Diblock Copolymer Poly Research Articles

Low molecular weight PEG-PLGA polymers provide a superior matrix for conjugated polymer nanoparticles in terms of physicochemical properties, biocompatibility and optical/photoacoustic performance.

The near-infrared absorbing conjugated polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) has been investigated as a contrast agent for optical and photoacoustic imaging. Lipophilic π-conjugated polymers can be efficiently encapsulated within self-assembling diblock copolymer poly(ethylene glycol) methyl ether-block-poly(lactide-co-glycolide) (PEG-PLGA) nanoparticles, although the effect of variations in PEG and PLGA chain lengths on nanoparticle properties, performance and biocompatibility have not yet been investigated. In this study, PEG-PLGA with different block lengths (PEG2kDa-PLGA4kDa, PEG2kDa-PLGA15kDa and PEG5kDa-PLGA55kDa) were used to encapsulate PCPDTBT. Nanoparticle sizes were smallest (<100 nm) when using PEG2kDa-PLGA4kDa, with <5% PCPDTBT content and a reduction in the total solids concentration of the organic phase. All PEG-PLGA nanoparticles were colloidally stable in water and serum-supplemented cell culture medium over 24 h at 37 °C, with slight evidence of protein surface adsorption. PEG2kDa-PLGA4kDa systems showed a threefold lower cytotoxicity (IC50 value) than the other two systems. Haemolytic activity was <2.5% for all systems and no platelet aggregation or inhibition of ADP-induced platelet aggregation was observed. Encapsulation of PCPDTBT within a PEG-PLGA matrix shifted fluorescence emission towards red wavelengths (760 nm in THF vs. 840 nm in nanoparticles) and reduced the quantum yield by 30-70-fold compared to THF. Nonetheless, PCPDTBT:PEG2kDa-PLGA4kDa systems had a marginally higher quantum yield and signal-to-background ratio in a phantom mouse compared with PEG2kDa-PLGA15kDa and PEG5kDa-PLGA55kDa systems. As a photoacoustic imaging probe, PCPDTBT:PEG2kDa-PLGA4kDa systems also showed a higher photoacoustic amplitude compared to higher molecular weight PEG-PLGA systems. Overall, the low molecular weight PEG2kDa-PLGA4kDa nanoparticle systems conferred the benefits of smaller sizes, reduced cytotoxicity and enhanced imaging performance compared to higher molecular weight matrix polymers.

Aggregation in Biocompatible Linear Block Copolymers: Computer Simulation Study

The self-organization of molecules of linear diblock copolymer poly(ethylene oxide)–polylactide and triblock copolymer polylactide–poly(ethylene oxide)–polylactide in aqueous solution is studied by the dissipative particle dynamics method, and quantitative comparison with the experimental data is performed. It is shown that the diblock copolymers are aggregated to spherical micelles, their average aggregation number increases with increasing both polymer concentration and hydrophobic block length. For the given type of molecules, the simulation results agree well with the experiment. For the case of triblock copolymers it is predicted that stable supramolecular aggregates of various morphologies exist in solution even at low concentrations.

FRET Reveals the Formation and Exchange Dynamics of Protein-Containing Complex Coacervate Core Micelles.

The encapsulation of proteins into complex coacervate core micelles (C3Ms) is of potential interest for a wide range of applications. To address the stability and dynamic properties of these polyelectrolyte complexes, combinations of cyan, yellow, and blue fluorescent proteins were encapsulated with cationic-neutral diblock copolymer poly(2-methyl-vinyl-pyridinium)128-b-poly(ethylene-oxide)477. Förster resonance energy transfer (FRET) allowed us to determine the kinetics of C3M formation and of protein exchange between C3Ms. Both processes follow first-order kinetics with relaxation times of ±100 s at low ionic strength (I = 2.5 mM). Stability studies revealed that 50% of FRET was lost at I = 20 mM, pointing to the disintegration of the C3Ms. On the basis of experimental and theoretical considerations, we propose that C3Ms relax to their final state by association and dissociation of near-neutral soluble protein–polymer complexes. To obtain protein-containing C3Ms suitable for applications, it is necessary to improve the rigidity and salt stability of these complexes.

Mesoporous Metallic Iridium Nanosheets.

Two-dimensional (2D) metals are an emerging class of nanostructures that have attracted enormous research interest due to their unusual electronic and thermal transport properties. Adding mesopores in the plane of ultrathin 2D metals is the next big step in manipulating these structures because increasing their surface area improves the utilization of the material and the availability of active sites. Here, we report a novel synthetic strategy to prepare an unprecedented type of 2D mesoporous metallic iridium (Ir) nanosheet. Mesoporous Ir nanosheets can be synthesized with close-packed assemblies of diblock copolymer (poly-(ethylene oxide)- b-polystyrene, PEO- b-PS) micelles aligned in the 2D plane of the nanosheets. This novel synthetic route opens a new dimension of control in the synthesis of 2D metals, enabling new kinds of mesoporous architectures with abundant catalytically active sites. Because of their unique structural features, the mesoporous metallic Ir nanosheets exhibit a high electrocatalytic activity toward the oxygen evolution reaction (OER) in acidic solution as compared to commercially available catalysts.

Acid/light dual-responsive biodegradable polymeric nanocarriers for efficient intracellular drug delivery

A novel amphiphilic acid/light dual-cleavable diblock copolymer poly(e-caprolactone)-acetal-nitrobenzyl ester-poly(ethylene glycol) (PCL-PEG) was prepared via the ring-opening polymerization of e-caprolactone using 5-propargylether-2-nitrobenzyl alcohol as the initiator and subsequent “click” coupling reaction with azide-terminated poly(ethylene glycol) containing acetal group. Both light-cleavable o-nitrobenzyl methyl ester (ONB) and acid-labile acetal were used as the linkages in between the hydrophilic and hydrophobic polymer blocks. In aqueous solution, the copolymer self-assembled into the spherical polymeric nanoparticles, which were stable under physiological conditions and retained the anticancer drug doxorubicin (DOX) inside. Triggered by acid or UV irradiation, the DOX release rate was significantly enhanced, due to the correspondent degradation of acetal or ONB linkages under the stimulus. In addition, confocal laser scanning microscopy studies further demonstrated the DOX-loaded nanodrug could be efficiently taken up by HeLa cells and exhibited the enhanced DOX release into the cytoplasm upon UV irradiation. Furthermore, in vitro cytotoxicity study verified UV irradiation could improve the antitumor efficacy of the nanodrug against HeLa cells. Thus, this work provides a new method of the design of dual-responsive biodegradable polymers for drug delivery.

Influence of pH-Responsive Monomer Content on the Behavior of Di-Block Copolymers in Solution and as Stabilizers of Pickering Latex Particle Emulsifiers

In this study, diblock copolymers poly(methyl methacrylate)—block—poly (2-dimethylaminoethyl methacrylate) (pMMA-b-pDMAEMA) are investigated for the steric stabilization of latex particles and the subsequent use of these latex particles as Pickering emulsifiers. Solution properties of the diblock copolymers highlight that the pDMAEMA block length influences the critical micelle concentration (CMC) and micelle hydrodynamic diameter in response to changes in pH and the pKa. The block length can also be used as a way to control the particle size of sterically stabilized polystyrene latex particles prepared via emulsion polymerization. The suspension properties of these latex particles are also presented. Emulsion studies using these latex particles as emulsifiers show that both continuous phase pH and electrolyte concentration affect emulsion stability to coalescence. At high pH, stable emulsions are formed due to the affinity of the particles to the interface. At low pH, protonation of the amine groups reduces the affinity and thus droplet coalescence is observed. Increasing the electrolyte concentration improves emulsion stability, but causes an increase in droplet size due to adsorption of flocculated/aggregated particles. Finally, it is shown that these latex particles can be used in conjunction with membrane emulsification techniques to produce emulsions with low polydispersity.

Methyl Methacrylate HIPE Solely Stabilized by Fluorinated Di-block Copolymer for Fabrication of Highly Porous and Interconnected Polymer Monoliths.

Preparation of stable water-in-oil (W/O) high internal phase emulsion (HIPE) containing methyl methacrylate (MMA) monomer as oil phase is a difficult task due to the significant solubility of MMA in water. Here, for the first time a fluorinated di-block copolymer (FDBC) poly (2-dimethylamino)ethylmethacrylate-b-poly (trifluoroethyl methacrylate) (PDMAEMA-b-PTFEMA) is proposed to stabilize HIPEs of MMA without the use of any co-stabilizer or thickening agent. Fluorinated segments in FDBC anchored well at oil/water interface of HIPE, offering high hydrophobicity to the partially hydrophilic MMA monomer and in turn stabilization to MMA-HIPE. By using fluorinated di-block copolymer as stabilizer, highly stable HIPEs can be obtained. In addition, highly interconnected porous monoliths were obtained after free radical polymerization, which are highly desirable materials in various practical applications including tissue engineering scaffolds, separation science, bio-engineering and so on. The as-prepared MMA-HIPEs possess high thermal stability without phase separation. The textural characteristics of as-prepared composites, such as pore size and distribution, can be easily controlled by simply varying the amount of FDBC and/or dispersed phase fraction. Moreover, the influence of di-block concentration on water uptake (WU) capability of the prepared porous monoliths is explored.

Tuning of the Morphology and Optoelectronic Properties of ZnO/P3HT/P3HT- b-PEO Hybrid Films via Spray Deposition Method.

The self-assembly of amphiphilic diblock copolymers yields the possibility of using them as a template for tailoring the film morphologies of sol-gel chemistry-derived inorganic electron transport materials, such as mesoporous ZnO and TiO2. However, additional steps including etching and backfilling are required for the common bulk heterojunction fabrication process when using insulating diblock copolymers. Here, we use the conducting diblock copolymer poly(3-hexylthiophene)- block-poly(ethylene oxide) (P3HT- b-PEO) in which P3HT acts as charge carrier transport material and light absorber, whereas PEO serves as a template for ZnO synthesis. The initial solution is subsequently spray-coated to obtain the hybrid film. Scanning electron microscopy and grazing-incidence small-angle X-ray scattering measurements reveal a significant change in the morphology of the hybrid films during deposition. Optoelectronic properties illustrate the improved charge separation and charge transfer process. Both the amount of the diblock copolymer and the annealing temperature play an important role in tuning the morphology and the optoelectronic properties. Hybrid films being sprayed from a solution with the ratio of ωZnO, ωP3HT, and ωP3HT- b-PEO of 2:1:1 and subsequent annealing at 80 °C show the most promising morphology combined with an optimal photoluminescence quenching. Thus, the presented simple, reagent- and energy-saving fabrication method provides a promising approach for a large-scale preparation of bulk heterojunction P3HT/ZnO films on flexible substrates.

Multifunctional Nanoplatform Based on pH-responsive Micelle Coated with Discontinuous Gold Shell for Cancer Photothermo-chemotherapy and Photoacoustic Tomography

Photothermo-chemotherapy, as a new strategy for cancer treatment, incorporates the complementary advantages of photothermal therapy and chemotherapy. In this study, a pH-sensitive diblock copolymer poly(aspartic acid-butanediamine)-poly(2-(diisopropylamino)ethyl methacrylate) (PAsp(DAB)-PDPA) was synthesized and self-assembled into doxorubicin-loaded micelle, which was further used as a template to form a gold nanoshell. After further modification with poly(ethylene glycol), the resulting nanoplatform provided good biocompatibility and desirable photo-thermal conversion efficiency to facilitate photothermal therapy. Meanwhile the nanoparticle also exhibited pH sensitivity, which prevented drug loss while circulating in the blood but enabled rapid drug release after endocytosis. An improved effect was achieved with the combination of photothermal therapy and chemotherapy. In addition, systemic delivery of the nanoplatform could be monitored by photoacoustic tomography. Thereby, this multifunctional nanoplatform would be highly potential for the diagnosis and therapy of cancer.

A pH-responsive prodrug delivery system self-assembled from acid-labile doxorubicin-conjugated amphiphilic pH-sensitive block copolymers

The development of intelligent drug delivery system that can efficiently deliver doxorubicin (DOX) to tumor site with controlled drug release performance and enhanced therapeutic efficacy is of great significance for cancer chemotherapy. In this report, a nano-prodrug system was prepared successfully by conjugating DOX to pH-sensitive amphiphilic diblock copolymer poly (ethylene glycol) methyl ether‑b‑poly (β‑amino esters) through acid-labile cis‑aconityl moiety (mPEG-b-PAE-cis-DOX). The resultant complex copolymer-drug was able to self-assemble into polymeric micelles (PMs) in an aqueous solution at low concentration, and the critical micelle concentration (CMC) was 3.6 mg/L which was increased as decrease of pH value. H-nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR), dynamic light scattering (DLS), transition electron microscopy (TEM), and classic acid-base titration were combined to confirm and characterize the chemical structure of the copolymer/drug conjugates and the physicochemical properties of the prodrug system. The DOX loading capacity, drug delivery and therapeutic efficacy of the conjugates were evaluated in vitro and in vivo. Notably, the antitumor experiments in tumor-bearing mice demonstrated that the pH-responsive nano-prodrug system effectively enhanced the therapeutic efficacy in comparison to free drug. All above results suggested that pH-responsive prodrug system has the potential to be effective carrier for the DOX delivery and pH-triggered controlled release.

Glycocalyx-Mimicking Nanoparticles Improve Anti-PD-L1 Cancer Immunotherapy through Reversion of Tumor-Associated Macrophages.

Immune checkpoint blockade by anti-PD-L1 monoclonal antibody (αPD-L1) has achieved unprecedented clinical benefits in certain cancers, whereas the therapeutic efficacy is often hindered by immunosuppressive tumor microenvironment mediated by tumor-associated macrophages (TAMs), which leads to innate resistance to this approach. To improve checkpoint blockade efficacy, the amphiphilic diblock copolymers poly(mannopyranoside/galactopyranoside methacrylate)- block-polystyrene are prepared by RAFT polymerization, which are sequentially self-assembled into glycocalyx-mimicking nanoparticles (GNPs) to neutralize TAMs. It is shown that GNPs can be specifically internalized by TAMs via lectin receptors, which results in upregulation of immunostimulatory IL-12 and downregulation of immunosuppressive IL-10, arginase 1, and CCL22, indicating functional reversion of protumor TAMs toward antitumor phenotype. The reversion of TAMs is proved to be mainly controlled by suppressing STAT6 and activating NF-κB phosphorylation. In vivo therapeutic studies have demonstrated that GNPs significantly enhance the therapeutic efficacy of αPD-L1 cancer therapy by reduction of tumor burden. Moreover, combination therapies with GNPs and αPD-L1 greatly improve immunosuppressive tumor microenvironment by reciprocal modulation of tumor-infiltrating effector and regulatory T cells. Notably, for the first time, our results demonstrate the reversion of TAMs and improvement of αPD-L1 cancer therapy by synthetic carbohydrate-containing nanomaterials. This research highlights a promising strategy for optimizing immune checkpoint blockade in cancer immunotherapy.

Synthesis of poly(N-isopropylacrylamide-b-N-vinylcarbazole) copolymers via RAFT polymerization and its stimuli responsive morphology in aqueous media

Here, we report the successful synthesis of series of stimuli responsive amphiphilic diblock copolymers (SRABCs) poly(N-isopropylacrylamide-b-N-vinylcarbazole) [poly(NIPAAm-b-NVK)] through reversible addition fragmentation chain transfer (RAFT) polymerization. Copolymers with fixed hydrophilic [poly(NIPAAm)] block length and variable (with three different) hydrophobic [poly(NVK)] block lengths were synthesized and the block length ratio was confirmed from their molecular weight data. The self-assembly nature of synthesized block copolymers was confirmed by determining critical micelle concentration (CMC). Self-assembled block copolymers showed rice-grain like morphology for copolymers having equivalent hydrophobic/hydrophilic chain length but in case of block copolymers having smaller and bigger hydrophobic chain length with respect to hydrophilic chain length displayed vesicular morphology. The thermo and pH responsiveness of the block copolymers was found to be influenced by variation in length and chemical composition of the blocks. Due to their thermo and pH responsiveness resulted self-assembled structures underwent morphology transitions from vesicular and rice grain like to micellar structure in aqueous medium. The probable applications of the studied stimuli responsive amphiphilic diblock copolymers can be found in the nanotechnology and biotechnology are indicated.

Synthesis of temperature, pH, light and dual-redox quintuple-stimuli-responsive shell-crosslinked polymeric nanoparticles for controlled release

Herein, we prepared a novel quintuple-stimuli-responsive shell-crosslinked (SCL) nanocontainer in respond to temperature, pH, light, and oxidation or reduction species. The well-defined amphiphilic diblock copolymer poly(2-methacryloyloxyethyl ferrocenecarboxylate)-(5-propargylether-2-nitrobenzyl bromoisobutyrate)-poly(dimethylaminoethyl methacrylate) (PMAEFc-ONB-PDMAEMA) was synthesized via atom transfer radical polymerization (ATRP) and click chemistry. The diblock copolymer self-assembled into spherical micelles with a uniform size in aqueous media as non-crosslinked (NCL) micelles, and then the micelles were crosslinked by N,N′-bis(bromoacetyl) cystamine (BBAC) through quaternization reaction between the nitrogen of DMAEMA and the bromine of BBAC to receive the SCL micelles which shrunk at higher temperature, swelled at acidic pH or a low concentration of hydrogen peroxide (H2O2), decrosslinked by a small amount of DL-dithiothreitol (DTT), and were disrupted with DTT and UV light. The multi-stimuli-sensitive properties of the SCL micelles were characterized in detail by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence spectra, and UV–Vis spectra. Owing to the protective effect of the crosslinked network, light response behaviors of the NCL and SCL micelles were different. In contrast to the single stimulus, the combined stimuli could trigger and regulate the release of hydrophobic drug model more effectively and precisely from the SCL micelles. The obtained multi-stimuli-responsive nanocontainers may lead to a new generation of controlled release in the fields of nanotechnology and biotechnology.

Morphologies and dielectric properties of epoxy thermosets containing poly(N-vinylcarbazole), fullerene-C60 and their charge transfer complex nanophases

Both poly(ethylene oxide)-block-poly(N-vinylcarbazole) (PEO-b-PVK) diblock copolymer and fullerene-capped poly(ethylene oxide) (PEO-C60) were synthesized in this work. The former was obtained via reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate process whereas the latter via click reaction of azido-capped poly(ethylene oxide) with fullerene-C60. Both of the amphiphiles were incorporated into epoxy to obtain the nanostructured thermosets. It was found that the PVK-C60 charge transfer complexes were formed in the ternary thermosetting blends of epoxy, PEO-b-PVK and PEO-C60. The nanostructured epoxy thermosets containing PVK or/and fullerene displayed the enhanced dielectric constants whereas the dielectric loss remained almost unchanged. Nonetheless, the dielectric constants were significantly decreased while both PEO-b-PVK and PEO-C60 were simultaneously incorporated into the thermosets. The depression in dielectric constant is attributable to the formation of the charge transfer complexes of PVK with fullerene-C60. It was found that the dielectric constants can be modulated with the contents of the PVK-C60 charge transfer complexes.

Synthetic Polymeric Mixed Micelles Targeting Lymph Nodes Trigger Enhanced Cellular and Humoral Immune Responses.

It has been widely accepted that lymph nodes (LNs) are critical targets of cancer vaccines because antigen presentation and initiation of T-cell-mediated immune responses occur primarily at these locations. In this study, amphiphilic diblock copolymer poly(2-ethyl-2-oxazoline)-poly(d,l-lactide) (PEOz-PLA) combined with carboxylterminated-Pluronic F127 was used to construct mixed micelles [carboxylated-nanoparticles (NPs)] for codelivery of antigen ovalbumin (OVA) and Toll-like receptor-7 agonist CL264 (carboxylated-NPs/OVA/CL264) to the LN-resident dendritic cells (DCs). The results showed that the small, sub-60 nm size of the self-assembled mixed micelles enables them to rapidly penetrate into lymphatic vessels and reach draining lymph nodes after subcutaneous injection. Furthermore, the surface modification with carboxylic groups imparted the carboxylated-NPs with endocytic receptor-targeting ability, allowing for DC internalization of carboxylated-NPs/OVA/CL264 via the scavenger receptor-mediated pathway. Because stimulation of CL264 in early endosomes will lead to a more effective immune response than that in late endo/lysosomes, the mass ratio of PEOz-PLA to carboxylated-Pluronic F127 in the mixed micelles was adjusted to release the encapsulated CL264 to the early endosome, resulting in increased expression of costimulatory molecules and secretion of stimulated cytokines by DCs. Moreover, the incorporation of PEOz outside the micellar shell effectively augmented MHC I antigen presentation through facilitating endosome escape and cytosolic release of antigens. This in turn evoked potent immune responses in vivo, including activation of antigen-specific T-cell responses, production of antigen-specific IgG antibodies, and generation of cytotoxic T-lymphocyte responses. Finally, immunization with the codelivery system in E.G7-OVA tumor-bearing mice could not only significantly inhibit tumor growth but also markedly prolong the survival of tumor-bearing mice. Taken together, carboxylated-NPs/OVA/CL264 have demonstrated great potential for clinical applications as an effective antitumor vaccine for further immunotherapy.

Effect of morphology on interactions between nanoparticle-stabilised air bubbles and oil droplets.

High-speed video analysis has enabled the interaction between a pair of millimetre-sized air bubbles to be studied in aqueous solution. The bubbles were grown in the presence of either poly(glycerol monomethacrylate)-poly(benzyl methacrylate) (PGMA-PBzMA) diblock copolymer spheres or poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) (PGMA-PHPMA-PBzMA) triblock copolymer worms prepared by polymerisation-induced self-assembly (PISA). A reduction in interfacial tension relative to air bubbles grown in the absence of nanoparticles indicated the adsorption of nanoparticles at the air-water interface. A concentration of 0.01% w/v PGMA-PBzMA spheres conferred air bubble stability after just 30 s interfacial ageing with stirring, whereas 300 s ageing was required for worms to prevent coalescence at the same copolymer concentration. However, longer coalescence times with interfacial age suggested greater worm adsorption on the air bubbles during this period. In striking contrast, although stable millimetre-sized n-dodecane droplets were obtained in the presence of 0.01% w/v copolymer worms, the copolymer spheres did not prevent coalescence at this low concentration. Finally, the multiphase interaction and stability of immiscible fluids in the presence of either spheres or worms was assessed. More specifically, an n-dodecane oil droplet and an air bubble were grown separately in the presence of either the spheres or worms and then brought into contact. In the absence of any nanoparticles, aqueous film drainage resulted in the formation of a compound droplet consisting of an air lens on the oil droplet. In the presence of 0.01% w/v nanoparticles, ageing times of either 30 s or 120 s were required to prevent formation of compound droplets when using spheres and worms, respectively. Moreover, this asymmetric system required much shorter ageing times in the presence of adsorbed nanoparticles to gain stability compared to either the symmetric air bubble or oil droplet systems. This stability is attributed to a bridging nanoparticle monolayer between the oil droplet and the air bubble.

Folic Acid Modified Polymeric Micelles for Intravesical Instilled Chemotherapy

In this study, a targeting micellar drug delivery system was developed for intravesical instilled chemotherapy of bladder cancer. The amphiphilic diblock copolymer poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL-b-PEO) with functional amino group (NH2) at the end of PEO block was synthesized. Then the copolymer was conjugated with folic acid (FA) and fluorescein isothiocyannate (FITC) via the PEO-NH2 terminus, and then assembled into micelles with the target moiety and fluorescence labeling. In addition, drug loaded micelles were also fabricated with anticancer drug doxorubicin (DOX) encapsulated in the hydrophobic core. The micelles were characterized in terms of size, drug loaded efficiency and critical micellization concentration (CMC) by means of DLS, UV and fluorescence spectra. In vitro cellular uptake and cytotoxicity studies showed that FA modified PCL-b-PEO-FA micelles have a greater targeting efficiency to human bladder cancer cell (T-24 cell) compared to PCL-b-PEO-NH2 micelles due to the conjugation of FA on the surface, while no targeting effect to normal tissue originated human embryonic kidney 293 (HEK-293) cells was observed, enabling the micelles a promising drug carrier for intravesical instilled chemotherapy of bladder cancer.

Diblock Copolymer PF-b-PDMAEMA as Effective Cathode Interfacial Material in Polymer Solar Cells.

An alcohol-soluble diblock copolymer poly[2,7-(9,9-dihexylfluorene)]15-block-poly[2-(dimethylamino)ethyl methacrylate]75 (denoted as PF15-b-PDMAEMA75) was employed as the cathode interfacial layer (CIL) in p-i-n polymer solar cells (PSCs). PF15-b-PDMAEMA75 contains a conjugated rigid block and a nonconjugated flexible block grafted with polar amino groups, and it can effectively lower the work function of the Al cathode and decrease the series resistance of the devices. When applied as the CIL in PSCs based on poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophenediyl]]:[6,6]-phenyl C71 butyric acid methyl ester, the champion power conversion efficiency of 8.80% was achieved, which is slightly higher than that of the PSCs using the well-known poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] as CIL under our experimental conditions, and much better than that of PSCs using Ca as CIL. The improvement of the performance is mainly attributed to the enhanced open-circuit voltage and fill factor. To the best of our knowledge, this is the first time a diblock copolymer has been used as a CIL in PSCs, and this study may provide a novel avenue for the design and synthesis of interfacial materials for high-performance PSCs.

Complex Morphology of the Intermediate Phase in Block Copolymers and Semicrystalline Polymers As Revealed by 1H NMR Spin Diffusion Experiments

Nanostructured multiphase polymers exhibiting a mobile and a rigid phase also contain a phase of intermediate mobility that is usually assumed to be a continuous, uninterrupted interphase layer. This assumption is contrary to recent molecular-resolution micrographs and contradicts results from NMR spin diffusion experiments, all of which suggest a nontrivial interface structure. In this contribution, we reconsider our previous 1H NMR spin diffusion data sets (Roos Colloid. Polym. Sci. 2014, 292, 1825) and perform optimized 2D and 3D numerical spin diffusion calculations to characterize the basic intermediate-phase morphological pattern, thus overcoming previous inconsistencies in data fitting. For the diblock copolymer poly(butadiene)-poly(styrene), PS-b-PB, we demonstrate that the interphase region comprises nanometer-size intermixed immobile, intermediate and mobile subregions. In contrast, for the semicrystalline polymer poly(e-caprolactone), PCL, the spin diffusion data are best reproduced by an inter...

Synthesis of Poly(methylene-b-ε-caprolactone) and Poly(ε-caprolactone) with Linear Alkyl End Groups: Synthesis, Characterization, Phase Behavior, and Compatibilization Efficacy

Diblock copolymers of poly(methylene-b-e-caprolactone) (PM-b-PCL) were synthesized in two steps: (a) polyhomologation, to obtain, following oxidative cleavage of the carbon–boron (PM, block1), an α-hydroxyl-ω-methyl polymethylene (PMOH, CH3–[CH2]m–OH) and, following the transfer reaction to the ring-opening polymerization catalyst, (b) ring-opening polymerization (ROP) of e-caprolactone (CL) (PCL, block2). In addition, a series of homopolymers derived from poly(e-caprolactone) (PCL) oligoesters containing an end group of docosyl (CH3–[CH2]21– or C22; C22–PCL) were obtained as a model to compare their physical properties by DSC with those of PM-b-PCL. The oligomers derived from PM-b-PCL and C22–PCL were characterized by 1H and 13C NMR, AFM, DSC, GPC, and MALDI-TOF. PM-b-PCL and C22–PCL were evaluated as compatibilizers for PE/PCL polymer blends. Identification and analysis of optimized blocks of PM-b-PCL by POM and SEM showed improved mixing of PE/PCL blends.