ABA Triblock Research Articles

Well-Defined ABA Triblock Copolymers Containing Carbazole and Ethynyl Groups: Living Anionic Polymerization, Postpolymerization Modification, and Thermal Cross-Linking

Well-Defined ABA Triblock Copolymers Containing Carbazole and Ethynyl Groups: Living Anionic Polymerization, Postpolymerization Modification, and Thermal Cross-Linking

How does the hydrophobic content of methacrylate ABA triblock copolymers affect polymersome formation?

AbstractPolymersomes are exciting self‐assembled structures with great potential in pharmaceutical applications. A systematic investigation of a novel series of methacrylate‐based polymersomes is reported in this study. Five well‐defined ABA triblock copolymers with A being based on tri(ethylene glycol) methyl methacrylate and B being based on 2‐(diethylamino)ethyl methacrylate (DMAEMA) were synthesized using a living polymerization method. The effect of the composition of the ABA triblock copolymers on the thickness of the hydrophobic membrane of the polymersomes and the release of a model drug is demonstrated.

One-Pot Synthesis of Supertough, Sustainable Polyester Thermoplastic Elastomers Using Block-Like, Gradient Copolymer as Soft Midblock

It remains challenging to synthesize supertough thermoplastic elastomers (TPEs) since the stretchability and tensile strength are mutually exclusive. Here, we report a one-pot strategy for the prep...

Importance of interfacial mixed layer to determine the middle block Tg in lamellar structures of uncross-linked and cross-linked hard-b-soft-b-hard triblock copolymers

We here discuss the importance of interfacial mixed layer on determination of the middle block Tg (Tg,B) of lamellar-forming hard-b-soft-b-hard ABA triblock copolymers. The detailed morphological characterization is first conducted by scattering measurements and model analyses, which provides the length fraction of B segments (fint,B) existing in the interfacial mixed layer to the overall B block chain. By investigating Tg for the neat triblock copolymers with various middle block lengths and volume fractions of the A blocks (φA), the variation of Tg,B is found to have a correlation with (fint,B). In the later section, the discussion related to Tg,B is made for the samples with cross-linked A block domains prepared via photo reaction. In this design, the original morphology is finely retained after the cross-linking, thereby enabling the extraction of the pure effects of the domain cross-linking on the physical properties. After the domain cross-linking, interestingly, the glass transition temperature of the B middle block (Tg,B) decreases, especially for the sample with φA > 0.5, where the reduction degree of Tg,B is determined by both the segmental density in the interface and fint,B.

Theory of Microphase Segregation in ABA Triblock Comb-Shaped Copolymers: Lamellar Mesophase

A theory describing lamellar mesophases formed in the melt of ABA triblock copolymers with strongly incompatible comblike blocks is developed using a combination of a strong-stretching self-consistent field (SS-SCF) analytical approach and numerical self-consistent field calculations based on the Scheutjens-Fleer (SF-SCF) methods. The structural and thermodynamic properties of the lamellae are analyzed as a function of their architectural parameters, i.e., grafting density and polymerization degree of the main and side chains in the comb-shaped blocks. In particular, we distinguish between the loops and bridges formed by the middle comb-shaped block and demonstrate how a fraction of the bridges connecting the neighboring AB interfaces of the lamellar layers and shear modulus of the mesophase are mediated by the architectural parameters of the comblike blocks. In particular, we predict an increase in the shear modulus upon replacement of the linear ABA triblock copolymers by comblike ones with the same composition. The asymptotic analytical predictions of the theory are complemented by the results of numerical modeling.

Patterns produced in water-oil-block copolymer systems

Phase diagrams for a ternary system consisting of water, oil and ABA triblock copolymers reveal a variety of ordered structures and patterns.

Effect of end-block chain length on rheological properties of ABA triblock copolymer hydrogels

Effect of end-block chain length on rheological properties of ABA triblock copolymer hydrogels

Highly efficient gel electrolytes by end group modified PEG-based ABA triblock copolymers for quasi-solid-state dye-sensitized solar cells

To get highly efficient quasi-solid-state dye-sensitized solar cells (QSS-DSSCs) with long-term stability using polymer gel electrolytes (PGEs), well-defined ABA triblock copolymers ([Poly(methyl methacrylate)]2-block-poly(ethylene glycol)) with different end functionality and components of I-/I3- liquid electrolytes (LEs) are studied and optimized for the fabrication of PGE-based QSS-DSSCs. Triblock copolymers are synthesized in a one-step reaction using bifunctional PEG-macro chain transfer agent (MCTA) by reversible addition-fragmentation chain transfer (RAFT) polymerization. Due to the high reactivity and toxicity of sulfur-containing trithiocarbonate end groups, ABA triblock copolymers prepared from RAFT polymerization are further modified to sulfur-free 2-methylpropionitrile and 4-cyanopentanoic acid end functional triblock copolymers by radical-induced exchange reactions. Dodecyl trithiocarbonate end functional PEG-MCTA and triblock copolymers absorb UV-light in the region of 260–380 nm, whereas sulfur-free carboxylic acid and 2-methylpropionitrile end functional polymers do not absorb in that UV-light region. Among three different end functional polymers, the carboxylic acid end functional triblock copolymer has the highest thermal stability. Based on electrochemical parameters, photovoltaic performance, and long-term stability, 1,2-dimethyl-3-propylimidazolium iodide (DMPII) ionic liquid and 4-tert-butylpyridine (TBP) additive containing acetonitrile-based I-/I3- LEs are effective for PGEs. The highest power conversion efficiency (PCE) for QSS-DSSCs achieved under simulated 1-sun illumination is up to 10.34%, which is comparable with the highest PCE of 10.39% for LE-DSSCs. Considering the high reactivity, thermal stability, UV-absorption, and the toxicity of the trithiocarbonate end group, the SGT-643-C triblock copolymer with carboxylic acid end group can be a promising candidate as a sulfur-free polymeric matrix for gel electrolytes of QSS-DSSCs.

Topology Reliable LCST‐Type Behavior of ABA Triblock Polymer and Influence on Water Condensation and Crystallization

As a kind of smart material, thermoresponsive hydrogels are widely investigated and applied in many fields. Due to the limitation of the freezing temperature of the water, it is a challenge to further broaden their sol-gel transition temperature (Tgel ) range, especially below 0°C. Herein, the lower critical solution temperature type of amphiphilic ABA triblock copolymers, synthesized via two-step reversible addition-fragmentation chain transfer (RAFT) polymerization is demonstrated. The hydrophilic A-block and the hydrophobic B-block are composed of poly(N,N-dimethylacrylamide) (PDMAA) and poly(diacetone acrylamide) (PDAAM), respectively. The degree of polymerization (DP) of both A-block and B-block shows a significant influence on the Tgel of triblock copolymer dispersion. By changing the length of these two blocks or physically blending these copolymers dispersions, the Tgel can be well adjusted in a temperature range from 45 to -10°C. Moreover, When the Tgel is higher than 4°C, the triblock copolymer coatings show a good anti-fogging property. And when the Tgel is around or lower than the freezing temperature of the water, aqueous dispersions of the triblock copolymer have an ice recrystallization inhibition activity, resulting in the decrease of average maximum grain size (MLGS) of ice crystal.

Effect of stereochemistry on nanoscale assembly of ABA triblock copolymers with crystallizable blocks

We report on the nanoscale assembly of poly(lactic acid)-b-poly(ethylene oxide)-b-poly(lactic acid) (PLA-PEO-PLA) triblock copolymers in water, focusing on the effect of stereochemistry, where the PLA blocks are statistical copolymers of l-lactide and d-lactide with l/d ratios of 100/0, 95/5, 90/10, 85/15, 75/25, and 50/50. Small-angle neutron scattering (SANS) shows a nearly constant d-spacing as concentration varies in triblock systems with l/d ratios of 90/10 and 95/5, which we attribute to inhomogeneity in the structure of these gels, supported by previous USANS and confocal microscopy studies. The SANS data fit well to a core-shell ellipsoid form factor model with a hard-sphere structure factor. Polymeric micelles with l/d ratios from 75/25 to 85/15 displayed very high aggregation numbers, consistent with a strong interaction between PLA chains and the enhanced storage modulus observed in rheological studies of these systems. While the 90/10 and 95/5 samples showed lower aggregation numbers, their SANS profiles shows close spacing between micelles, which may promote a high fraction of intermicellar bridging chains, also consistent with a higher storage modulus. Overall, these results provide insight into the micellar assembly behavior of block copolymers with a crystallizable block, and indicate that tuning stereochemistry of PLA-based block copolymers is an effective means of modifying micellar properties for specific applications.

Sustainable Thermoplastic Elastomers Derived from Lignin Bio‐Oils via an ABA Triblock Copolymer Strategy

AbstractA lignin‐derived polyacrylate, namely, poly(guaiacyl acrylate) (PGA), is evaluated as an end block in linear ABA triblock copolymer‐based sustainable thermoplastic elastomers. Triblock copolymers containing a rubbery poly(methyl acrylate) (PMA) midblock and glassy PGA end blocks are prepared via Cu(0)‐mediated living radical polymerization or single electron transfer living radical polymerization. A suite of triblock copolymers with different block ratios and a constant end block molecular weight is prepared. Even a low‐end block content (<5% mole ratio) can significantly increase the material's mechanical strength (3–7 folds) and long elongation at break. The enhanced mechanical properties are attributed to microphase separation morphologies evidenced by calorimetric and scattering analyses. These elastomers also exhibit enhanced thermal stability compared with that of their parent homopolymers.

Enhancement of Mechanical Properties of ABA Triblock Copolymer-Based Elastomers by Incorporating Partial Cross-Links on the Soft Bridge Chains

We propose a simple molecular design of glassy-b-soft-b-glassy ABA triblock copolymer-based elastomers with enhanced mechanical properties by blending a very small amount of photoreactive cross-lin...

High-throughput prediction of stress\u2013strain curves of thermoplastic elastomer model block copolymers by combining hierarchical simulation and deep learning

We achieved high-throughput prediction of the stress–strain (S–S) curves of thermoplastic elastomers by combining hierarchical simulation and deep learning. ABA triblock copolymer with a phase-separated structure was used as a thermoplastic elastomer model. The S–S curves of the ABA triblock copolymers were calculated from the hierarchical simulation of self-consistent field theory calculations and coarse-grained molecular dynamics simulations. Because such hierarchical simulations require considerable computational resources, we applied a deep learning technique to accelerate the prediction. Sets of phase-separated structures and the S–S curves obtained from the hierarchical simulation were used to train a 3D convolutional neural network. Using the trained network, we confirmed that the predicted S–S curves of the untrained structures accurately reproduced the simulation results. These results will enable us to design novel polymers and phase-separated structures with desired S–S curves by high-throughput screening of a wide variety of structures.Graphic abstract

Bio-based ABA triblock copolymers with central degradable moieties

A set of (poly-α-methylene-γ-butyrolactone)–co-(poly-δ-decalactone)–co-(poly-α-methylene-γ-butyrolactone) (PMBL-co-PDL-co-PMBL) ABA block copolymers containing different stimuli cleavable groups at the central point of the poly(δ-decalactone) (PDL) block were synthesized by a combination of Ring Opening Transesterification Polymerization (ROTEP) of DL, diol end-group functionalization as α-bromoester and Atom Transfer Radical Polymerization (ATRP) of α -methylene-γ-butyrolactone (MBL). Diols containing acetal, spiroacetal, thioacetal and disulphide units were used as initiators for the bulk room temperature controlled polymerization of δ-decalactone (DL) using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. PDL diols were functionalized in a one-pot two-steps procedure using N-(2-bromoisobutyryl)imidazole (BiB-Im). The resulting macroinitiators were chain extended by atom transfer radical polymerization (ATRP) in DMF at 50 °C using MBL as methacrylic-like monomer and the conventional CuCl/CuCl2/2,2′-bipyridine catalyst system. The cleavage behaviour of the copolymers under reductive, acidic and photooxidative conditions has been studied and the resulting AB block copolymers structurally characterized.

A Monte Carlo simulation of water + oil + ABA triblock copolymer ternary system II. Rheology under shear flow field by Monte Carlo Brownian Dynamics method

A water/oil/amphiphilic polymer ternary system is analyzed by Monte Carlo (MC) method using a lattice model to determine the thermal equilibrium distribution by changing the component ratio. Particularly the rheological properties such as shear stress and viscosity are evaluated via Monte Carlo Brownian Dynamics (MCBD) simulation, in which the flexibility of polymer movement is considered by the bond fluctuation model and the shear force is expressed by the Kramers potential. Our analysis on the micelle pattern for each concentration ratio shows that, the increase of polymer concentration decreases the solute (water, polymer) mobility, and exponentially increases the viscosity. These results in our simulation reflect general phenomena in concentrated colloid system. By assuming that the polymer orientation dominates the stress of system by the elasticity between polymer bonds, we newly find that from the polymer placement under the shear field, the shear stress itself exponentially increases while raising the concentration. Even in the category of lattice model, our study indicates the possibility of acquiring new knowledge on Dynamics by using a polymer model with specific consideration on flexible mobility and MCBD method.

Facile topological transformation of ABA triblock copolymers into multisite, single-chain-folding and branched multiblock copolymers via sequential click coupling and anthracene chemistry

Telechelic PtBA-b-PSt-b-PtBA copolymers were designed to achieve on-demand topological transformation into multisite, single-chain-folding and branched multiblock copolymers via click/click-like reactions.

Synthesis of ABA triblock copolymer nanoparticles by polymerization induced self-assembly and their application as an efficient emulsifier

ABA triblock copolymer nanoparticles of PHPMA-b-PS-b-PHPMA were synthesized by PISA and demonstrated to be an efficient emulsifier.

A spontaneously healable robust ABA tri-block polyacrylate elastomer with a multiphase structure

Multiphase structural designed acrylate elastomer capable of autonomously repairing structures and restoring functions upon damage was developed via an effective method, realizing good mechanical properties.

Proton conducting ABA triblock copolymers with sulfonated poly(phenylene sulfide sulfone) midblock obtained via copper-free thiol-click chemistry

The synthesis and characterization of novel proton conducting ABA triblock copolymers are reported. Structure-properties relationship of the block copolymers has been investigated at both the microscopic and macroscopic levels.

Hydrogen-bonding mediated self-assembly of amphiphilic ABA triblock copolymers into well-defined giant vesicles

A straightforward and efficient access towards the generation of well-defined giant vesicles (∼3 μm in diameters), featured by Hydrogen-bonded DAP–DAP dimerization, and the amphiphilic interactions is reported.