Triblock Terpolymers Research Articles

Multicompartment microparticles of SBM triblock terpolymers: Morphological transitions through homopolymer blending

AbstractBlock copolymers (BCPs) have recently been explored in spherical confinement to form internally structured microparticles. While the behavior of AB diblock copolymers in confinement is comparably well studied, knowledge on confined ABC triblock terpolymers is still rather sparse. The latter are especially interesting as the third block allows the formation of a broader variety of multicompartment microparticles (MMs), but their synthesis is often realized through sequential polymerization, which can be work intensive and challenging. Here, we demonstrate that blending linear ABC triblock terpolymers with homopolymers is a versatile and straightforward method to tune the microphase behavior in MMs. We systematically blend polystyrene-block-polybutadiene-block-poly(methyl methacrylate) (SBM or PS-b-PB-b-PM) with homopolymers of hPS, hPB, or hPM, to study the feasibility of this approach to replicate specific morphologies or access new ones. We utilize Shirasu Porous Glass (SPG) membrane emulsification and evaporation-induced confinement assembly (EICA) to produce narrowly size-dispersed MMs with defined inner structure. We analyze the MMs with dynamic light scattering (DLS), as well as transmission and scanning electron microscopy (TEM, SEM). We show that the resulting blend morphologies can be identical to those of the unblended SBM at same composition and that, depending on the location in the ternary microphase diagram, one SBM morphology can be converted into multiple different morphologies. Graphical Abstract

Individual and simultaneous encapsulation and delivery of incompatible dyes in biocompatible multicompartment terpolymer micelles

Multicompartment micelles (MCMs) can deliver incompatible drug payloads because MCMs derive from the self-assembly of a terpolymer containing one hydrophilic block and two incompatible solvophobic blocks. In particular, MCMs resulting from the self-assembly of poly((sulfamate-carboxylate)isoprene)-block-polystyrene-block-poly(ethylene oxide) (PISC-b-PS-b-PEO) undergo irreversible transition to regular micelles at an alkaline pH. However, several aspects of these MCMs remain unexplored, such as the chemical transformation of PISC-b-PS-b-PEO into an amino-acid functional terpolymer, potential applications of these nanoparticles as dual drug delivery systems and their biocompatibility. In exploring these opportunities, we found that more than 90% of N-S bonds of sulfamate groups (of the PISC block) are cleaved upon acidic treatment of PISC-b-PS-b-PEO terpolymers, which are chemically transformed into a new polyzwitterion triblock terpolymer, that is, poly((amino-carboxylate)isoprene)-block-polystyrene-block-poly(ethylene oxide) (PACIS-b-PS-b-PEO), but retain their MCM morphology. Into these MCMs, two incompatible (Nile Red (hydrophobic) and eosin (hydrophilic)) guest molecules can be loaded separately and together in the predesigned cores without significantly disturbing the structure, as shown by cryo-TEM and light scattering. In addition to their high stability, PACIS-b-PS-b-PEO MCMs are also pH-responsive, whether loaded or unloaded, based on fluorescence spectroscopy and light scattering. In cytotoxicity tests, loaded and unloaded PACIS-b-PS-b-PEO nanoparticles proved nontoxic to various cell lines, including Balb/3T3 and MCF10A, with efficient cellular uptake, as shown by fluorescence imaging. Therefore, our findings highlight PACIS-b-PS-b-PEO as a versatile platform for preparing MCMs for multiple drug delivery.

High-resolution three-dimensional imaging of topological textures in nanoscale single-diamond networks.

Topological defects-extended lattice deformations that are robust against local defects and annealing-have been exploited to engineer novel properties in both hard and soft materials. Yet, their formation kinetics and nanoscale three-dimensional structure are poorly understood, impeding their benefits for nanofabrication. We describe the fabrication of a pair of topological defects in the volume of a single-diamond network (space group Fd m) templated into gold from a triblock terpolymer crystal. Using X-ray nanotomography, we resolve the three-dimensional structure of nearly 70,000 individual single-diamond unit cells with a spatial resolution of 11.2 nm, allowing analysis of the long-range order of the network. The defects observed morphologically resemble the comet and trefoil patterns of equal and opposite half-integer topological charges observed in liquid crystals. Yet our analysis of strain in the network suggests typical hard matter behaviour. Our analysis approach does not require a priori knowledge of the expected positions of the nodes in three-dimensional nanostructured systems, allowing the identification of distorted morphologies and defects in large samples.

The Valence-Dependent Activity of Colloidal Molecules as Ice Recrystallization Inhibitors.

Inspired by advances in cryopreservation techniques, which are essential for modern biomedical applications, there is a special interest in the ice recrystallization inhibition (IRI) of the antifreeze protein (AFPs) mimics. There are in-depth studies on synthetic materials mimicking AFPs, from simple molecular structure levels to complex self-assemblies. Herein, we report the valence-dependent IRI activity of colloidal organic molecules (CMs). The CMs were prepared through polymerization-induced particle-assembly (PIPA) of the ABC-type triblock terpolymer of poly(acryloxyethyl trimethylammonium chloride)-b-poly(benzyl acrylate)-b-poly(diacetone acrylamide) (PATAC-b-PBzA-b-PDAAM) at high monomer conversions. Stabilized by the cationic block of PATAC, the strong intermolecular H-bonding and incompatibility of the PDAAM block with PBzA contributed to the in situ formation of Janus particles (AX1) beyond the initial spherical seed particles (AX0), as well as the high valency clusters of linear AX2 and trigonal AX3. Their distribution was controlled mainly by the polymerization degrees (DPs) of PATAC and PDAAM blocks. IRI activity results of the CMs suggest that the higher fraction of AX1 results in the better IRI activity. Increasing the fraction of AX1 from 27% to 65% led to a decrease of the mean grain size from 39.8% to 10.9% and a depressed growth rate of ice crystals by 58%. Moreover, by replacing the PDAAM block with the temperature-responsive one of poly(N-isopropylacrylamide) (PNIPAM), temperature-adjustable IRI activity was observed, which is well related to the reversible transition of AX0 to AX1, providing a new idea for the molecular design of amphiphilic polymer nanoparticle-based IRI activity materials.

Substrate Channeling in Compartmentalized Nanoreactors.

Thermo- and photoresponsive nanoreactors based on shell cross-linked micelles (SCMs) for the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of ketones have been developed from poly(2-oxazoline) triblock terpolymers. The nanoreactors incorporate thermoresponsive poly(2-isopropyl-2-oxazoline) as the hydrophilic corona and are covalently cross-linked with a photoswitchable spiropyran molecule. UV irradiation or changes in temperature trigger morphology switching of the polymer-based nanoreactors that alters the hydrophobicity in separate layers of the SCMs, resulting in dynamic substrate selectivity of the ATH in water. Control experiments and kinetic studies show that the thermoresponsive outer layer induces the gated behavior for more hydrophobic substrates, whereas the photoresponsive cross-linking layer induces the gated behavior for less hydrophobic substrates. The nanoreactors mimic the multichannels in Nature, transporting substrates and reagents into the catalytic core which can be controlled through external triggers such as temperature and light wavelengths. Additionally, the nanoreactors can be easily recovered and reused with continued high activity and selectivities.

Core–Shell Double Gyroids Directed by Selective Solvation for ABC Triblock Terpolymers

Core–Shell Double Gyroids Directed by Selective Solvation for ABC Triblock Terpolymers

Effect of Micellar Morphology on the Temperature-Induced Structural Evolution of ABC Polypeptoid Triblock Terpolymers into Two-Compartment Hydrogel Network.

We investigated the temperature-dependent structural evolution of thermoreversible triblock terpolypeptoid hydrogels, namely poly(N-allyl glycine)-b-poly(N-methyl glycine)-b-poly(N-decyl glycine) (AMD), using small-angle neutron scattering (SANS) with contrast matching in conjunction with X-ray scattering and cryogenic transmission electron microscopy (cryo-TEM) techniques. At room temperature, A100M101D10 triblock terpolypeptoids self-assemble into core-corona-type spherical micelles in aqueous solution. Upon heating above the critical gelation temperature (T gel), SANS analysis revealed the formation of a two-compartment hydrogel network comprising distinct micellar cores composed of dehydrated A blocks and hydrophobic D blocks. At T ≳ T gel, the temperature-dependent dehydration of A block further leads to the gradual rearrangement of both A and D domains, forming well-ordered micellar network at higher temperatures. For AMD polymers with either longer D block or shorter A block, such as A101M111D21 and A43M92D9, elongated nonspherical micelles with a crystalline D core were observed at T < T gel. Although these enlarged crystalline micelles still undergo a sharp sol-to-gel transition upon heating, the higher aggregation number of chains results in the immediate association of the micelles into ordered aggregates at the initial stage, followed by a disruption of the spatial ordering as the temperature further increases. On the other hand, fiber-like structures were also observed for AMD with longer A block, such as A153M127D10, due to the crystallization of A domains. This also influences the assembly pathway of the two-compartment network. Our findings emphasize the critical impact of initial micellar morphology on the structural evolution of AMD hydrogels during the sol-to-gel transition, providing valuable insights for the rational design of thermoresponsive hydrogels with tunable network structures at the nanometer scale.

Expanding the Formation Region of Double Gyroid Structures from ABC Triblock Terpolymers by Solution Casting

Expanding the Formation Region of Double Gyroid Structures from ABC Triblock Terpolymers by Solution Casting

Core-Shell Double Gyroids Directed by Selective Solvation for ABC Triblock Terpolymers.

The formation of ABC triblock terpolymers through solution casting is still challenging. In this study, core-shell double gyroid network structures are fabricated via solution casting using poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) (F)-b-[poly(4-vinylpyridine) (P4VP) (P)]-b-[polystyrene (PS) (S)] (FPS) triblock terpolymers in N,N-dimethylformamide (DMF). Upon heat treatment, the polymer tends to form a sphere-in-lamellar structure at the F/S interface. Given the solubility properties of each component in DMF, it is anticipated that the effective volume fraction of F relative to P would increase in concentrated solutions and the effective volume fraction of S would decrease. The microphase-separated structure derived from the DMF solution consistently results in the formation of a network structure composed of a core-shell double gyroid, with F as the matrix, P as the shell, and S as the core, and their periodic lengths gradually increase to 110.8, 131.8, and 162.7nm as increase molecular weights of PS blocks to 13.8, 20.7, and 28.8kg mol-1. Based on the solubility properties of the polymer components highlighted in this study, the solvent selection strategy is broadly applicable to ABC triblock terpolymers featuring various polymer components, offering a more efficient avenue for fabricating core-shell double gyroid structures.

ABC block copolymer micelles driving the thermogelation: Scattering, imaging and spectroscopy

Thermoresponsive polymers have attracted much scientific attention due to their capacity for temperature-driven hydrogel formation. For biomedical applications, such as drug delivery, this transition should be tuned below body temperature to facilitate controlled and targeted drug release. We have recently developed a thermoresponsive polymer that forms gel at low concentrations (2 w/w%) in aqueous media and offers a cost-effective alternative to thermoresponsive systems currently being applied in clinics. This polymer is an ABC triblock terpolymer, where A, B, and C correspond to oligo(ethylene glycol) methyl ether methacrylate with average Mn 300 g mol−1 (OEGMA300), n-butyl methacrylate (BuMA), and di(ethylene glycol) methyl ether methacrylate (DEGMA). To investigate the self-assembly and the gelation mechanism in diluted solutions, we used small-angle neutron scattering (SANS) on 1 w/w% (below the gelation concentration) and 5 w/w% solutions (above the gelation concentration). As a comparison, we also investigated the solutions of the most studied thermoresponsive polymer, namely, Pluronic F127, an ABA triblock bipolymer made of ethylene glycol (A) and propylene glycol (B) blocks. SANS revealed that the in-house synthesised polymer forms elliptical cylinders, whose length increases significantly with temperature. In contrast, Pluronic F127 solutions form core-shell spherical micelles, which slightly elongate with temperature. Transmission electron microscopy images support the SANS findings, with tubular/worm structures being present. Variable-temperature circular dichroism (CD) and proton nuclear magnetic resonance (1H NMR) spectroscopy experiments reveal insights on the tacticity, structural changes, and molecular origin of the self-assembly.

Stable and unstable tiling patterns formed by ABC miktoarm star triblock terpolymers of symmetric interactions

Several discrepancies exist among previous self-consistent field calculations of symmetrically interacting ABC miktoarm star triblock terpolymer melts. Here we address this issue by including all known tiling patterns, as well as several lamellar-type phases known to bound the regions in the parameter space occupied by these patterns. After carefully studying the effect of numerical parameters on the free-energy accuracy, the central region of the phase diagram is constructed in detail; both the (3.4.6.4) pattern and the three-dimensional phase of hierarchical-hexagonal lamellae are found to be stable for the first time. The energetic and entropic contributions to the free-energy density of several phases are analyzed and compared in detail to reveal their stability mechanisms, including the important (32.4.3.4) pattern. Comparisons to previous studies of the same model system are present throughout, with our results resolving the aforementioned discrepancies and providing a sound basis for future work to build upon. Published by the American Physical Society 2024

Highly Frustrated Poly(ionic liquid) ABC Triblock Terpolymers with Exceptionally High Morphology Factors.

In this work, we report the successful synthesis of 17 unique compositions of a poly(ionic liquid) (PIL) ABC triblock terpolymer, poly(S-b-VBMIm-TFSI-b-HA), where S is styrene, VBMIm-TFSI is vinylbenzyl methylimidazolium bis(trifluoromethanesulfonyl)imide, and HA is hexyl acrylate. Nine distinct morphologies were observed, including two-phase and three-phase disordered microphase separated (D2 and D3), two-phase hexagonally packed cylinders (C2), core-shell hexagonally packed cylinders (CCS), three-phase lamellae (L3), two-phase lamellae (L2), core-shell double gyroid (Q230), spheres-in-lamellae (LSI), and a three-phase hexagonal superlattice of cylinders (CSL). The LSI morphology was unambiguously confirmed using small-angle X-ray scattering and transmission electron microscopy. Morphology type significantly impacted the ion conductivity of the PIL ABC triblock terpolymers, where remarkable changes in morphology factor (normalized ion conductivity) were observed with only small changes in the conducting volume fraction, i.e., PIL block composition. An exceptionally high morphology factor of 2.0 was observed from the PIL ABC triblock terpolymer with a hexagonal superlattice morphology due to the three-dimensional narrow, continuous PIL nanodomains that accelerate ion conduction. Overall, this work demonstrates the first systematic study of highly frustrated single-ion conducting ABC triblock terpolymers with a diverse set of morphologies and exceptionally high morphology factors, enabling the exploration of transport-morphology relationships to guide the future design of highly conductive polymer electrolytes.

Hybrid anionic block copolymerization: From organocatalysis‐streamlined crossover to internally microphase‐separated aggregates

AbstractPolyolefin‐b‐poly(ethylene oxide) (PEO) represents the most widely investigated amphiphilic block copolymers. So far, one‐pot continuous synthesis of such hybrid block copolymers has only been fulfilled by anionic polymerization through sequential addition of vinyl monomers and ethylene oxide (EO). It still remains challenging to achieve altogether high block efficiency, high polymerization efficiency, and high molar mass for PEO. Here, we report a one‐pot hybrid block copolymerization approach to polyisoprene/polystyrene(PI/PS)‐b‐PEO, in which PI/PS are formed by sBuLi‐initiated anionic vinyl‐addition polymerization, then in situ employed as macroinitiators for the anionic ring‐opening polymerization (ROP) of EO aided by an organic Lewis pair. The cooperative (dual‐ion‐complexing) catalytic effect of organobase and triethylborane is proven, for the first time, effective for lithium alkoxide initiator system, allowing to achieve at room temperature high ROP activity (complete EO conversion and PEO of 3–64 kg/mol reached in 1–6 h), narrow molar mass distribution, controlled block lengths and composition. Density functional theory calculation shows that phosphazene bases are particularly effective, compared with N‐heterocyclic bases, for complexing with Li+ and enhancing the nucleophilicity of oxyanion. The rate of ROP is also affected by Li+‐induced aggregation of the chain‐end ion pairs, which though can be offset by adequate catalyst loadings. The versatility of this approach is further demonstrated in the one‐pot synthesis of tri‐/tetrablock ter‐/quaterpolymers constituted by PI, PS, PEO, and poly(propylene oxide). Of great interest, PS‐b‐PI‐b‐PEO triblock terpolymer with a specific composition is found to form internally microphase‐separated micellar aggregates when dispersed in water.

Morphology and confinement effects on crystallization kinetics in polyethylene containing block copolymers

This paper investigates the morphology and crystallization kinetics of polyethylene (PE) containing block copolymers, differing in block number (di- vs. triblock copolymers) and composition (ABA triblock co- vs. ABC triblock terpolymers). In these block copolymers, the crystallizable PE block is linked to amorphous poly(methyl methacrylate) (PMMA) and/or polystyrene (PS) blocks, and for one triblock terpolymer, poly(ethylene oxide) (PEO) was introduced as an additional crystallizable block. The topological confinement exerted by the covalent linkage of PE to the other blocks (glassy PMMA and PS, PEO) in combination with the morphological confinement into different PE microdomains (cylinders, lamella) significantly influence the crystallization behavior, resulting in slower crystallization kinetics compared to pure PE. The strongest effects were observed for triblock terpolymers, where the lamellar PE domains are disrupted by PS cylinders or distorted PS domains. This research enhances our understanding of block copolymers with confined crystallizable segments, aiding in tailored material design.

Cross-domain Chirality Transfer in Self-Assembly of Chiral Block Copolymers.

Chirality transfer is essential to acquire helical hierarchical superstructures from the self-assembly of supramolecular materials. By taking advantage of chirality transfers at different length scales through intra-chain and inter-chain chiral interactions, helical phase (H*) can be formed from the self-assembly of chiral block copolymers (BCPs*). In this study, chiral triblock terpolymers, polystyrene-b-poly(ethylene oxide)-b-poly(L-lactide) (PS-PEO-PLLA), and polystyrene-b-poly(4-vinylpyridine)-b-poly(L-lactide) (PS-P4VP-PLLA) are synthesized for self-assembly. For PS-PEO-PLLA with an achiral PEO mid-block that is compatible with PLLA (chiral end-block), H* can be formed while the block length is below a critical value. By contrast, for the one with achiral P4VP mid-block that is incompatible with PLLA, the formation of H* phase would be suppressed regardless of the length of the mid-block, giving cylinder phase. Those results elucidate a new type of chirality transfer across the phase domain that is referred as cross-domain chirality transfer, providing complementary understanding of the chirality transfer at the interface of phase-separated domains.

Cross‐domain Chirality Transfer in Self‐Assembly of Chiral Block Copolymers

AbstractChirality transfer is essential to acquire helical hierarchical superstructures from the self‐assembly of supramolecular materials. By taking advantage of chirality transfers at different length scales through intra‐chain and inter‐chain chiral interactions, helical phase (H*) can be formed from the self‐assembly of chiral block copolymers (BCPs*). In this study, chiral triblock terpolymers, polystyrene‐b‐poly(ethylene oxide)‐b‐poly(L‐lactide) (PS‐PEO‐PLLA), and polystyrene‐b‐poly(4‐vinylpyridine)‐b‐poly(L‐lactide) (PS‐P4VP‐PLLA) are synthesized for self‐assembly. For PS‐PEO‐PLLA with an achiral PEO mid‐block that is compatible with PLLA (chiral end‐block), H* can be formed while the block length is below a critical value. By contrast, for the one with achiral P4VP mid‐block that is incompatible with PLLA, the formation of H* phase would be suppressed regardless of the length of the mid‐block, giving cylinder phase. Those results elucidate a new type of chirality transfer across the phase domain that is referred as cross‐domain chirality transfer, providing complementary understanding of the chirality transfer at the interface of phase‐separated domains.

Block copolymer self-assembly derived mesoporous magnetic materials with three-dimensionally (3D) co-continuous gyroid nanostructure.

Magnetic nanomaterials are gaining interest for their many applications in technological areas from information science and computing to next-generation quantum energy materials. While magnetic materials have historically been nanostructured through techniques such as lithography and molecular beam epitaxy, there has recently been growing interest in using soft matter self-assembly. In this work, a triblock terpolymer, poly(isoprene-block-styrene-block-ethylene oxide) (ISO), is used as a structure directing agent for aluminosilicate sol nanoparticles and magnetic material precursors to generate organic-inorganic bulk hybrid films with co-continuous morphology. After thermal processing into mesoporous materials, results from a combination of small angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) are consistent with the double gyroid morphology. Nitrogen sorption measurements reveal a type IV isotherm with H1 hysteresis, and yield a specific surface area of around 200 m2 g-1 and an average pore size of 23 nm. The magnetization of the mesostructured material as a function of applied field shows magnetic hysteresis and coercivity at 300 K and 10 K. Comparison of magnetic measurements between the mesoporous gyroid and an unstructured bulk magnetic material, derived from the identical inorganic precursors, reveals the structured material exhibits a coercivity of 250 Oe, opposed to 148 Oe for the unstructured at 10 K, and presence of remnant magnetic moment not conventionally found in bulk hematite; both of these properties are attributed to the mesostructure. This scalable route to mesoporous magnetic materials with co-continuous morphologies from block copolymer self-assembly may provide a pathway to advanced magnetic nanomaterials with a range of potential applications.

PDEGMA-b-PDMAEMA-b-PLMA triblock terpolymers and their cationic analogues: synthesis, stimuli responsive self-assembly and micelleplex formation

Temperature and pH-responsive triblock terpolymers of the type PDEGMA-b-PDMAEMA-b-PLMA and their quaternized analogs are synthesized and utilized for micelleplex formation with linear DNA.

Poly(Ionic Liquid) ABC Triblock and ABCBA Pentablock Terpolymer Electrolytes for Lithium Metal Batteries

In this study, poly(ionic liquid) (PIL) ABC triblock and ABCBA pentablock terpolymers (PILTTP and PILPTP, respectively) were synthesized to investigate the impact of chain architecture (ABC versus ABCBA) on properties....

Directed Self-Assembly of Diamond Networks in Triblock Terpolymer Films on Patterned Substrates.

Block copolymers (BCPs) are particularly effective in creating soft nanostructured templates for transferring complex 3D network structures into inorganic materials that are difficult to fabricate by other methods. However, achieving control of the local ordering within these 3D networks over large areas remains a significant obstacle to advancing material properties. Here, we address this challenge by directing the self-assembly of a 3D alternating diamond morphology by solvent vapor annealing of a triblock terpolymer film on a chemically patterned substrate. The hexagonal substrate patterns were designed to match a (111) plane of the diamond lattice. Commensurability between the sparse substrate pattern and the BCP lattice produced a uniformly ordered diamond network within the polymer film, as confirmed by a combination of atomic force microscopy and cross-sectional imaging using focused ion beam scanning electron microscopy. The successful replication of the complex and well-ordered 3D network structure in gold promises to advance optical metamaterials and has potential applications in nanophotonics.