Hybrid Block Copolymers Research Articles

A new strategy for fabricating organic photovoltaic devices with stable D/A double-channel network to enhance performance using self-assembling all-conjugated diblock copolymer

In this study, we demonstrate the cooperative self-assembly of [6,6]-phenyl C61-butyric acid methyl ester (PCBM) and an all-conjugated poly(2,5-dihexyloxy-p-phenylene)-b-poly(3-hexylthiophene) (PPP-P3HT) block copolymer to yield organic photovoltaic devices with enhanced solar cell performance and long-term stability. By a combination of TEM, GISAXS and GIWAXS structural investigations, it was found that a PPP-P3HT/PCBM hybrid film adopts a donor/acceptor (D/A) double-channel network (DCN) structure via simple spin-coating by self-organizing highly ordered and long-ranged crystalline P3HT nanofibrils as a hole-transporting channel, and the surrounding amorphous PPP domain with PCBM confined and dispersed within as the other electron-transporting channel. As a consequence of the structural development, the block copolymer hybrid solar cells could afford significant improvements in the charge transporting property and enhanced exciton separation, leading to a substantial improvement in the power conversion efficiency (PCE) of the resulting device. The photovoltaic devices with the DCN structure gave a high average PCE of 3.43% as compared to only 2.77% from a conventional P3HT/PCBM bulk heterojuction (BHJ) solar cell. Notably, the DCN solar cell showed significant improvements in thermal stability over the P3HT/PCBM BHJ solar cell in accelerated testing experiments. This enhancement is believed to be due to the nanoconfinement effect of the double-channel structure on the PCBM molecules, thereby averting PCBM aggregation problems typically occurring in BHJ devices. These results show promise for the practical usage of all-conjugated block copolymers with different main chain moieties towards the fabrication of organic photovoltaic devices with superior stability and competitive optoelectronic properties.

Nanoparticle-Driven Assembly of Highly Conducting Hybrid Block Copolymer Electrolytes

Hybrid nanostructured materials comprising block copolymers, nanoparticles, and lithium salts have the potential to serve as electrolytes in non-flammable rechargeable lithium batteries. Here we show that the addition of functionalized nanoparticles, at an optimized concentration, into lamellar block copolymer electrolytes, results in an increase in ionic conductivity. This is due to the occurrence of a lamellar-to-bicontinuous phase transition, driven by the addition of nanoparticles. The magnitude of the increase in conductivity is consistent with a simple model that accounts for the morphology of the conducting channels. The conductivity of the optimized hybrid electrolyte is only 6% lower than that of an idealized nanostructured electrolyte with perfectly connected conducting pathways and no dead ends.

Synthesis and Application of Protein-Containing Block Copolymers.

Proteins possess an impressive array of functionality ranging from catalytic activity to selective binding and mechanical strength, making them highly attractive for materials engineering. Conjugation of synthetic polymers to proteins has the potential to improve the physical properties of the protein as well as provide functionality not typically found in native proteins, such as stimuli-responsive behavior and the programmable ability to self-assemble. This viewpoint discusses the design of protein-polymer conjugates, an important class of block copolymers. Use of these hybrid molecules in biological and catalytic applications is highlighted, and the ability of the polymer to direct the solution and solid-state self-assembly of the hybrid block copolymers is reviewed. Future challenges in polymer and material science that will enable these hybrid molecules to reach their potential as protein-based materials are outlined.

Sub-20 nm Microphase-Separated Structures in Hybrid Block Copolymers Consisting of Polycaprolactone and Maltoheptaose

The present review summarizes our recent results regarding the synthesis and morphological characterization of sugar-based hybrid block copolymers (BCPs) consisting of maltoheptaose (MH) and poly(ε-caprolactone) (PCL). The AB-, AB2-, AB3-, ABA-, and A2B-type BCPs, in which the A and B blocks are MH and PCL, respectively, were synthesized by combining the living polymerization and click reaction. The in-situ small angle X-ray scattering experiments revealed the formation of ordered microphase-separated structures with a sub-20 nm periodicity.

A poly(polyoxometalate)-b-poly(hexanoic acid) block copolymer: synthesis, self-assembled micelles and catalytic activity

A poly(polyoxometalate)-polymer hybrid block copolymer (H-BCP) was preparedviaring-opening metathesis polymerization (ROMP). The H-BCP self-assembles into hybrid micelles with a poly(polyoxometalate) shell and a polymer core in acetonitrile.

Composite Block Copolymer Electrolytes for Lithium Metal Batteries

Lithium metal has been widely investigated for next generation rechargeable batteries due to its extremely high theoretical specfic capacity. However, lithium dendrite formation at the lithium metal anode-electrolyte interfaces is considered to be one of major factors in deteriorating the performance of lithium metal batteries. To suppress the lithium dendrite growth, solid polymer electrolytes (SPE) with high mechanical strength and electrochemical stability have been studied to replace liquid electrolyte. In this case, using SPE in lithium metal batteries, low ionic conductivity and high interfacial resistance of SPEs are still remained critical problems. In order to achieve the high ionic conductivity and mechanical strength simultaneously in solid polymer electrolytes for lithium metal batteries, we applied block copolymer (BCP) composed of structural and ionic conducting domains in this study. In addition, we fabricated organic/inorganic hybrid block copolymer composite electrolytes with ionic liquids and nanoparticles for improving ionic conductivity and mechanical strength. The effects of composite block copolymer electrolytes were evaluated in terms of ionic conductivity as well as mechanical strength. In addition, interfacial resistance and ESW (electrochemical stability window) were also performed to understand the functions of hybrid components. In particular, these properties could be crucially affected by change of composition of block copolymer and hybrid components, which resulted in the different behavior inside polymer matrix and interface between electrode/electrolyte.

Synthesis and self-assembly of well-defined elastin-like polypeptide-poly(ethylene glycol) conjugates.

A series of stimulus-responsive elastin-like polypeptide-poly(ethylene glycol) (ELP-PEG) block copolymers was synthesized. The polymeric building blocks were conjugated via the efficient and specific strain-promoted alkyne-azide cycloaddition (SPAAC). For this purpose, ELP and PEG blocks were functionalized with azide and cyclooctyne moieties, respectively. Azides were introduced by applying a recently developed pH-controlled diazotransfer reaction on the primary amines present in ELP (N-terminus and lysine side chains). By varying pH, ELP-blocks with one or two azides were obtained, which subsequently allowed us to synthesize both ELP-PEG diblock copolymers and miktoarm star polymers. Triggering the phase transition of the ELP-block resulted in the formation of an amphiphilic block copolymer, which self-assembled into micelles. This is the first example of an ELP-containing hybrid block copolymer in which PEG as the hydrophilic corona-forming domain is combined with a stimulus-responsive ELP-block. The encapsulation of a hydrophobic fluorescent dye was shown to exemplify the potential of the micelles to serve as nanocarriers for hydrophobic drugs, with the PEG corona providing stealth and steric protection of encapsulated materials.

Preparation and characterization of poly(ethylene glycol)-block-poly[ε-(benzyloxycarbonyl)-l-lysine] thin films for biomedical applications

The nanoscale architectures evident in the thin films of self-assembling hybrid block copolymers—which are tailored to inherit the advantageous properties of their constituent synthetic (homo)polymer and polypeptide blocks—have continued to inspire a variety of new applications in different fields, including biomedicine. The thin films of symmetric hybrid block copolymer, α-methoxy-poly(ethylene glycol)-block-poly[e-(benzyloxycarbonyl)-l-lysine], MPEG112-b-PLL(Z)17, were prepared by solvent casting in five different solvents and characterized using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy, Thermogravimetric analysis, Derivative Thermogravimetric analysis, Differential Scanning Calorimetry, Contact Angle goniometry, Wide-Angle X-ray Diffraction, and Scanning Electron Microscopy. Film thickness was estimated to be 51 ± 23 μm by the “step-height” method, using a thickness gauge. Although no significant change to the block copolymer’s microstructure was observed, its solvent-cast films displayed divergent physical and thermal properties. The resulting cast films proved more thermally stable than the bulk but indicated greater block miscibility. Additionally, the thin films of MPEG112-b-PLL(Z)17 preserved the microphase separation exhibited by the bulk copolymer albeit with appreciable loss of crystallinity. The surface properties of the polymer–air interface were diverse as were the effects of the casting solvents. Oriented equilibrium morphologies are also evident in some of the as-cast thin films.

Long‐Range Ordered Self‐Assembly of Novel Acrylamide‐Based Diblock Copolymers for Nanolithography and Metallic Nanostructure Fabrication

Novel acrylamide-based hard-soft hybrid block copolymers generate high-quality nanolithographic patterns satisfying high-resolution, long-range ordering, low defect density, moderate etch selectivity, and easy pattern transfer onto a substrate. The resulting patterns can also be used as a scaffold for metallic nanostructures such as aligned nanowires and nanomeshes with extraordinary structural regularity.

Side-Chain Amino-Acid-Based pH-Responsive Self-Assembled Block Copolymers for Drug Delivery and Gene Transfer

Developing safe and effective nanocarriers for multitype of delivery system is advantageous for several kinds of successful biomedicinal therapy with the same carrier. In the present study, we have designed amino acid biomolecules derived hybrid block copolymers which can act as a promising vehicle for both drug delivery and gene transfer. Two representative natural chiral amino acid-containing (l-phenylalanine and l-alanine) vinyl monomers were polymerized via reversible addition-fragmentation chain transfer (RAFT) process in the presence of monomethoxy poly(ethylene glycol) based macro-chain transfer agents (mPEGn-CTA) for the synthesis of well-defined side-chain amino-acid-based amphiphilic block copolymers, monomethoxy poly(ethylene glycol)-b-poly(Boc-amino acid methacryloyloxyethyl ester) (mPEGn-b-P(Boc-AA-EMA)). The self-assembled micellar aggregation of these amphiphilic block copolymers were studied by fluorescence spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Potential applications of these hybrid polymers as drug carrier have been demonstrated in vitro by encapsulation of nile red dye or doxorubicin drug into the core of the micellar nanoaggregates. Deprotection of side-chain Boc- groups in the amphiphilic block copolymers subsequently transformed them into double hydrophilic pH-responsive cationic block copolymers having primary amino groups in the side-chain terminal. The DNA binding ability of these cationic block copolymers were further investigated by using agarose gel retardation assay and AFM. The in vitro cytotoxicity assay demonstrated their biocompatible nature and these polymers can serve as "smart" materials for promising bioapplications.

Multicolor Emission: Multicolor Emission of Hybrid Block Copolymer–Quantum Dot Microspheres by Controlled Spatial Isolation of Quantum Dots (Small 16/2013)

Multicolor Emission: Multicolor Emission of Hybrid Block Copolymer–Quantum Dot Microspheres by Controlled Spatial Isolation of Quantum Dots (Small 16/2013)

Synthesis of Polypeptide Block Copolymer Hybrids by the Combination of N‐Carboxyanhydride Polymerization and RAFT

The synthesis of hybrid bioconjugates via the ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs) using a synthetic macroinitiator is described. Poly(n-butyl acrylate), polystyrene, and poly(N-isopropyl acrylamide) are synthesized (polydisperity index,Đ < 1.1) using reversible addition-fragmentation chain transfer (RAFT) as the synthetic tool. A phthalimidomethyl trithiocarbonate RAFTchain transfer agentis used to prepare well-defined, end-functional polymers, which after deprotection result in amine terminal macroinitiators. The subsequent initiating systems could successfully be chain extended with ε-benzyloxycarbonyl-l-lysine or γ-benzyl-l-glutamate as the NCAs to produce a library of polymer-polypeptide conjugates. In doing so, a novel procedure for directly synthesizing bioconjugates via a non-modular route without the need for excessive purification and isolation steps is described.

Multifunctional Poly(ethylene glycol): Synthesis, Characterization, and Potential Applications of Dendritic–Linear–Dendritic Block Copolymer Hybrids

Emerging dendritic-linear-dendritic (DLD) hybrids that possess synergetic properties of linear and highly functional branched dendritic polymers are becoming important macromolecular scaffolds in f ...

Hybrid Block Copolymers Constituted by Peptides and Synthetic Polymers: An Overview of Synthetic Approaches, Supramolecular Behavior and Potential Applications

Hybrid block copolymers based on peptides and synthetic polymers, displaying different types of topologies, offer new possibilities to integrate the properties and functions of biomacromolecules and synthetic polymers in a single hybrid material. This review provides a current status report of the field concerning peptide-synthetic polymer hybrids. The first section is focused on the different synthetic approaches that have been used within the last three years for the preparation of peptide-polymer hybrids having different topologies. In the last two sections, the attractive properties, displayed in solution or in the solid state, together with the potential applications of this type of macromolecules or supramolecular systems are highlighted.

Multicolor Emission of Hybrid Block Copolymer–Quantum Dot Microspheres by Controlled Spatial Isolation of Quantum Dots

Multicolor emitting microspheres with three dimensionally controlled nanostructures are produced via a simple and efficient method. Location control and separation of the quantum dots (QDs) within the microspheres are achieved by a supramolecular assembly of block copolymer micelles to control the Förster resonance energy transfer efficiency between the different-colored QDs. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A one component methodology for the fabrication of honeycomb films from biocompatible amphiphilic block copolymer hybrids: a linear–dendritic–linear twist

The development of a facile method for the fabrication of breath figure (BF) films from hydrophobic polymers is gaining significant importance for their accessibility as templates in fields ranging from electronics and cell culturing to sensing and catalysis. By introducing polyester-based dendritic linkers, a library of micrometre sized honeycomb structures was successfully fabricated from amphiphilic linear–dendritic–linear hybrids comprising hydrophobic PCL or PLA and hydrophilic PEG blocks. From the array of produced films, the incorporation of a third generation dendritic linker was found to generate well-ordered honeycomb films in the several hundreds of micrometre range. This one component approach minimizes the number of unknown parameters and represents a fully reliable methodology for the fabrication of functional BFs from challenging and biocompatible polymers.

Organic/Inorganic Hybrid Block Copolymer Electrolytes with Nanoscale Ion-Conducting Channels for Lithium Ion Batteries

A series of organic/inorganic hybrid block and random copolymers were prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3-(3,5,7,9,11,13,15-heptaisobutylpentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1-yl)propyl methacrylate (MA-POSS) as monomers in order to study the effect of polymer morphology and POSS content on the properties of polymer electrolytes. Flexible and dimensionally stable free-standing films were made from the hybrid block and random copolymers mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) when the contents of MA-POSS unit were larger than 31 and 16 mol %, respectively. The ionic conductivity of the solid-state block copolymer (PBP) electrolyte was found to be 1 order of magnitude higher than that of the random copolymer (PRP) electrolyte when they had similar MA-POSS content, although their glass transition temperature values of their ion-conducting segments were quite clos...

Conformational and thermal analyses of α‐methoxy‐poly(ethylene glycol)‐block‐poly[ϵ‐(benzyloxycarbonyl)‐l‐lysine] hybrid block copolymers

AbstractHybrid block copolymers find applications in drug delivery, tissue engineering, biomimetics and bioimaging, amongst others, mainly due to their propensity to form phase‐separated microdomains as well as to the aggregation of their polypeptide segments. They not only enhance control over structure at the nanometre scale but also yield materials that can interface with various biosystems for different utilities. α‐Methoxy‐poly(ethylene glycol)‐block‐poly[ϵ‐(benzyloxycarbonyl)‐l‐lysine] hybrid block copolymers of varying degrees of polymerization, MPEGn‐b‐PLL(Z)m, were synthesized by N‐carboxyanhydride ring‐opening polymerization and characterized using infrared and NMR spectroscopy and gel permeation chromatography. Their secondary structures and bulk conformations were investigated using circular dichroism spectroscopy and wide‐angle X‐ray diffraction, respectively, whereas thermogravimetric analysis (TGA), derivative TGA and differential scanning calorimetry were employed for thermal analyses. The resulting block copolymers exhibited microphase separation and suppressed degrees of crystallinity with increasing l‐lysine content and adopted α‐helix and β‐sheet secondary structures in aqueous milieu. The copolymers were also more thermally stable than their constituent homopolymers. Interestingly, the effects of the retention of the Nϵ‐benzyloxycarbonyl moiety on polymer properties proved considerable. The hybrid block copolymers herein afforded hierarchical structures of potential utility in the biomedical and pharmaceutical fields. © 2012 Society of Chemical Industry

Facile fabrication of novel polyhedral oligomeric silsesquioxane/carboxymethyl cellulose hybrid hydrogel based on supermolecular interactions

Reactive octa-aminopropyl polyhedral oligomeric silsesquioxane (POSS-NH2) has a nano-sized structure with a cubic silica core and octa-aminopropyl groups distributed at eight corners. Carboxymethyl cellulose (CMC) is often used as a hydrogel polymer because of its water-solubility, renewability, biodegradability and biocompatibility. Novel POSS/CMC hybrid hydrogel was fabricatied here by the aggregation of POSS-NH2 nanoparticles and the formation of POSS-CMC hybrid block copolymers, which was driven by the hydrogen bonding interactions between the amino groups of POSS-NH2 and the carboxyl groups of CMC. d-(+)-gluconic acid δ-lactone (DGL) was used to alter the pH of the system which can further control the formation of hydrogen-bonding interactions. Our method provides a facile and effective route to fabricate novel hybrid hydrogel based on CMC or other cellulose derivatives.

Tunable Surface Properties from Sequence-Specific Polypeptoid–Polystyrene Block Copolymer Thin Films

Tunability of polymer surface properties depends crucially on both the chemical composition of the polymer and the physics of the chains (e.g., surface segregation, chain shape, etc.). Polypeptoids, which are non-natural biomimetic polymers based on an N-substituted glycine backbone, provide a flexible model system in which monomer sequence, chain shape, and self-assembled structure can easily be controlled to understand their influence on surface properties. We demonstrate the influence of the amount and sequence of hydrophobic monomers in a predominantly hydrophilic peptoid chain on the surface properties of a hybrid block copolymer, poly(peptoid-b-styrene). Just three fluorinated groups in peptoid sequences consisting of up to 45 hydrophilic monomers in length were needed to lower the surface energy of the peptoid and allow for its maximal surface segregation. Positioning these fluorinated groups in the middle of a chain as opposed to the chain ends resulted in a change in chain conformation at the sur...