Coil Diblock Copolymers Research Articles

Metallo-Supramolecular Rod–Coil Block Copolymer Thin Films for Stretchable Organic Field Effect Transistor Application

Herein, to decrease the synthetic burden of the rod–coil diblock copolymers, the coordination-driven self-assembly approach is utilized to readily construct a series of polystyrene (PS)-block-poly(3-hexylthiophene) (P3HT) copolymers with dynamic heteroleptic coordination bonds between the two blocks. In detail, the chain length of the PS is varied for a fixed P3HT chain length to produce block copolymers, namely, PS85–Zn–P3HT187 (P1) and PS161–Zn–P3HT187 (P2), with comparable electrical performance to that of homopolymer P3HT (P0) in the unstrained state, along with enhanced crack onset strain and much less reduced mobility under 25–100% strain. The ability to maintain the charge transport characteristics is due to the longer coil chain length and amorphous PS regions for the dissipation of strain energy. The organic field effect transistors of P2 with a longer PS segment show only a slight change in mobility from 5.48 × 10–3 to 1.40 × 10–3 cm2 V–1 s–1 under 25–100% and maintain this mobility even after being subjected to 100 repeated stretching/releasing cycles at 50% strain. This proof-of-concept demonstration of the proposed molecular engineering approach based on the metallo-supramolecular method provides a suitable route to the molecular design of stretchable polymer semiconductors with balanced mechanical and electrical behaviors.

Crosslinking Modulated Hierarchical Self-Assembly of Rod–Coil Diblock Copolymer Patchy Nanoparticles

Crosslinking Modulated Hierarchical Self-Assembly of Rod–Coil Diblock Copolymer Patchy Nanoparticles

Microphase separation in helix-coil block copolymer melts: computer simulation.

By means of molecular dynamics simulation, the process of the microphase separation in the melts of diblock helix-coil copolymers comprising a flexible and a helical block was studied. The resulting microstructures were examined, and the spatial distribution of the blocks and molecular packing were investigated. The phase diagram was built in terms of the fraction of the helical block and the incompatibility parameter of the blocks. The comparison of the diagrams for helix-coil and the classic coil-coil copolymer blends was carried out. It was shown that the total region where the ordering into distinctive microstructures takes place is similar for both diagrams. But for the helix-coil copolymers the area of the cylinders splits into the region of those with circular and elliptical cross-sections; the bicontinuous phase area is much wider; in the lamellar phases, the helical blocks were oriented precisely perpendicular to the lamellar interface, forming a cohesive interlocked structure of densely packed helices.

Secondary Structures of Polypeptide-Based Diblock Copolymers Influence the Microphase Separation of Templates for the Fabrication of Microporous Carbons

In this study, we synthesized two forms of the polypeptide-based rod–coil diblock copolymer poly(ethylene oxide-b-γ-benzyl-l-glutamate) (PEO-b-PBLG), comprising hydrophilic PEO as the coil segment ...

Tilted Lamellar Phase of the Rod–Coil Diblock Copolymer: Dissipative Particle Dynamics Simulation

The tilted lamellar phase of a symmetric rod–coil diblock copolymer is studied by dissipative particle dynamics simulation over a wide range of degrees of block segregation. The microphase separation in the copolymer and the orientational ordering of rigid blocks in the tilted phase are investigated. For the first time, spatial profiles of the orientational order parameter and the density of monomer units of rigid and flexible blocks at various values of χN are calculated and the influence of this parameter on the value of the tilt angle is studied.

Synthesis and Solution Self-Assembly Properties of Cyclic Rod-Coil Diblock Copolymers.

Typical cyclic diblock polymers are synthesized from their linear precursors via the ring-closure strategy in dilute conditions. Here we demonstrate a pseudo-high-dilution condition strategy for the efficient synthesis of cyclic rod-coil diblock copolymer from its linear precursor in selective solvents. The critical association concentration (CAC) of linear precursor is used for the control of unimer concentration during cyclization, while high copolymer synthetic concentrations are achieved via the dynamic equilibrium between unimers and micelles. The effects of CAC and micelle concentration on cyclization yield are studied and pure cyclic rod-coil diblock copolymer was obtained after azide resin treatment. Property investigations show the cyclic rod-coil copolymer has a larger second virial coefficient than its linear counterpart and self-assembles in selective solvents to form larger but looser spherical micelles due to its constraint topological structure.

Elastic properties of liquid-crystalline bilayers self-assembled from semiflexible-flexible diblock copolymers.

The mechanical response and shape of self-assembled bilayer membranes depend crucially on their elastic properties. Most of the studies focused on the elastic properties of fluid membranes, despite the ubiquitous presence of membranes with liquid-crystalline order. Here the elastic properties of liquid-crystalline bilayers self-assembled from diblock copolymers composed of a semiflexible block are studied theoretically. Specifically, the self-consistent field theory (SCFT) is applied to a model system composed of semiflexible-flexible diblock copolymers dissolved in flexible homopolymers that act as solvents. The free energy of self-assembled tensionless bilayer membranes in three different geometries, i.e. planar, cylindrical and spherical, is obtained by solving the SCFT equations using a hybrid method, in which the orientation-dependent functions are treated using the spherical harmonics, whereas the position-dependent operators are treated using the compact difference schemes. The bending modulus κM and Gaussian modulus κG of the bilayer are extracted from the free energies. The effects of the molecular parameters of the system, such as the chain rigidity and the orientational interaction, are systematically examined.

Construction of Rod-Forming Single Network Mesophases in Rod–Coil Diblock Copolymers via Inversely Designed Phase Transition Pathways

The string method is introduced to the self-consistent mean-field theory for rod–coil diblock copolymers to investigate the phase transition kinetics. The equal arc length parametrization used in our improved string method is constrained on both the density and orientation order parameters to obtain accurate and stable minimum energy pathways (MEP). Focusing on different single networks formed by rods as the target structures, we developed an inverse design strategy of kinetic pathways. By designing distinct initial structures (lamellae or cylinders) with specific symmetry matching the target structure as the two ends of the string, we calculated the MEP and analyzed the effects of chain rigidity on the phase transition kinetics. The results indicate that the reordering transition between lamellae belonging to the same crystallographic plane group can induce the formation of metastable single networks. The shape and arrangement of the rigid rods will influence the epitaxial phase transition. The long-term stability of the target structures can be regulated by tailoring the block composition as well as the geometrical asymmetry between rigid and flexible segments, which may guide the experiments to fabricate long-lived single networks.

Tuning Structures of Mesogen‐Jacketed Liquid Crystalline Polymers and Their Rod–Coil Diblock Copolymers by Varying Chain Rigidity

AbstractTwo mesogen‐jacketed liquid crystalline (LC) polymers with different rigid side‐chain cores, poly[2,5‐bis(tert‐butoxylcarbonyl)styrene] (PM1) and poly[2,5‐bis(4‐tert‐butoxylcarbonyl phenyl)styrene] (PM3), as well as their corresponding block copolymers (BCPs), poly(dimethylsiloxane)‐b‐PM1 (PDMS‐b‐PM1) and PDMS‐b‐PM3, are synthesized and characterized. The LC phase structures of the homopolymers and the microphase‐separated structures of the BCPs can be controlled by changing the rigidity of the polymer chains with the different rigid side‐chain cores used. The LC phase structure of PM1 homopolymer is dependent on its molecular weight (MW). On the other hand, PM3 is always amorphous below thermal decomposition temperature regardless of its MW, owing to much higher rigidity of PM3 compared with that of PM1. Although both BCPs can self‐assemble into lamellae (LAM) and hexagonally packed cylinders (HEX) with varying compositions, PDMS‐b‐PM3 can form the HEX structure at a smaller weight fraction of the PM3 block because PDMS‐b‐PM3 possesses a larger geometric asymmetric factor compared with PDMS‐b‐PM1. For PDMS‐b‐PM1 with a large enough MW, it can form hierarchically ordered nanostructures, including the LAM or HEX nanostructure of the BCP and the columnar nematic phase of the PM1 block.

Self-Seeding of Block Copolymers with a π-Conjugated Oligo(p-phenylenevinylene) Segment: A Versatile Route toward Monodisperse Fiber-like Nanostructures

Three well-defined crystalline–coil diblock copolymers of oligo(p-phenylenevinylene)-b-poly(N-isopropylacrylamide) (OPV5-b-PNIPAM18, OPV5-b-PNIPAM49, and OPV5-b-PNIPAM75; the subscripts represent the number of repeat units of each block) with the same crystallizable core-forming OPV segment but different corona-forming PNIPAM blocks of various chain lengths were synthesized. Their solution self-assembly behavior was examined in methanol, ethanol, and isopropanol. Both the solvent and the length of the PNIPAM block were found to affect the self-assembly of the block copolymers. In methanol, OPV5-b-PNIPAM18 formed a mixture of fiber-like micelles of uniform width and two-dimensional platelet-like structures with fiber-like micelles protruding from the ends. In ethanol and in isopropanol, this polymer only formed long fiber-like micelles of uniform width. OPV5-b-PNIPAM49 formed long fiber-like micelles (several micrometers) of uniform width in all three solvents, but under the same self-assembly conditions, ...

In Situ Synthesis of Coil–Coil Diblock Copolymer Nanotubes and Tubular Ag/Polymer Nanocomposites by RAFT Dispersion Polymerization in Poly(ethylene glycol)

Hollow polymeric nanotubes have the potential to be employed as advanced nanomaterials in a variety of applications; however, their synthesis from the assembly of coil–coil diblock copolymers (DBCPs) has typically been limited. Herein, we report a novel method for synthesis of coil–coil DBCP nanotubes by implementing RAFT dispersion polymerization in low molecular weight poly(ethylene glycol) (PEG). This method for the in situ synthesis of coil–coil DBCP nanotubes is particularly versatile and can be achieved with a range of block copolymers including poly(N-isopropylacrylamide)-block-polystyrene (PNIPAM-b-PS), poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS), and poly(methyl methacrylate)-block-polystyrene (PMMA-b-PS). Using this approach, several interesting coil–coil DBCP tubular morphologies are observed, including single-wall nanotubes, multiwall nanotubes, and porous nanotubes. Furthermore, RAFT dispersion polymerization conducted in the presence of Ag nanoparticles can be used to yield complex t...

Syntheses and Controllable Self-Assembly of Luminescence Platinum(II) Plane–Coil Diblock Copolymers

Polystyrenes have been synthesized with terminal groups of luminescence square-planar platinum(II) complexes, which can be conceptually regarded as plane–coil diblock copolymers. They can self-assemble into spherical micelles with a core of polystyrenes and a corona of planar platinum(II) complexes in the chloroform/methanol mixture solvents, while free-standing bilayered sheets form in the toluene/methanol mixture solvents. With increasing methanol content in the latter case, where the solvent quality was highly deteriorated for polystyrene blocks, the sheetlike nanostructures are readily transformed into spherical micelles. Pt···Pt and/or π–π stacking interactions between the planar platinum(II) blocks contributed significantly to these aggregate morphologies and their evolutions, leading to remarkable luminescence enhancements. This work represents a novel approach to design and synthesize luminescence platinum(II) plane–coil diblock copolymers, in which the planar platinum(II) complexes are for the fi...

Striped patterns self-assembled from rod–coil diblock copolymers on spherical substrates

In this work, the structures and topological defects of striped patterns self-assembled from rod–coil diblock copolymers confined on spherical substrates were examined using dissipative particle dynamics simulations.

Formation and Reversible Morphological Transition of Bicontinuous Nanospheres and Toroidal Micelles by the Self‐Assembly of a Crystalline‐b‐Coil Diblock Copolymer

AbstractWe herein report the formation of two complex nanostructures, toroidal micelles and bicontinuous nanospheres, by the self‐assembly of the single structurally simple crystalline‐b‐coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]‐b‐poly(styrene), PTFEP‐b‐PS, in one solvent (THF) and without additives. The nature of these nanostructures in solution was confirmed by DLS and cryo‐TEM experiments. The two morphologies are related by means of a new type of reversible morphological evolution, bicontinuous‐to‐toroidal, triggered by changes in the polymer concentration. WAXS experiments showed that the degree of crystallinity of the PTFEP chains located at the core of the toroids was higher than that in the bicontinuous nanospheres, thus indicating that the final morphology of the aggregates is mostly determined by the ordering of the PTFEP core‐forming blocks.

Formation and Reversible Morphological Transition of Bicontinuous Nanospheres and Toroidal Micelles by the Self-Assembly of a Crystalline-b-Coil Diblock Copolymer.

We herein report the formation of two complex nanostructures, toroidal micelles and bicontinuous nanospheres, by the self-assembly of the single structurally simple crystalline-b-coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]-b-poly(styrene), PTFEP-b-PS, in one solvent (THF) and without additives. The nature of these nanostructures in solution was confirmed by DLS and cryo-TEM experiments. The two morphologies are related by means of a new type of reversible morphological evolution, bicontinuous-to-toroidal, triggered by changes in the polymer concentration. WAXS experiments showed that the degree of crystallinity of the PTFEP chains located at the core of the toroids was higher than that in the bicontinuous nanospheres, thus indicating that the final morphology of the aggregates is mostly determined by the ordering of the PTFEP core-forming blocks.

Assembly structure and rod orientation of rod–coil diblock copolymer films

The self-assembly and rod orientation of rod–coil (RC) diblock copolymer (DBC) films confined between two identical impenetrable and rod-selective walls was investigated by performing dissipative particle dynamics simulations. Various structures, such as a wetting layer near the surfaces, perpendicular cylinders, parallel cylinders and island-like structures, were observed. Thus a morphological phase diagram as a function of the film thickness and rod length was presented. A long-range rod–rod orientational order was observed in the assembly structures for a rod block above a critical rod length. The critical rod length for the disorder–order transition of the rod orientation was found to be dependent on the assembly structure and film thickness. Our results indicate that the rod length and film thickness influence both the assembly structure and the rod orientation of RC DBCs. The assembly structure and the critical rod length for the disorder–order orientational transition in rod–coil diblock copolymer films depend on the property of the wall surface and the film thickness.

Donor–Acceptor Poly(3‐hexylthiophene)‐block‐Pendent Poly(isoindigo) with Dual Roles of Charge Transporting and Storage Layer for High‐Performance Transistor‐Type Memory Applications

Field‐effect transistor memories usually require one additional charge storage layer between the gate contact and organic semiconductor channel. To avoid such complication, new donor–acceptor rod–coil diblock copolymers (P3HT44‐b‐Pison) of poly(3‐hexylthiophene) (P3HT)‐block‐poly(pendent isoindigo) (Piso) are designed, which exhibit high performance transistor memory characteristics without additional charge storage layer. The P3HT and Piso blocks are acted as the charge transporting and storage elements, respectively. The prepared P3HT44‐b‐Pison can be self‐assembled into fibrillar‐like nanostructures after the thermal annealing process, confirmed by atomic force microscopy and grazing‐incidence X‐ray diffraction. The lowest‐unoccupied molecular orbital levels of the studied polymers are significantly lowered as the block length of Piso increases, leading to a stronger electron affinity as well as charge storage capability. The field‐effect transistors (FETs) fabricated from P3HT44‐b‐Pison possess p‐type mobilities up to 4.56 × 10−2 cm2 V−1 s−1, similar to that of the regioregular P3HT. More interestingly, the FET memory devices fabricated from P3HT44‐b‐Pison exhibit a memory window ranging from 26 to 79 V by manipulating the block length of Piso, and showed stable long‐term data endurance. The results suggest that the FET characteristics and data storage capability can be effectively tuned simultaneously through donor/acceptor ratio and thin film morphology in the block copolymer system.

Organic–inorganic rod–coil block copolymers comprising substituted polyacetylene and poly(dimethylsiloxane) segments

Organic–inorganic rod–coil diblock copolymers comprising substituted polyacetylene and PDMS were synthesized through a precursor route based on anionic polymerization.

Phase Diagram of Rod–Coil Diblock Copolymer Melts

A unified phase diagram is presented for rod–coil diblock copolymer melts in the isotropic phase regime as a function of the asymmetric parameter. The study is based on free energy calculation, which incorporates three-dimensional spatial variations of the volume fraction with angular dependence. The wormlike-chain model is used in a self-consistent field treatment. Body-centered cubic, A15, hexagonal, gyroid, and lamellar structures where the rod segments are packed inside the convex rod–coil interface are found stable. As the conformational asymmetric parameter increases, the A15 phase region expands and the gyroid phase region reduces. The stability of the structures is analyzed by concepts such as packing frustration, spinodal limit, and interfacial curvature.

Synthesis and characterization of diblock copolymers based on poly(3-hexylthiophene) and photo-responsive poly(methyl methacrylate-random-2-methyl methaspirooxazine)

The rod–coil diblock copolymers combining the conductive feature of a conjugated polymer and nanoscale morphologies arising from microphase separation of dissimilar blocks are attractive as potential materials for electronic applications. Herein, we report on the synthesis and properties of a novel diblock copolymer containing a rod-block of regioregular poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate-random-2-methyl methaspirooxazine) (P3HT-b-P(MMA-r-MSp)) as photo-responsive coil-block. Well-defined rod–coil P3HT-b-P(MMA-r-MSp) diblock copolymers with average molecular weight of around 10,000 and low molar mass dispersities (ÐM) below 1.5 were successfully synthesized via the combination of quasi-living Grignard metathesis polymerization and atom transfer radical polymerization (ATRP). Post-polymerization end-group modifications of the as-obtained P3HT were then successfully realized to give a macroinitiator for the ATRP of MMA and MSp co-monomers, resulting in the P3HT-b-P(MMA-r-MSp) diblock copolymers. The structure and properties of the resulting diblock copolymers were characterized by proton nuclear magnetic resonance (1H NMR), gel permeation chromatography, Fourier transform infrared, UV–visible spectroscopy, and differential scanning calorimetry.