Miktoarm Star Terpolymers Research Articles

Thin film and bulk morphology of PI-PS-PMMA miktoarm star terpolymers with both weakly and strongly segregated arm pairs

A series of three homologous ABC miktoarm star terpolymers having a polyisoprene (PI), a polystyrene (PS) and a poly(methyl methacrylate) (PMMA) arm, is synthesized by living anionic polymerization. While the volume fraction of the PI and the PS blocks are kept equal and constant, the volume fraction of the PMMA block is varied. The room temperature bulk structure is characterized using small-angle X-ray scattering and transmission electron microscopy, while the structure of thin films is investigated using scanning electron microscopy, atomic force microscopy and X-ray reflectometry. For both bulk and thin films, it is found that the sample with the lowest volume fraction of PMMA has a morphology distinctly different from the two samples with larger PMMA volume fraction. All data for both bulk and thin film samples are consistent with an alternating lamellar structure for the lowest PMMA volume fraction sample. The two higher PMMA volume fraction samples show standing rod structure, however the details of the packing in the PMMA matrix differ depending on sample thickness. Overall, a structure with PI domains screened from interacting with PMMA by a PS shell is seen for both samples. In bulk, core-shell cylinders pack hexagonally, while a 100 nm thin film of the sample with the largest volume fraction of PMMA shows a square-lattice packing. The structuring is driven by two factors: i) the strong segregation of the PI-PMMA arm pair together with the weak segregation of the two arm pairs with a PS block and ii) the geometrical constraints resulting from the star architecture. No wetting layers are observed for any of the thin film samples, neither at the air-polymner surface or at the polymer-substrate interface.

High-Entropy Microdomain Interlocking Polymer Electrolytes for Advanced All-Solid-State Battery Chemistries.

All-solid-state polymer electrolytes (ASPEs) with excellent processivity are considered one of the most forward-looking materials for large-scale industrialization. However, the contradiction between improving the mechanical strength and accelerating the ionic migration of ASPEs has always been difficult to reconcile. Herein, a rational concept is raised of high-entropy microdomain interlocking ASPEs (HEMI-ASPEs), inspired by entropic elasticity well-known in polymer and biochemical sciences, by introducing newly designed multifunctional ABC miktoarm star terpolymers into polyethylene oxide for the first time. The tailor-made HEMI-ASPEs possess multifunctional polymer chains, which induce themselves to assemble into micro- and nanoscale dynamic interlocking networks with high topological structure entropy. HEMI-ASPEs achieve excellent toughness, considerable ionic conductivity, an appreciable lithium transference number (0.63), and desirable thermal stability (Td > 400°C) for all-solid-state lithium metal batteries. The Li|HEMI-ASPE-Li|Li symmetrical cell shows a stable Li plating/stripping performance over 4000h, and a LiFePO4 |HEMI-ASPE-Li|Li full cell exhibits a high capacity retention (≈96%) after 300 cycles. This work contributes an innovative design concept introducing high-entropy supramolecular dynamic networks for ASPEs.

Dendrons and Dendritic Terpolymers: Synthesis, Characterization and Self-Assembly Comparison.

To the best of our knowledge, this is the very first time that a thorough study of the synthetic procedures, molecular and thermal characterization, followed by structure/properties relationship for symmetric and non-symmetric second generation (2-G) dendritic terpolymers is reported. Actually, the synthesis of the non-symmetric materials is reported for the first time in the literature. Anionic polymerization enables the synthesis of well-defined polymers that, despite the architecture complexity, absolute control over the average molecular weight, as well as block composition, is achieved. The dendritic type macromolecular architecture affects the microphase separation, because different morphologies are obtained, which do not exhibit long range order, and various defects or dislocations are evident attributed to the increased number of junction points of the final material despite the satisfactory thermal annealing at temperatures above the highest glass transition temperature of all blocks. For comparison reasons, the initial dendrons (miktoarm star terpolymer precursors) which are connected to each other in order to synthesize the final dendritic terpolymers are characterized in solution and in bulk and their self-assembly is also studied. A major conclusion is that specific structures are adopted which depend on the type of the core connection between the ligand and the active sites of the dendrons.

Novel amphiphilic ABC 3-miktoarm star azo-copolymer with polypeptide chain: Synthesis, self-assembly and photo-responsive behavior

Well-defined amphiphilic ABC 3-miktoarm star terpolymer containing hydrophilic methoxy poly(ethylene glycol) (MPEG), hydrophobic poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PAzoMA) and poly(γ-benzyl-L-glutamic acid) (PBLG) was synthesized by a combination of copper-mediated atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP). MPEG was modified to bear two different functional groups, which were further modified to the initiator of ATRP and ROP for the preparation of the amphiphilic ABC-type 3-miktoarm star terpolymers (MPEG) (PAzoMA) (PBLG). The spindle-like micelles were formed from the amphiphilic 3-miktoarm star terpolymer through a solution self-assembly due to the rigid ɑ-helical conformation of PBLG block and the π-π interaction between PBLG block with PAzoMA block in the star terpolymer. The investigation of the photo-isomerization behavior of (MPEG) (PAzoMA) (PBLG) in solution and in micellar solution showed that trans–cis isomerization in solution was quicker than that in micellar solution, and H- or J-aggregates of the azobenzene groups in the aggregates did not be observed. On the basis of the experimental results, the formation mechanisms of the spindle-like micelles were suggested and the obtained results may expand the self-assembly research field.

Alternating Gyroid Network Structure in an ABC Miktoarm Terpolymer Comprised of Polystyrene and Two Polydienes.

The synthesis, molecular and morphological characterization of a 3-miktoarm star terpolymer of polystyrene (PS, = 61.0 kg/mol), polybutadiene (PB, = 38.2 kg/mol) and polyisoprene (PI, = 29.2 kg/mol), corresponding to volume fractions (φ) of 0.46, 0.31 and 0.23 respectively, was studied. The major difference of the present material from previous ABC miktoarm stars (which is a star architecture bearing three different segments, all connected to a single junction point) with the same block components is the high 3,4-microstructure (55%) of the PI chains. The interaction parameter and the degree of polymerization of the two polydienes is sufficiently positive to create a three-phase microdomain structure as evidenced by differential scanning calorimetry and transmission electron microscopy (TEM). These results in combination with small-angle X-ray scattering (SAXS) and birefringence experiments suggest a cubic tricontinuous network structure, based on the I4132 space group never reported previously for such an architecture.

Morphology and Wetting Stability of Nanofilms of ABC Miktoarm Star Terpolymers

The morphology and wetting stability of nanofilms formed by AyByCz miktoarm star terpolymers were explored by many-body dissipative particle dynamics. The length ratio of C- to A-arm (w = z/y) rang...

Mesoscopic Detection of the Influence of a Third Component on the Self-Assembly Structure of A2B Star Copolymer in Thin Films.

The most common self-assembly structure for A2B copolymer is the micellar structure with B/A segments being the core/corona, which greatly limits its application range. Following the principle of structure deciding the properties, a reformation in the molecular structure of A2B copolymer is made by appending three segments of a third component C with the same length to the three arms, resulting (AC)2CB 3-miktoarm star terpolymer. A reverse micellar structure in self-assembly is expected by regulating the C length and the pairwise repulsive strength of C to A/B, aiming to enrich its application range. Keeping both A and B lengths unchanged, when the repulsion strength of C to A is much stronger than C to B, from the results of mesoscopic simulations we found, with a progressive increase in C length, (AC)2CB terpolymer undergoes a transition in self-assembled structures, from a cylindrical structure with B component as the core, then to a deformed lamellar structure, and finally to a cylindrical structure with A component as the core. This reverse micellar structure is formed with the assistance of appended C segments, whose length is longer than half of B length, enhancing the flexibility of three arms, and further facilitating the aggregation of A component into the core. These results prove that the addition of a third component is a rational molecular design, in conjunction with some relevant parameters, enables the manufacturing of the desired self-assembly structure while avoiding excessive changes in the involved factors.

On-Demand Oil-Water Separation by Environmentally Responsive Cotton Fabrics.

Environmentally responsive cotton fabrics were fabricated by dip-coating ABC miktoarm star terpolymers, which contain reactive poly(3-triisopropyloxysilylpropyl methacrylate) blocks, hydrophobic poly(dimethylsiloxane) (PDMS) blocks, and hydrophilic poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) blocks. The functionalized cotton fabrics with perfectly alternating PDMS and PDMAEMA blocks show underoil superhydrophobicity and underwater superoleophobicity. The wettability and permeability of the functionalized fabrics can be readily adjusted by the contacting medium. More interestingly, surface reconstruction causes a reduction in the breakthrough pressure of the nonwetting phase. The adaptive permeability endows the functionalized cotton fabrics with the capability to separate heavy oil–water–light oil ternary mixtures.

Evolution in the morphological behaviour of a series of fluorine-containing ABC miktoarm star terpolymers

Fluorine-containing amphophilic polymers, as well as star polymers, have shown extremely abundant self-assembled morphologies because of microphase separation within the assemblies. Taking advantage of these characteristics, we prepared a series of ABC miktoarm star terpolymers with poly(ethylene glycol) (PEG) as a hydrophilic block, as well as poly(2-ethylhexylmethacrylate) (PEHMA) as a hydrophobic chain. Poly(1H,1H,5H-octafluoropentylmethacrylate) (POFPMA) was chosen as the third segment of terpolymers because of its super-hydrophobic/oleophobic characteristics. The terpolymers were synthesised via atom transfer radical polymerisation (ATRP), single electron transfer living radical polymerisation (SET-LRP) and azide-alkyne Huisgen cycloaddition (click reaction). Herein, we investigated the self-assembled behaviours of nanoaggregates formed by varying the length of POFPMA and PEHMA chains of the terpolymers in aqueous solution. The tunable miktoarm star polymer favoured the transformation of nanoassemblies, from patchy spherical micelles to patchy spherical aggregates, spherical micelles, egg-like micelles, segmented-worm micelles, shuttle-like micelles and vesicles. Interestingly, special discontinuous aggregations arranged into lines were observed, which has been seldom found before. The independent control of both of the hydrophobic parameters of terpolymers enhanced the nanostructures of polymeric assemblies of ABC miktoarm terpolymers, providing a reliable method to explore the compartmentalisation behaviours of soft matter assemblies.

Nanoscale Archimedean Tilings Formed by 3-Miktoarm Star Terpolymer Thin Films.

3-Miktoarm star terpolymer architecture (3µ-ABC), consisting of three dissimilar polymer chains, A, B, and C connected at a junction point, provides a unique opportunity in the design of complex nanoscale patterns such as Archimedean tilings that are not accessible from linear ABC terpolymers. In this work, the synthesis and the self-assembly of 3-miktoarm star terpolymers, namely, polystyrene-arm-poly(2-vinylpyridine)-arm-polyisoprene (3µ-SPI) into Archimedean tiling patterns is described. Several 3µ-SPI terpolymers are produced via a mid-functional PS-b-P2VP, synthesized by sequential anionic polymerization, using a 1,1-diphenylethylene bearing a tert-butyldimethylsilyl-protected hydroxyl functionality as a core molecule. PI arms with different sizes are then linked to the deprotected hydroxyl function of the core molecule via a Steglich esterification. Solvent-annealed 3µ-SPI thin films exhibit nanoscale prisms arranged into a (4.6.12) Archimedean tiling pattern. Depending on the size of the low etch-resistant PI arm and the solvent selected to promote the self-assembly of 3µ-SPI thin films, the voided columns occupy the square or decagonal sites of the (4.6.12) pattern. The use of this (4.6.12) tiling produced for the first time from self-assembled 3µ-ABC thin films can be a promising route to build 2D photonic crystals having complete photonic band gaps, where the light propagation is completely prohibited.

Studies on the 3-Lamellar Morphology of Miktoarm Terpolymers

The morphologies of ABC miktoarm star terpolymer consisting of polystyrene (PS), polyisoprene (PI), and poly(2-vinylpyridine) (P2VP) were studied by combining small-angle neutron and X-ray scattering (SANS and SAXS) and transmission electron microscopy. We find that this system displays a rich morphological behavior including an alternate lamellar (ALT.LAM), cylinder in undulated lamellar (CYLULAM), and 3-lamellar (LAM-3) phase. While the SAXS data alone were insufficient to conclusively differentiate between possible phases, we show that the use of selective deuteration and SANS is essential to unambiguously identify the morphology. In particular, the primary peak in SANS for the miktoarm polymer containing deuterated PS was found to be lower than the next two higher order peaks. Such an unusual scattering pattern for a lamellar morphology was verified by self-consistent field theory calculations when the relative strength of the interaction between PI–P2VP over PS–PI is equal to or greater than 2 (χIV/χ...

3-Miktoarm Star Terpolymers via Janus Polymerization: One-Step Synthesis and Self-Assembly

Janus polymerization combines cationic and anionic polymerizations into the two ends of a single growing chain and presents a novel pathway to produce topologically defined polymers. In this contribution, we report a one-step synthesis of 3-miktoarm star terpolymers of poly(ethylene glycol)-star-poly(e-caprolactone)-star-poly(e-caprolactone-co-tetrahydrofuran) (PEG-star-PCL-star-P(CL-co-THF)) via Janus polymerization using lutetium triflates (Lu(OTf)3) and methoxypoly(ethylene glycol) epoxy (mPEG-EO) as catalyst and macroinitiator, respectively. Self-assembly of PEG-star-PCL-star-P(CL-co-THF) into vesicles in aqueous solution depends on the ratio of hydrophilic and hydrophobic block of the terpolymers. Coassembly of the terpolymer with a PCL homopolymer (MW = 3000), on the other hand, increases shell thickness and vesicle diameter. Furthermore, nanorods and needle-shaped aggregates featuring high aspect ratios are obtained upon self-assembly at an interface. This unique behavior can be attributed to cryst...

Bulk and Surface Morphologies of ABC Miktoarm Star Terpolymers Composed of PDMS, PI, and PMMA Arms

DIM miktoarm star copolymers, composed of polydimethylsiloxane [D], poly(1,4-isoprene) [I], and poly(methyl methacrylate) [M], were synthesized using a newly developed linking methodology with 4-allyl-1,1-diphenylethylene as a linking agent. The equilibrium bulk morphologies of the DIM stars were found to range from [6.6.6] tiling patterns to alternating lamellar and alternating cylindrical morphologies, as determined experimentally by small-angle X-ray scattering and transmission electron microscopy and confirmed by dissipative particle dynamics and self-consistent field theory based arguments. The thin film morphologies, which differ from those found in the bulk, were identified by scanning electron microscopy, coupled with oxygen plasma etching. Square arrays of the PDMS nanodots and empty core cylinders were formed on silica after oxygen plasma removal of the poly(1,4-isoprene) and poly(methyl methacrylate) which generated nanostructured substrates decorated with these features readily observable.

Synthesis, characterization, and property of biodegradable PEG-PCL-PLA terpolymers with miktoarm star and triblock architectures as drug carriers.

A series of amphiphilic terpolymers with miktoarm star and triblock architectures of poly(ethylene glycol) (PEG), poly(ε-caprolactone) (PCL) and poly(l-lactide acid) (PLLA) or poly(DL-lactide acid) (PDLLA) terpolymers were synthesized as carriers for drug delivery. The architecture, molecular weight and crystallization behavior of the terpolymers were characterized. Anticancer drug doxorubicin was encapsulated in the micelles to investigate their drug loading properties. The miktoarm star terpolymers exhibited stronger crystallization capability, smaller size and better stability than that of triblock polymeric micelle, owing to the lower CMC values of miktoarm star polymeric micelle. Furthermore, the drug-loaded miktoarm star polymeric micelles showed the cumulative DOX release account of the micelles with PDLLA blocks was 65.3% while the release account of the corresponding micelles containing PLLA blocks was 45.2%. The IC50 values of drug-loaded miktoarm star polymeric micelle were lower than triblock polymeric micelle. Meanwhile, Confocal laser scanning microscopy (CLSM) and Flow Cytometry results demonstrated that the miktoarm star micelles were more favorable for cellular internalization. The miktoarm star micelles with PDLLA blocks were promising carriers for anticancer drug delivery.

Multi-Dimensional Self-Assembly of a Dual-Responsive ABC Miktoarm Star Terpolymer.

This letter reports the first 2D self-assembly of ABC miktoarm star terpolymers based on dual-responsive polycaprolactone-arm-poly(N-isopropylacrylamide)-arm-poly(2-dimethylaminoethyl methacrylate) (μ-CID), which self-assembled into multilayer nanosheets comprising polycaprolactone single crystals in tetrahydrofuran (THF)/methanol mixed solvents. Interestingly, the nanosheets showed pH-responsive morphological transitions in aqueous solutions, yielding multidimensional assemblies, including 2D hexagonal aggregates, patchy nanofibrils, and patchy vesicles, at different pH values. The nanosheets also exhibited thermoresponsive transition to spherical patchy micelles at a temperature above the lower critical solution temperature (LCST) of the poly(N-isopropylacrylamide) block. This study offers a novel system for fundamental study on the self-assembly of miktoarm star terpolymers.

Light/temperature dual-responsive ABC miktoarm star terpolymer micelles for controlled release

A novel light- and temperature-responsive amphiphilic ABC miktoarm star terpolymer consisting of hydrophilic poly(ethylene glycol) (PEG), light-responsive poly(2-nitrobenzyl methacrylate) (PNBM), and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) arms, PEG(-b-PNBM)-b-PNIPAM, was synthesized via a combination of atom transfer radical polymerization (ATRP) and click reaction. In aqueous solution, the obtained miktoarm star terpolymer self-assembled into spherical micelles with PNBM cores and hybrid PEG/PNIPAM coronas. When heating above the phase transition temperature of PNIPAM, larger aggregates with mixed PNBM/PNIPAM cores and PEG coronas were formed. Upon UV light irradiation, the initial micelles were disrupted and reassembled into some large micelle complexes. Fluorescence emission measurements showed that Nile red encapsulated in the polymeric micelles could be released by stimuli of UV light or temperature change. More interestingly, the UV triggered release could be strengthened in basic conditions but weakened in acidic conditions. The prepared light- and temperature-responsive polymeric micelles may have great potential in applications such as nanocarriers and biotechnology for controlled drug and bioagent delivery.

Multicompartment Micelles by Aqueous Self-Assembly of μ-A(BC) n Miktobrush Terpolymers.

The aqueous self-assembly of μ-A(BC)nmiktobrush terpolymers has been studied using dynamic light scattering and cryogenic transmission electron microscopy. In this system, the A block is hydrophilic poly(ethylene oxide), “O”, the B block is hydrophobic poly(methylcaprolactone), “C”, and the C block is hydrophobic and oleophobic poly(perfluoropropylene oxide), “F”. Two terpolymers were examined: one with an average of about two C blocks and two F blocks and another with an average of about three C blocks and two F blocks. In both cases, the total molar mass is near 40 kg mol–1, and the volume fraction of the single O block is greater than 50% of the whole. Both samples form multicompartment micelle structures with subdivided solvophobic cores of C and F domains. The morphologies observed are generally analogous to those previously observed for the self-assembly of μ-ABC miktoarm star terpolymers, namely, “raspberry” and “hamburger” micelles; however, an intriguing multicompartment polymersome morphology with compartmentalized solvophobic bilayers is also observed. These results are interpreted in terms of the relative strengths of the competing interactions among the three blocks and the solvent and in terms of the constraints imposed by the miktobrush architecture.

Tunable Pickering Emulsions with Environmentally Responsive Hairy Silica Nanoparticles.

Surface modification of the nanoparticles using surface anchoring of amphiphilic polymers offers considerable scope for the design of a wide range of brush-coated hybrid nanoparticles with tunable surface wettability that may serve as new class of efficient Pickering emulsifiers. In the present study, we prepared mixed polymer brush-coated nanoparticles by grafting ABC miktoarm star terpolymers consisting of poly(ethylene glycol), polystyrene, and poly[(3-triisopropyloxysilyl)propyl methacrylate] (μ-PEG-b-PS-b-PIPSMA) on the surface of silica nanoparticles. The wettability of the as-prepared nanoparticles can be precisely tuned by a change of solvent or host-guest complexation. 1H NMR result confirmed that such wettability change is due to the reorganization of the polymer chain at the grafted layer. We show that this behavior can be used for stabilization and switching between water-in-oil (W/O) and oil-in-water (O/W) emulsions. For hairy particles initially dispersed in oil, W/O emulsions were always obtained with collapsed PEG chains and mobile PS chains at the grafted layer. However, initially dispersing the hairy particles in water resulted in O/W emulsions with collapsed PS chains and mobile PEG chains. When a good solvent for both PS and PEG blocks such as toluene was used, W/O emulsions were always obtained no matter where the hairy particles were dispersed. The wettability of the mixed polymer brush-coated silica particles can also be tuned by host-guest complexation between PEG block and α-CD. More importantly, our result showed that surprisingly the resultant mixed brush-coated hairy nanoparticles can be employed for the one-step production of O/W/O multiple emulsions that are not attainable from conventional Pickering emulsifiers. The functionalized hairy silica nanoparticles at the oil-water interface can be further linked together utilizing poly(acrylic acid) as the reversible linker to form supramolecular colloidosomes, which show pH-dependent release of cargo.

Archimedean Tilings and Hierarchical Lamellar Morphology Formed by Semicrystalline Miktoarm Star Terpolymer Thin Films.

3-Miktoarm star terpolymer architecture provides a window of opportunity in the design of complex "three-colored" patterns at the nanometer scale. Here, the directed self-assembly (DSA) of 3-miktoarm star terpolymer (poly(1,1-dimethyl silacyclobutane)-arm-polystyrene-arm-poly(d,l-lactide acid)) (PDMSB-arm-PS-arm-PLA, noted hereafter 3 μ-DSL) into a hierarchical lamellar morphology is described. Excellent orientational order has been achieved by templating the asymmetric hierarchical lamellar morphology with topographical substrates. Increasing the PLA volume fraction leads to the formation of a hexagonal [6.6.6] Archimedean tiling which coexists with a metastable square symmetry [4.8.8] tiling stabilized by the step between terraces. Stability of the [6.6.6] tiling over the [4.8.8] one is also demonstrated with GISAXS measurements.

Synthesis of Well-Defined Polyethylene-Based 3-Miktoarm Star Copolymers and Terpolymers

Novel polyethylene (PE)-based 3-miktoarm star copolymers A2B, (AB)2B and terpolymers (AC)2(BC) [A: PE; B, C: polystyrene (PS) or poly(methyl methacrylate) (PMMA)] were synthesized by combining boron chemistry, polyhomologation, and atom transfer radical polymerization (ATRP). 1,4-Pentadiene-3-yl 2-bromo-2-methylpropanoate was first synthesized followed by hydroboration with thexylborane to afford B-thexylboracyclanes, a multi-heterofunctional initiator with two initiating sites for polyhomologation and one for ATRP. After polyhomologation of dimethylsulfoxonium methylide the α,ω-dihydroxyl polyethylene (PE-OH)2-Br produced served as macroinitiator for the ATRP of styrene to afford (PE-OH)2-(PS-Br). Both (PE-OH)2-Br and (PE-OH)2-(PS-Br) were transformed to two new trifunctional macroinitiators (PE-Br)2-Br and (PE-Br)2-(PS-Br) through esterification reactions and used for the synthesis of (AB)2B and (AC)2(BC) 3-miktoarm star co/terpolymers. All intermediates and final products were characterized by 1H NMR, ...