Macromolecular Brushes Research Articles

Photoregenerable nanoadsorbents with macromolecular brushes for the clearance of bilirubin in serum

The ultrahigh concentration of bilirubin (BR) is recognized as a key factor leading to biliary cirrhosis and irreversible brain damage, with the efficient removal of BR from blood being an effective therapy against these conditions. However, the practical application of adsorbents for blood purification is often compromised by their poor regenerative performance. Therefore, by leveraging the excellent structure-function properties of stimuli-responsive materials, we developed photoregenerable nanoadsorbents (SiO2@MAzoPy–x) with excellent cyclic removal performance. We employed azobenzene macromolecule brushes as the functional ligand to enhance the adsorption performance of the nanoadsorbents and enable efficient regeneration. The best-performing nanoadsorbent exhibited BR adsorption rates of 69.71 % and 65.20 % in phosphate-buffered saline (PBS) and simulated plasma, respectively, and showed superior adsorption efficiency in patients’ serum compared to the unmodified SiO2 (≤ 5.4 %). The binding mechanism suggested that BR and the nanoadsorbent interacted through hydrophobic and electrostatic forces. Importantly, the nanoadsorbents could be photoregenerated with a recovery rate of 99 % in PBS after five regeneration experiments using a green process. Owing to their superior photoregenerative properties, the proposed nanoadsorbents show promise for clinical application.

Synthesis of macromolecular brush and its thermal degradation studies

The di-1,2-propanediol ester of fumaric acid (Diol) is synthesized and polymerized to yield the macromolecular brush (PDiol). The structure of monomers and their polymer is confirmed by Fourier transform infrared spectroscopy (FTIR) studies. The PDiol material shows the number average molecular weight (Mn ) as 951 g/mol, weight average molecular weight (Mw ) as 4,378 g/mol, and a polydispersity index (PDI) of 4.6. The hydroxyl value for PDiol is 471 (mg KOH/g). The thermal degradation property of the brush is investigated using thermogravimetric analysis (TGA). The cyclic intra and inter loops are formed while annealing at a temperature of around 200 °C. Using the TG curves recorded at different heating rates and by applying advanced isoconversional methods by model-free kinetics, the apparent activation energy for the thermal degradation (Ea-D) at different reaction extents (α) are calculated and discussed. Advanced methods are also used to refine the apparent activation energy data. The Ea-D values for PDiol range from 100 to 155 kJ/mol. For a lifetime of 20,000 h, the 20% degraded PDiol can withstand a temperature of 39 °C.

Ion Pairing and Dielectric Decrement in Glycosaminoglycan Brushes.

Cell-surface polysaccharides are essential to many aspects of physiology, serving as a highly conserved evolutionary feature of life and as an important part of the innate immune system in mammals. Here, as simplified biophysical models of these sugar coatings, we present results of molecular dynamics simulations of hyaluronic acid and heparin brushes that show important effects of ion pairing, water dielectric decrease, and coion exclusion. As in prior studies of macromolecular crowding under physiologically relevant salt concentrations, our results show equilibria with electroneutrality attained through screening and pairing of brush anionic charges by monovalent cations at the atomistic detail. Most surprising is the reversal of the Donnan potential obtained from both nonpolarizable and Drude polarizable force fields, in contrast to what would be expected based on electrostatic Boltzmann partitioning alone. Water dielectric decrement within the brush domain is also associated with Born hydration-driven cation exclusion from the brush. We observe that the primary partition energy attracting cations to attain brush electroneutrality is the ion pairing or salt-bridge energy. Potassium and sodium pairings to glycosaminoglycan carboxylates and sulfates show similar abundance of contact-pairing and solvent-separated pairing. We conclude that in these crowded macromolecular brushes, ion-pairing, Born-hydration, and electrostatic potential energies all contribute to attain electroneutrality and should therefore contribute in mean-field models to accurately represent brush electrostatics.

High-performance asymmetric supercapacitors of advanced double ion-buffering reservoirs based on battery-type hierarchical flower-like Co3O4-GC microspheres and 3D holey graphene aerogels

We have prepared 2D macromolecular brushes of G>N-PEGm nanosheets and CNT>N-PEGm from the Graphene and CNTs with methoxypolyethylene glycol (mPEG) via Nitrene Chemistry, respectively. Owing to a typical solvothermal method, the hierarchical flower-like spheres of Co3O4-G>N-PEGm-CNT>N-PEGm (Co3O4-GC) ternary composites have been synthetized, which present honeycomb-like structures as “ion-buffering reservoir” and substantial ion-diffusion channels in the ultrathin 2–4 nm Co3O4 nanosheets. And as typical battery-type positive electrode materials, a high capacity of Co3O4-GC can be calculated up to 173.3 mAh g−1 at 0.5 A g−1 (the specific capacitance can be achieved to 1783 F g−1). On the other hand, 3D holey reduced graphene oxide and carboxylic CNT aerogels (HRGOCNTc, denoted as HRGC) formed with holey graphene and the acid-modified CNTc are summarized as 282.3 Fg−1 (78.4 mAh g−1) at 0.5 A g−1, demonstrating excellent long cycling performance. The advanced double “ion-buffering reservoirs” of asymmetric supercapacitors Co3O4-GC//3D HRGC energy devices are further fabricated based on advanced battery-type Co3O4-GC as positive electrode and 3D HRGC aerogels as negative electrode, meanwhile the asymmetric devices with excellent electrochemical performance also exhibit 42.6 Wh kg−1 at power densities of 775 W kg−1 and 81.1% capacitance maintained after 10,000 cycles for energy-storage and energy-conversion potential application.

Responsive Adsorption of N-Isopropylacrylamide Based Copolymers on Polymer Brushes.

We investigate the adsorption of pH- or temperature-responsive polymer systems by ellipsometry and neutron reflectivity. To this end, temperature-responsive poly (N-isopropylacrylamide) (PNIPAM) brushes and pH-responsive poly (acrylic acid) (PAA) brushes have been prepared using the “grafting onto” method to investigate the adsorption process of polymers and its reversibility under controlled environment. To that purpose, macromolecular brushes were designed with various chain lengths and a wide range of grafting density. Below the transition temperature (LCST), the characterization of PNIPAM brushes by neutron reflectivity shows that the swelling behavior of brushes is in good agreement with the scaling models before they collapse above the LCST. The reversible adsorption on PNIPAM brushes was carried out with linear copolymers of N-isopropylacrylamide and acrylic acid, P(NIPAM-co-AA). While these copolymers remain fully soluble in water over the whole range of temperature investigated, a quantitative adsorption driven by solvophobic interactions was shown to proceed only above the LCST of the brush and to be totally reversible upon cooling. Similarly, the pH-responsive adsorption driven by electrostatic interactions on PAA brushes was studied with copolymers of NIPAM and N,N-dimethylaminopropylmethacrylamide, P(NIPAM-co-MADAP). In this case, the adsorption of weak polycations was shown to increase with the ionization of the PAA brush with interactions mainly located in the upper part of the brush at pH 7 and more deeply adsorbed within the brush at pH 9.

Biomimetic Asymmetric Polymer Brush Coatings Bearing Fencelike Conformation Exhibit Superior Protection and Antifouling Performance.

Antifouling surfaces with optimized conformation and compositional heterogeneities are presented with the goal of improving the efficacy of surface protection. The approach exploits the adhesive group (thiol or catechol chain end) to anchor asymmetric polymer brushes (APBs) bearing amphiphilic side chains with synergistic nonfouling and fouling-release abilities onto the surface. The conformation of the APB surface is close to the fencelike structure, which mimics lubricating protein lubricin, endowing the surface with capacity of enhanced protection and antiadhesivity, even facing the high compression of fouling. By utilizing a poly(Br-acrylate-alkyne) macroagent comprising alkynyl and 2-bromopropionate groups, we prepared a series of APB surfaces based on polyacrylate-g-poly(ethylene oxide)/poly(pentafluorophenyl methacrylate) (PA-g-PEO/PPFMA) APBs to explore the influence of the content of the fluorinated segment and bioinspired topological polymer chemistry on their antifouling performance. The APB surfaces can not only provide compositional heterogeneities of PEO and fluorinated segments in each side chain but also give a high surface coverage because of the characteristic of high grafting density of macromolecular brushes. It was found for the first time, as far as we are aware, the fencelike APB surface shows excellent antifouling performance with less protein adsorption (up to 91% off) and cell adhesion (up to 84% off) in comparison with the controlled substrate under relatively long incubation time.

Influence of Macromolecular Brushes with Polyimide Backbones and Poly(methyl methacrylate) Side Chains on Structure, Physical, and Transport Properties of Polyphthalamide

Composite films based on polyamide (poly(m‐phenylene‐iso‐phthalamide)) (PA) and a brush‐like polymer with polyimide (PI) backbone and side poly(methyl methacrylate) chains (PI‐PMMA) were prepared by mixing individual solutions of PA and PI‐PMMA and subsequent film casting. Macromolecular brushes with the same backbone length and density of side chains but with various lengths of side PMMA chains were synthesized via activator generated by electron transfer atom transfer radical polymerization. Interactions between PA and PI‐PMMA, as well as distribution of PI‐PMMA filler inside the PA matrix, were studied by viscometry, dynamic light scattering, differential scanning calorimetry, scanning electron microscopy, and IR spectroscopy. The mechanical properties of polymer samples were also investigated. Microphase separation was revealed in PA/PI‐PMMA films. The length of side chains influences interactions between PA and PI‐PMMA. At the same time, the degree of reduction in the rigidity parameters and in the elasticity parameter depends on the side chain length. Diffusion membranes were prepared on the basis of compositions with the best mechanical properties; these membranes proved to be highly efficient in pervaporation of methanol–hexane mixture. It was established that the fluxes and separation factors of the studied membranes are several times higher as compared to the corresponding characteristics of known commercial membranes. POLYM. ENG. SCI., 60:481–490, 2020. © 2019 Society of Plastics Engineers

Janus macromolecular brushes for synergistic cascade-amplified photodynamic therapy and enhanced chemotherapy

The aggregation-caused quenching (ACQ) effect of photosensitizers and multidrug resistance are the major obstacles in photodynamic therapy (PDT) and chemotherapy, respectively. Synergistic photo-chemotherapy is a promising cancer treatment to overcome the short boards of each single therapy. However, the fabrication of nanocarriers acting as both photosensitizers in PDT and the vehicle of drug release is a key challenge. Herein, we constructed a well-defined porphyrin-containing Janus macromolecular brush and used it as both a photosensitizer and a pH-responsive vehicle for DOX release. The Janus macromolecular brush with pH-responsive side chains and porphyrin units linked covalently in each repeat unit was synthesized by the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and click chemistry. The high grafting content of porphyrin units in the macromolecular brush improved the DOX loading capability by π–π stacking and therefore reduced the total treatment dose of DOX-loaded macromolecular brush nanoparticles (NPs). The pH-responsive side chains played triple roles in synergistic cascade-amplified PDT and enhanced chemotherapy including an executor of controlled drug release, a ligand with a mitochondria-targeting feature, and a barrier to reduce the ACQ effect of porphyrin units. In vitro and in vivo studies confirmed that the DOX-loaded macromolecular brush NPs exhibited high phototoxicity and significant tumor inhibition efficacy. Statement of SignificanceSynergistic photodynamic therapy (PDT) and chemotherapy has emerged as a promising cancer treatment to overcome the challenges of a single modality. Herein, we constructed new pH-responsive vesicles using porphyrin-containing Janus macromolecular brushes as theranostic nanocarriers to encapsulate high-loading doxorubicin (DOX) for synergistic cascade-amplified PDT and enhanced chemotherapy. The high grafting content of porphyrin units in Janus macromolecular brushes improved DOX loading capability by π–π stacking for enhanced chemotherapy. Moreover, pH-responsive side chains subsequently enhanced the suppression of the aggregation-caused quenching (ACQ) effect of porphyrins for cascade-amplified PDT. In vitro and in vivo studies confirmed that DOX-loaded macromolecular brush nanoparticles exhibited high phototoxicity and significant tumor inhibition efficacy.

Macromolecular Brushes Based on Poly(L-Lactide) and Poly(ε-Caprolactone) Single and Double Macromonomers via ROMP. Synthesis, Characterization and Thermal Properties.

Single and double poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) macromonomers having a norbornenyl polymerizable group were prepared by conventional Ring Opening Polymerization (ROP). These macromonomers were further subjected to ring opening metathesis polymerization (ROMP) reactions in order to produce double polymer brushes consisting of PLLA or PCL side chains on a polynorbornene (PNBE) backbone. Statistical or block ring opening metathesis copolymerization of the PLLA and PCL macromonomers afforded the corresponding random and block double brushes. Sequential ROMP of the single PLLA, PCL and PLLA macromonomers resulted in the synthesis of the corresponding triblock copolymer brush. The molecular characteristics of the macromolecular brushes were obtained by 1H-NMR spectroscopy and Size Exclusion Chromatography. The thermal properties of the samples were studied by thermogravimetric analysis, TGA, Differential Thermogravimetry, DTG and Differential Scanning Calorimetry, DSC.

Enhancing hydroxide conductivity of anion exchange membrane via incorporating densely imidazolium functionalized graphene oxide

This study presents a generic method to increase the hydroxide conductivity of anion exchange membranes by tuning the microphase separation structure. Graphene oxide was functionalized with macromolecular brushes for the first time by a precipitation polymerization method. Densely-functionalized imidazolium groups were aligned in the configuration of macromolecular brushes to act as hydroxide-conductive groups, which endow the functionalized graphene oxide with a high ion exchange capacity value of 3.05 mmol g−1. Polymer-inorganic composite membrane for anion exchange membrane fuel cell was fabricated by incorporating the imidazolium-functionalized graphene oxide into imidazolium-functionalized bisphenol A-type polysulfone. The dense imidazolium groups manipulated the aggregation of conductive groups at the polymer/filler interfaces to induce the well-defined microphase structure of composite membranes, constructing low-resistance channels for ionic transport. The activation energy of hydroxide transport in composite membranes was reduced to 25.17–13.62 kJ mol−1, in comparison with 28.63 kJ mol−1 for control membrane. The hydroxide conductivity of composite membrane was elevated to 22.02 mS cm−1 at 30 °C, which is 2.10 times of that for control membrane. The maximum power density of single fuel cell of 78.7 mW cm−2 at 60 °C was thus achieved.

Macromolecular Brushes by Combination of Ring-Opening and Ring-Opening Metathesis Polymerization. Synthesis, Self-Assembly, Thermodynamics, and Dynamics

Statistical and block copolymerization of poly(l-lactide) (PLLA) and poly(e-caprolactone) (PCL) macromonomers having an end norbornenyl group was performed via ring-opening metathesis polymerization (ROMP) to produce the corresponding statistical and block brush copolymers consisting of PLLA and PCL side chains on a polynorbornene (PNBE) backbone. The molecular characteristics of the macromolecular brushes were determined by 1H NMR spectroscopy and size exclusion chromatography equipped with various detectors. These complex topologies allow addressing important questions on the physics of semicrystalline polymers. These include the role of (i) a doubly grafted PCL or PLLA chain on a NBE moiety (in the macromonomers) and the role of (ii) brush architecture on the crystallization behavior and dynamics of block and statistical copolymers. Significant differences were found between the macromonomers and the corresponding brush copolymers at the crystalline lamellar and spherulitic superstructure levels. In th...

Nanoparticles from Amphiphilic Heterografted Macromolecular Brushes with Short Backbones

Heterografted macromolecular brushes are highly grafted macromolecules with two different side chains attached to a backbone. When endowed with an amphiphilic character, these can serve as unique stabilizers of biphasic systems and solute carriers and yield interesting self-assembled structures. Herein, we report on the solution structure of amphiphilic double-brush copolymers with short backbones—i.e., comparable to the length of the side-chains—in a selective solvent for one of the grafted blocks. As determined by small-angle neutron scattering measurements, poly(ethylene glycol)/poly(d,l-lactide) double brushes adopt a cylindrical structure with highly extended backbones in DMSO. In contrast, brushes undergo intermolecular self-assembly into spherical nanoparticles in water, with aggregation numbers that vary inversely with backbone degree of polymerization. While considerably less susceptible to intermolecular association than linear diblocks of similar hydrophobic and hydrophilic block lengths, the i...

Diphilic Macromolecular Brushes with a Polyimide Backbone and Poly(methacrylic acid) Blocks in Side Chains

Novel macromolecular brushes with a polyimide backbone and diphilic diblock copolymer side chains consisting of a hydrophilic block of poly(methacrylic acid) adjacent to the backbone and the outer hydrophobic block of poly(methyl methacrylate) are synthesized. The synthesis includes the grafting of poly(tert-butyl methacrylate) to the polyimide chain followed by the polymerization of methyl methacrylate on the graft copolyimide as a branched multicenter macroinitiator. Brushes with diphilic side chains are obtained via the acidic hydrolysis of ester groups in the first block of side chains. The grafting polymerization of methacrylates is performed according to the “grafting from” approach by the method of pseudoliving atom transfer radical polymerization using two methodologies of polymerization activated by either copper- or iron-containing complexes. Conditions providing the controlled regime of the polymerization processes under study are found, and pathways for the targeted regulation of the degree of polymerization of methacrylate blocks and their grafting density are determined. As is shown by dynamic light scattering and transmission electron microscopy, the macromolecules of brushes with diphilic side chains form in ethanol homotypic, obviously spherical, supramolecular micellar structures with hydrodynamic radii in the range from 40 to 120 nm depending on the length and grafting density of the two blocks in diphilic side chains.

Solute-Triggered Morphological Transitions of an Amphiphilic Heterografted Brush Copolymer as a Single-Molecule Drug Carrier

We describe the use of an amphiphilic macromolecular brush based on poly(ethylene glycol) (PEG) and poly(d,l-lactide) (PLA) as a stabilizer of hydrophobic solutes. The brush, which in solution adopted an extended backbone conformation consequent with excluded volume effects of the side chains, retained an elongated character in water following the hydrophobic collapse of PLA and the backbone triggered by a rapid change in solvent quality. However, in the presence of hydrophobic solutes at low concentrations in a homogeneous environment, the brush formed spherical unimolecular nanoparticles achieving high solute encapsulation efficiency. As solute content increased and exceeded what appears to be a limit for intramolecular solubilization, intermolecular assembly took place along with the formation of large aggregates, the properties of which were highly dependent on the solute. This first observation of the solute-triggered unimolecular collapse of an amphiphilic macromolecular brush should find important ...

Macromolecular Brushes as Stabilizers of Hydrophobic Solute Nanoparticles.

Macromolecular brushes bearing poly(ethylene glycol) and poly(d,l-lactide) side chains were used to stabilize hydrophobic solute nanoparticles formed by a rapid change in solvent quality. Unlike linear diblock copolymers with the same hydrophilic and hydrophobic block chemistries, the brush copolymer enabled the formation of ellipsoidal β-carotene nanoparticles, which in cosolvent mixtures developed into rod-like structures, resulting from a combination of Ostwald ripening and particle aggregation. The stabilizing ability of the copolymer was highly dependent on the mobility of the hydrophobic component, influenced by its molecular weight. As shown here, asymmetric amphiphilic macromolecular brushes of this type may be used as hydrophobic drug stabilizers and potentially assist the shape control of nonspherical aggregate morphologies.

Synthesis of amphiphilic block-type macromolecular brushes with cleavable pendant chains and fabrication of micelle-templated polymer nanocapsules

Macromolecular brushes with cleavable pendant chains were synthesized by controlled free radical polymerizations and functional nanocapsules were fabricated on the basis of the brush polymers.

Synthesis and Characterization of PEG Polymer Brushes via Cyclopolymerization of 1,2,3-Triazole Tethered Diacrylates

Poly(ethylene glycol) (PEG) macromolecular brushes were synthesized directly via reversible addition-fragmentation chain transfer polymerization cyclopolymerization of diacrylate monomers bearing PEG functional groups through the formation of 11-member rings. The diacrylate monomers bearing PEG functional groups are the 1,2,3-triazole-tethered diacrylate macromolecular monomers with di erent PEG lengths synthesized via the so-called “click” chemistry. The bulky hindrance of PEG chains affected the polymerization behavior of the diacrylate macromolecular monomers, and the diacrylate monomers showed strong tendency to cyclopolymerization rather than crosslinking. NMR analysis and gel permeation chromatography profiles proved the high efficiency of cyclopolymerization without side reactions. The aqueous solutions of the obtained PEG macromolecular brushes were fluorescent under UV excitation. The fluorescence depended dramatically on the concentration of brush-like polymers due to the aggregation of cyclopolymer in water, and could be quenched by the addition of DNA.

Nanodomain analysis with cluster‐SIMS: application to the characterization of macromolecular brush architecture

We present the application of cluster‐SIMS for the analysis of the nanoscopic surface of diblock brush terpolymers (DBTs). This novel SIMS technique differs from conventional SIMS. It uses Au4004+ projectiles at 520 keV and an event‐by‐event bombardment/detection regime for the analysis of co‐localized molecular species. The performance of this SIMS method was tested on ‘bottle brush’ block molecules featuring a vertical aligned backbone structure. We were able to assess the extent of secondary ion emissions from the surface and analyze the degree of ordered alignment for DBTs by the fluorocarbon surface coverage. We demonstrate the feasibility of characterizing the homogeneity of macromolecular films at the nanoscale. Copyright © 2015 John Wiley & Sons, Ltd.

Micellar and fractal aggregates formed by two triblock terpolymers with different arrangements of one charged, one neutral hydrophilic and one hydrophobic block

We have studied the self-assembled structures of two triblock amphiphilic polyelectrolytes of different topologies, containing a charged poly[sodium(sulfamate/carboxylate)isoprene] (SCPI) block, a polystyrene (PS) hydrophobic block and a hydrophilic neutral poly(ethylene oxide) (PEO) block in aqueous solutions, using Small Angle Neutron Scattering (SANS) and Light Scattering (LS). SANS reveals micellar and fractal aggregates in coexistence for both systems. In the case of SCPI-b-PS-b-PEO there is a higher content in fractal aggregates in comparison with PS-b-SCPI-b-PEO. In both cases the micellar aggregates are stable under different solution conditions, whereas the fractal aggregates appear to break upon addition of salt in the PS-b-SCPI-b-PEO system. The detailed picture of the micellar aggregates is consistent with the anticipated morphology of charged and neutral spherical macromolecular brushes, extended to mixed and sequential brushes. The analytical description obtained by SANS is used to interpret the LS data which is very sensitive to the presence of two species and therefore provides information on average values of the measured parameters.

Synthesis of conjugates combining macromolecular brushes and rigid macrocycles

A synthesis route towards conjugates comprised of two macromolecular brushes and a central shape persistent macrocycle utilizing atom transfer radical polymerization techniques is presented. The extended brush conformation could be visualized by atomic force microscopy on mica substrates, which allows for the observation of the position of the macrocycle within individual brush-cycle-brush conjugates. As a result of the architecture and the properties of the combined structure elements a functional macromolecule is obtained that might regulate accessibility to a central shape persistent macrocycle via reversible brush-coil transitions.