Brush-like Copolymer Research Articles

Bioinspired Polysaccharide-Derived Zwitterionic Brush-like Copolymer as an Injectable Biolubricant for Arthritis Treatment.

Developing highly efficient and biocompatible biolubricants for arthritis treatment is extraordinarily demanded. Herein, inspired by the efficient lubrication of synovial joints, a paradigm that combines natural polysaccharide (chitosan) with zwitterionic poly[2-(methacryloyloxy) ethyl phosphorylcholine] (PMPC), to design a series of brush-like Chitosan-g-PMPC copolymers with highly efficient biological lubrication and good biocompatibility is presented. The Chitosan-g-PMPC copolymers are prepared via facile one-step graft polymerization in aqueous medium without using any toxic catalysts and organic solvents. The as-prepared Chitosan-g-PMPC copolymers exhibit very low coefficient of friction (μ < 0.01) on Ti6 Al4 V alloy substrate in both pure water and biological fluids. The superior lubrication is attributed primarily to the hydrated feature of PMPC side chains, interface adsorption of copolymer as well as to the hydrodynamic effect. In vivo experiments confirm that Chitosan-g-PMPC can alleviate the swelling symptom of arthritis and protect the bone and cartilage from destruction. Due to their facile preparation, distinctive lubrication properties, and good biocompatibility, Chitosan-g-PMPC copolymers represent a new type of biomimetic lubricants derived from natural biopolymer for promising arthritis treatment and artificial joint lubrication.

From Unimolecular Template to Silver Nanocrystal Clusters: An Effective Strategy to Balance Antibacterial Activity and Cytotoxicity.

Silver nanomaterials have attracted a great deal of interest due to their broad-spectrum antimicrobial activity. However, it is still challenging to balance the high antibacterial efficiency with low damage to biological cells of silver nanostructures, especially when the diameter decreases to less than 10 nm. Here, we developed a new type of Ag nanohybrid material via a unimolecular micelle template method, which presents amazing antibacterial activities and almost noncytotoxicity. First, water-soluble multiarm star-shaped brushlike copolymer α-CD-g-[(PEO40-g-PAA50)-b-PEO5]18 was precisely synthesized and its micelle behavior in different solvents was revealed. Then, nanocrystal clusters assembled by Ag grains (Ag@Template NCs) were prepared through an in situ redox route using the unimolecular micelle of α-CD-g-[(PEO40-g-PAA50)-b-PEO5]18 as the soft template, AgNO3 as a precursor, and tetrabutylammonium borohydride (TBAB) as the reducing agent. The overall size of the achieved Ag@Template NCs is controlled by the template structure at around 40 nm (Dh in DMF), and the size of the Ag grain can be easily regulated from ∼1 to ∼5 nm by adjusting the feeding ratio of AgNO3/acrylic acid (AA) units in the template from 1:10 to 1:1. Benefitting from the structural design of the template, all Ag@Template NCs prepared here exhibit excellent dispersibility and chemical stability in different aqueous environments (neutral, pH = 5.5, and 0.9% NaCl physiological saline solution), which play a crucial role in the long-term storage and potential application in a complex physiological environment. The antibacterial and cytotoxicity tests indicate that Ag@Template NCs display much better performance than Ag nanoparticles (Ag NPs), which have a comparable overall size of ∼25 nm. The inhibitory capability of Ag@Template NCs to bacteria strongly depends on the grain size. Specifically, the Ag@Template-1 NC assembled by the smallest grains (1.6 ± 0.3 nm) presents the best antibacterial activity. For E. coli (-), the MIC value is as low as 5 μg/mL (0.36 μg/mL of Ag), while for S. aureus (+), the value is around 10 μg/mL (0.72 μg/mL of Ag). The survival rate of L02 cells and lactate dehydrogenase assay together illustrate the low cytotoxicity possessed by the prepared Ag@Template NCs. Therefore, the proposed Ag@Template NC structure successfully resolves the high reactivity, instability, and fast oxidation issues of the ultrasmall Ag nanoparticles, and integrates high antibacterial efficiency and nontoxicity to biological cells into one platform, which implies its broad potential application in biomedicine.

Graphene oxide/brush-like polysaccharide copolymer nanohybrids as eco-friendly additives for water-based lubrication

In this work, a novel hybrid additive for water-based lubrication combining graphene oxide (GO) and brush-like chitosan-based copolymer (chitosan-graft-poly (N-isopropylacrylamide), Chitosan-g-PNIPAM) was developed. The GO/Chitosan-g-PNIPAM nanohybrids were fabricated by a facile in-situ non-covalent assembly strategy. The tribological performance of nanohybrids with different mass ratios of GO and copolymer was investigated. The results demonstrated superior friction-reducing and anti-wear properties at high contact load condition. It could reduce the mean coefficient of friction (COF) by 40% compared with pristine GO and by 84% compared with individual copolymer. Meanwhile, the wear rate was also decreased by 15% and 47%, respectively. Furthermore, this work provides a novel approach to develop green nanoadditives for water-based lubrication through rational combination of 2D materials and brush-like copolymer.

Outstanding antifouling performance of poly(vinylidene fluoride) membranes: Novel amphiphilic brushlike copolymer blends and one‐step surface zwitterionization

ABSTRACTIn this study, we endowed a poly(vinylidene fluoride) (PVDF) membrane with outstanding antifouling ability by blending the hierarchical amphiphilic brushlike copolymer [poly(hydroxyethyl methacrylate)‐b‐polydimethylsiloxane‐b‐poly(hydroxyethyl methacrylate)]‐g‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) with different initial monomer/initiator feed ratios and performing a one‐step surface zwitterionization of spontaneously segregated poly(N,N‐dimethyl aminoethyl methacrylate) segments. Interestingly, nanoscale granular micelles were formed on the surface during zwitterionization because of the migration and self‐assembly of the amphiphilic copolymer; this contributed to the membrane hydrophilicity and antifouling ability. During the filtration of the model foulant bovine serum albumin (BSA) aqueous solution, the BSA rejection ratio and flux recovery ratio increased remarkably to 94.8 and 100.0%, respectively. Moreover, the modified membranes also possessed stable and durable antifouling properties after three cycles of BSA filtration. Thus, this study provided a versatile method for constructing a PVDF ultrafiltration membrane that could achieve high permeability and good antifouling properties in efficient wastewater treatment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47637.

Copper catalyst efficiency for the CuAAC synthesis of a poly(N-isopropylacrylamide) conjugated hyaluronan.

Poly(N-isopropylacrylamide) conjugated hyaluronan (HA-pN), a brush-like copolymer system which serves as a polymer vehicle for cellular and drug delivery, has been previously synthesized via the copper catalyzed azide-alkyne reaction (CuAAC) using a combination of copper sulfate and ascorbic acid (CuAsc) as the catalytic system of choice. Bromotris(triphenylphosphine) copper(I) (CuBr(PPh3)3) is an alternative catalytic compound containing a phosphorous ligand which stabilizes copper in the +1 oxidative state in aqueous solvents and can be employed at true catalyst concentrations. CuAsc and CuBr(PPh3)3 were compared for their efficiency; 1) in the synthesis of HA-pN via CuAAC; 2) in producing thermoresponsive compositions and 3) in being extracted from the polymeric compositions. The synthesis of the brush copolymer was carried out under strict Schlenk conditions, then characterized by ATR-FTIR, 1H NMR, ICP-SFMS, and rheological measurements. CuBr(PPh3)3 catalyzed CuAAC leads to better grafting in water, at a true catalyst concentration, compared to CuAsc. Polymeric solutions exhibited similar traits of increasing mechanical stiffness with rising temperature. Despite purification via chelation and/or dialysis, residual copper was present in similar concentrations in the final polymers. In the CuAAC driven copolymer synthesis of the HA-pN, CuBr(PPh3)3 is a better catalyst than CuAsc.

Robust poly(lactic acid) membranes improved by polysulfone-g-poly(lactic acid) copolymers for hemodialysis

A novel brush-like copolymer was synthesized to toughen and modify PLA membrane. Modified PLA membrane showed improved mechanical, thermal and filtration performances.

Preparation of pH-sensitive nanoparticles with core-shell-corona morphology as an oral drug carrier

In this study, an oral cancer drug delivery system based on quercetin encapsulated polymeric nanoparticles was evaluated. Oral delivery of quercetin achieved using a pHresponsive nanoparticle system composed of amphiphilic brushlike copolymer, which were prepared from poly(ethylene glycol) as a hydro� philic domain, poly(e�caprolactone) as a hydrophobic part and ma lic acid as a pH sensitive fragment. Syn� thesis of the brushlike copolymer was started by ring opening polymerization of e�caprolactone (CL) in pres� ence of DLmalic acid as an initiator. The polycaprolactone and methoxy poly(ethylene glycole) were acry� lated with acryloyl chloride and then their copolymer were synthesized via free radical polymerization. All products were identified by FTIR and 1H NMR analysis. The nanoprecipitation method was used for preparing drug (quercetin) loaded nanoparticles. The TEM images and zetasizer results showed that the size of the particles increases with increasing pH of media. The nanoparticles have coreshellcorona (CSC) mor� phology, and carboxyl groups in the shell are responsible for changing in the particle size during variation of the pH value. The drug release pattern was found biphasic with an initial burst followed by a slow, sustained release, which was remarkably affected by the pH of media.

Preparation and characterization of brush-like PEGMA-graft-PDA coating and its application for protein separation by CE

In this paper, a novel brush-like copolymer consisting of poly(ethylene glycol) methyl ether methacrylate and 2-aminoethyl methacrylate (AEMA) named as poly(PEGMA300-co-AEMA) was synthesized by atom transfer radical polymerization (ATRP), and then, poly(PEGMA300-co-AEMA) copolymer was immobilized onto material surfaces through polydopamine (PDA)-anchored coating. The defined copolymer structure was characterized by nuclear magnetic resonance hydrogen spectroscopy (1H NMR) and gel permeation chromatography (GPC). The chemical component and surface morphology of the brush-like copolymer-graft-PDA coating were studied by using X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), respectively. The hydrophilicity of the brush-like copolymer-graft-PDA coating was investigated by using static water contact angle. The protein-resistant property of the brush-like copolymer-graft-PDA coating was investigated by using quartz crystal microbalance with dissipation (QCM-D), and finally the coating was applied to capillary inner surface for protein separation by capillary electrophoresis (CE).

Morphology and fracture toughness of nanostructured epoxy thermosets containing macromolecular miktobrushes composed of poly(ε-caprolactone) and polydimethylsiloxane side chains

In this work, we investigated the nanostructures and mechanical properties of epoxy thermosets containing a macromolecular miktobrush composed of poly(e-caprolactone) (PCL) and polydimethylsiloxane (PDMS) side chains. The novel macromolecular miktobrush was synthesized via the combination of reversible addition–fragmentation chain transfer and ring-opening polymerizations. In the brush-like copolymer the molar ratio of PCL to PDMS was controlled to be 1:1 and the length of PCL chains was controlled to be close to that of PDMS chains (i.e., L PDMS = 1000). The densely grafted miktobrush copolymer was incorporated into epoxy and the nanostructured thermosets were obtained as evidenced by means of transmission electron microscopy and dynamic mechanical thermal analysis. The results of small-angle X-ray scattering showed that the formation of nanostructures in the thermosets followed a self-assembly mechanism. The measurement of critical stress intensity factor (K 1C) showed that the nanostructured thermosets displayed the improved fracture toughness owing to the formation of nanostructures.

Synthesis and characterization of pH-responsive and folated nanoparticles based on self-assembled brush-like PLGA/PEG/AEMA copolymer with targeted cancer therapy properties: A comprehensive kinetic study

In this study, a novel nanocarrier was synthesized based on methacrylated poly(lactic-co-glycolic acid) (mPLGA) as a lipophilic domain, acrylated methoxy poly(ethylene glycol) (aMPEG) as hydrophilic part and N-2-[(tert-butoxycarbonyl)amino] ethyl methacrylamide (Boc-AEMA) as pH-responsive segment. Radical polymerization of the above-mentioned three modified monomers produces amphiphilic brush-like copolymer. The protecting amine group (Boc) was selectively deprotected and the latter targeted copolymer was produced through the reaction of this copolymer with activated folic acid. Nanoprecipitation method was used to prepare quercetin-loaded nanoparticles. Dynamic light scattering (DLS) analysis showed that the produced nanoparticles had nanometric size (<100nm) and low polydispersity in size at different pHs. Higuchi and Korsmeyer–Peppas models were applied to evaluate release mechanisms and kinetics. Based on in-vitro degradation study, we found that the brush-like copolymer underwent a rapid weight loss in acidic pH.

Brush‐like copolymer as a physically adsorbed coating for protein separation by capillary electrophoresis

A brush-like copolymer consisting of poly(ethylene glycol) methyl ether methacrylate and N,N-dimethylacrylamide (PEGMA-DMA) was synthesized and used as a novel static physically adsorbed coating for protein separation by capillary electrophoresis for the first time, in order to stabilize electroosmotic flow (EOF) and suppress adsorption of proteins onto the capillary wall. Very stable and low EOF was obtained in PEGMA-DMA-coated capillary at pH 2.2-7.8. The effects of molar ratio of PEGMA to DMA, copolymer molecular mass, and pH on the separation of basic proteins were discussed. A comparative study of bare capillary with PEGMA-DMA-coated capillary for protein separation was also performed. The basic proteins could be well separated in PEGMA-DMA-coated capillary over the investigated pH range of 2.8-6.8 with good repeatability and high separation efficiency because the copolymer coating combines good protein-resistant property of PEG side chains with excellent coating ability of PDMA-contained backbone. Finally, the coating was successfully applied to the fast separation of other protein samples, such as protein mixture and egg white, which reveals that it is a potential coating for further proteomics analysis.

Controlled Interfacial Assembly and Transfer of Brushlike Copolymer Films

The self-assembly and compression of polybutadiene-bpoly(ethylene oxide) (PBd-PEO) at the air/water interface enables control over surface density, height, and film structure. Interfacial transfer was performed by a combination of Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques, resulting in monolayer and bilayer films. Ellipsometry and wettability results were used to characterize the efficiency of transfer and to determine the properties of the resulting films, confirming a brushlike monolayer. Importantly, a high surface density is essential to obtain the desired film structure (i.e. a dense brush) and surface properties. The films were challenged by adsorption of fibrinogen, and the results are consistent with the notion of a PEO-enriched, and protein-repellant, bilayer surface. Such a bilayer film provides an opportunity for a tunable biomaterial interface to probe cell-surface interactions.

Preparation of hydrophilic and fouling resistant poly(vinylidene fluoride) hollow fiber membranes

Amphiphilic brush-like copolymer P(MMA-r-PEGMA) was synthesized by a radical polymerization method. The copolymer was characterized by the nuclear magnetic resonance proton spectra ( 1H NMR) and gel permeation chromatography (GPC). Poly(vinylidene fluoride) (PVDF) hollow fiber membrane was then prepared by the phase inversion method using the copolymer as the macromolecular additive. The effect of P(MMA-r-PEGMA) on the phase inversion process was investigated using a light transmission experiment. The surface enrichment of amphiphilic copolymer in the PVDF hollow fiber was characterized by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological structures of both dry and wet membranes were observed by scanning electron microscopy (SEM). The hydrophilicity, water permeation flux, anti-fouling and carbon ink rejection performance of the hollow fiber were characterized respectively. All these results demonstrated that PVDF hollow fibers fabricated by the single-step method showed high permeation flux, good hydrophilicity and fouling resistance.

Solvent-Dependent Friction Force Response of Poly(ethylenimine)-graft-poly(ethylene glycol) Brushes Investigated by Atomic Force Microscopy

Lateral and normal forces between a surface-bound, brushlike copolymer, poly(ethylenimine)-graft-poly(ethylene glycol) (PEI-g-PEG), and a silica colloidal probe were investigated with atomic force microscopy (AFM) and related to the relative mass of the solvent absorbed within the polymer as measured with the quartz crystal microbalance. PEI-g-PEG was adsorbed onto an oxide-passivated silicon wafer through its exposure to physiologically buffered solutions of the polymer. Frictional forces were measured between the colloidal probe and the substrate by AFM as the polarity of the solvent was systematically varied. Reduced friction forces and greater film thicknesses were encountered under solvents of higher polarity, which are attributed to the extended conformation of the brushlike copolymer under these conditions. Lateral and normal forces detected between the colloidal probe and this surface-bound PEI-g-PEG were found to be similar under certain solvent conditions to those measured for poly(L-lysine)-graft-poly(ethylene glycol), a brushlike copolymer with a different molecular architecture. To this end, friction force studies of both symmetric and asymmetric PEI-g-PEG-coated interfaces served to identify the contributions of conformational and bridging effects in the observed tribological behavior.

Aqueous Lubrication of SiC and Si3N4 Ceramics Aided by a Brush-like Copolymer Additive, Poly(l-lysine)-graft-poly(ethylene glycol)

We have examined the adsorption properties of poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG)—a brush-like polymer—on Si3N4 and SiC surfaces and determined its impact on the aqueous lubrication of Si3N4 and SiC at various speeds and applied loads. The addition of PLL-g-PEG in aqueous solution reduces the interfacial friction forces significantly for self-mated sliding contacts of these two ceramics, as compared to lubrication with water or buffer solution alone. For SiC, the improved lubricating performance by addition of PLL-g-PEG was apparent for all tested speeds (from 1.4 to 185 mm/s under 2 N load). For Si3N4, the effect was more apparent in the slow-speed regime (≤20 mm/s under 2 N load) than in the high-speed regime (>100 mm/s), where extremely low coefficients of friction (μ ≤ 0.006) are readily achieved by aqueous buffer solution alone. It was further observed that the optimal lubricating effect with Si3N4 is achieved when the tribopairs are first run-in in polymer-free aqueous buffer to render the sliding surfaces smooth, after which the PLL-g-PEG copolymer is added to the buffer solution.

Lubrication Properties of a Brushlike Copolymer as a Function of the Amount of Solvent Absorbed within the Brush

The shear forces between poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG)-modified SiO2 tribopairs have been measured with colloidal-probe, lateral force microscopy (LFM) and related to the mass of solvent absorbed within the brushlike structure of immobilized PEG chains. The amount of solvent (per unit substrate area) absorbed within the tethered, brushlike polymer, referred to as areal solvation, Ψ, appears to be of importance in determining the lubrication properties of the tethered polymers. In this study, the degree of solvation was varied by choosing different solvents (aqueous buffer solution, methanol, ethanol, and 2-propanol) and was determined by a technique that combines the results of quartz crystal microbalance (QCM-D) experiments and optical waveguide lightmode spectroscopy (OWLS). The highest degree of solvation was measured for aqueous buffer solutions, and a progressive decrease in solvation of PLL-g-PEG was observed in moving from methanol to ethanol to 2-propanol. A concomitant increase in the measured shear force was observed with this decrease in solvation. The lubrication mechanism of the PLL-g-PEG-coated SiO2 tribopair is discussed in terms of solvation and solvent quality and compared with the lubrication mechanism of the corresponding tribopair where only one surface is coated with the polymer brush.

Preferential Solvation and Its Effect on the Lubrication Properties of a Surface-Bound, Brushlike Copolymer

We have investigated the collapse−stretching transition of a surface-bound, brushlike copolymer, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), and the consequence of such transitions on the frictional properties of this coating. The frictional properties of the interface have been measured by colloidal-probe lateral force microscopy (LFM) in liquid environments on the nanoscale. The collapse−stretching transition has been induced through the systematic variation of the chemical composition of the binary solvent mixture comprised of an aqueous buffer solution and 2-propanol. The influence of solvent composition on the polymer conformation was monitored by comparing measurements conducted with optical waveguide lightmode spectroscopy (OWLS) and quartz crystal microbalance with dissipation monitoring (QCM-D). The combined approach employing QCM-D and OWLS has allowed the quantification of the mass of solvent molecules absorbed in the brushlike structure of PLL-g-PEG and has revealed a significant p...

Synthesis and characterization of a brush-like copolymer of polylactide grafted onto chitosan

A brush-like poly( dl)-lactide grafted onto chitosan as the backbone was investigated. The graft copolymerization was carried out with triethylaluminum as catalyst in toluene at 70 °C. It was found that a greater lactide content in the feeding ratio results in a higher grafting percentage. FTIR spectrometry, 1H NMR, DSC scanning, and wide-angle X-ray scattering, respectively, are used to characterize these branch copolymers. A copolymer has a definite melting point when the molar feeding ratio of lactide to chitosan is more than 10:1, and the Δ H of the copolymers increases with the feed ratio of lactide to chitosan in feeding.

Combinatorial Study of Surface Pattern Formation in Thin Block Copolymer Films

Surface pattern formation in diblock copolymer films is investigated as a function of film thickness h and molecular mass M. Smooth films are observed for certain h ranges centered about multiples of the lamellar thickness L0, and we attribute this effect to an increase in the surface chain density with h in the outer brushlike copolymer layer. We also observe apparently stable labyrinthine surface patterns for other h ranges, and the average size of these patterns is found to scale as lambda approximately L0(-2.5). Hole and island patterns occur for h ranges between those of the labyrinthine patterns and the smooth regions, and their size similarly decreases with L0 and M.