Rod-coil Diblock Copolymers Research Articles

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.

Adsorption of block copolymers on solid surfaces: A Monte Carlo study.

Using hyper-parallel tempering Monte Carlo simulation, multiple histogram reweighting method, and finite size scaling, we investigate the adsorption of fully flexible and rod-coil chains on the square lattice. We find that the phase behaviour changes with the chain length and flexibility. For homonuclear rod-coil chains, the phase diagram consists of only gas-disorder liquid critical point. Weakening of the interaction energy between the segments belonging to two different subunits gives rise to an order-disorder transition. The topology of the resulting phase diagram depends on the chain length and flexibility. For short chains, both fully flexible and rod-coil diblock copolymers form lamellar ordered phase with fully stretched chains, and the order-disorder transition is of the first order. The phase diagrams are similar for both chain architectures and consist of two binodals meeting in the triple point. When the chain length increases the order-disorder transition becomes second-order and the difference in the phase behaviour between the fully flexible and the rod-coil diblock copolymers becomes more pronounced. While for the former chain architecture the topology of the phase diagram involves a λ-line which meets the gas-disordered liquid binodal in the critical end-point, in the latter case the λ-line meets the gas-disordered liquid critical point and forms the tricritical point. We trace back these changes to the change in the morphology of the ordered phase. The mechanism of the order-disorder transition involves the formation of domains resembling those observed during the spinodal decomposition process. The domains subsequently merge and arrange into lamellae. These observations are supported by integral geometry analysis.

Self-assembly of rod-coil diblock copolymers within a rod-selective slit: a dissipative particle dynamics simulation study.

Dissipative particle dynamics simulations are performed to investigate the self-assembly of rod-coil diblock copolymers R(N(R))C(N-N(R)) within a rod-selective slit. The self-assembled structure of the confined system is sensitively dependent on the rigidity kθ and the fraction fR of the rod block and the slit height H. From the phase diagram of structures with respect to kθ and fR for N = 12 and H = 6, we observe four main structures including disordered cylinder (DC) structure, hexagonally packed cylinders (HPC) perpendicular to the slit surfaces, and lamellar structures parallel (L∥) and perpendicular (L⊥) to surfaces. And structure transitions can be achieved by tuning kθ. The effect of the slit height on the self-assembled structure is also studied for R6C6 and R7C5 copolymers with large kθ. For R6C6, different structures near surfaces and in the interior of slit are observed in relatively wide slits. Whereas for R7C5, L⊥ structure, whose lamellar domain spacing decays exponentially with H, is generally generated. Our results suggest an effective way to control the ordering of rod-coil diblock copolymers under nanoscale confinement.

Phase transformation and self-assembly behavior of supramolecular rod–comb block copolymers

We investigated the self-assembly behavior of a series of supramolecular rod–comb block copolymer complexes made by the hybridization of rod–coil diblock copolymers of poly (2,5-di(2-ethylhexyloxy)-1,4-phenylene vinylene)-b-poly(2-vinyl pyridine) (PPV-b-P2VPf) with different volume fractions, f, of the P2VP coils and an anionic surfactant, dodecyl benzenesulfonic acid (DBSA), that selectively interacts with the P2VP to form the side-chain comb teeth. The resulting hybrids show hierarchically ordered structures at multiple length scales, forming so-called structure-in-structure morphology. Notably, for PPV-b-P2VP0.56(DBSA)x, the larger-scale structure changes from a lamellar phase, to a broken lamella, and eventually to a hexagonally packed strip phase with increasing DBSA molar ratio (x) to P2VP monomer unit. Furthermore, simultaneous SAXS and WAXS measurements showed that the order-disorder transition temperatures of larger-scale structures in the PPV-P2VP0.56(DBSA) rod–comb systems were higher than those associated with the pristine PPV-P2VP0.56 polymers. The large-scale structure of PPV-P2VP0.56(DBSA) exists at temperatures around 210 °C even though the rod–rod interaction between PPV blocks disappear at ∼120 °C, signifying that the formation of the P2VP(DBSA) lamellar mesophase plays a critical role in forming the large-scale hexagonally packed strip structures.

Synthesis, optical properties and photovoltaic applications of hybrid rod–coil diblock copolymers with coordinatively attached CdSe nanocrystals

Hybrid rod–coil diblock copolymers containing coordinatively binded CdSe nanocrystals in the coil block give better solar cell performance over their corresponding diblock copolymers without CdSe attachment.

Bulk and solution properties of a thermo-responsive rod–coil block polymer based on poly(N-isopropylacrylamide)

Molecular weight dependence on thermoresponsive behaviors of rod–coil diblock copolymers (x indicates the DP of rod PHIPPVTA blocks).

Liquid crystalline assembly of rod-coil diblock copolymer and homopolymer blends by dissipative particle dynamics simulation.

Liquid crystalline assembly of rod-coil diblock copolymers blended with coil or rod homopolymers is investigated by dissipative particle dynamics simulation, considering systematically the effect of the interactions between rods and coils, the volume fraction and length of the added coil or rod homopolymers. The addition of coil or rod homopolymers induces disorder-order or order-liquid crystalline transition. In rod-coil/coil blends, the solubilization of homopolymers will saturate at a certain amount of homopolymers and then the excess homopolymers will be segregated into the central regions of coil block domains, forming "wet-dry mixture" lamellae. The solubility capacity decreases with increasing homopolymer length, determined by the competition between the mixing entropy and the elastic entropy. In rod-coil/rod blends, due to the orientational interactions between rods, the length matched rod homopolymers directly interdigitate with rod blocks with less entropy loss, thus prompting the formation of a bilayer liquid crystalline phase. The rod domain spacing Dr remains unchanged and conversely the coil domain spacing Dc becomes thin, to occupy more interfacial area. With the addition of shorter rod homopolymers, the overall lamellar spacing D of blends monotonically increases with the volume fraction of homopolymers, similar to the case of rod-coil/coil blends. Generally, rod homopolymers have a more significant impact on the liquid crystalline assembly of the blends, compared with the coil homopolymers. Our results indicate that blending with coil or rod homopolymers into a rod-coil system is an effective method to induce liquid crystal phase transition and control the phase spacing of the ordered structure.

The fusion mechanism of small polymersomes formed by rod–coil diblock copolymers

The fusion mechanism of polymersomes self-assembled by rod-coil copolymers is intrinsically different from that of liposomes due to the effect of chain topology on conformational entropy and molecular packing. The influences of membrane tension, coil-block length, rod-block length, mutual compatibility between the solvent and the rod-coil block, and π-π interaction strength on the fusion pathway are explored by dissipative particle dynamics. The fusion process of spontaneously formed polymersomes generally consists of four stages. In the kissing stage, hopping of rod-blocks forms a connection between two vesicles of a one-legged rod-coil copolymer. In the adhesion stage, a stalk is developed by a few link-up rods and then a stretched diaphragm with rods lying parallel to the stretching direction is formed in the hemi-fusion stage. Eventually, a pore is developed and expanded in the fusion stage. If the membrane tension (τ) is adjusted by deflation/inflation of the polymersomes, the hemi-fusion diaphragm disappears. As τ is reduced, multiple stalks take shape and lead to the formation of inverted micelles, which is the rate-determining step and raises the fusion time substantially. As τ is elevated, a neck is developed after the stalk formation. The fusion process is significantly accelerated. τ of spontaneously formed vesicles varies with the coil-block length, rod-block length, solvent quality, and π-π interaction strength. There exists a critical value of τ below which the fusion process cannot be completed and a hemi-fused polymersome is formed. In addition to τ, the anisotropic steric interactions within the rod layers also resist hopping of longer rod-blocks. The coil layers develop a barrier impeding fusion between vesicles with longer coil-blocks. Consequently, lowering the solvent quality for the coil-block or rod-block facilities the fusion process due to the formation of a thinner coil layer.

Photovoltaic properties and femtosecond time‐resolved fluorescence study of polyoxometalate‐containing rod–coil diblock copolymers

ABSTRACTThe photovoltaic properties and exciton decay dynamics of three polyoxometalate (POM)‐containing hybrid rod–coil diblock copolymers (HDCPs), PS‐Mo6‐PT1–3, are studied. Single‐component photovoltaic cells of PS‐Mo6‐PT2 and inverted solar cells based on ZnO nanorod arrays/PS‐Mo6‐PT1–3 are fabricated showing power conversion efficiencies only up to 0.055%. To understand the poor photovoltaic performance, femtosecond fluorescence up‐conversion technique is used to study the exciton decay dynamics of all three HDCPs. Drastically different fluorescence dynamics of the three HDCPs are observed in dilute solutions, which is attributed to the different extent and different type of interpolymer association depending on the P3HT rod block length and the cluster loading ratio. While both cation‐mediated POM cluster association and P3HT‐P3HT π‐stacking contribute significantly to PS‐Mo6‐PT2 aggregation, the aggregation of PS‐Mo6‐PT1 and that of PS‐Mo6‐PT3 is driven predominantly by cluster association and π‐stacking, respectively. In conjunction with the high residual polarization anisotropy, it is concluded that charge transfer from P3HT excitons to POM clusters in all three HDCPs is inefficient. An improved system with direct π‐conjugation between the POM clusters and the rod block addressing this issue has been proposed. © 2013 Wiley Periodicals, 2014, 52, 122–133

A novel conducting amphiphilic diblock copolymer containing regioregular poly(3-hexylthiophene)

Amphiphilic rod-coil diblock copolymers combining the conductive features of a conjugated polymer and nanoscale morphologies arising from micro-phase separation of dissimilar blocks are attractive as potential materials for electronic applications. The synthesis and properties are reported for a novel amphiphilic diblock copolymer containing a block of regioregular poly(3-hexylthiophene) (P3HT) and poly(methyl methacrylate-random-2-hydroxyethyl methacrylate) (P(MMA-r-HEMA)) as the hydrophilic block. Well-defined rod-coil P3HT-b-P(MMA-r-HEMA) amphiphilic diblock copolymers with molar masses of around 11,000 and low molar mass dispersities (ĐM) below 1.5 were successfully synthesized via the combination of quasi-living Grignard metathesis (GRIM) polymerization and atom transfer radical polymerization (ATRP). P3HT was first obtained in a regioregular form with an average molecular weight of around 7,200 g/mol and ĐM below 1.3. Post-polymerization end-group modifications of the asobtained P3HT were then successfully realized to give a macroinitiator for the ATRP of MMA and HEMA co-monomers, resulting in the P3HT-b-P(MMA-r-HEMA) diblock copolymers. The structure and properties of the resulting diblock copolymers were characterized by proton nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy and modulated differential scanning calorimetry (MDSC). Open image in new window

Diffusion Mechanisms of Entangled Rod–Coil Diblock Copolymers

Mechanisms of entangled rod–coil diblock copolymer diffusion are investigated using tracer diffusion simulations and experiments in a matrix of entangled coil homopolymers, demonstrating that the d...

Remarkably Rich Variety of Nanostructures and Order–Order Transitions in a Rod–Coil Diblock Copolymer

A remarkably rich variety of nanophase-separated structures and various order–order transitions are observed in a series of low-molecular weight (MW) rod–coil block copolymers (BCPs) with the rod blocks of different lengths (LRod’s). The rod–coil diblock copolymer studied herein is poly(dimethylsiloxane)-b-poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PDMS-b-PMPCS), in which PMPCS is a rod-like polymer and exhibits an MW-dependent liquid crystalline (LC) phase behavior. When the polymerization degree of the PMPCS rod block (NRod) is less than 32 (LRod < 8 nm), the PMPCS block is always amorphous in the entire temperature range. And the corresponding PDMS-b-PMPCS BCPs with NRod from 11 to 29 and the volume fraction of the PMPCS rod (fRod) from 43% to 67% self-assemble into various equilibrium nanostructures after annealed at temperatures above the glass transition temperatures of the PMPCS blocks. When NRod = 11 and fRod = 43%, the BCP forms a lamellar structure (LAM); when NRod = 15 and fRod = 51%, the BCP forms a double gyriod structure (GYR) ; when NRod = 20 and fRod = 57%, the BCP forms a GYR structure after annealed below 180 °C and transforms to the Fddd structure after annealed above 180 °C; when NRod = 29 and fRod = 67%, the nanostructure of the BCP after annealed below 180 °C is hexagonally packed cylinders (HEX) and changes to a body centered cubic structure (BCC) after annealed above 180 °C. When NRod > 32 (LRod > 8 nm), the PMPCS rod block is amorphous at low temperatures and transforms to a stable columnar LC phase after annealed at high temperatures. Correspondingly, the PDMS-b-PMPCS BCP with NRod = 44 and fRod = 75% forms a HEX structure after annealed at lower temperatures at which the PMPCS block is amorphous, and the nanostructure transforms to LAM after the sample is annealed at higher temperatures at which the PMPCS block enters into the LC phase. Therefore, only by a small change of the rod length in the low-MW PDMS-b-PMPCS rod–coil BCPs, various nanostructures including LAM, GYR, Fddd, HEX, and BCC are obtained. In addition, by increasing annealing temperatures, GYR-to-Fddd and HEX-to-BCC transitions are observed in the BCPs with the amorphous PMPCS, and a HEX-to-LAM transition occurs in the BCP when the LC PMPCS block undergoes an isotropic-to-LC phase transformation.

Phase Behavior of the Blend of Rod–Coil Diblock Copolymer and the Corresponding Coil Homopolymer

Blending with a homopolymer is an effective approach to tailor the microphase-separated morphology of block copolymers. It has been established for the blends of coil–coil diblock copolymer (A-b-B) with the corresponding homopolymer (h-A) that h-A can be solubilized uniformly into A mcirodomain to induce structure transformation when its molecular weight is smaller than that of the A block, i.e., α = Mh-A/Mb-A < 1. Here we examine if the microdomain structure of a rod–coil diblock copolymer, poly(2,5-diethylhexyloxy-1,4-phenylenevinylene)-block-poly(methyl methacrylate) (DEH-PPV-b-PMMA), may be systematically tuned by blending with PMMA hompolymer (h-PMMA). The blends over the major composition window were found to undergo macrophase separation even when the value of α was as low as 0.3. The phase separation led to the formation of a copolymer-rich phase and a homopolymer-rich phase, in which microphase separation occurred, yielding a well-ordered lamellar structure and a sponge structure, respectively. T...

Self-assembly of cyclic rod-coil diblock copolymers

The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (χN)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more "symmetrical," due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly.

Synthesis, Characterizations, and Morphological Studies of Polyoxometalate‐Containing Rod–Coil Diblock Copolymers

AbstractA set of hybrid rod–coil diblock copolymers containing different sizes of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as the rod block and a polystyryl‐type (PS) coil block with covalently linked polyoxometalates (POMs) as side chains have been synthesized. The P3HT rod blocks, synthesized using Grignard metathesis polymerization, and the PS coil block, prepared by atom transfer radical polymerization were successfully coupled using “click” chemistry to form the rod–coil diblock copolymers (PS‐PTn). POM cluster attachment was performed on the diblock copolymers through a post‐polymerization functionalization approach. The thin film morphology of the diblock copolymers prior to cluster attachment shows a strong dependence on the solvent and the size of the P3HT block. Following cluster attachment, the hybrid diblock copolymers show much less solvent and size dependence in phase‐separated morphologies of their pristine films. The sporadic and isolated conducting domains seen in the pristine films change to widespread worm‐like conducting networks after thermal annealing; such morphologies are conducive to photovoltaic properties.

Structural and mechanical properties of polymersomes formed by rod–coil diblock copolymers

Polymersomes formed by rod–coil diblock copolymers (RxCy) are fundamentally different from those of coil–coil diblock copolymers. RxCy denotes the polymer comprising of x rod-like beads and y coil-like beads. The morphological phase diagram of RxCy in selective solvents and the essential physical properties of the RxCy-polymersomes are explored by using dissipative particle dynamics. Our simulation results show that small-sized polymersomes can only take shape for short coil-block lengths. Moreover, the rod-block length cannot be too long and π–π stacking must be weak because anisotropic rod packing actually resists membrane bending and thus vesicle formation. The detailed membrane structures of polymersomes are also investigated and it is found that the rods within the membrane are highly interdigitated which is intrinsically different from the ordered bilayer of the liposomes formed by triblock copolymers (Rx)2Cy. The structural and mechanical properties of RxCy-polymersomes are studied as well. As the coil-block length is increased, both the thickness and area density of the rod domain decline. Since the coil stretching in the inner corona is more distinct than that in the outer one, significant interdigitation results due to the outward movement of the inner leaflet for relaxing overcrowded coil-blocks. The membrane tension exhibits a maximum while the stretching and bending moduli display a minimum at the intermediate coil-block length as y varies from 1 to 3. Fusion between two polymersomes of R5Cy is investigated and the outcome relates to the membrane tension. R5C2-polymersomes fuse most easily. However, R5C1-polymersomes do not proceed beyond the hemifusion stage and R5C3-polymersomes can not even move past the initial kissing stage.

Understanding the mechanism of poly(3-hexylthiophene)-b-poly(4-vinylpyridine) as a nanostructuring compatibilizer for improving the performance of poly(3-hexylthiophene)/ZnO-based hybrid solar cells

The final device efficiencies of excitonic solar cells are strongly dependent on interface processes. However, it is still very challenging to clearly track the effects of inter-molecular processes at the mesoscopic level, while controlling the morphology and interface structure on the nanometer length scale. We report on the realization of a step-change improvement in poly(3-hexylthiophene)/ZnO-based hybrid solar cells, which is enabled by engineering the hybrid interface using a rod–coil diblock copolymer, poly(3-hexylthiophene)-b-poly(4-vinylpyridine) (P3HT-b-P4VP), as a nanostructuring compatibilizer in the P3HT/ZnO bulk heterojunctions. Upon evaporation of the solvent, the P3HT blocks of the copolymer cocrystallize with the homopolymer P3HT chains and phase separate from the ZnO domains, resulting in the P4VP blocks sitting at the edge of crystalline P3HT microdomains, or in other words, at the interfacial region between the P3HT and ZnO domains. P3HT-b-P4VP could enhance the crystallinity of P3HT and help spontaneously assemble P3HT into nanowires, while at the same time impeding the macrophase separation of the ZnO nanoparticles by taking advantage of the coordination interaction between the P4VP block and the ZnO nanoparticles, bridging the ZnO nanoparticles and the P3HT nanowires, thereby effectively improving the power-conversion efficiency. We show that a suitable nanostructuring compatibilizer induces selective intermolecular interactions, thus creating a preferential interface energetic landscape and morphological order, which consequently drive a strong improvement in the exciton dissociation and charge transport by decreasing recombination losses.

Controlling morphology and improving the photovoltaic performances of P3HT/ZnO hybrid solar cells via P3HT-b-PEO as an interfacial compatibilizer

The well-defined rod–coil diblock copolymer poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-b-PEO) was used as the interfacial compatibilizer for P3HT/ZnO (1 : 2 w/w) hybrid heterojunction solar cells. The power conversion efficiency of the device was enhanced from 0.5 to 0.98% in the presence of 0–10 wt% P3HT-b-PEO under illumination of AM 1.5G (100 mW cm−2), resulting from the morphology variation. In the P3HT/ZnO/P3HT-b-PEO ternary blends, the block copolymer does not influence the crystallinity of ZnO NPs, but does influence the crystallinity of P3HT and the dispersion of ZnO NPs. An enhanced crystalline and fiber-like P3HT and more uniform dispersion of ZnO NPs are observed with a small amount of P3HT-b-PEO (10 wt%) loading, leading to a smaller domain size, enhanced interfacial area for charge separation and a favored active layer morphology for improving the device performance. On the other hand, the incorporated P3HT-b-PEO could also suppress macrophase separation during long time thermal annealing and improve the device thermal stability. These results demonstrated that the promising effect of the rod–coil diblock copolymers interfacial compatibilizer for controlling the morphology and improving the performance of hybrid bulk heterojunction solar cells.

Enhancing organic–inorganic hybrid solar cell efficiency using rod–coil diblock polymer additive

Organic–inorganic hybrid bulk heterojunction (BHJ) solar cells have attracted much attention due to their low cost fabrication, flexibility, and long life. However, the compatibility between organic and inorganic materials is still an issue that needs to be solved to achieve high power conversion efficiency (PCE). The larger size and dense characteristics of inorganic nanocrystals make it hard to control the morphology and phase separation of organic–inorganic hybrid thin films by conventional processes like thermal annealing and solvent annealing. In this study, we have carried out a systematic investigation using an additive: rod–coil diblock copolymer poly(3-hexyl thiophene)-b-poly(2-vinyl pyridine) (P3HT-b-P2VP) to P3HT:TiO2 to make a ternary system. That improves the compatibility between the P3HT homopolymer and the TiO2 nanorod hybrid materials and results in enhanced performance of the hybrid solar cell. The hydrophobic characteristics of the P3HT segment of the copolymer are compatible with the P3HT homopolymer, and the P2VP segment, containing a pyridine moiety is more compatible with hydrophilic TiO2. The results of atomic force microscopy and X-ray diffraction spectroscopy studies of hybrid films reveal that the crystallization behavior of the homopolymer P3HT in the film can be tuned by incorporating different weight ratios of P3HT-b-P2VP. The efficiency of charge separation is also improved as observed by greater photoluminescence quenching. Furthermore, the power conversion efficiency of the solar cell fabricated from this new hybrid system was increased threefold as compared with the one without the additive (1.20% vs. 0.42%), which indicates that the amphiphilic P3HT-b-P2VP can effectively modulate the interfacial interactions between the conducting polymer and nanocrystals in both solution and film to have the appropriate morphology for high efficient solar cells.

Cylinder-to-gyroid phase transition in a rod–coil diblock copolymer

In this communication, the morphology of well-defined P3DDT-b-PMMA with a 65.2% PMMA coil volume fraction is revealed as a hexagonally packed cylinder structure by X-ray scattering experiments after thermal annealing. Upon heating, an order-to-order transition (OOT) between cylindrical and gyroidal structures is observed at temperatures above 170 °C. The evolution of the cylinder to the gyroid occurs while the crystalline structure of the P3DDT block disappears, suggesting the conformation of the P3DDT-b-PMMA at high temperatures is similar to coil–coil block copolymers. The phenomena reported here can provide a different viewpoint of the self-assembly behaviors of poly(3-alkylthiophene)-containing rod–coil block copolymers. The novel rare gyroid structure of this rod–coil copolymer is useful to fabricate long sought of bicontinuous structure for highly efficient polymer solar cells.