ABA Triblock Copolymers Research Articles

One-pot synthesized ABA tri-block copolymers for high-performance organic field-effect transistors

A series of P3HT-b-PHA-b-P3HT tri-block copolymers were synthesized in one pot and fabricated into organic field-effect transistors by a blending method.

Anatomy of triply-periodic network assemblies: characterizing skeletal and inter-domain surface geometry of block copolymer gyroids.

Triply-periodic networks (TPNs), like the well-known gyroid and diamond network phases, abound in soft matter assemblies, from block copolymers (BCPs), lyotropic liquid crystals and surfactants to functional architectures in biology. While TPNs are, in reality, volume-filling patterns of spatially-varying molecular composition, physical and structural models most often reduce their structure to lower-dimensional geometric objects: the 2D interfaces between chemical domains; and the 1D skeletons that thread through inter-connected, tubular domains. These lower-dimensional structures provide a useful basis of comparison to idealized geometries based on triply-periodic minimal, or constant-mean curvature surfaces, and shed important light on the spatially heterogeneous packing of molecular constituents that form the networks. Here, we propose a simple, efficient and flexible method to extract a 1D skeleton from 3D volume composition data of self-assembled networks. We apply this method to both self-consistent field theory predictions as well as experimental electron microtomography reconstructions of the double-gyroid phase of an ABA triblock copolymer. We further demonstrate how the analysis of 1D skeleton, 2D inter-domain surfaces, and combinations therefore, provide physical and structural insight into TPNs, across multiple length scales. Specifically, we propose and compare simple measures of network chirality as well as domain thickness, and analyze their spatial and statistical distributions in both ideal (theoretical) and non-ideal (experimental) double gyroid assemblies.

Nano-porous structuresviaself-assembly of amphiphilic triblock copolymers: influence of solvent and molecular weight

Self-assembly of ABA triblock copolymer micelles into porous materials which are subsequently used as filtration membranes.

Synthesis of novel guanidine-based ABA triblock copolymers and their antimicrobial honeycomb films

Novel antimicrobial poly(methacryl guanidine hydrochloride)-block-polystyrene-block-poly(methacryl guanidine hydrochloride) triblock copolymers were synthesizedviaRAFT polymerization and fabricated into antimicrobial honeycomb films.

Multimodal Underwater Adhesion Using Self-assembled Dopa-bearing ABA Triblock Copolymer Networks.

Self-assembled mechanically robust Dopa-bearing triblock copolymer networks improve underwater adhesion through both energy dissipation and interfacial bonding. Polymer networks that incorporate energy dissipating motifs could improve the performance of high-performance wet adhesives rather than only by interfacial bonds.

Polymer Electrolytes Containing Solvate Ionic Liquids: A New Approach To Achieve High Ionic Conductivity, Thermal Stability, and a Wide Potential Window

We describe here the electrochemical properties and battery performance of polymer electrolytes composed of ABA-triblock copolymers and Li-glyme solvate ionic liquids (SILs), which consist of the [Li(glyme)]+ complex cation and bis(trifluoromethanesulfoly)amide ([TFSA]−) anion, to simultaneously achieve high ionic conductivity, thermal stability, and a wide potential window. Three different block copolymers, consisting of a SIL-incompatible A segment (polystyrene, PSt) and SIL-compatible B segments (poly(methyl methacrylate) (PMMA), poly(ethylene oxide) (PEO), and poly(butyl acrylate) (PBA)) were synthesized. The SILs were solidified with the copolymers through physical cross-linking by the self-assembly of the PSt segment. The thermal and electrochemical properties of the polymer electrolytes were significantly affected by the stability of the [Li(glyme)]+ complex in the block copolymer B segments, and the preservation of the SILs contributed to their thermal stabilities and oxidation stabilities greater...

Controlled Sol–Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger

AbstractProducing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light‐controlled mechanical sol–gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2‐phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light‐controlled sol–gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self‐assembly of a thermoresponsive polymer, leading to macroscopic light‐controlled sol–gel transitions.

Controlled Sol-Gel Transitions of a Thermoresponsive Polymer in a Photoswitchable Azobenzene Ionic Liquid as a Molecular Trigger.

Producing ionic liquids (ILs) that function as molecular trigger for macroscopic change is a challenging issue. Photoisomerization of an azobenzene IL at the molecular level evokes a macroscopic response (light-controlled mechanical sol-gel transitions) for ABA triblock copolymer solutions. The A endblocks, poly(2-phenylethyl methacrylate), show a lower critical solution temperature in the IL mixture containing azobenzene, while the B midblock, poly(methyl methacrylate), is compatible with the mixture. In a concentrated polymer solution, different gelation temperatures were observed in it under dark and UV conditions. Light-controlled sol-gel transitions were achieved by a photoresponsive solubility change of the A endblocks upon photoisomerization of the azobenzene IL. Therefore, an azobenzene IL as a molecular switch can tune the self-assembly of a thermoresponsive polymer, leading to macroscopic light-controlled sol-gel transitions.

Dissipative particle dynamics simulation of the relaxation behaviour of a triblock copolymer supramolecular network

Since block copolymers self-assemble into various nanostructures and these are widely used in soft materials such as cosmetics and paints, these continue to be the subjects of fundamental studies that progress new technologies. ABA triblock copolymers self-organise into supramolecular networks in which crosslinked structures change upon heating and other external stimulation. Supramolecular networks that consist of ABA triblock copolymers have three components: bridges, loops and dangles. These supramolecular networks have structural regions (clusters) in which end blocks of polymer chains are aggregated and connected by the internal blocks of the polymer chains. Despite of the importance of relaxation behaviour during the measurement and control of polymer materials, the molecular-level behaviour of these systems has not been addressed. We observed pull-out phenomenon that the ends of these polymers detach from clusters, and estimated characteristic detachment times by counting the number of detachments and compared it with the time of longest relaxation in that system.

Microphase‐Separated Morphology and Liquid Crystal Orientation in Block Copolymers Comprising a Main‐Chain Liquid Crystalline Central Segment Connected to Side‐Chain Liquid Crystalline Segments at Both Ends

AbstractThe self‐assembly behavior of ABA triblock copolymers comprising side‐chain (SC) liquid crystalline (LC) polymer (A blocks) and a main‐chain (MC) LC polyester (B block) is investigated for SCLC segment volume fractions (ϕ) ranging from 22% to 81%. At ϕ = 81% and 65%, the MCLC segments form cylinders and spheres, respectively, embedded in an SCLC matrix. At ϕ ≤ 56%, block copolymers form lamellar microdomains in which each segment forms smectic layers parallel to the lamellae. Whereas MCLC segments are mostly extended along the lamella normal but are folded to fit within the lamellae, the SCLC segment backbone is more elongated, traversing the smectic layers. Such backbone dimensions and mesogens' orientation in the SCLC segment are explained in light of the small interfacial area with the B5 segment, which is conserved even when the SCLC segment is in the isotropic liquid state.

Thermo- and pH- dual responsive inorganic-organic hybrid hydrogels with tunable luminescence

A thermo- and pH- dual responsive luminescent hydrogel was successfully constructed by coupling dysprosium-containing polyoxometalates Na9DyW10O36 (DyW10) with the ABA triblock copolymer, where the B block is PEO and the A block is the thermosensitive poly(methoxydi(ethylene glycol) methacrylate- co - N , N -dimethylaminoethyl methacrylate). The complex hybrid underwent a sol-gel phase transition above the lower critical solution temperature (LCST) of the A block. DyW10 was electrostatically encapsulated into the hydrophobic domain of the A block with enhanced photoluminescence. When temperature cooled down, the luminescence could be restored. By addition of acids to protonate the A block, and emission of DyW10 was simultaneously enhanced. Sensitivity of poly( N , N -dimethy laminoethyl methacrylate) (PDMAEMA) to pH also enabled the emission of DyW10/copolymer hydrogel to be reversibly switched by alternating acid/base treatments.

Discovering Synthesis Routes to Hexagonally Ordered Mesoporous Niobium Nitrides Using Poloxamer/Pluronics Block Copolymers

Ordered mesoporous transition metal nitrides are interesting as high-surface-area catalyst supports, as materials for energy conversion and storage devices, and as a platform for investigating mesostructured superconductors. The Pluronics/poloxamer family of ABA triblock copolymers has been widely used to produce crystalline ordered mesoporous transition metal oxides, but is considered to pose a major challenge in the synthesis of the corresponding nitrides and other classes of inorganic materials. We report a synthesis of hexagonally-ordered mesoporous niobium nitrides based on commercially available ABA triblock copolymers of the poloxamer/Pluronics family. Employing in situ small- and wide-angle synchrotron x-ray scattering (SAXS/WAXS), we demonstrate that successful thermal processing conditions are confined to a narrow parameter window, which explains previous challenges to access such nitrides. These studies further suggest synthesis of high quality nitrides via e.g. rapid thermal processing. We ant...

A Triblock Copolymer Design Leads to Robust Hybrid Hydrogels for High-Performance Flexible Supercapacitors.

We report here an intriguing hybrid conductive hydrogel as electrode for high-performance flexible supercapacitor. The key is using a rationally designed water-soluble ABA triblock copolymer (termed as IAOAI) containing a central poly(ethylene oxide) block (A) and terminal poly(acrylamide) (PAAm) block with aniline moieties randomly incorporated (B), which was synthesized by reversible additional fragment transfer polymerization. The subsequent copolymerization of aniline monomers with the terminated aniline moieties on the IAOAI polymer generates a three-dimensional cross-linking hybrid network. The hybrid hydrogel electrode demonstrates robust mechanical flexibility, remarkable electrochemical capacitance (919 F/g), and cyclic stability (90% capacitance retention after 1000 cycles). Moreover, the flexible supercapacitor based on this hybrid hydrogel electrode presents a large specific capacitance (187 F/g), superior to most reported conductive hydrogel-based supercapacitors. With the demonstrated additional favorable cyclic stability and excellent capacitive and rate performance, this hybrid hydrogel-based supercapacitor holds great promise for flexible energy-storage device.

Single-ion triblock copolymer electrolytes based on poly(ethylene oxide) and methacrylic sulfonamide blocks for lithium metal batteries

Single-ion conducting polymer electrolytes represent the ideal solution to reduce concentration polarization in lithium metal batteries (LMBs). This paper reports on the synthesis and characterization of single-ion ABA triblock copolymer electrolytes comprising PEO and poly(lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl)imide) blocks, poly(LiMTFSI). Block copolymers are prepared by reversible addition-fragmentation chain transfer polymerization, showing low glass transition temperature (−55 to 7 °C) and degree of crystallinity (51–0%). Comparatively high values of ionic conductivity are obtained (up to ≈ 10−4 S cm−1 at 70 °C), combined with a lithium-ion transference number close to unity (tLi+ ≈ 0.91) and a 4 V electrochemical stability window. In addition to these promising features, solid polymer electrolytes are successfully tested in lithium metal cells at 70 °C providing long lifetime up to 300 cycles, and stable charge/discharge cycling at C/2 (≈100 mAh g−1).

Polystyrene-block-polyethylene-block-polystyrene triblock copolymers: Synthesis and crystallization-driven self-assembly behavior

In this work, we reported the synthesis of a series of novel semicrystalline ABA triblock copolymers with polyethylene midblock and polystyrene endblocks via the combination of ring-opening metathesis polymerization (ROMP), hydrogenation and reversible addition-fragmentation chain transfer (RAFT) polymerization. First, an α,ω-dihydroxyl-terminated polycyclooctadiene (PCOD) was synthesized via the ROMP of cyclooctadiene by the use of the Grubbs second generation catalyst and with cis-2-butene-1,4-diol as the chain transfer agent. The α,ω-dihydroxyl-terminated PCOD was then hydrogenated into an α,ω-dihydroxyl-terminated polyethylene (PE); the latter was allowed to react with 2-methyl-2-[(dodecylsulfanylthiocarbonyl) sulfanyl]propanoic acid to afford a macromolecular chain transfer agent (i.e., Macro-CTA) for the RAFT polymerization of styrene. By controlling the lengths of PS endblocks, a series of polystyrene-block-polyethylene-block-polystyrene (PS-b-PE-b-PS) triblock copolymers were obtained. The successful synthesis of the ABA triblock copolymers were demonstrated by means of nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The results of differential scanning calorimetry (DSC) and atomic force microscopy (AFM) indicate that the PS-b-PE-b-PS triblock copolymers were microphase-separated in bulks and their morphologies were quite dependent on the mass ratios of PE to PS blocks. Transmission electron microscopy (TEM), atomic force microscopy (AFM) and dynamic light scattering (DLS) showed that the triblock copolymers displayed crystallization-driven self-assembly (CDSA) behavior in selective solvent (viz. 1,4-dioxane). Depending on the lengths of PS blocks, the CDSA behavior of all the triblock copolymers generated spherical and cylindrical micelles. It was found that the quantity of the cylindrical micelles increased with decreasing the lengths of PS blocks.

Physicochemical Characterization of a Photoinduced Sol–Gel Transition of an Azobenzene-Containing ABA Triblock Copolymer/Ionic Liquid System

We have previously reported that an ABA triblock copolymer with poly(ethylene oxide) as the B block and a thermo-/photoresponsive random copolymer of 4-phenylazophenyl methacrylate (AzoMA) and N-isopropylacrylamide (NIPAm) (P(AzoMA-r-NIPAm)) as the A block exhibited a reversible photoinduced sol–gel transition in a hydrophobic ionic liquid. Such reversible sol–gel transitions can be used to realize photohealable ion gels. This study contributes to a deeper physicochemical understanding of the photoinduced sol–gel transitions observed in the ion gel, showing that the glassy state of P(AzoMA-r-NIPAm) block domains is responsible for the long relaxation times. Importantly, the controlled photoisomerization of azobenzene moieties allows the glass transition temperature of P(AzoMA-r-NIPAm) block domains to be varied by choosing irradiation conditions. The photoinduced sol–gel transition can be understood as an elastic solid–viscoelastic liquid or a viscoelastic solid–viscoelastic liquid transition, depending o...

Triblock Copolymer Elastomers with Enhanced Mechanical Properties Synthesized by RAFT Polymerization and Subsequent Quaternization through Incorporation of a Comonomer with Imidazole Groups of about 2.0 Mass Percentage

ABA triblock copolymer elastomers (TBCPEs) were first synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization, for which poly(isobornyl acrylate) (PIBA) was chosen as the dispersed hard microdomains, whereas poly(n-butyl acrylate)-co-poly(1-vinylimidazole) (P(BA-co-VI)) was chosen as the rubbery matrix. Two much distinct glass transition temperatures were found, corresponding to the soft matrix and hard microdomains, respectively. Although the mass percentages of the incorporated third comonomer, 1-vinylimidazole, were just about 2.0%, the imidazole groups on the TBCPE chains could be ionically cross-linked by 1,6-dibromohexane to bring these TBCPEs into much strong ones, half-cross-linked TBCPEs-HC and full-cross-linked TBCPEs-FC. It is interesting to demonstrate that the ultimate tensile strength for TBCPEs-FC could be increased up to 10 times that for TBCPEs, and the elastic recovery could also be improved to above 90%, while the elongation at break just showed modest dec...

One-Pot Synthesis of Charged Amphiphilic Diblock and Triblock Copolymers Via High-Throughput Cu(0)-Mediated Polymerization.

Block copolymers containing functionalized monomers, for example those containing charged groups, can be used for many purposes, one of which is the design of polymeric supramolecular materials based on electrostatic interactions. In this paper the synthesis of diblock copolymers and ABA-triblock copolymers containing poly(n-butyl acrylate) as a first or middle block and poly(2-(dimethylamino)ethyl acrylate), poly(1-ethoxyethyl acrylate) and poly(1-ethoxyethyl-2-carboxyethyl acrylate) as second or outer blocks, resulting in block copolymers that can contain positive or negative charges, is reported. The polymerizations were performed and optimized via one-pot sequential monomer addition reactions via Cu(0)-mediated polymerization using an automated parallel synthesizer. Different initiators, monomer concentrations and polymerization times were tested. While a bromide-containing initiator led to the best results for most monomers, when polymerizing 2-(dimethylamino)ethyl acrylate the use of a chloride-containing initiator was necessary. Due to the slower polymerization using this initiator, a longer polymerization time was needed before addition of the second monomer. Using the optimized conditions, the diblock and triblock copolymers could be synthesized with good control over molecular weight and dispersities around 1.1 were obtained.

Degradable thermosensitive injectable hydrogels with two-phase composite structure from aqueous solutions of poly(N-isopropylacrylamide-co-5,6-benzo-2-methylene-1,3-dioxepane)—poly(ethylene glycol) triblock copolymers and biopolymers

Novel degradable thermosensitive injectable hydrogels with two-phase composite structure and improved mechanical strength were prepared by adding sodium alginate or dextran to the aqueous solution of a hydrolytically degradable ABA triblock copolymer with poly(ethylene glycol) middle block and poly(N-isopropylacrylamide) containing in-chain ester groups as side blocks. The two-phase structure, demonstrated by SEM measurements, resulted as a consequence of the triblock copolymer-biopolymer incompatibility. The biopolymer addition decreased the gelation temperature (T gel) and strongly improved the viscoelastic properties of the resulted hydrogel, whose behavior at 37 °C turned from liquid-like to a gel-like one. The composite hydrogels displayed low gelation time and high stability (i.e., no sign of syneresis after 42 days) at 37 °C. They partially degraded in PBS at 37 °C as a consequence of the hydrolysis of the in-chain ester groups of the thermosensitive blocks, leading to a progressive increase of T gel and decrease of gel strength. The ability of the composite hydrogels to control the release rate of drugs was tested in PBS at 37 °C by employing 5-flurouracil (5FU) and chlorambucil (CLB) as model drugs with different hydrophilicity. 5FU displayed a pretty fast release rate, unlike CLB whose release rate was much slower, no effect of the biopolymer nature being noticed. During the drug release experiments, the hydrogels showed a moderate mechanical stability, although higher than in the absence of the biopolymer, and also progressively dissolved within 12–17 days because of the hydrogel erosion phenomenon, probably accelerated by the partial degradation of the triblock copolymer.

Biodegradable Strain-Promoted Click Hydrogels for Encapsulation of Drug-Loaded Nanoparticles and Sustained Release of Therapeutics.

Biodegradable polycarbonate-based ABA triblock copolymers were synthesized via organocatalyzed ring-opening polymerization and successfully formulated into chemically cross-linked hydrogels by strain-promoted alkyne-azide cycloaddition (SPAAC). The synthesis and cross-linking of these polymers are copper-free, thereby eliminating the concern over metallic contaminants for biomedical applications. Gelation occurs rapidly within a span of 60 s by simple mixing of the azide- and cyclooctyne-functionalized polymer solutions. The resultant hydrogels exhibited pronounced shear-thinning behavior and could be easily dispensed through a 22G hypodermic needle. To demonstrate the usefulness of these gels as a drug delivery matrix, doxorubicin (DOX)-loaded micelles prepared using catechol-functionalized polycarbonate copolymers were incorporated into the polymer solutions to eventually form micelle/hydrogel composites. Notably, the drug release rate from the hydrogels was significantly more gradual compared to the solution formulation. DOX release from the micelle/hydrogel composites could be sustained for 1 week, while the release from the micelle solution was completed rapidly within 6 h of incubation. Cellular uptake of the released DOX from the micelle/hydrogel composites was observed at 3 h of incubation of human breast cancer MDA-MB-231 cells. A blank hydrogel containing PEG-(Cat)12 micelles showed almost negligible toxicity on MDA-MB-231cells where cell viability remained high at >80% after treatment. When the cells were treated with the DOX-loaded micelle/hydrogel composites, there was a drastic reduction in cell viability with only 25% of cells surviving the treatment. In all, this study introduces a simple method of formulating hydrogel materials with incorporated micelles for drug delivery applications.