Graft Chains Research Articles

Preparation of All Amorphous PMMA Resins Based on the Graft Architecture with a Flexible Main Chain for Simultaneous Enhancement of Thermal and Mechanical Toughness

AbstractThis study shows the design of poly(methyl methacrylate) (PMMA)‐based glassy polymers with simultaneous improvement of thermal resistance and mechanical toughness, based on the graft architecture with a low glass transition (Tg) flexible main chain. The microphase‐separated structure of the flexible main chain and the glassy graft chains in this design may be key to these improved properties. Notably, the graft copolymer depicts the ductile fracture, and the microscopy observation for the fractured sample exhibits the presence of abundant void formation with relatively homogenous size and interval throughout the sample. The void formation could originate from the preferential fracture of aggregated flexible components distributed throughout the sample, indicating the effective role of the flexible main chain on the suppression of the internal stress. The novelty of the present study is on the use of simple graft architecture for enhancing the toughness of glassy resins. This idea is indeed distinct from the conventional approach to improve toughness by adding plasticizer or rubber particles, therefore opening a new method for the creation of high‐functional glassy polymers.

A novel humanized Chi3l1 blocking antibody attenuates acetaminophen-induced liver injury in mice.

Acetaminophen (APAP) overdose is a leading cause of acute liver injury in the USA. The chitinase 3-like-1 (Chi3l1) protein contributes to APAP-induced liver injury (AILI) by promoting hepatic platelet recruitment. Here, we report the development of a Chi3l1-targeting antibody as a potential therapy for AILI. By immunizing a rabbit successively with the human and mouse Chi3l1 proteins, we isolated cross-reactive monoclonal antibodies (mAbs) from single memory B cells. One of the human and mouse Chi3l1 cross-reactive mAbs was humanized and characterized in both in vitro and in vivo biophysical and biological assays. X-ray crystallographic analysis of the lead antibody C59 in complex with the human Chi3l1 protein revealed that the kappa light contributes to majority of the antibody-antigen interaction; and that C59 binds to the 4α-5β loop and 4α-helix of Chi3l1, which is a functional epitope and hotspot for the development of Chi3l1 blocking antibodies. We humanized the C59 antibody by complementarity-determining region grafting and kappa chain framework region reverse mutations. The humanized C59 antibody exhibited similar efficacy as the parental rabbit antibody C59 in attenuating AILI in vivo. Our findings validate Chi3l1 as a potential drug target for AILI and provide proof of concept of developing Chi3l1 blocking antibody as a therapy for the treatment of AILI.

Thermoformable and transparent one-component nanocomposites based on surface grafted cellulose nanofiber

One-component nanocomposites based on poly(methyl methacrylate)(PMMA) and polystyrene (PS) grafted cellulose nanofiber (CNF) with high polymer graft percentage were fabricated. At relative ambient conditions, less active vinyl monomer, MMA, and styrene were grafted from CNF via surface-initiated Cu(0)-mediated reversible deactivation radical polymerizations (RDRP), and PMMA/PS grafted CNFs could reach a graft percentage as high as 7550 % and 3530 %, respectively. The one-component composite films were manufactured by simple hot-pressing subsequentially. Optical transparency, thermal stability, and glass transition temperature of one-component nanocomposites were enhanced dramatically in contrast with the bicomponent nanocomposite. The uniform fracture surface confirmed the uniform dispersity by morphological observation. Mechanical tests indicated that break elongation and tensile strength ascended notably, and tensile modulus slightly descended as the graft percentage increased for PS and PMMA grafted CNF one-component composite. It was concluded that for glassy graft chains, obtaining one-component nanocomposites with high enough graft chain length was essential to achieve moderated mechanical performance without compromising optical properties and thermal manufacturing ability.

Facile optimization of grafted chain length on antifouling properties based on hyperbranched polyglycerol

Surface-grafted polymer brushes for enhancing biofouling resistance are determined by both the grafting density and chain length of brush on the antifouling membrane surfaces. However, the relations and internal regularities between the arrangement of polymer brush and the permeability and antifouling properties remain unsolved. The accurate effect of chain length is lost on the biofouling resistance behaviors. Herein, antifouling membrane surfaces of hyperbranched polyglycerol (HPG) brushes are obtained via tuning the chain lengths of HPG brush. The wettability and proteins' static adsorption are dramatically improved with the increase of HPG chain lengths. The parameter of chain volume overlap is preliminarily involved to describe the spatial distribution of HPG brushes. Unexpectedly, we demonstrate that the chain length of HPG is critical and a medium-length HPG brush displays an emerging permeability by a dense enough chain volume overlap (Dv) of the HPG architecture. The biofouling resistance behaviors are optimized using the response surface methodology. As the HPG brush grafting density increased, a higher flux recovery regardless of the chain lengths is observed. Qualitative and quantitative assays of E. coli and S. aureus attachment further reveal the low fouling characteristics of hyperbranched membrane surfaces. A deeper understanding of how the chain length of polymer brushes impacts permeability and the anti-biofouling property provides general guidance on the effectiveness of grafted polymer brushes.

Revisiting the structure of copolymer via anionic hybrid copolymerization of methyl methacrylate and ε-caprolactone

Anionic hybrid copolymerization of vinyl and cyclic monomers provides a powerful strategy to synthesize heteropolymers. Yet, there are some open questions regarding its mechanism and the structure of the resulted polymer. We reported that the copolymer (Poly(MMA- co -CL)) of methyl methacrylate (MMA) and ε-caprolactone (CL) via such copolymerization was random. However, a recent study proposed that the copolymer might be simple graft one with poly(methyl methacrylate) (PMMA) as the main chain and poly(ε-caprolactone) (PCL) as the graft chain. In this study, we synthesized a model graft copolymer (PMMA- g -PCL) by using a combination of reversible complexation-mediated polymerization and ring-opening polymerization, and made comparison with Poly(MMA- co -CL) in their properties and hydrolysis. Differential scanning calorimeter (DSC) measurements show that the graft copolymer PMMA- g -PCL possesses two glass transitions and a melt peak. In contrast, Poly(MMA- co -CL) exhibits only one glass transition without a melt peak because it is amorphous, clearly indicating that it is random. Proton nuclear magnetic resonance ( 1 H NMR) measurements reveal that the hydrolysis of PMMA- g -PCL yields only PMMA oligomers. However, the hydrolyzed products of Poly(MMA- co -CL) consist of MMA and CL units. The facts further indicate that the copolymer Poly(MMA- co -CL) is random. Considering that the transesterification reactions are unavoidable in the anionic hybrid copolymerization, the copolymer should consist of random main chain and random branches. • The present study demonstrates that anionic hybrid copolymerization of MMA and CL generally yields random copolymer but not graft copolymer. • Transesterification is not the essential step in the anionic hybrid copolymerization, but it can cause branching of the copolymer. • The hybrid copolymer of MMA and CL consists random main chain and random branches.

Silk Fibroin-g-Polyaniline Platform for the Design of Biocompatible-Electroactive Substrate.

The structural modification of biopolymers is a current strategy to develop materials with biomedical applications. Silk fibroin is a natural fiber derived from a protein produced by the silkworm (Bombyx mori) with biocompatible characteristics and excellent mechanical properties. This research reports the structural modification of silk fibroin by incorporating polyaniline chain grafts through a one-pot process (esterification reaction/oxidative polymerization). The structural characterization was achieved by 1H-NMR and FT-IR. The morphology was studied by scanning electron microscopy and complemented with thermogravimetric analysis to understand the effect of the thermal stability at each step of the modification. Different fibroin silk (Fib): polyaniline (PAni) mass ratios were evaluated. From this evaluation, it was found that a Fib to PAni ratio of at least 1 to 0.5 is required to produce electroactive polyaniline, as observed by UV-vis and CV. Notably, all the fibroin-g-PAni systems present low cytotoxicity, making them promising systems for developing biocompatible electrochemical sensors.

Poly(ε-caprolactone)-Based Graft Copolymers: Synthesis Methods and Applications in the Biomedical Field: A Review.

Synthetic biopolymers are attractive alternatives to biobased polymers, especially because they rarely induce an immune response in a living organism. Poly ε-caprolactone (PCL) is a well-known synthetic aliphatic polyester universally used for many applications, including biomedical and environmental ones. Unlike poly lactic acid (PLA), PCL has no chiral atoms, and it is impossible to play with the stereochemistry to modify its properties. To expand the range of applications for PCL, researchers have investigated the possibility of grafting polymer chains onto the PCL backbone. As the PCL backbone is not functionalized, it must be first functionalized in order to be able to graft reactive groups onto the PCL chain. These reactive groups will then allow the grafting of new reagents and especially new polymer chains. Grafting of polymer chains is mainly carried out by "grafting from" or "grafting onto" methods. In this review we describe the main structures of the graft copolymers produced, their different synthesis methods, and their main characteristics and applications, mainly in the biomedical field.

Preparation and characterization of sodium polyacrylate grafted montmorillonite nanocomposite for the adsorption of cadmium ions form aqueous solution

High-efficiency adsorbents made from clay minerals have a wide application in remediation of soil and water pollution, especially in the treatment of refractory and highly toxic heavy metals. Montmorillonite itself has a good adsorption capacity and a large modification space for its layered structure. Therefore, carboxylate polymer grafted montmorillonite was developed to improve the adsorption capacity of heavy metals in this paper. Two kinds of modified preparation routes were compared, and a series of batch adsorption tests were conducted to evaluate the influence degree of parameters (contact time, pH, temperature, and cadmium concentration). The structural changes of montmorillonite samples before and after modification were characterized by a series of microscopic analyses and measurement techniques. The results show that the silicon hydroxyl produced by the hydrolysis of silane coupling agent can indeed be grafted by dehydration condensation with Si/Al-OH on clay surface. The grafting chain can be greatly increased by C=C double bond breaking polymerization. The polycarboxylate group can effectively improve the adsorption performance of modified montmorillonite for cadmium ions. The maximum adsorption capacity of modified montmorillonite increased by about 224.75%, reaching 63.49 mg/g. The adsorption model of montmorillonite conforms to Langmuir monolayer adsorption model, while modified montmorillonite samples exhibit Freundlich adsorption model and S-type isothermal adsorption curve characteristics of resin. The preparation method of neutralizing after polymerization of acrylic acid was proposed to be better, which provides technical guidance for scientific and efficient application.

Covalent grafting of alkyl chains on laser-treated titanium surfaces through silanization and phosphonation reactions

This work evaluates the efficiency of silanization and phosphonation reactions for the grafting of alkyl chains on the surface of titanium treated by nanosecond laser. The light blue squama-like oxide layers with dominating anatase and rutile were obtained. The silanization using alkoxysilanes with C12 and C18 alkyl chains was attempted in tetrahydrofuran, in pure liquid phase and in vapor phase. The phosphonation with octylphosphonic acid was performed in boiling water solutions. The obtained surfaces were characterized by Raman and X-ray photoelectron spectrometry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Their hydrophobicity was evaluated using static contact angle measurements.The modification in pure liquid silane and in vapor phase allowed obtaining high loadings (6 and 10 at.% Si respectively) of grafted groups and the formation of polycondensed silane layers. The silanization in tetrahydrofuran resulted in partial monolayer coverage. The phosphonation in boiling water solutions allowed obtaining significant P loading (up to 7 at.%) and full monolayer coverage. Both silanization and phosphonation increased the hydrophobicity of laser-treated surfaces. However, the modification with octylphosphonic acid in water solutions is more appropriate since milder conditions of chemical functionalization and lower concentrations of the modifier are necessary to obtain similar organic loading and hydrophobicity.

Advances in atom transfer radical polymerization of modified grain

Atom transfer radical polymerization (ATRP) is a kind of controllable reactive radical polymerization method with potential application value. The modification of graphene oxide (GO) by ATRP reaction can effectively control various graft polymer molecules Chain length and graft density, giving GO different functionality, such as good solvent dispersibility, environmental sensitive stimulus responsiveness, biocompatibility, and the like. In this paper, ATRP reaction and GO surface non-covalent bonding ATRP polymer molecular chain were directly initiated from GO surface immobilization initiator. The ATRP reaction modified GO was reviewed, and the process conditions and research methods of ATRP modification reaction were summarized, as well as pointed out the functional characteristics and application prospect of GO functionalized composites.

Fabrication of ultrafiltration membrane surface with synergistic anti-fouling effect of “dispersion-impedance” and anti-fouling mechanism of dye

Four kinds of hydrophilic chains with diverse microstructures, namely anhydride (MA), melamine (MEL), polyethylene glycol (PEG)-g-MEL and MEL-g-polyethyleneimine (PEI) were introduced into the membrane surface by the “surface deposition and grafting” method in this work. The influence of the flexibility and rigidity for the grafting chains on the anti-fouling capacity to the positively charged alcian blue (AB8GX) and the negatively charged methyl blue (MB) was investigated. The results revealed that the impact of flexibility and rigidity for the grafting chains is more significant on both the adhesion of dye on the membrane surface and the microstructure of the fouling layer formed on the membrane surface than the hydrophilicity and the charging property of the membrane surface. The “dispersion–impedance” dual synergistic mechanism of anti-dye-fouling combined with flexible chain of PEI and rigid chain of MEL was explained through analyzing and characterizing the degree of dye accumulation on the membrane surface and the adhesion between dye and the membrane surface. More specifically, the PEI chain induces a dispersing capacity on the dyes, while the MEL chain can hinder the association between the dye molecules and the adhesion and aggregation on the membrane surface to further retard the adsorption of dye on the membrane surface. The steric hindrance effect of the MEL-g-PEI chains further increases the difficulty of dyes to approach and attach on the upper surface of membrane. They will all significantly weaken the adhesion force for dyes on the membrane surface and delay the formation of irreversible fouling. This work provides not only an idea for the development of membrane surfaces with high anti-dye-fouling properties, but also provides fruitful insights by revealing the anti-dye-fouling mechanism of the membrane surfaces.

Study for removing of silica nanoparticle in pure isopropyl alcohol with a cation exchange membrane

Semiconductors are becoming increasingly miniaturized and structurally complex. During their manufacture, isopropyl alcohol (IPA), which has a low surface tension, is often used to prevent structural corruption during cleaning. A previous study examined the removal of impurities (silica nanoparticles (SNPs)) in IPA/water solutions using an anion exchange membrane and reported the removal mechanism. That study found that SNP removal in high ratio IPA was difficult. In the present study, SNP removal in IPA was tested using three different cation exchange membranes, and the differences in their removal performance were evaluated. Zeta potential measurements and molecular dynamics (MD) simulations were performed to elucidate the removal mechanism, and membrane surface-SNP interactions were evaluated by atomic force microscopy (AFM). The zeta potential of the cation exchange membrane in IPA was positive. The reason for this phenomenon is discussed based on the results of MD simulations. The results suggested that Na+, which is the counter ion in the ion exchange group, remains near the membrane surface. The difference in the removal ratio between the cation exchange membranes was examined by AFM, suggesting that the tentacle effect of the graft chains on the surface suppressed the re-desorption of SNPs once adsorbed, contributing to the high removal ratio. These results are expected to contribute significantly to developing membranes with a high removal ratio of SNPs in IPA.

Coarse-Grained Simulation of Bottlebrush: From Single-Chain Properties to Self-Assembly.

Bottlebrush polymers consist of a linear backbone with densely grafted side chains. They are known to have a range of properties of interest, such as enhanced mechanical strength and rapid self-assembly into large domains, and have attracted attention as promising candidates for applications in photonics, lithography, energy storage, organic optoelectronics, and drug delivery. Here, we present a coarse-grained model of bottlebrush polymers that is able to reproduce their experimentally observed persistence lengths and chain conformations in the melt. The model is then used to investigate the morphologies of this class of materials for various chain architectures and grafting densities.

In situ polymerization preparation and mechanical properties of nanocomposites based on PA10T/10I-block-PEG copolymer and graphene oxide

Poly (decamethylene terephthalamide/decamethylene isophthalamide)-block-polyvinyl alcoho) (PA10T/10I-PEG) copolymer/graphene oxide (GO) composites were prepared via in-situ melt polymerization and two different nano-filler addition approaches were compared. The relationship between the micro-structure and performance of the elastomer composites prepared by one-step and two-step methods was explored. The results show that the two-step method significantly promoted the dispersion of the GO in a polymer matrix, and facilitated the grafting of more hard molecular chains. Thus, the elastic modulus and tensile strength of the nano-composite have been significantly improved by the presence of GO. This was because of the strong interaction between the functional groups on the surface of the GO and the hard molecular chains. This would be also be favorable to load transfer across the interface. Additionally, the elongation at the break of composites increased by 10% with the addition of a small amount of GO (0.2% wt). This is because hard domains tend to be enriched on the surface of GO in composites and act as a lubricating layer at the interface between the GO and matrix, leading to increased deformation ability. This work provides an effective strategy to prepare elastomer composites with high strength and toughness.

Precise Control of Li+ Directed Transport via Electronegative Polymer Brushes on Polyolefin Separators for Dendrite‐Free Lithium Deposition

AbstractNonuniform ion flux triggers uneven lithium (Li) deposition and continuous dendrite growth, severely restricting the lifetime of Li‐metal batteries (LMBs). Herein, an electronegative poly(pentafluorophenyl acrylate) (PPFPA) polymer brush‐grafted Celgard separator signed as PPFPA‐g‐Celgard is designed to precisely construct one‐dimensionally directed Li+ flux at the nanoscale so as to realize faster ion transport and ultra‐stable Li deposition. The grafting of PPFPA polymer chains is enabled by the simple bio‐inspired engineering of surface‐initiated atom transfer radical polymerization chemistry. Both theoretical and experimental analyses demonstrate an obvious increase by almost two times in Li+ affinity and ion transfer kinetics for PPFPA‐g‐Celgard over the Celgard separator. Reversible and stable Li plating/stripping can be realized by rapidly switching from 0.5 to 6 mA cm‐2. Besides, the Li | PPFPA‐g‐Celgard | LiFePO4 full cell exhibits universal and long‐term cyclability with a capacity retention of 83% over 700 cycles in ether electrolyte and 92.9% for over 300 cycles in carbonate electrolyte as well. This study represents a new direction for the general design of advanced separators with typical surface topochemistry and self‐limited ion transport channels in the application of high‐performance LMBs.

Cross-linked anion-exchange membrane with side-chain grafted multi-cationic spacer for electrodialysis: Imparting dual anti-fouling and anti-bacterial characteristics

Polyimide (SPI) was functionalized using dianhydride with a high electron density in the carbonyl carbon atoms, and on active-sites (2,4,6-tris(dimethylaminomethyl) phenol: TAP) multi-cationic groups were grafted. Further, we fabricated multi-cationic cross-linked anion-exchange membrane (AEM) with tuneable polymer design by varying number of carbon chain in cross-linker spacer. CrQSPI@3 AEM with C3 spacer, exhibited 2.85 meq/g ion-exchange capacity, 21.4% water uptake, 20.7% swelling ratio, 13.87 × 10–2 S/cm membrane conductivity, and assessed as optimized membrane for further experimental analysis. Architectural strategy including cross-linking, and side chain grafting of multi-cationic groups provides fine control over properties, stabilities, hydrophilic-hydrophobic characteristics, anti-fouling and anti-bacterial nature. Anti-fouling nature of CrQSPI@3 AEM were gaged by impedance spectroscopy, chronopotentiometry, and electrodialysis experiments, while anti-bacterial nature was studied against water borne Escherichia coli (E. coli). High electro-dialytic performance of CrQSPI@3 AEM (current efficiency: 97.4%, and energy consumption: 0.92 kW h/kg of NaCl removed) along with better stabilities, anti-fouling and anti-bacterial properties, revealed its suitability for water desalination and other diversified electrochemical applications. Described method provides facile membrane fabrication with superior performance to obtain deep in-sight understanding of structural features.

Unveiling the Side-Chain Effect on Ionic Conductivity of Poly(ethylene oxide)-Based Polymer-Brush Electrolytes

Polymer-brush architectures have attracted great interests in solid-state electrolytes for battery applications due to the facilitated segmental dynamics and latent capacity to fabricate single ion conductors. The effect of side chain architectures on the ionic conductivity of the polymer-brush electrolytes (PBEs), however, still requires a systematic exploration. This work describes a detailed study on the structure–property relationship between the side chain architectures and the ion-conducting behaviors of PBEs. By means of thermodynamic, spectroscopic, and electrochemical characterizations, factors of both chain length and graft density are investigated to elucidate the mechanism. Our results show that as the chain length increases, the ionic conductivity exhibits first an increase in the short amorphous range and then a drop in the long crystalline range. Moreover, investigation on graft density demonstrates that the amorphous PBEs achieve the highest ionic conductivity at a fully grafted configuration, indicating the significance of branched side chain architecture. For crystalline PBEs, proper regulation of graft density can alleviate the crystallization of the side chains and therefore increase the ionic conductivity. These results would improve our understanding of ion-conducting behaviors in PBEs and provide insights for designing advanced solid polymer electrolytes.

PEO-Grafted Gold Nanopore: Grafting Density, Chain Length, and Curvature Effects

PEO-Grafted Gold Nanopore: Grafting Density, Chain Length, and Curvature Effects

Enhancement of strength and toughness of bio-nanocomposites with good transparency and heat resistance by reactive processing

SummaryGrowing concerns in addressing environmental challenges are driving the rapid advancement of both bio-based and environmental friendly materials. Biodegradable polymers have been compounded with various nanofillers to fulfill the multiple requirements in real applications. However, current technologies remain to be improved in terms of the intrinsic inferior performance and the lack of interfacial interactions. In this work, we employed a facile route to develop bio-nanocomposites integrating multiple functionalities by reactive processing of polylactide and reactive boehmite nanorods. The grafting of polymer chains onto the surface of the nanorods encourages fully homogeneous dispersion of nanofillers with even 30 wt% loadings. Such nanocomposites exhibit simultaneously enhanced tensile strength, modulus, ductility, and impact strength. Moreover, the bio-based nanocomposites present promising features such as high transparency, improved flame resistance, and heat resistance. This work demonstrates exciting opportunities to produce bio-plastics with diverse functionalities in versatile applications of sustainable packaging industry and engineering plastics.

Compensation for Orientation Birefringence of PMMA by Blending Bottlebrush Polymers Composed of Well-Controlled Graft Chains.

The birefringence of optical polymers is a great issue in optical devices, inhibiting major applications of polymers to optical lenses and films. In this study, we have synthesized effective bottlebrush polymers with which we could attain almost zero birefringence when mixed with optical poly(methyl methacrylate) (PMMA). In detail, the PMMA bottlebrush polymers (PMMA-BBP) were synthesized by the ring-opening metathesis polymerization (ROMP) of norbornene-terminated PMMA macromonomers prepared via atom transfer radical polymerization (ATRP). Linear PMMA and PMMA-BBP were mixed to fabricate blend-film samples (PMMA/PMMA-BBP), which were uniaxially drawn to introduce molecular orientations. Linear PMMA possessed a negative value for its orientation birefringence, while the value of PMMA/PMMA-BBP increased as the PMMA-BBP content increased, whose orientation birefringence could reach almost zero when the ratio of the linear PMMA to PMMA-BBP became 73:27, regardless of the magnitude of the strain. The results reveal that the orientation birefringence of PMMA can be effectively controlled and removed by blending the appropriate content of PMMA-BBP.