Comb-like Copolymers Research Articles

Effect of Architecture on Micelle Formation and Liquid-Crystalline Ordering in Solutions of Block Copolymers Comprising Flexible and Rigid Blocks: Rod-Coil vs Y-Shaped vs Comblike Copolymers.

Micelle formation of amphiphilic block copolymers of various architectures comprising both flexible and rodlike blocks were studied in a selective solvent via dissipative particle dynamics (DPD) simulations. Peculiarities of self-assembly of Y-shaped (insoluble rigid block and two flexible soluble arms) and comblike (soluble flexible backbone with insoluble rigid side chains) copolymers are compared with those of equivalent rod-coil diblock copolymers. We have shown that aggregation of the rigid blocks into the dense core of the micelles is accompanied by their nematic ordering. However, the orientation order parameter and aggregation number of the micelles are strongly dependent on macromolecular architecture. Relatively small micelles of pretty high nematic order parameter, S2 ≈ 0.5-0.8, are the features of the Y-shaped and rod-coil copolymer micelles. They are characterized by different responses to the solvent quality worsening. The aggregation number of the rod-coil diblock copolymer micelles increases and that of the Y-shaped copolymer micelles decreases at the solvent quality worsening. However, the order parameter grows in both cases, achieving a maximum value for the Y-shaped copolymer micelles. Herewith, the core elongates. On the contrary, comblike copolymers self-assemble into bigger spherical micelles whose core possesses a lower nematic order of the rods, S2 ≈ 0.3-0.4. The aggregation number is shown to depend on the length of the combs (on the number of repeating elements in the architecture). Possible physical reasons for such behavior of the systems are discussed.

Comb-like solid polymer electrolyte based on polyethylene glycol-grafted sulfonated polyether ether ketone

Solid polymer electrolytes based on a novel comb-like copolymer, polyethylene glycol-grafted sulfonated polyether ether ketone (SPEEK-g-PEG), was designed and synthesized through the reaction between partially hydroxyl-functionalized sulfonated polyether ether ketone (SPEEK) and epoxy-functionalized PEG. The resulting SPEEK-g-PEG was fully characterized by FTIR, 1H NMR, TGA, and DSC. All data proved the successful grafting of PEG onto the SPEEK main chain. The resulting comb-like structure effectively inhibited the crystallization of PEG. After doping with a lithium salt, the obtained SPEEK-g-PEG polymer electrolyte membrane showed an improved ionic conductivity. The effects of chain length and PEG grafting ratio on the ionic conductivity of SPEEK-g-PEG were also investigated by electrochemical impedance spectroscopy (EIS). Moreover, the effect of this comb-like structure on increasing the ionic conductivity is higher than that of SPEEK/PEG blends, making these comb-like SPEEK-g-PEG copolymers attractive for an application in LIBs.

Novel Comb-Like Copolymer Dispersant for Polypropylene/CaCO3 Composites and Its Influence on Dispersion, Crystallization, Mechanical, and Thermal Properties

ABSTRACTA novel comb-like copolymer with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was first used as the dispersant of CaCO3 particles in polypropylene (PP). The dispersion of CaCO3 particles in PP matrix was significantly improved in the presence of comb-like copolymer dispersant because of the strong repulsive force caused by steric hindrance effect. The influences of the coating amount of comb-like copolymer dispersant on crystallization behaviors, mechanical properties, and thermal stabilities were systematically investigated. The crystallization temperature, crystallinity, and crystallization rate of PP/CaCO3 composites prepared with monolayer-coated CaCO3 were all improved, where the monolayer comb-like copolymer coating remained as a rigid layer and provided a noticeable nucleating effect. The PP/CaCO3 composites coated with monolayer SP comb-like copolymer also had the best mechanical properties, including tensile strength, Young’s modulus, flexural modulus, and impact strength because of the good dispersion of CaCO3 particles in PP matrix. The thermal stability of PP/CaCO3 composites were measured by thermogravimetric analysis. The results showed that SP comb-like copolymer dispersant treated CaCO3 filled composites had excellent thermal stability than untreated and neat PP, especially for the composite prepared with monolayer-coated CaCO3.

Effect of carboxylate content in comb-like AA–IPEG copolymer as a dispersant for cement-based systems

AA–IPEG comb-like copolymer is a kind of polycarboxylate-based dispersant for cement-based systems. Copolymers with different carboxylate contents were synthesised using isoprenyl oxy polyethylene glycol ether (IPEG) and acrylic acid (AA) as raw materials, further modified with maleic anhydride. The copolymers were characterised by Fourier transform infrared spectroscopy, gel permeation chromatography and surface tension measurements. The dispersion of cement paste mixed with copolymer was studied by means of the zeta potential, adsorption behaviour, cement paste fluidity, setting time and scanning electron microscopy. It was found that the copolymer with a higher carboxylate content exhibited lower adsorption on the surface of cement particles and more negative zeta potential, and resulted in longer retention dispersion and setting time at the same dosage; however, excessive carboxylate content decreased the dispersing force of cement particles. Therefore, for more efficient dispersants for cement-based systems, there is a proper proportion between carboxylate content and poly(ethylene oxide) chains as the side groups on backbone chains.

Morphology and linear rheology of comb-like copolymer melts with high grafting density: Ⅰ. PVSt-g-(PS-b-PE) comb-like block copolymers

Comb-like block copolymers PVSt-g-(PS-b-PE) (PVSt: poly(4-(vinylpheneyl)-1-butene)) with high grafting density were successfully synthesized based on “Graft onto” strategy. The grafting density of PVSt-g-(PS-b-PE) was 35–39% (branch chain number per 100 repeating units of the backbone). By introducing PS block in the side chains, the total PS volume fraction in the copolymers could be adjusted to explore the influence of the volume fraction of total PS component (PVSt backbone + PS block) on morphology (at melt state) and linear rheological response of the copolymers. Compared to PSVS-g-PE copolymers with similar grafting density in the previous work (Macromolecules, 2015, 48, 7640), PVSt-g-(PS-b-PE) copolymers showed a microphase-separated structure at the melt state. The volume fraction of total PS in the comb-like block copolymers determined the type of morphology. When the volume fraction of PS changed from 11% to 55%, the microphase-separated structure changed from poor-order spherical structure to poor-order lamellar morphology, and all the samples of PVSt-g-(PS-b-PE) showed a typical rheological behavior of network-like structure. At the same time, the G′ curve and G″ curve were more away from each other at intermediate frequency with the increasing of PS content. The reason resulted from the formation of different microphase-separated structure types in the PVSt-g-(PS-b-PE).

Influence of comb-like copolymer dispersants with different molecular structures on the performance of CaCO3 suspension in organic system

ABSTRACTA series of comb-like copolymer poly(styrene-co-maleic anhydride)-graft-poly(ε-caprolactone) (SMA-g-PCL, SP) with variation in PCL side chain length and side chain density were synthesized and employed as an efficient dispersant for CaCO3 suspension in organic solvent. The effects of molecular structures of comb-like copolymer on adsorption, rheological behavior, and suspension stability were investigated systemically to elucidate the governing dispersing mechanism. The molecular structures of comb-like copolymer not only significantly influenced the adsorption behavior but also the rheological behavior and suspension stability. Calculations based on the scaling law and Flory theory made a profound understanding of the impact of the molecular structure of comb-like copolymer on dispersion property. The results revealed that the steric repulsive force was enhanced by increasing of side chain length or density. However, the surface area for one molecule on CaCO3 surface was also increased for its larger radius of the hemispheres of comb-like copolymer. This led to the worse activity of adsorption. The dispersion of CaCO3 was due to the synergistic effects of adsorption and steric hindrance effect, which resulted that the comb-like copolymer with moderate length and density of side chain presented the best dispersability.

Structural, Viscoelastic, and Electrochemical Characteristics of Self-Assembled Amphiphilic Comblike Copolymers in Aqueous Solutions.

Self-assembly in aqueous solutions of an amphiphilic comblike polyelectrolyte (80C12) that consists of a polystyrene (PS) backbone onto which quaternary ammonium pendant moieties have been grafted has been investigated by light scattering and cryo-transmission electron microscopy measurements in the presence of KCl and methylviologen dication (MV2+) under conditions mimicking those for electrochemical measurements. Polymer chains self-assemble within branched cylindrical micelles that display viscoelastic properties, characterized by a relaxation time of 4 s. To tune this time, 80C12 was mixed with a polyoxyethylene nonionic surfactant (Brij C12E10). Relatively increasing the amount of the latter leads to a decrease in the relaxation time of the 80C12 solution. Correlatively, electrochemical experiments with a rotating disk electrode show a transition of the mass transport rate, which deviates from the classical Newtonian behavior in the same velocity domain. This result generalizes what has been already observed with solutions of linear polymers of high molecular weight and wormlike micelles based on surfactants subjected to elongational deformations. Moreover, the critical times derived from rheological and electrochemical experiments display the same trend.

Self-assembly of comb-like amphiphilic copolymers in aqueous solution

Comb-like amphiphilic copolymers (polysoaps) have been studied by small-angle neutron scattering and light scattering techniques. The copolymer was synthesized by randomly grafting pendant quaternized alkylamine moieties (surfactant-like unit) to a polystyrene (hydrophobic) chain. In aqueous solution, the polymers self-assembled into platelet aggregates at low concentrations. When the electrostatic repulsions are screened by increasing the polymer concentration or by the addition of salt, hydrophobic interactions lead to a faster aggregation of platelets and leads to a phase separation. As the polymer concentration increases, the platelets extend by the edges to yield a final smectic organization of large sized lamellae. As a consequence visco-elastic solutions or hydrogels were formed at higher concentrations.

Mixed micelles obtained by co-assembling comb-like and grafting copolymers as gene carriers for efficient gene delivery and expression in endothelial cells.

Gene delivery can enhance the endothelialization of biomaterial surfaces. However, the lack of efficient target function is still the major concern that hinders the clinical application of gene therapy. With the aim to develop a specific targeting gene carrier for endothelial cells (ECs), the Cys-Arg-Glu-Asp-Val-Trp (CREDVW) peptide was linked to the comb-like copolymer of poly(lactide-co-3(S)-methyl-morpholine-2,5-dione)-poly(poly(ethylene glycol) monomethacrylate) (PLMD-PPEGMA) to form the CREDVW modified copolymer PLMD-PPEGMA-CREDVW, which could enhance the special recognition of ECs. Mixed micelles were then prepared by co-assembling this comb-like copolymer and the amphiphilic grafting copolymer poly(lactide-co-3(S)-methyl-morpholine-2,5-dione)-g-polyethylenimine (PLMD-g-PEI). These mixed micelles with the CREDVW-functional peptide exhibited good pEGFP-ZNF580 (pDNA) binding ability and could condense it into complexes with proper size and positive zeta potential. The MTT results demonstrated the low cytotoxicity of the CREDVW-modified mixed micelle/pDNA complexes. The internalization efficiency of the CREDVW-modified complexes with targeting function was about two times higher than the dysfunctional CREVDW-modified complexes. Besides, the transfection efficiency of these complexes was more pronounced, compared to the control group, PEI(10 kDa)/pDNA, as detected by means of in vitro transfection studies. Western blot analysis demonstrated relatively high protein levels in the transfected cells by CREDVW-modified mixed micelle/pDNA complexes, up to 75%, in comparison to the control group (26%). In addition, the cell migration ability was significantly improved as demonstrated by the wound healing assay. These results indicated that the mixed micelles could act as an active targeting gene carrier, having both tunable gene transfection efficiency and low cytotoxicity, which are beneficial for the endothelialization of biomaterial surface.

Phosphonated superplasticizers synthesis: adsorption, dispersion and fluidification ability on calcium carbonate suspensions.

Superplasticizers are chemical admixtures used to fluidize cement pastes. Among them, polycarboxylate are comb-like copolymers with carboxylic acid and poly(ethylene glycol) side chains. We present here the synthesis of various polycarboxylate-like copolymers including phosphonic acid functions. Their adsorption, dispersion and fluidification efficiencies are evaluated on calcium carbonate suspensions, a mineral material commonly used to simulate early-age cement behaviour.

A Si-doped flexible self-supporting comb-like polyethylene glycol copolymer (Si-PEG) film as a polymer electrolyte for an all solid-state lithium-ion battery

A Si-doped PEG-based crosslinked comb-like copolymer is an excellent polymer electrolyte for Li-ion batteries at low temperatures.

Methacrylic block copolymers by sulfur free RAFT (SF RAFT) free radical emulsion polymerisation

We demonstrate the use of sulfur free reversible addition–fragmentation chain transfer polymerisation (RAFT) as a versatile tool for the controlled synthesis of methacrylic block and comb-like copolymers.

Bioresorbable polypeptide-based comb-polymers efficiently improves the stability and pharmacokinetics of proteins in vivo.

Stimuli-responsive polypeptides are a promising class of biomaterials due to their tunable physicochemical and biological properties. Herein, a series of novel pH- and thermo-responsive block copolymers based on polypeptides were synthesized by ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxyanhydride in the presence of poly(ethylene glycol)-diamine macroinitiator followed by aminolysis. The resulting polypeptide-based triblock copolymer, poly[(2-(dibutylamino)ethyl-l-glutamate)-co-(γ-benzyl-l-glutamate)]-poly(ethylene glycol)-b-poly[(2-(dibutylamino)ethyl-l-glutamate)-co-(γ-benzyl-l-glutamate)] (PNLG-co-PBLG-b-PEG-b-PBLG-co-PNLG), exists as a low viscous sol at low pH and temperature (≤pH 6.4, 25 °C) but it transforms to a soft gel under physiological conditions (pH 7.4 and 37 °C). The physical properties of the polypeptide gel can be tuned by controlling the ratio between hydrophobic PBLG and pH-sensitive PNLG blocks. The polypeptide-based copolymer did not show any noticeable cytotoxicity to fibroblast cells in vitro. It was found that subcutaneous injection of the polypeptide copolymer solution into the dorsal region of Sprague-Dawley (SD) rats formed a gel instantly without major inflammation. The gels were completely biodegraded in six weeks and found to be bioresorbable. Human growth hormone (hGH)-loaded polypeptide-based biodegradable copolymer sols readily formed a viscoelastic gel that inhibited an initial burst and prolonged the hGH release for one week. Overall, due to their bioresorbable and sustained release protein characteristics, polypeptide hydrogels may serve as viable platforms for therapeutic protein delivery and the surface tunable properties of polypeptide hydrogels can be exploited for other potential therapeutic proteins.

Spontaneous onion shape vesicle formation and fusion of comb-like block copolymers studied by dissipative particle dynamics

The formation of an onion shape vesicle.

Shaping nanofiltration channels in a carbonaceous membrane via controlling the pyrolysis atmosphere.

This work investigates the effect of atmosphere on pyrolysis of a polymer matrix (precursor) for directing its transformation towards more disordered graphene species and smaller graphitic nanograins. These two structural characteristics are crucial to the generation of nano-channels (NCs) pertinent to nanofiltration (NF). Two measures are explored hereby to conduct the study: varying the pyrolysis atmosphere and implementing highly dispersed nickel atomic clusters (Ni-clusters) in the coating matrix undergoing pyrolysis. A thermally reactive polymer precursor is developed to allow the above two measures to act more effectively. The various pyrolysis atmospheres employed include inert Ar, a reducing H2/N2 gas mixture, and weak oxidizing CO2. In the absence of the Ni-clusters, the H2/N2 atmosphere restrains the extent of graphitization through a chain transfer effect of H2 that ceases the free radical chain propagation, whereas CO2, owing to its high critical temperature (Tc) nature, shows the capability to reduce nanograin sizes. As for the catalytic roles of the embedded Ni-clusters, they vary with the pyrolysis atmosphere applied: offering coke nuclei for the growth of carbonaceous grains in Ar, enhancing gasification of carbon in CO2, and repressing the extent of aromatization via hydrogenation in H2/N2. The carbonaceous membranes (CnMs) obtained under the above pyrolysis conditions are distinguished by the distribution density and structure of NCs evolved, which locate primarily in the boundaries of nanograins. The NF of an aqueous solution of methylene blue (MB, 10 ppmw) is utilized to assess these CnMs to show impacts of the NCs on the separation performance.

Comb-like copolymer dispersant for PP/CaCO3 composites: effects of particle concentration on properties of composites

Abstract A comb-like copolymer poly (styrene-co-maleic anhydride)-graft-poly (ε-caprolacton) (SMA-g-PCL, SP) with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was used as an effective dispersant for CaCO3 in the polypropylene (PP) matrix. The effects of CaCO3 concentration on crystallization behaviors, mechanical properties, and thermal stabilities were studied systematically. The results revealed that the dispersion of CaCO3 in the PP matrix was markedly improved owing to the steric hindrance effect caused by PCL, and the SP-coated CaCO3 was a very effective nucleating agent for PP. Proper CaCO3 concentration corresponded to the improvement of crystallization temperature, crystallinity, and crystallization rate of PP. There was only a slight improvement in yield stress but great improvement in Young’s modulus, flexural modulus, and impact strength. However, the excessive CaCO3 filler deteriorated the mechanical properties. The good dispersion of SP-coated CaCO3 in the PP matrix also accounted for the improvement of thermal stability. The initial decomposition temperature of the PP/CaCO3 composite with 7.4 wt.% CaCO3 increased 35°C compared with neat PP.

Diverse morphologies of self-aggregates from dodecyl chain grafted poly(2-hydroxyethyl aspartamide) in aqueous solution

A series of amphiphilic graft copolymers, poly(2-hydroxyethyl aspartamide) grafted with dodecyl chains with different degree of substitution (DS), were synthesized and their self-aggregates showing various morphologies in aqueous media were prepared by direct dissolution method. Spherical micelles, wormlike micelles, tubular networks, and vesicles observed by TEM were found to be a function of DS of the hydrophobic dodecyl chain, and those self-assembled nanostructures can be explained in terms of interfacial energy and packing parameter. To our knowledge, this is the first report of diverse morphologies for a comb-like amphiphilic graft copolymer system. Our system suggests very attractive advantages for biomedical applications and for mass production of aggregates by direct dissolution into water without an organic solvent. Open image in new window

Study of optical and electrical properties of thin films of the conducting comb-like graft copolymer of polymethylsiloxane with poly(3-hexyltiophene) and poly(ethylene) glycol side chains for low temperature NO2 sensing

This work presents an investigation on graft comb copolymer of polymethylsiloxane (PMS) with poly(3-hexyltiophene) (P3HT) and poly(ethylene) glycol as functional side groups. This segmented copolymer was investigated as a NO2 gas sensing material. Gas sensing, optical and electrical properties of thin films of graft polymers and clean P3HTs (regioregular and regiorandom) are tested and compared. The thin films of investigated materials obtained by spin coating method on interdigital transducers and surface plasmon resonance (SPR) sensor structure are characterized by using atomic force microscopy method and Raman spectroscopy. High changes of resistance and SPR signal caused by action of NO2 in the concentration of ppm range were observed. It showed that such graft polymers are promising materials for resistance and optical gas sensors operating at low temperatures. Obtained results showed that resistance and sensitivity of graft polymers depend on the content of P3HT and PMS backbone chain length. An optical SPR NO2 gas sensor and resistance NO2 sensor based on graft polymer thin films display a very fast response time and a fast regeneration time at low temperature (50°C) in a dry gaseous environment. Resistance sensor investigation showed that the sensitivity of graft polymers to 5ppm of NO2 can be about 20 times higher than in the case of clean P3HTs.

Synthesis of a novel comb-like copolymer used as dispersant in organic solvent and influence of free comb-like copolymer on CaCO3 suspension

ABSTRACTA novel comb-like copolymer poly (1e)-graft-poly (ε-caprolactone) (SMA-g-PCL, SP), which can be used as an effective CaCO3 dispersant in organic solvent, was prepared via the esterification reaction between SMA and PCL. The structures and compositions of the graft copolymer were determined by Fourier transform infrared spectrometry (FTIR), H-nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC), respectively. The influences of free comb-like copolymer on CaCO3 suspension viscosity and rheological behavior were investigated. It was found that the particle-binding bridge generated among CaCO3 particles through hydrogen bonding and/or electrostatic interactions increased the suspension viscosity as well as the depletion flocculation. On the other hand, it was noteworthy that the free comb-like copolymer could make the CaCO3 suspension evolve from shear-thinning fluid or nearly Newtonian fluid into shear-thickening fluid. It was attributed to the formation of a transient network through intermolecular associations between the adsorbed SP and the free polymer chains under the action of shear. Finally, the fitting parameters from the Herschel–Bulkley model were in good agreement with the evolution of the rheological behavior of CaCO3 suspension.

Antitumor gemcitabine conjugated micelles from amphiphilic comb-like random copolymers

Gemcitabine is an important pyrimidine antimetabolite that inhibits cellular DNA synthesis. However, the therapeutic efficacy and clinical benefit of gemcitabine are severely compromised due to its rapid plasma metabolism and low selectivity towards tumor tissues. To overcome these limitations, we prepared novel PEGylated gemcitabine-contained comb-like copolymers poly(monomethoxyl PEG350 methylacrylate ⿿co- 5⿲-O-vinyladipyl- gemcitabine) (poly(mPEG350MA-co-VAG) and (poly(mPEG1000MA-co-VAG), which could self-assemble into micelles and displayed enhanced antitumor activity. The copolymers and the formed micelles were well characterized for their structure, critical aggregation concentration (CAC), morphology, cellular uptake, cell cytotoxicity, and controlled drug release. Cellular uptake and in vitro cytotoxicity assays against human lung cancerous cells (A549) demonstrated that these micelles could be effectively internalized and induced cell apoptosis. These micelles efficiently inhibited tumor growth when injected intravenously into A549 cell derived xenograft tumor bearing Balb/C nude mice using a dose of 10mg/kg in terms of reduced tumor volume compared to free gemcitabine. In conclusion, PEGylated micelles could protect gemcitabine from rapid plasma metabolism, provided a sustained release and showed enhanced antitumor activity, thus have the potential to be used as novel anticancer drug delivery vehicle.