composition, grafting density, equilibrium swelling, surface wettability, surface morphology, amperometric response, cyclic voltammograms, and other properties were evaluated for the modified SPPEs, successively. The modified SPPEs exhibited significant changes in their properties depending on the preparation concentrations, but all the resulting sensors showed excellent stability and repeatability. The modified sensors demonstrated favorable sensitivity to hydrogen peroxide and L-ascorbic acid. Furthermore, notable temperature-induced variations in electrical signals were observed as the electrodes were subjected to temperature fluctuations above and below the lower critical solution temperature (LCST). The ability to reversibly respond to temperature variations, coupled with the tunability of PNIPAM's thermoresponsive properties, opens up new possibilities for the design of sensors that can adapt to changing environments and optimize their performance accordingly.

High Antifouling Performance of Weakly Hydrophilic Polymer Brushes: A Molecular Dynamics Study.

The antifouling performance of polymer brushes usually improves with increasing hydrophilicity of the grafted polymer. However, in some cases, less hydrophilic polymers show comparable or better antifouling performance than do more hydrophilic polymers. We investigate the mechanism of this anomalous behavior using molecular dynamics (MD) simulations of coarse-grained (CG) models of weakly and strongly hydrophilic polymers. The antifouling performance is evaluated from the potential of mean force of a model protein. The strongly hydrophilic polymer exhibits a better antifouling performance than the weakly hydrophilic polymer when the substrate of the polymer brush is repulsive. However, when the substrate is sufficiently attractive, the weakly hydrophilic polymer brush becomes more effective than the strongly hydrophilic brush in a certain range of grafting density. This is because the weakly hydrophilic polymer chains form a tightly packed layer that prevents the adsorbate molecule from contacting the substrate. We also perform all-atom (AA) MD simulations for several standard polymers to examine the correspondence with the CG polymer models. The weakly hydrophilic CG polymer is found to be similar to poly[N-(2-hydroxypropyl)methacrylamide] and poly(2-hydroxyethyl methacrylate), both of which have a hydroxyl group in a monomer unit. The strongly hydrophilic CG polymer resembles zwitterionic poly(carboxybetaine methacrylate). A discussion referring to the adsorption free energies of proteins on surfaces calculated in previous AA MD studies suggests that the higher antifouling performance of less hydrophilic polymer brushes can be realized for various combinations of protein and surface.

Organic nanoparticles with tunable size and rigidity by hyperbranching and cross-linking using microemulsion ATRP

Unlike inorganic nanoparticles, organic nanoparticles (oNPs) offer the advantage of "interior tailorability," thereby enabling the controlled variation of physicochemical characteristics and functionalities, for example, by incorporation of diverse functional small molecules. In this study, a unique inimer-based microemulsion approach is presented to realize oNPs with enhanced control of chemical and mechanical properties by deliberate variation of the degree of hyperbranching or cross-linking. The use of anionic cosurfactants led to oNPs with superior uniformity. Benefitting from the high initiator concentration from inimer and preserved chain-end functionality during atom transfer radical polymerization (ATRP), the capability of oNPs as a multifunctional macroinitiator for the subsequent surface-initiated ATRP was demonstrated. This facilitated the synthesis of densely tethered poly(methyl methacrylate) brush oNPs. Detailed analysis revealed that exceptionally high grafting densities (~1 nm-2) were attributable to multilayer surface grafting from oNPs due to the hyperbranched macromolecular architecture. The ability to control functional attributes along with elastic properties renders this "bottom-up" synthetic strategy of macroinitiator-type oNPs a unique platform for realizing functional materials with a broad spectrum of applications.

Concepts and Approaches to Reduce or Avoid Protein Corona Formation on Nanoparticles: Challenges and Opportunities.

This review describes the formation of a protein corona (or its absence) on different classes of nanoparticles, its basic principles, and its consequences for nanomedicine. For this purpose, it describes general concepts to control (guide/minimize) the interaction between artificial nanoparticles and plasma proteins to reduce protein corona formation. Thereafter, methods for the qualitative or quantitative determination of protein corona formation are presented, as well as the properties of nanoparticle surfaces, which are relevant for protein corona prevention (or formation). Thereby especially the role of grafting density of hydrophilic polymers on the surface of the nanoparticle is discussed to prevent the formation of a protein corona. In this context also the potential of detergents (surfactants) for a temporary modification as well as grafting-to and grafting-from approaches for a permanent modification of the surface are discussed. The review concludes by highlighting several promising avenues. This includes (i) the use of nanoparticles without protein corona for active targeting, (ii) the use of synthetic nanoparticles without protein corona formation to address the immune system, (iii) the recollection of nanoparticles with a defined protein corona after in vivo application to sample the blood proteome and (iv) further concepts to reduce protein corona formation.

XPS Depth-Profiling Studies of Chlorophyll Binding to Poly(cysteine methacrylate) Scaffolds in Pigment-Polymer Antenna Complexes Using a Gas Cluster Ion Source.

X-ray photoelectron spectroscopy (XPS) depth-profiling with an argon gas cluster ion source (GCIS) was used to characterize the spatial distribution of chlorophyll a (Chl) within a poly(cysteine methacrylate) (PCysMA) brush grown by surface-initiated atom-transfer radical polymerization (ATRP) from a planar surface. The organization of Chl is controlled by adjusting the brush grafting density and polymerization time. For dense brushes, the C, N, S elemental composition remains constant throughout the 36 nm brush layer until the underlying gold substrate is approached. However, for either reduced density brushes (mean thickness ∼20 nm) or mushrooms grown with reduced grafting densities (mean thickness 6-9 nm), elemental intensities decrease continuously throughout the brush layer, because photoelectrons are less strongly attenuated for such systems. For all brushes, the fraction of positively charged nitrogen atoms (N+/N0) decreases with increasing depth. Chl binding causes a marked reduction in N+/N0 within the brushes and produces a new feature at 398.1 eV in the N1s core-line spectrum assigned to tetrapyrrole ring nitrogen atoms coordinated to Zn2+. For all grafting densities, the N/S atomic ratio remains approximately constant as a function of brush depth, which indicates a uniform distribution of Chl throughout the brush layer. However, a larger fraction of repeat units bound to Chl is observed at lower grafting densities, reflecting a progressive reduction in steric congestion that enables more uniform distribution of the bulky Chl units throughout the brush layer. In summary, XPS depth-profiling using a GCIS is a powerful tool for characterization of these complex materials.

Acyl chloride-mediated synthesis of rhodanine-modified UiO-66 for high-efficiency silver recovery

Silver (Ag) recovery is essential for ecological protection, human health and economic benefits. Effective capture of Ag(I) from wastewater is still challenging due to insufficient accessible sites of adsorbents. Herein, an acyl chloride-mediated strategy is developed to synthesize rhodanine (Rd) modified UiO-66 derivatives for Ag(I) adsorption. Benefitting from the high grafting density of Rd, the optimal Rd-modified UiO-66-NH2 (UiO-66-NH2@20Rd) features an ultra-high uptake capacity (maximum capacity of 923.9 mg·g−1) and selectivity (maximum selectivity coefficient of 1665.52) for Ag(I). Almost 90 % of Ag(I) could be captured in one minute over UiO-66-NH2@20Rd and maintained a removal rate of 98.9 % even after six cycles. Moreover, a fixed-bed column test demonstrates that approximately 21,780 bed volumes of Ag(I) simulated wastewater can be effectively treated, indicating great promise for practical application. Mechanism investigation illustrates that outstanding performance can be attributed to the synergistic effect of Ag(I) adsorption and reduction on dense rhodanine sites. This study highlights that such a general strategy can provide a valuable avenue toward various functional adsorption materials.

Quantitative Comparison of the Hydration Capacity of Surface-Bound Dextran and Polyethylene Glycol.

We have quantified and compared the hydration capacity (i.e., capability to incorporate water molecules) of the two surface-bound hydrophilic polymer chains, dextran (dex) and poly(ethylene glycol) (PEG), in the form of poly(l-lysine)-graft-dextran (PLL-g-dex) and poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), respectively. The copolymers were attached to a negatively charged silica-titania surface through the electrostatic interaction between the PLL backbone and the surface in neutral aqueous media. While the molecular weights of PLL and PEG were fixed, that of dex and the grafting density of PEG or dex on the PLL were varied. The hydration capacity of the polymer chains was quantified through the combined experimental approach of optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation monitoring (QCM-D) to yield a value for areal solvation (Ψ), i.e., mass of associated solvent molecules within the polymer chains per unit substrate area. For the two series of copolymers with comparable stretched chain lengths of hydrophilic polymers, namely, PLL(20)-g-PEG(5) and PLL(20)-g-dex(10), the Ψ values gradually increased as the initial grafting density on the PLL backbone increased or as g decreased. However, the rate of increase in Ψ was higher for PEG than dextran chains, which was attributed to higher stiffness of the dextran chains. More importantly, the number of water molecules per hydrophilic group was clearly higher for PEG chains. Given that the -CH2CH2O- units that make up the PEG chains form a cage-like structure with 2-3 water molecules, these "strongly bound" water molecules can account for the slightly more favorable behavior of PEG compared to dextran in both aqueous lubrication and antifouling behavior of the copolymers.

Amphiphilic polysiloxane graft guanidine salts with a combination of low environmental toxicity and high antifungal activity

Banana Fusarium wilt is one of the most serious diseases that restricts the banana industry. How to achieve efficient, low toxicity, and long-term inhibition of pathogenic fungal spores (Fusarium oxysporum f. sp. cubense, race 4, Foc4) that grow in soil has become a challenge in the field of chemical control of plant diseases in recent years. Based on the special antimicrobial mechanism of guanidine salts, which can effectively inhibit microbes by forming transmembrane stomata on the plasma membrane, we were inspired to introduce hydrophilic guanidine salts to hydrophobic PDMS chains to potentially balance high antimicrobial activity and low environmental toxicity. In this work, a series of novel amphiphilic polysiloxane graft guanidine salts (PDMS-g-GH) were synthesized based on our previous works, i.e., polysiloxane graft primary amine salts (PDMS-g-AH), in which the primary amine salt groups were converted to guanidine salt groups. The molecular weight of the polymer, the grafting density of guanidine salts, the distribution of guanidine salt units on the main chain (random or block), the in vitro antifungal activities and the anti-Foc4 activities in soil, the adsorption characteristics in soil, and the environmental toxicity after soil adsorption were systematically studied. The results confirmed that compared with PDMS-g-AH, PDMS-g-GH showed stronger antifungal activity against Foc4 and long-term antifungal activity against Foc4 in soil, but its environmental toxicity was significantly reduced. These results support the potential application of PDMS-g-GH for the prevention and control of banana Fusarium wilt and other soil-borne fungal diseases.

Synthesis and self-assembly of high grafting density core-shell bottlebrush polymer with amphiphilic side chain

Self-assembly of bottlebrush polymers are widely studied in photonic bandgap materials, biomedical materials and nanomaterial with different structures. In this work, high grafting density bottlebrush polymer with amphiphilic QPDMA[FeCl4]-b-PS side chains grafting on every carbon atom of the backbone are prepared via grafting from approach. The para-isocyanobenzoate monomer modified with chain transfer agent (CTA) is designed and synthesized to prepared polymer backbones with CTA grafting on each atoms. The core-shell bottlebrush block copolymer is prepared by sequential reversible addition-fragmentation chain transfer polymerization of dimethylaminoethyl methacrylate and styrene. The inner core follows quaternization and ion exchange to form water soluble QPDMA[FeCl4] magnetic block. The resulting core-shell bottlebrush magnetic polymer (PCN-g-[QPDMA[FeCl4]-b-PS]) self-assembles into nanowires with magnetic QPDMA[FeCl4] as core and PS as corona in the shell selected solvent dichloromethane, the length of nanowires increases with self-assembly time. While it self-assembles into nanoparticle clusters in core selected aqueous solution. And, the thermal and magnetic properties are affected by the self-assembly morphology. Especially, the as prepared PCN-g-[QPDMA[FeCl4]-b-PS] and the nanoparticles cluster self-assembly are paramagnetic, but the nanowire self-assembly is superparamagnetic.