Graft Polymerization Research Articles

Constructing amidoxime adsorption sites on the core-shell structured natural silk protein for uranium capture

Amidoxime-based fiber adsorbents hold significant promise for uranium extraction. However, a notable issue is that these adsorbents primarily originate from synthetic polymer materials, which, aside from providing good mechanical support, have no other functions. In recent study, we shifted our focus to silk fiber (SF), a natural protein fiber known for its unique core-shell structure and rich amino acids. The shell layer, due to its abundant functional groups, makes it easily modifiable, while the core layer provides excellent mechanical strength. Leveraging these inherent properties, an amidoxime-based fiber adsorbent was developed. This adsorbent utilizes amino and carboxyl groups for enhanced performance synergistically. This method involves establishing uranium affinity sites on the outer sericin layer of SF via chemical initiation of graft polymerization (CIGP) and amidoximation (SF-g-PAO). The water absorption ratio of SF-g-PAO is as high as 601.16 % (DG = 97.17 %). Besides, SF-g-PAO demonstrates an exceptional adsorption capacity of 15.69 mg/g in simulated seawater, achieving a remarkable removal rate of uranyl ions at 95.06 %. It can withstand a minimum of five adsorption-elution cycles. Over a 4-week period in natural seawater, SF-g-PAO displayed an adsorption capacity of 4.95 mg/g. Furthermore, SF-g-PAO also exhibits impressive uranium removal efficiency in real nuclear wastewater, with a removal rate of 63 % in just 15 min and a final removal rate of 90 %. It is hoped that this SF-g-PAO, prepared through this straightforward method and characterized by the synergistic action of amino and carboxyl groups, can offer innovative insights into the development of uranium extraction adsorbents.

Study of the high-energy alpha particles influence on the styrene accumulation kinetics and functional groups during the synthesis of proton-exchange membranes based on PVDF.

The study investigates the effect of alpha irradiation on the graft copolymerization of styrene with polyvinylidene fluoride (PVDF). Using methods of radiation-chemical modification, a proton exchange membrane (PEM) with a uniform distribution of functional sulfate groups throughout the entire volume was developed. Grafting of styrene was carried out at different temperatures and solution concentrations. Functional sulfo-groups were added to the graft polymer by sulfonation, with the addition of solvents. The degree of grafting (DG), water absorption (W) and exchange capacity (IEC) correlate well with the absorbed dose and alpha particle fluence. Research into this method will allow us to develop an affordable industrial technology for widespread implementation.

RETRACTED: Advanced multi-functional regenerative and self-healing tight ultrafiltration membrane for dye/salt wastewater efficient purification

Membrane fouling and membrane damage during membrane operation significantly reduce the permeate flux and separation efficiency, and the preparation of ultrafiltration membranes with renewable and self-healing properties is particularly critical for the sustainable recycling of water resources. Herein, we report a novel tight ultrafiltration membrane, which achieves self-healing properties by incorporating modified β-cyclodextrin (β-CD) monomers into the membrane, forming hydrogel by utilizing UV-induced graft polymerization and covalently binding to the membrane substrate, and then utilizing modified Azo to self-assemble into the hydrophobic cavities of the β-CD via host–guest interactions to construct host–guest chemistry to achieve regenerative anti-fouling properties. In addition, the chemical damage caused by UV-induced during the regeneration process is somewhat avoided by the modified azobenzene (Azo) and β-CD. Taking the renewing membrane as an example, the regeneration test shows that the membrane still has high flux recovery (FRR = 92.5 %) and stable separation performance after three regenerations. Physical self-healing tests showed that the dye/salt rejection recovery of the renewing membrane was greater than 95 % for all four common dyes and salts. In the case of chemical damage, a new peak appears in the XPS at 165.4 eV, demonstrating of the reliability of the actual self-healing of chemical damage. Meanwhile, the results of the mechanical properties of the renewing membrane before and after damage show that the membrane can still maintain high mechanical properties after physical self-healing has occurred. This novel anti-fouling and self-healing tight ultrafiltration membrane for practical high salinity textile wastewater separation has a broad application prospect.

Hydrogel-Reactive-Microenvironment Powering Reconfiguration of Polymer Architectures.

Reconfiguration of architected structures has great significance for achieving new topologies and functions of engineering materials. Existing reconfigurable strategies have been reported, including approaches based on heat, mechanical instability, swelling, origami/kirigami designs, and electromagnetic actuation. However, these approaches mainly involve physical interactions between the host materials and the relevant stimuli. Herein, a novel, easy-manipulated, and controllable reconfiguration strategy for polymer architectures is proposed by using a chemical reaction of host material within a hydrogel reactive microenvironment. 3D printed polycaprolactone (PCL) lattices transformed in an aqueous polyacrylamide (PAAm) hydrogel precursor solution, in which ultraviolet (UV) light triggered heterogeneous grafting polymerization between PCL and AAm. In situ microscopy shows that PCL beams go through volumetric expansion and cooperative buckling, resulting in transformation of PCL lattices into sinusoidal patterns. The transformation process can be tuned easily and patterned through the adjustment of the PCL beam diameter, unit cell width, and UV light on-off state. Controlling domain formation is achieved by using UV masks. This framework enables the design, fabrication, and programming of architected materials and inspires the development of novel 4D printing approaches.

Ternary nanocomposite of RAFT‐polymerized DMAEMA‐functionalized graphene oxide, manganese dioxide and polyaniline as active electrode material for supercapacitor

AbstractGraphene and its derivatives are promising energy storage devices due to their high specific surface area, chemical and thermal durability and high charge transfer power. Still, their stacking and aggregate behavior can limit their practical application. To address this issue, reversible addition–fragmentation chain‐transfer (RAFT) polymerization as controlled radical polymerization was applied to functionalize the surface of graphene oxide with poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) via the ‘grafting from’ method. This strategy enhances the distance between graphene sheets by occupying physical volume while improving effective charge transfer through tertiary amine groups participating in the doping process. X‐ray diffraction was used to determine interlayer spacing after polymer grafting, which increased from 0.28 to 1.71 nm after polymer grafting. The hybridization of materials with diverse properties was used to enhance charge transfer capability for supercapacitor applications. PDMAEMA‐functionalized graphene oxide, nano‐manganese dioxide and polyaniline were combined to create a successful nanocomposite as electrode active material. The morphological structure and chemical composition of the synthesized nanocomposite were analyzed, and its electrochemical performance was evaluated using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The nanocomposite exhibited a maximum specific capacitance, energy density and power density of 364.72 F g−1 (at a scan rate of 50 mV s−1), 239.08 Wh kg−1 and 678.34 W kg−1, respectively. The final nanocomposite's energy storage capacity significantly increased compared to the individual components due to hybridization's synergistic impact, reducing charge transfer resistance. © 2024 Society of Industrial Chemistry.

Characterizing the shear response of polymer-grafted nanoparticles.

Grafting polymer chains to the surface of nanoparticles overcomes the challenge of nanoparticle dispersion within nanocomposites and establishes high-volume fractions that are found to enable enhanced material mechanical properties. This study utilizes coarse-grained molecular dynamics simulations to quantify how the shear modulus of polymer-grafted nanoparticle (PGN) systems in their glassy state depends on parameters such as strain rate, nanoparticle size, grafting density, and chain length. The results are interpreted through further analysis of the dynamics of chain conformations and volume fraction arguments. The volume fraction of nanoparticles is found to be the most influential variable in deciding the shear modulus of PGN systems. A simple rule of mixture is utilized to express the monotonic dependence of shear modulus on the volume fraction of nanoparticles. Due to the reinforcing effect of nanoparticles, shortening the grafted chains results in a higher shear modulus in PGNs, which is not seen in linear systems. These results offer timely insight into calibrating molecular design parameters for achieving the desired mechanical properties in PGNs.

A novel covalent grafting method between cellulose and ferulic acid through HRP enzyme/acetylacetone/L-Ascorbic acid ternary dual initiator system

In the application of natural dyes, using environmentally and human body harmful metal dyes was still the mainstream dyeing method in the process of cellulose fiber dyeing with natural dyes. This study proposed a new method that can catalyzed the covalent grafting of cellulose materials with Ferulic acid (FA), the ternary system consisting of horseradish peroxidase (HRP), acetylacetone (ACAC) and L-Ascorbic acid (AA). The grafting process of cellulose materials with FA was systematically studied, and the optimal grafting polymerization conditions was determined using orthogonal experimental analysis. In the experiment, it was found that the morphology and structure of cellulose materials significantly affect their grafting polymerization performance with FA, and the change rule of their grafting rate was cotton fabric (3.84%) < cotton yarn (4.54%) < tencel fabric (4.70%) < tencel yarn (53.06%) < cotton cellulose (5.59%) < corn starch (6.70%). The grafted fabrics have excellent color fastness, antibacterial and UV resistance performance. Finally, the structural characteristics of cellulose and its analogues grafted with FA were characterized through FT-IR, 1H NMR, and the possible free radical covalent polymerization mechanism between cellulose materials and FA was analyzed.

Radiation and Radical Grafting Compatibilization of Polymers for Improved Bituminous Binders-A Review.

This review scrutinizes current research on new methods for enhancing bituminous binder performance through radiation and radical grafting of polymer modifiers of bitumen. It investigates innovative methods, including using waste polymers as modifiers and applying radiation for polymer grafting, to overcome challenges like high costs, low aging resistance, and storage stability issues, of which separation of phases polymer/bitumen is the most significant obstacle. These advanced modification techniques promise sustainability through the decrease of the carbon footprint of transportation systems by improving the properties and durability of binders. Additionally, this review discusses the parameters and mechanistic aspects from a scientific perspective, shedding light on the underlying processes that contribute to the improved performance of modified bituminous binders.

Nanoparticles bearing germanium based photoinitiators at their surface: Preparation and use in grafting-from photopolymerization reactions

In recent decades, there has been a growing interest in surface modifications utilizing “grafting-from” techniques within both industrial and academic fields. Among others, this technology continues to drive innovation in biomedicine, enabling the design and fabrication of advanced materials and devices with tailored properties for a wide range of applications, from regenerative medicine and drug delivery to diagnostics and therapeutics. This strategy relies on the covalent attachment of (photo)initiating species to surfaces. The coupled initiators are exploited to produce reactive sites such as radicals upon exposure to heat or light. Subsequently, polymerization reactions are induced, leading to surface coupled polymer brushes.In order to provide new perspectives in surface modification techniques, we present a novel and unique method for producing mesoporous organic/inorganic hybrid nanoparticles via the “grafting-from” method. This was accomplished by immobilizing a novel, low-toxic and visible light sensitive photoinitiator (based on triacylgermanium moieties) onto silica nanoparticles. Surface-initiated photopolymerizations of styrene and acrylate monomers were conducted to produce polymer shells on the surface of the nanoparticles. The grafted layers had a thickness in the range of 6–12 nm. Furthermore, the polymer grafting density is discussed in detail ranging between 0.17 and 0.23 chains per square nanometer.

QbD Assisted Optimization of Microwave-assisted Synthesis of Polyacrylamide Grafted Tragacanth: Characterization and Instrumental Analysis

Background: Polysaccharides have recently attracted a lot of attention in the designing of drug delivery systems due to their wide availability, lack of toxicity, and numerous ways that their nature, structure, and functionality can be altered. Methods: Microwave-assisted synthesis of graft copolymer of tragacanth (TRA) is done with poly-acrylamide (PAM) by free radical polymerization using ceric ammonium nitrate (CAN) as initiator. Grafting polymer concentration, CAN concentration, and exposure time were selected as independent variables, and their effect is studied for Grafting Efficiency (GE) and Intrinsic viscosity (IV) using Box-Behnken optimization design. Results: A quadratic model was suggested by the software for further statistical evaluation. On the basis of the desirability approach, optimized parameters for microwave-assisted synthesis were demon-strated, and further grafted TRA (Gr-TRA) was synthesized. Gr-TRA was studied for various charac-terization and elemental analysis. Gr-TRA showed the highest swelling index and least weight loss during the chemical resistance test. Further instrumental analyses like FTIR, XRD, and elemental anal-ysis confirmed the formation of Gr-TRA. Conclusion: Based on all of the above findings, the synthesis of PAM-grafted TRA has been optimized and could be used as a new pharmaceutical excipient in designing different dosage forms.

Investigation of TPEG comb polymer as filtration and rheological additives for high-temperature water-based drilling fluid

During oil and gas drilling, high-temperature and high-salt considerably deteriorate the rheological and filtration properties of drilling fluid. In this study, two novel comb polymers P-TPEG-10 and P-TPEG-24, with different side chain lengths, were synthesised as filtration and rheological additives for drilling fluids under high-temperature and high-salt environments. When 2 wt% isopentenyl polyoxyethylene ether (TPEG) comb polymer was added to bentonite water-based drilling fluid (BT-WBDF), the viscosity and yield point of the drilling fluid were considerably improved, the filtration loss was considerably reduced before and after hot rolling at 220 ℃ and BT-WBDF could resist 15 wt% NaCl or 0.5 wt% CaCl2. P-TPEG-10 has a better viscosity-increasing effect than P-TPEG-24, and P-TPEG-24 has a better filtration control effect than P-TPEG-10. The excellent rheological and filtration control effects are attributed to the spatial network structure formed by the comb polymer and bentonite particles. Strong hydration groups such as sulfonic groups on the main chain and the intercalation of polyethylene glycol (PEG) side chains increases the thickness of the diffusion double electric layer of bentonite particles and inhibit the aggregation of BT particles. BT-WBDF maintains a reasonable particle size distribution, thus forming a thin and dense filter cake, and effectively reducing the filtration volume. It is expected to play an essential role in the filtration and rheological control of high temperature drilling fluid.

Preparation of xyloglucan-grafted poly(N-hydroxyethyl acrylamide) copolymer by free-radical polymerization for in vitro evaluation of human dermal fibroblasts

Xyloglucan is a rigid polysaccharide that belongs to the carbohydrate family. This hemicellulose compound has been widely used in biomedical research because of its pseudoplastic, mucoadhesive, mucomimetic, and biocompatibility properties. Xyloglucan is a polyose with no amino groups in its structure, which also limits its range of applications. It is still unknown whether grafting hydrophilic monomers onto xyloglucan can produce derivatives that overcome these shortcomings. This work aimed to prepare the first copolymers in which N-hydroxyethyl acrylamide is grafted onto tamarind xyloglucan by free-radical polymerization. The biocompatibility of these structures in vitro was evaluated using human dermal fibroblasts. Gamma radiation-induced graft polymerization was employed as an initiator by varying the radiation dose from 5–25 kGy. The structure of the graft copolymer, Xy-g-poly(N-hydroxyethyl acrylamide), was verified by thermal analysis, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The findings indicate that the degree of grafting and the cytotoxicity/viability of the xyloglucan-based copolymer were independent of dose. Notably, the grafted galactoxyloglucan exhibited efficient support for human dermal fibroblasts, showing heightened proliferative capacity and superior migration capabilities compared to the unmodified polymer. This copolymer might have the potential to be used in skin tissue engineering.

Modeling Elongational Rheology of Model Poly((±)-lactide) Graft Copolymer Bottlebrushes

The shear and elongational rheology of graft polymers with poly(norbornene) backbone and one poly((±)-lactide) side chain of length Nsc = 72 per two backbone repeat units (grafting density z=0.5) was investigated recently by Zografos et al. [Macromolecules 56, 2406–2417 (2023)]. Above the star-to-bottlebrush transition at backbone degrees of polymerization of Nbb>70, increasing strain hardening was observed with increasing Nbb, which was attributed to side-chain interdigitation resulting in enhanced friction in bottlebrush polymers. Here we show that the elongational rheology of the copolymers with entangled side chains and an unentangled backbone can be explained by the Hierarchical Multi-mode Molecular Stress Function (HMMSF) model, which takes into account hierarchical relaxation and dynamic dilution of the backbone by the side chains, leading to constrained Rouse relaxation. In nonlinear viscoelastic flows with larger Weissenberg numbers, the effect of dynamic dilution is increasingly reduced leading to stretch of the backbone chain caused by side chain constraints and resulting in strain hardening. If the backbone is sufficiently long, hyperstretching is observed at larger strain rates, i.e. the stress growth is greater than expected from affine stretch.

Bioinspired thermo-responsive membrane with hybrid micro/nanostructure for water gating and emulsion separation

Smart membranes with tunable wettability hold great promise for controllably oil/water mixtures separations, including oil-water mixtures and surfactant stability oil/water emulsions. Herein, a thermo-responsive membrane with bioinspired hybrid micro/nanostructure was constructed on commercial PVDF membrane, which exhibits excellent thermo-responsive performance and antifouling ability. In this process, the thermo-responsive polymer graft to membrane surface via thiol-ene click reaction, preserve the high interfacial roughness and excellent switching wettability between hydrophilicity/underwater oleophobicity at 25 °C and hydrophobicity at 50 °C. The membrane can be applied in various surfactant stability oil-in-water emulsions and water-in-oil emulsions, demonstrating high separation efficiency, recyclability for various kinds of emulsions. The hybrid micro/nanostructures render the membrane with excellent antifouling performance. The membranes show good potentials for smart liquid separation such as on-demand oil-spill cleanup, remote controllable operation of oil/water emulsion separation device.

Force-induced desorption of copolymeric comb polymers

We investigate a lattice model of comb copolymers that can adsorb at a surface and that are subject to a force causing desorption. The teeth (the comb’s side chains) and the backbone of the comb are chemically distinct and can interact differently with the surface. That is, the strength of the surface interaction can be different for the monomers in the teeth and in the backbone. We consider several cases including (i) the uniform case where the number of teeth is fixed and the lengths of the branches in the backbone and the lengths of the teeth are all identical, (ii) the case where the teeth are short compared to the branches in the backbone, (iii) the situation where the teeth are long compared to the backbone, and (iv) the case where the number of teeth approaches infinity. We obtain expressions for the free energies in the thermodynamic limit in terms of those for self-avoiding walks and discuss the nature of the phase diagrams of the model.

Multifunctional graft-IPN hydrogels of cellulose nanofibers and poly(N-isopropyl acrylamide) via silver-promoted decarboxylative radical polymerization

Interpenetrating polymer networks (IPNs) have emerged as innovative materials for a wide range of applications. Owing to the crosslinked structure of their polymer components, IPNs exhibit superior properties relative to their single component counterparts. Here, we report a new class of multifunctional graft-interpenetrating polymer network (graft-IPN) hydrogel composites of poly(N-isopropylacrylamide) (PNIPAM) grafted onto cellulose nanofibers (CNFs) via silver(I)-promoted decarboxylative polymerization. This novel approach involves the Ag-promoted graft polymerization and the crosslinking of PNIPAM in the CNF network, forming a hybrid of semi-IPN and graft-copolymer hydrogel. Different from conventional PNIPAM-CNF IPNs, the CNFs in graft-IPN hydrogels form an interconnected network as a result of crosslinking between neighboring grafted PNIPAM. Silver nanoparticles (AgNPs) are also formed in situ in the graft-IPN hydrogel matrix, demonstrating the dual functionality of silver as both a catalyst in the polymerization and an eventual antibacterial agent in the hydrogel. The network structure of graft-IPN hydrogels can be controlled by crosslinker and Ag(I) concentration, therefore modulating their thermo-responsive, mechanical, and swelling properties. The grafting of PNIPAM from CNFs shifts the volume phase transition to 36 °C and significantly improves the mechanical strength and swelling capacity of the hydrogels. Ultimately, this work demonstrates the excellent potential of these multifunctional graft-IPN hydrogels with controllable thermosensitivity, mechanical strength and anti-microbial activity as engineered biomaterials for advanced applications in biomedicine, engineering, and industry.

Design of hydrophobic polymer brush for mitigation of membrane wetting in membrane distillation- computer simulation

Defined as an assembly of polymer chains which are tethered by one end to a surface or an interface, polymer brushes have found many applications. In particular, grafting of hydrophilic polymer brushes to the membrane surface was used to mitigate fouling of filtration membranes. As well, hydrophobic polymer brushes were grafted on top of a solid substrate to be used for organic selective pervaporation. In this work, grafting of hydrophobic brushes to the surface of membranes for membrane distillation (MD) is proposed to prevent MD membranes from wetting. This is not an experimental work but a computer simulation of designing the polymer brush or patterned polymer brush to optimize their effect on wetting prevention. It was found that such an effect increases with an increase in the distance between brushes, the contact angle and the radius of the cylindrical polymer brush. Considering the decrease in the effective area of the membrane used for vapor permeation by grafting of polymer brush, the optimal distance between the brushes was found to be twice as large as the brush diameter for millimeter-sized brush and three times as large as the brush diameter of micro- or nanometer sized brushes.

Removal of diclofenac sodium from aqueous solution using different ionic liquids functionalized tragacanth gum hydrogel prepared by radiation technique

Diclofenac sodium (DCF) was reported as an important emerging environmental pollutant and its removal from wastewater is very urgent. In this study, different alkyl substituted ionic liquids (1-alkyl −3-vinyl- imidazolium bromide [CnVIm]Br, n = 4, 6, 8, 10, 12) functionalized tragacanth gum (TG-CnBr) are prepared by radiation induced grafting and crosslinking polymerization. The adsorption behaviors of ionic liquids functionalized tragacanth gum for diclofenac sodium from aqueous solutions are examined. The adsorption capacity of TG-CnBr for diclofenac sodium increases with the increasing of alkyl chain length of the imidazolium cation and the hydrophobicity of the hydrogels. The maximum adsorption capacity by TG-C12Br for diclofenac sodium at 30, 40 and 50 °C were 327.87, 310.56 and 283.29 mg/g, respectively. The adsorption of TG-C12Br towards diclofenac sodium was little decreased with NaCl increasing. The removal efficiency was still remained 94.55 % within 5 adsorption-desorption cycles by 1 M HCl. Also, the adsorption mechanism including electrostatic attraction, hydrophobic interaction, hydrogen bonding, and π − π interaction was proposed.

Ion-Selective Potentiometry with Plasma-Initiated Covalent Attachment of Sensing Membranes onto Inert Polymeric Substrates and Carbon Solid Contacts.

The physical delamination of the sensing membrane from underlying electrode bodies and electron conductors limits sensor lifetimes and long-term monitoring with ion-selective electrodes (ISEs). To address this problem, we developed two plasma-initiated graft polymerization methods that attach ionophore-doped polymethacrylate sensing membranes covalently to high-surface-area carbons that serve as the conducting solid contact as well as to polypropylene, poly(ethylene-co-tetrafluoroethylene), and polyurethane as the inert polymeric electrode body materials. The first strategy consists of depositing the precursor solution for the preparation of the sensing membranes onto the platform substrates with the solid contact carbon, followed by exposure to an argon plasma, which results in surface-grafting of the in situ polymerized sensing membrane. Using the second strategy, the polymeric platform substrate is pretreated with argon plasma and subsequently exposed to ambient oxygen, forming hydroperoxide groups on the surface. Those functionalities are then used for the initiation of photoinitiated graft polymerization of the sensing membrane. Attenuated total reflection-Fourier transform infrared spectroscopy, water contact angle measurements, and delamination tests confirm the covalent attachment of the in situ polymerized sensing membranes onto the polymeric substrates. Using membrane precursor solutions comprising, in addition to decyl methacrylate and a cross-linker, also 2-(diisopropylamino)ethyl methacrylate as a covalently attachable H+ ionophore and tetrakis(pentafluorophenyl)borate as ionic sites, both plasma-based fabrication methods produced electrodes that responded to pH in a Nernstian fashion, with the high selectivity expected for ionophore-based ISEs.

Synthesis and electrochemical testing of polyaniline attached manganese dioxide and functionalized multi-walled carbon nanotubes based active composite material

This work deals with the synthesis and electrochemical testing of a ternary nanocomposite named MnO2-NH-PANI/FMWCNTs. The testing showed a specific capacitance of 356F/g of the material at a scan rate of 5 mV s−1 with retention of it up to 5000 cycles at 5 mA cm−2. The nanocomposite achieved a specific energy of 14.8 Wh kg−1 at a specific power of 1250 W kg−1. The formation of stable films of the electroactive materials on electrode substrates was achieved by the polymer-grafted metal oxide. Therefore, the work highlighted the importance of polymer grafting on electroactive materials for supercapacitor application.