Rod-coil Block Copolymers Research Articles

A novel luminescent sensor for disaccharide detection in food: Synthesis and application of a water-soluble rod-coil ionic block copolymer

A simple and low cost method for detecting disaccharide in food product is important for people who need control the consumption of saccharides in daily life. In this study, a water soluble rod-coil ionic block copolymer poly[2,7-(9,9-dihexyl-fuorene)]-b-cationic quaternized-poly[2-(dimethylamino)ethyl methacrylate] (PF-b-PDI) was employed as luminescent sensor for detection of lactose, sucrose and maltose in food. It was found that the PF-b-PDI could emit vision fluorescence with the existence of hydroquinone (HQ) in aqueous, but would be quenched by the oxidization of hydrogen peroxide (H2O2). The glucose oxidase (GOx) could be used for catalyzing the glucose to generate the H2O2. And the sucrase, maltase and lactase could respectively catalyze sucrose, maltose and lactose to glucose. With the selectivity and catalyst of enzyme, the PF-b-PDI aqueous blend with HQ showed fluorescence sensitive to sucrose, maltose and lactose with detection limit value of 1.36 μM, 1.09 μM and 3.08 μM, respectively. Moreover, the detection of lactose in milk samples by this method just revealed 0.44% of average deviation compared to standard lactose solution, which mean this method was suitable for detecting lactose in milk.

Temperature-controlled formation of inverse mesophases assembled from a rod–coil block copolymer

Temperature was adjusted to control the formation of inverse mesophases which can be used as templates to prepare inorganic materials.

Hierarchically ordered nanostructures of a supramolecular rod-coil block copolymer with a hydrogen-bonded discotic mesogen

Supramolecular liquid crystalline block copolymers prepared via hydrogen bonding exhibit hierarchical structures that can be tuned by varying the molar ratio of the discotic hydrogen-bonding acceptor to the block copolymer donor.

Stability of the Gyroid Phase in Rod–Coil Systems via Thermodynamic Integration with Molecular Dynamics

The stability of the gyroid phase in a coarse-grained model of rod-coil block copolymers is ascertained by using a field-based thermodynamic integration method to calculate free-energy differences between competing phases. The scope of the original methodology is expanded in terms of both its implementation by designing guiding fields suitable for molecular dynamics simulations (besides Monte Carlo simulations) and its applications by describing the formation of bicontinuous phases with linear rod-coil amphiphilic chains and with bolaamphiphilic molecules. For both types of systems, results are presented that complement those from previous studies, providing a quantitative metric to pinpoint the conditions and molecular parameters that render the gyroid phase more stable than other competing morphologies.

Persistent Formation of Self-Assembled Cylindrical Structure in a Liquid Crystalline Block Copolymer Constructed by Hydrogen Bonding

A series of supramolecular liquid crystalline block copolymers (SLCBCPs) were prepared by hydrogen-bonding interaction between poly(dimethylsiloxane)-b-poly(2-vinylterephthalic acid) (PDMS-b-PM1H) and [4-(4′-hexyloxy)styryl]pyridine (NC6). PDMS-b-PM1H serves as the hydrogen-bonding donor and NC6 as the hydrogen-bonding acceptor. The SLCBCPs are obtained by mixing the hydrogen-bonding acceptor and donor in pyridine. Through increasing the molar ratio of pyridine to carboxyl, the SLCBCPs can transform from coil–coil block copolymers (BCPs) to rod–coil ones. When the ratio of pyridine to carboxylic acid is 0.50 or lower, the SLCBCPs are coil–coil-like. However, when the ratio exceeds 0.50, the SLCBCPs behave like rod–coil BCPs because the supramolecular block PM1H(NC6) exhibits liquid crystalline (LC) behavior owing to the “jacketing” effect. Small-angle X-ray scattering and transmission electron microscopy experiments were employed to characterize the microphase-separated nanostructures of the SLCBCPs. Inte...

Head-Tail Asymmetry as the Determining Factor in the Formation of Polymer Cubosomes or Hexasomes in a Rod-Coil Amphiphilic Block Copolymer.

The self-assembly of a rod-coil amphiphilic block copolymer (ABCP) led to Im3‾ m and Pn3‾ m polymer cubosomes and p6mm polymer hexasomes. This is the first time that these structures are observed in a rod-coil system. By varying the hydrophobic chain length, the initial concentration of the polymer solution, or the solubility parameter of the mixed solvent, head-tail asymmetry is adjusted to control the formation of polymer cubosomes or hexasomes. The formation mechanism of the polymer cubosomes was also studied. This research opens up a new way for further study of the bicontinuous and inverse phases in different ABCP systems.

Vertically Oriented Nanostructures of Poly(3-dodecylthiophene)-Containing Rod–Coil Block Copolymers

We synthesized star-shaped 18-arm polystyrene-block-poly(3-dodecylthiophene) copolymers ((PS-b-P3DDT)18) having lamellar microdomains, based on the cyclodextrin (CD) core. Without any surface modifications on a silicon substrate, thin films of (PS-b-P3DDT)18 showed vertically oriented lamellar microdomains by thermal annealing. This is attributed to the entropic penalty induced by star-shaped chain architecture. In contrast, a parallel orientation was observed in the film morphology of the corresponding linear PS-b-P3DDT. We also found that the P3DDT crystals were confined in the lamellar microdomains of (PS-b-P3DDT)18 as edge-on structure.

Self‐Assembly of Rod‐Coil Block Copolymers on Carbon Nanotubes: A Route toward Diverse Surface Nanostructures

In this work, it is reported that poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers (BCPs) can disperse carbon nanotubes (CNTs) in solution and form various surface nanostructures on the CNTs via solution self-assembly. In an organic solvent that dissolves the BCPs, the PBLG rod blocks adsorb on CNT surfaces, and the BCPs form conformal coatings. Then, by the introduction of water, a selective solvent for PEG blocks, the BCPs in the coatings further self-assemble into diverse surface nanostructures, such as helices (left-handed or right-handed), gyros, spheres, and rings. The morphology of the surface nanostructure can be tailored by initial organic solvent composition, preparation temperature, feeding ratio of BCPs to CNTs, degree of polymerization of PBLG blocks, and diameter of the CNTs.

Stimuli-responsive fiber-like micelles from the self-assembly of well-defined rod-coil block copolymer

A series of photoluminescent fiber-like micelles were obtained in solutions via self-assembly of well-defined rod-coil block copolymers, poly[2,7-(9,9-dihexyl-fuorene)]-b-poly[2-(dimethylamino)ethyl methacrylate] (PFH-b-PDMAEMA), which prepared by combining controlled Suzuki-coupling and atom transfer radical polymerization (ATRP) in a “double controlled” manner. The length of micelles can be varied by changing the solvent mixtures, probably because of the H-type aggregation of the PFH block. The morphology and photoluminescence of these micelles were pH- or temperature-responsive in aqueous. The fluorescence intensity increased with temperature increased and became stronger as the pH increased (pH < 9) but reduced again when the pH further increased (pH > 9). And the morphologies of micelles transited into shorter linear or shuttle-like structures with the change of pH and showed aggregation as temperature-induced. These phenomena may be mainly caused by the structure of micelles and the effect of hydrophillic-hydrophobic transformation of the PDMAEMA corona. Our work provides a push to the synthesis and self-assembly of well-defined rod-coil polymer, and also provides insights into the stimuli-responsive properties of fiber-like micelles.

Facile approach for rapid self-assembly of rod-coil block copolymers

Rod-coil block copolymers (BCPs) can self-assemble into nanostructures that are useful for the fabrication of nanodevices. However, BCPs are generally difficult to self-assemble into highly ordered nanostructures due to their low chain mobility and strong rod-rod interaction. A facile approach is developed to achieve rapid self-assembly of rod-coil BCPs by blending them with selective additive and annealing in vacuum. Poly(diethyl hexyl oxy-p-phenylene vinylene)-b-poly(methyl methacrylate) (DEHPPV-b-PMMA or PVM) was used as a model copolymer to validate this approach. By adding 30 wt% of a rod-selective additive, p-phenylene vinylene (PV), into the PVM containing 67% (v/v) PMMA, the copolymer can easily self-assemble into lamellae structure at 150 °C for 1.5hr under 0.05 torr. This is a significant improvement over the 200 °C for 60 h for the sample without additive and vacuum annealing. This energy conservation process should have broad application in the fabrication of highly ordered nanostructure using BCPs.

Facile Synthesis of a High Molecular Weight Amphiphilic Aramid–ROMP Block Copolymer

Herein we report the facile synthesis of an amphiphilic rod–coil block copolymer obtained by the coupling of an amine-terminated poly(dimethylpropylamine norbornene imide) (PDMAPNI) and a pentafluorophenol ester-terminated poly(dimethoxybenzyl p-aminobenzoate) (PAram). Postpolymerization amide N-deprotection of the block copolymer yielded a strongly aggregating water-soluble rod–coil copolymer. Transmission electron microscopy revealed the formation of large ribbonlike aggregates with sizes up to 50 nm in thickness and 300 nm in length.

RETRACTED ARTICLE: The highest power conversion efficiencies in poly(3-hexylthiophene)/fullerene photovoltaic cells modified by rod-coil block copolymers under different annealing conditions

A best-performing morphology was proposed for poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction (BHJ) solar cells by thermal and solvent annealings in the presence of rod-coil block copolymers subsuming hydrophilic and hydrophobic coily blocks. Unlike uncompatibilized photovoltaic cells, the power conversion efficiency (PCE) dropping during both thermal and solvent annealings was prevented for all BHJ devices compatibilized with either hydrophobic- or hydrophilic-based copolymers. The observed behavior was assigned to ever increasing trend of the fill factor (FF) and increasing or marginally decreasing trend of short circuit current density (J sc ). Although PCEs were higher in untreated hydrophobic-compatibilized devices (e.g., 4.07 vs. 1.52%), the hydrophilic-compatibilized systems further benefited from thermal and solvent annealings (e.g., 4.78 vs. 3.71%). The J sc and PCE peaked at 12.10 mA/cm2 and 4.85%, respectively, within 1 h under solvent annealing by 20 wt% of P3HT7150-b-polystyrene compatibilizer. Based on dynamic secondary ion mass spectrometry (DSIMS) analyses, the vertical homogeneity increased for compatibilized BHJs during both thermal and solvent annealings, leading to very high FFs (~69%).

Facile Construction of Metallo-supramolecular Poly(3-hexylthiophene)-block-Poly(ethylene oxide) Diblock Copolymers via Complementary Coordination and Their Self-Assembled Nanostructures

Complementary coordination of two predesigned 2,2':6',2″-terpyridine-based ligands to a ZnII ion led to the exclusive formation of a heteroleptic bis(terpyridine) complex under ambient conditions. This highly self-selective process was facilitated by 9-anthracenyl substituents at the 6,6″-positions of a terpyridine, which not only decelerated the formation rate of its homoleptic complex, but also provided π-stacking stabilization in the heteroleptic complex. Facile construction of metallo-supramolecular poly(3-hexylthiophene) (P3HT)-block-poly(ethylene oxide) (PEO) diblock copolymers was realized using the complementary ligand pair. The morphological studies of the amphiphilic block copolymers in solution were conducted by atomic force microscopy and transmission electron microscopy, indicating that the self-assembled core-shell morphology such as spherical and fibrillar nanostructures could be controlled by adjusting the rod-coil block ratios. The heteroleptic complexes residing at the junction between two polymer blocks could be readily dissociated by EDTA to afford the unshelled P3HT nanofiber networks, and restored by treatment of bifunctional ZnII-terpyridine-capped PEO to redisperse the aggregates. The presented supramolecular methodology highlights the merits of complementary metal-ligand coordination, and offers a new approach to engineering nanostructures assembled from rod-coil block copolymers.

Annealing-free multi-thermal techniques comprising aging, cycling and seeding to enhance performance of thick P3HT:PCBM photovoltaic cells via developing hairy crystals

Distinct multi-thermal treatments comprising cycling, aging, and seeding were introduced to prepare very thick bulk heterojunction (BHJ) active layers (ca. 800nm) of poly(3-hexylthiophene) (P3HT):phenyl-C71-butyric acid methyl ester (PC71BM) photovoltaic cells. To this end, various P3HT48800-based rod-coil block copolymers having the coily blocks of polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(ethylene glycol) (PEG) were synthesized. The grazing incidence X-ray scattering, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) analyses proved that the dielectric coily blocks, which were excluded from the P3HT crystalline structure, accumulated on the crystals surface without decreasing the crystal quality and formed hairy crystals. The multi-thermal techniques facilitated stacking of the growth planes in π-π direction for the P3HT crystals, thereby, this dimension was improved from 5 to 27nm for conventionally prepared BHJs to 53–265nm for multi-thermally developed ones. The hydrophobic coily blocks were capable of neutralizing the influence of the PCBM molecules presence in the growth environment, which resulted in the larger P3HT crystals in a similar condition. By switching the conventional spin coating approach to the cycling, aging, and seeding methods, the P3HT crystals and the PCBM clusters were gradually coarsened and the respective d-spacings decreased. This trend enhanced the hole mobility (=8.8×10−5cm2/Vs), electron mobility (=2.5×10−3cm2/Vs), short circuit current density (Jsc=12.02mA/cm2), fill factor (FF=69%), and power conversion efficiency (PCE=4.39%) up to the maximum values for seeding approach. Moreover, the higher percentages of face-on orientation were detected in the BHJs with lower d-spacings in the hexyl side chain direction. Hairy P3HT48800-b-PS crystals developed by seeding method possessed the highest face-on orientation (~5.5%).

Block copolymer compatibilized polymer: fullerene blend morphology and properties

Recent studies have shown the role of block copolymer as compatibilizer in tuning the phase separated morphology of the active layer so as to improve the overall photovoltaic efficiency of organic photovoltaic (OPV) devices. Here, we substantiate this observation by investigating the role of a rod-coil block copolymer poly-(3-hexylthiophene)-b-polystyrene (P3HT-b-PS) as compatibilizer in influencing the blend morphology and device performance of several polymer:fullerene blend systems. Fullerene derivatives N-(3-methoxypropyl)-2-(carboxyethyl)-5-(4-cyanophenyl) fulleropyrrolidine (NCPF) and N-(3-methoxypropyl)-2-(carboxyethyl)-5-(5, 5-difluorobenzo-dioxole) fulleropyrrolidine (FFNCPF) were synthesized using Prato reaction, while P3HT-b-PS copolymer was synthesized using the combination of Grignard metathesis, ATRP, and click chemistry. The addition of P3HT-b-PS in P3HT:PCBM blend led to the formation of more homogenous structure compared to the pure P3HT:PCBM blend. Also, a reduction in domain size was observed in P3HT: FFNCPF system upon P3HT-b-PS addition which can be attributed to the compatibilization effect of BCP. Incorporation of P3HT-b-PS block copolymer was found to effectively alter the thin film nanostructure of polymer/fullerene derivative blends and polymer crystalline structure. Maximum enhancement in power conversion efficiency (PCE) of compatabilized P3HT:PCBM blend system was noticed followed by P3HT:FFNCPF and P3HT:NCPF. The moderate improvement in photovoltaic properties can be correlated with face-on orientation of P3HT crystallites and the segregation of the fullerene domains at the bulk heterojunction (BHJ) cathode interface which facilitates the efficient charge collection as respective electrodes.

Superhelices Self-Assembled from Polypeptide-Based Polymer Mixtures: Multistranded Features.

Poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers and poly(γ-benzyl-l-glutamate) (PBLG) homopolymers can cooperatively self-assemble into superhelical structures in aqueous solution. Herein, we discovered that the helices can have multiple strands with tunable characteristics. The strand number was dependent on the initial polymer concentration of the self-assembly, the self-assembly temperature, and the weight fraction of the block copolymers in the mixture. Higher initial polymer concentrations or lower weight fractions of the block copolymers induced the formation of helices with larger diameters and higher strand numbers, and helices prepared at higher temperatures had higher strand numbers. Based on an analysis of the correlation between the geometric parameters of the helices and the strand number, a possible mechanism for the formation of multistranded superhelices is suggested.

Exploiting Host–Guest Interactions for the Synthesis of a Rod–Rod Block Copolymer with Crystalline and Liquid‐Crystalline Blocks

AbstractBy making use of the host–guest interactions between the host molecule tris‐o‐phenylenedioxycyclotriphosphazene (TPP) and the rod–coil block copolymer (BCP) poly(ethylene oxide)‐block‐poly(octyl 4′‐octyloxy‐2‐vinylbiphenyl‐4‐carboxylate) (PEO‐b‐PVBP), the supramolecular rod–rod block copolymer P(EO@TPP)‐b‐PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid‐crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed. The self‐assembled nanostructure is thus clearly affected by the interplay between the two blocks. On the basis of wide‐ and small‐angle X‐ray scattering analysis, we conclude that the supramolecular rod–rod BCP can self‐assemble into a cylinder‐in‐cylinder double hexagonal structure.

Exploiting Host-Guest Interactions for the Synthesis of a Rod-Rod Block Copolymer with Crystalline and Liquid-Crystalline Blocks.

By making use of the host-guest interactions between the host molecule tris-o-phenylenedioxycyclotriphosphazene (TPP) and the rod-coil block copolymer (BCP) poly(ethylene oxide)-block-poly(octyl 4'-octyloxy-2-vinylbiphenyl-4-carboxylate) (PEO-b-PVBP), the supramolecular rod-rod block copolymer P(EO@TPP)-b-PVBP was constructed. It consists of a crystalline segment P(EO@TPP) with a hexagonal crystalline structure and a columnar nematic liquid-crystalline segment (PVBP). As the PVBP segments arrange themselves as columnar nematic phases, the crystalline structure of the inclusion complex P(EO@TPP), which has a smaller diameter, is destroyed. The self-assembled nanostructure is thus clearly affected by the interplay between the two blocks. On the basis of wide- and small-angle X-ray scattering analysis, we conclude that the supramolecular rod-rod BCP can self-assemble into a cylinder-in-cylinder double hexagonal structure.

Self-assembled block copolymer templates for atomic layer deposition: The effect of processing solvent

In this study thin films of a rod-coil block copolymer (BCP) are deposited from different solvents and used as templates for atomic layer deposition (ALD) of ZnO. The BCP, P3HT-b-PEO, is known to self-organize into fiber-like phase-separated nanostructures, with central crystalline P3HT domains and outer amorphous PEO domains. The P3HT block in this study is short so that the size of the P3HT domains in the films is solvent insensitive. However, processing from poor PEO solvents results in thin PEO domains and good PEO solvents allow extended PEO chains and wide domains. The crystallinity of the P3HT-block and the affinity of the PEO-block to the ALD ZnO precursors lead to selective deposition of ZnO in the PEO domains. Therefore, the solvent-controlled morphology of the PEO domains in the BCP films can be translated to the size, distribution and morphology of the deposited ZnO. We show that films with swollen PEO domains have higher ZnO uptake compared to films with collapsed PEO chains. Furthermore, oriented PEO domains template oriented ZnO domains and wormlike morphologies direct wormlike ZnO nanostructures. Therefore, solvent selection is a toll to manipulate the BCP self-assembly and hence the ALD template and the morphology of the hybrid organic/inorganic film.

High efficient and stabilized photovoltaics via morphology manipulating in active layer by rod-coil block copolymers comprising different hydrophilic to hydrophobic dielectric blocks

The poly(3-hexylthiophene) (P3HT)-based block copolymers were synthesized with hydrophilic and hydrophobic dielectric blocks including poly(ethylene glycol) (PEG), poly(methyl methacrylate) (PMMA), and poly(styrene) (PS), and employed as morphology modifiers (10–80wt%) in P3HT: phenyl-C71-butyric acid methyl ester (PC71BM) bulk heterojunction (BHJ) solar cells. The advantages and drawbacks of the coily blocks were also outlined from perspective of photovoltaic characteristics. A novel matrix-bridged disperses model was proposed to map out well-connected BHJ networks, which was consistent with the scattering data. Rod-coil block copolymers simultaneously controlled some main properties, i.e., crystallinity, d-spacing, domain sizes, and stability. Hydrophobic-based block copolymers (P3HT-b-PS and P3HT-b-PMMA) increased crystallinity, P3HT crystallite size, and PC71BM cluster size and decreased d-spacings. This reflected larger and denser P3HT crystallites and coarser and more packed PC71BM clusters. P3HT crystallites grew up to ∼60 and 30nm in (100) and (020) directions, respectively. In 30wt% of P3HT7150-b-PS, PC71BM clusters were also the largest (=38.87nm). A fully interdigitated hexyl chains (10.05Å) was acquired in 80wt% of P3HT7150-b-PS. Impressing trends of the P3HT-b-PMMA copolymers resembled that of P3HT-b-PS ones, but with a smoother slope. In contrast, hydrophilic-based block copolymers (P3HT-b-PEG and P3HT-b-PEG-b-P3HT) resulted in finer and looser P3HT crystallites and PC71BM clusters. The largest d-spacings in the directions of the hexyl side chains (=19.97Å) and π-π stacking (=4.95Å) were detected in 80wt% of P3HT7150-b-PEG750. The lowest (=3.51Å) and highest (=5.63Å) d-spacings for PC71BM clusters appeared in 80wt% of P3HT7150-b-PS and P3HT7150-b-PEG750, respectively. Unlike PEG-based block copolymers, in P3HT-b-PS and P3HT-b-PMMA ones, lower P3HT molecular weights conduced to higher power conversion efficiencies (PCE=4.43%). The short current density (Jsc=11.68mA/cm2), open circuit voltage (Voc=0.63V), and fill factor (FF=63%) were maximized in well-modified photovoltaic devices.