Organic Block Copolymers Research Articles

An organic dielectric filler polyethylene glycol-polyaniline block copolymer with low-density used in PVDF-based composites

In order to meet the ever-increasing demand for lightweight and flexibility with the development of aeronautics, astronautics and wearable technology, dielectric ceramics are inappropriate for the polymer-based dielectric materials due to their high density. An organic semiconductor material polyethylene glycol-polyaniline multi-alternating block (more than triblock) copolymer (with a low density ∼ 0.9 g/cm3) was designed. This polymer had a good solubility in polar solvents (e.g. DMF and DMSO) which could provide it with a good processing performance and a good dispersion in PVDF matrix. Its alternating block structure had a special role in the charge transport of PANI segments, providing composites with high dielectric constant and overcoming the poor breakdown strength problem of conductive filler-based dielectric composites, even better than BaTiO3. The breakdown strength of PEG-PANI/PVDF composite was 10.74 kV/mm and the dielectric constant was 86.64 (100 Hz) at 20 vol%, better than BaTiO3/PVDF (9.89 kV/mm and 45.23).

The application of organic polyethylene glycol-polyaniline multi-alternating block (more than triblock) copolymer in polymer-based dielectric composites

Due to their high density, dielectric ceramics are no longer appropriate for the areas with a light weight demand such as aeronautics, astronautics and wearable devices. In order to meet the ever-increasing demand for lightweight and flexibility dielectric composites, an organic semiconductor material linear polyethylene glycol-polyaniline multi-alternating block (more than triblock) copolymer (with low density) was designed based on the Williamson ether synthesis. FT-IR, 1HNMR, XRD, DSC and TG results confirmed the success of the synthesis. Its SEBS-based dielectric composites behavior was studied. The results indicated that the copolymer not only possessed a lighter density (~0.9 g/cm3) compared with ceramics (~6–8 g/cm3), but also exhibited better dielectric performances as a dielectric filler. The dielectric constant was 14.52 at a content of 11.5 vol% and the breakdown strength was 33.12 KV·mm−1, compared to ceramic BaTiO3 composite having 9.03 and 20.09 KV·mm−1

Multiscale simulation and kinetic network model analysis of the self-assembly of amphiphilic systems

Amphiphilic building blocks play an important role in fabricating nanomaterials. To achieve the precise control of self-assembled nanostructures, it is important to understand the self-assembly process at both microscopic and mesoscopic scale. Multiscale simulations could simulate the self-assembly process in both microscopic and mesoscopic scale, and get the metastable and equilibrium assembled structures and the corresponding trajectories. Based on these trajectories, we can further build the kinetic network model and obtain the kinetic transition pathway of the self-assembly process. This approach provides the theoretical principles for designing novel self-assembly building blocks and achieving novel self-assembled structures. In this article, we review our recent progress on the study of mechanisms of self-assembly of amphiphilic building blocks, such as small organic molecules, block copolymers and patchy particles by combining multiscale simulation and kinetic network model analysis.

Synthesis and Formation Mechanism of All-Organic Block Copolymer-Directed Templating of Laser-Induced Crystalline Silicon Nanostructures.

This report describes the generation of three-dimensional (3D) crystalline silicon continuous network nanostructures by coupling all-organic block copolymer self-assembly-directed resin templates with low-temperature silicon chemical vapor deposition and pulsed excimer laser annealing. Organic 3D mesoporous continuous-network resin templates were synthesized from the all-organic self-assembly of an ABC triblock terpolymer and resorcinol-formaldehyde resols. Nanosecond pulsed excimer laser irradiation induced the transient melt transformation of amorphous silicon precursors backfilled in the organic template into complementary 3D mesoporous crystalline silicon nanostructures with high pattern fidelity. Mechanistic studies on laser-induced crystalline silicon nanostructure formation revealed that the resin template was carbonized during transient laser-induced heating on the milli- to nanosecond timescales, thereby imparting enhanced thermal and structural stability to support the silicon melt-crystallization process at temperatures above 1250 °C. Photoablation of the resin material under pulsed excimer laser irradiation was mitigated by depositing an amorphous silicon overlayer on the resin template. This approach represents a potential pathway from organic block copolymer self-assembly to alternative functional hard materials with well-ordered 3D morphologies for potential hybrid photovoltaics, photonic, and energy storage applications.

One-step preparation of polyimide-inlaid amine-rich porous organic block copolymer for efficient removal of chlorophenols from aqueous solution

A novel polyimide-inlaid amine-rich porous organic block copolymer (PI-b-ARPOP) was prepared via one-step polymerization by using different molar ratios of melamine (MA)/terephthalaldehyde (TA)/pyromellitic dianhydride (PMDA), at molar ratios of 4/3/1, 4/2/2 and 4/1/3. The copolymer contained both aminal groups belonging to ARPOP and imide groups belonging to PI, and the bonding styles of the monomers and growth orientations of the polymeric chains were diversiform, forming an excellent porous structure. Notably, MA/TA/PMDA (4/2/2) had a surface area and pore volume of 487.27 m2/g and 1.169 cm3/g, respectively. The adsorption performance of the materials towards 2,4-dichlorophenol (2,4-DCP) in ultra-pure water was systematically studied. The pH value of 7 was optimal in aqueous solution. Na+ and Cl− ions did not negatively affect the adsorption process, while humic acid (HA) slightly decreased the capacity. The equilibrium time was 40 sec, and the maximum adsorption capacity reached 282.49 mg/g at 298 K. The removal process was endothermic and spontaneous, and the copolymer could maintain its porous structure and consistent performance after regeneration by treatment with alkali. Moreover, to further assess the practical applicability of the material, the adsorption performance towards 2,4-DCP in river water was also investigated. This paper demonstrated that the PI-b-ARPOP can be an efficient and practical adsorbent to remove chlorophenols from aqueous solution.

Characterizing morphology in organic systems with resonant soft X-ray scattering

Resonant soft X-ray scattering (R-SoXS) has proven to be a highly useful technique for studying the morphology of soft matter thin films due to the large intrinsic contrast between organic materials and the anisotropic nature of the resonant electronic state transitions from which the contrast originates. This allows R-SoXS users to measure spatial composition correlations from crystalline and amorphous phases in heterogeneous organic samples, infer relative domain purity, and determine average local molecular ordering correlations. R-SoXS has been used to study the morphology of organic photovoltaics, organic thin film transistors, biological systems, and block copolymer engineering applications. The mesoscopic morphological information compliments molecular packing information determined with hard X-rays, so that complex structure–property relationships can be elucidated over a large range of length scales. Extensions of R-SoXS have also emerged that make use of more advanced sample setups or different experimental geometries than normal transmission, such as θ–2θ reflectivity or grazing incidence.

Directed Self-assembly of Topcoat-free, Integration-friendly High-^|^chi; Block Copolymers

To extend the scaling beyond the most widely used poly(styrene-b-methyl methacrylate) (PS-b-PMMA), organic high-χ block copolymers (BCPs) were developed. Vertically oriented BCP domains were obtained by simple coat and bake process without application of an additional layer of a topcoat material. In addition, process-friendly conditions including low bake temperature (< 200 °C) and short bake time (≤ 5 min) provided a simple scheme to integrate these high-χ block copolymers to standard lithography process and pre-patterns defined by 193i lithography. Successful demonstration of directed self-assembly of these high-χ block copolymers on 193i-defined guiding pre-patterns offers a simple route to access well-aligned perpendicular lamellae and cylinders with a pitch less than 20 nm.

Artificial reticular structure by continuous titanium oxide frameworks

A series of macroporous titania films were fabricated using spherical soft colloids of polystyrene-block-poly(oxyethylene) (PS-b-PEO) and the macrostructure was systematically varied from reticular to spherical and large spherical according to the synthetic conditions. This macroreticular structure, which has never been organized by templating with organic assemblies/aggregates to date, was obtained with the controlled condensation of oxide frameworks in the presence of the soft PS-b-PEO colloids. The formation of reticular type pores was very sensitive to the synthetic conditions, which were optimized one-by-one for improving this unique colloidal PS-b-PEO templating approach for the precise structural design of inorganic oxide film as a more extendable method. Such spaces in the artificial reticular structure by continuous titania frameworks were designed in the range of macroscale to mesoscale. Accordingly, a new family of reticular type porous materials, which are suitable as porous platforms with very high surface area and allow smooth/rapid diffusion of targeted molecules, will be provided by this colloidal templating approach of organic block copolymer combined with the controlled condensation of frameworks for a variety of compositions.

Fast synthesis of an inorganic–organic block copolymer in a droplet-based microreactor

In this report, we used a non-lithographic embedded template method to fabricate a polyvinyl silane (Kion) microfluidic device. The device possesses a good solvent resistance, thermal stability and air-impermeability. The device was used for the synthesis of an inorganic–organic block copolymer through the generation and merging of reactant droplets. The SP-b-PMMA block copolymer was synthesized successfully by the atom transfer free radical polymerization (ATRP) process with a high conversion and narrow polydispersity in a very short reaction time, about ten minutes. The results obtained using the droplet-based microreactor were much better than those obtained with a macroscale batch reactor. Moreover, the as-synthesized SP-b-PMMA block copolymer was used to generate a highly ordered self-assembled ceramic pattern hence demonstrating the high quality of the block copolymer with superior molecular weight distribution control.

Synthesis, characterization and morphological studies of some novel siloxane-based block copolymeric materials containing organometallic as well as organic polyesteramides

A series of semi-aromatic diamine monomers (1,m-bis (4-amino benzoyloxy) alkanes; m = 2–6) having in-built ester linkages with variable methylene spacers were synthesized in two steps from aliphatic diols and p-nitrobenzoyl chloride and characterized by their melting points, elemental analysis, FTIR, 1H and 13C NMR spectroscopic studies. The diamines were then polymerized in-situ with ferrocene-based organometallic and terephthaloyl- as well as isophthaloyl-based organic acyl chlorides along with telechelic polydimethylsiloxane oligomer to produce a novel set of ferrocene-containing siloxane-based block copolymers and their organic analogues. The corresponding polyesteramides of the synthesized copolymers, without siloxane segment, were also prepared for comparative studies. The structural features of the organometallic and organic block copolymers along with their respective polyesteramides were confirmed by their physical properties and spectroscopic studies. The molecular parameters of all these materials were determined by static laser light scattering (LLS) technique and glass transition temperatures (Tg) were obtained by differential scanning calorimetry (DSC). The materials were soluble in sulphuric acid and partially soluble in common organic solvents at room temperature, yet become readily soluble upon N-trifluoroacetylation. The morphological information of the synthesized materials was obtained by X-ray diffraction and surface studies (SEM and AFM).

Length Control and Block-Type Architectures in Worm-like Micelles with Polyethylene Cores

We present evidence for "living"-like behavior in the crystallization-driven self-assembly of triblock copolymers with crystallizable polyethylene middle blocks into worm-like crystalline-core micelles (CCMs). A new method of seed production is introduced utilizing the selective self-assembly of the triblock copolymers into spherical CCMs in appropriate solvents. Seeded growth of triblock copolymer unimers from these spherical CCMs results in worm-like CCMs with narrow length distributions and mean lengths that depend linearly on the applied unimer-to-seed ratio. Depending on the applied triblock copolymer, polystyrene-block-polyethylene-block-polystyrene (SES) or polystyrene-block-polyethylene-block-poly(methyl methacrylate) (SEM), well-defined worm-like CCMs with a homogeneous or patch-like corona, respectively, can be produced. In a subsequent step, these worm-like CCMs can be used as seeds for the epitaxial growth of a different polyethylene containing triblock copolymer. In this manner, ABA-type triblock co-micelles containing blocks with a homogeneous polystyrene corona and those with a patch-like polystyrene/poly(methyl methacrylate) corona were prepared. While the epitaxial growth of SEM unimers from worm-like SES CCMs with a homogeneous corona yields triblock co-micelles almost quantitatively, the addition of SES unimers to patchy SEM wCCMs results in a mixture of ABA- and AB-type block co-micelles together with residual patchy wCCMs. Following reports on self-assembled block-type architectures from polymers containing core-forming polyferrocenylsilane blocks, these structures represent the first extension of the concept to block co-micelles from purely organic block copolymers.

Synthesis and characterization of organic-inorganic hybrid block copolymers containing a fully condensed ladder-like polyphenylsilsesquioxane

A series of inorganic–organic hybrid block copolymers were synthesized via atom transfer radical polymerization using a fully condensed, ladder-like structured polyphenylsilsesquioxane end-functionalized macroinitiator. The inorganic portion, ladder-like polyphenylsilsesquioxane, was synthesized in a one-batch, base-catalyzed system, whereas organic hard and soft monomers, styrene, and n-butyl acrylate, were polymerized and copolymerized on the ends of the linear, inorganic backbone. Synthesized hybrid diblock, triblock, and random copolymers were characterized by 1H NMR, 29Si NMR, gel permeation chromatography, static light scattering, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. Hybrid block copolymers were well-defined with low polydispersity (<1.4) and exhibited enhanced thermal properties in the form of increased glass transition and degradation onset temperatures over their organic analogues.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Study on the preparation and properties of novel block copolymeric materials based on structurally modified organometallic as well as organic polyamides and polydimethylsiloxane

AbstractSome novel ferrocene‐containing polyamide‐based block copolymer materials with telechelic polydimethylsiloxane oligomer and their organic analogues were prepared by solution‐phase polycondensation of ferrocene‐based organometallic and terephthaloyl‐ as well as isophthaloyl‐based organic acyl chlorides with a series of semi‐aromatic diamines having ether linkages together with variable aliphatic character. The corresponding polyamides of the synthesized materials, without polydimethylsiloxane segment, were also prepared for comparison of physicochemical properties. None of the synthesized organometallic and organic block copolymers along with their respective polyamides melted below 300 °C and their structural features were confirmed by their physical properties and spectroscopic studies. The weight‐average molecular weights and molecular parameters of all these materials were determined by the static laser light scattering technique. The materials were soluble in sulfuric acid and partially soluble in common organic solvents, and yet became readily soluble upon N‐trifluoroacetylation. The synthesized materials were further characterized by their water absorption characteristics, X‐ray diffraction studies and surface morphology (SEM and AFM) and thermal (DSC and TG) analyses, and their structure–property relationships were elucidated from these studies. The energies of pyrolysis for these materials were calculated by the Horowitz and Metzger method. © 2012 Society of Chemical Industry

Synthesis and characterization of mesoporous zirconium oxide thin films

Zirconium oxide (ZrO2) has generated wide interest because of its potential in applications such as solid oxide fuel cells, catalysts and optical devices. In these applications, it is important to control the grain size of the material and increase the surface area by introducing porosity with tailored pore size. This paper presents a synthesis route for the preparation of mesoporous zirconia using spin-coating method combined with block copolymer templating evaporation induced self assembly (EISA). The hybrid mesophase was formed by zirconium oxychloride precursor ZrOCl2·8H2O and Brij 700 poly-ethylene oxide based block copolymer template C18H37(OCH2CH2). FT-IR and Raman measurements of the hybrid mesophase provided information on the possible intermolecular interactions between the precursor and the copolymer template. The results indicate a weak ion-dipole interaction between the inorganic precursor and the organic template after the solvent evaporation, possibly directly between the zirconium and the oxygen of the poly-ethylene oxide chain. The removal of the organic block copolymer by heat treatment resulted in mesoporous zirconia with pore size of ~4-8 nm and crystalline grain size of ~10-17 nm. The morphology in thin films depended significantly on the solvent quality and the block copolymer concentration. Tailoring the surface morphology and the grain size resulted in super-hydrophilic mesoporous zirconia thin films in contrast to water contact angle of 50° on conventional tetragonal zirconium oxide.

In this issue

AbstractCress caps: Who's in command of what?pp. 406–416Common garden cress (Lepidium sativum) is a reasonably close kin to Arabidopsis thaliana, close enough to serve as a large‐scale (20×) germination model, readily dissected to study biological processes genetically defined by the genomic sequence of A. thaliana. Müller et al. set out to explore the inner secrets of germination and seedling establishment using complementary features of the two plants. The two‐step germination procedure begins with the rupture of the maternal testa, which reveals the endosperm cap that covered the radicle. The second step is the rupture of the endosperm cap by the radicle. Proteomic evaluation of the process revealed that the endosperm cap is not a food storage organ but a regulatory structure, dealing with stress and heat shock proteins, antioxidants, gluconeogenesis and glycolysis. magnified imageProtein purification faces a mesoporous age: Personalized protein–peptide fractionationpp. 496–505A chronic researcher complaint about mass spectrometric analysis of bodily fluids is the limited range of concentrations that can be handled. “All they want is 10 orders of magnitude.” Would it be ok if they were served up in segments? Bouamrani et al. use mesoporous silica chips to fractionate plasma peptides and proteins into groups by size, physical and chemical characteristics. These chips have pore size ranges determined by tri‐block copolymers. A mix of silica sol‐gel and selected organic block copolymer is spun onto the surface of a silicon wafer. After a series of heating and washing steps, the organic copolymer is removed, leaving pores of a specified size range that can retain and store compatible peptides and proteins. For this proof of principle test, 26 standard peptides and proteins were diluted into serum. Neurotensin could be detected at 2 ng/mL in serum. magnified imageFace to face – Serum versus plasma, marker versus markerpp. 532–540Let's face it – we all run into situations we're not quite prepared for, otherwise we wouldn't have “reality” television programs. A situation proteomic researchers encounter when working with blood samples is the choice of extracting markers from serum or plasma. Schwenk et al. explored the differences in protein and peptide intensity profiles for markers extracted from plasma and serum using magnetic antibody bead arrays. Plasma and serum were identical for 79% of antibodies by this assay, but these were not identical faces – they could be grouped by donor‐specific and sample‐type subgroups. magnified image

Cover Picture: Proteomics 3'10

AbstractCress caps: Who's in command of what?Common garden cress (Lepidium sativum) is a reasonably close kin to Arabidopsis thaliana, close enough to serve as a large‐scale (20×) germination model, readily dissected to study biological processes genetically defined by the genomic sequence of A. thaliana. Müller et al. set out to explore the inner secrets of germination and seedling establishment using complementary features of the two plants. The two‐step germination procedure begins with the rupture of the maternal testa, which reveals the endosperm cap that covered the radicle. The second step is the rupture of the endosperm cap by the radicle. Proteomic evaluation of the process revealed that the endosperm cap is not a food storage organ but a regulatory structure, dealing with stress and heat shock proteins, antioxidants, gluconeogenesis and glycolysis.Müller, K. et al., Proteomics 2010, 10, 406–416.Protein purification faces a mesoporous age: Personalized protein–peptide fractionationA chronic researcher complaint about mass spectrometric analysis of bodily fluids is the limited range of concentrations that can be handled. “All they want is 10 orders of magnitude.” Would it be ok if they were served up in segments? Bouamrani et al. use mesoporous silica chips to fractionate plasma peptides and proteins into groups by size, physical and chemical characteristics. These chips have pore size ranges determined by tri‐block copolymers. A mix of silica sol‐gel and selected organic block copolymer is spun onto the surface of a silicon wafer. After a series of heating and washing steps, the organic copolymer is removed, leaving pores of a specified size range that can retain and store compatible peptides and proteins. For this proof of principle test, 26 standard peptides and proteins were diluted into serum. Neurotensin could be detected at 2 ng/mL in serum.Bouamrani, A. et al., Proteomics 2010, 10, 496–505.Face to face – Serum versus plasma, marker versus markerLet's face it – we all run into situations we're not quite prepared for, otherwise we wouldn't have “reality” television programs. A situation proteomic researchers encounter when working with blood samples is the choice of extracting markers from serum or plasma. Schwenk et al. explored the differences in protein and peptide intensity profiles for markers extracted from plasma and serum using magnetic antibody bead arrays. Plasma and serum were identical for 79% of antibodies by this assay, but these were not identical faces – they could be grouped by donor‐specific and sample‐type subgroups.Schwenk, J. M. et al. Proteomics 2010, 10, 532–540.

Environment-sensitive stabilisation of silver nanoparticles in aqueous solutions

We describe the preparation and characterisation of inorganic–organic hybrid block copolymer silver nanoparticles via the preparation of spherical multi-responsive polymeric micelles of poly( N-methyl-2-vinyl pyridinium iodide)- block-poly(ethylene oxide), P2MVP 38- b-PEO 211 and poly(acrylic acid)- block-poly(isopropyl acrylamide), PAA 55- b-PNIPAAm 88 in the presence of AgNO 3. Hence, the P2MVP and PAA segments were employed to fix Ag + ions within the micellar core (25 °C) or shell (60 °C), while the PEO segments ensured spontaneous reduction of Ag + ions into metallic Ag, as well as colloidal stabilisation. Spherical and elongated composite core–shell(–corona) nanoparticles (CNPs) were formed containing several small, spherical silver nanoparticles within the micellar core or shell. As the co-assembly of the oppositely charged copolymers into micelles is electrostatically driven, the CNPs can be destabilised by, for example, addition of simple salts, i.e., the CNPs are stimuli responsive. CNP size and morphology control can be achieved via the preparation protocol. For example, heating to 60 °C, i.e., above the PNIPAAm LCST, results in core–shell–corona CNPs with the Ag-NPs situated in the aggregate shell.

Hierarchical Porous Silica Films with Ultralow Refractive Index

Fabrication of hierarchical porous thin films with controlled pore dimension and shape is a current challenge in materials science. In this work, bimodal hierarchical hybrid organic−inorganic thin films with pores in the meso and macro range have been fabricated. The first order of porosity is obtained through a self-assembly process using organic block copolymers as templates for mesopores; the mesophase in the films is well-ordered and has a tetragonal symmetry. We have introduced fluorinated organic nanoparticles of around 70 nm in the precursor solution to act as template of the second order of porosity. The introduction of the nanoparticles has not affected the organization of the mesophase and after the film deposition the nanoparticles become randomly dispersed within the mesostructured matrix. The organization of the mesophase has been studied in situ by small-angle X-ray scattering using synchrotron light; conventional and high-resolution transmission electron microscopy have been used for direct...

Direct Preparation of High Surface Area Mesoporous SiC-Based Ceramic by Pyrolysis of a Self-Assembled Polycarbosilane-block-Polystyrene Diblock Copolymer

Direct pyrolysis of a self-assembled inorganic−organic block copolymer can be a promising route for fabricating the ordered ceramic nanostructures based on the achievements of organic−organic block copolymers. Here we report the synthesis of a novel polycarbosilane-block-polystyrene diblock copolymer by ring-opening living anionic polymerization in a THF and n-hexane solvent system at −48 °C. The resulting block copolymer revealed phase-separation behavior in the nanoscale to form a self-assembled nanostructure that was converted to a mesoporous ceramic phase after heating at 800 °C. The pyrolyzed ceramic product exhibited well-ordered mesoporous SiC-based ceramic structures with a high BET surface area of 1325 m2 g−1 and an average mesopore size of 7.8 nm containing a large amount of micropores.

Self-assembly of an organic–inorganic block copolymer for nano-ordered ceramics

Self-assembly is a promising approach for achieving controlled nanoscale architectures in ceramics. The addition of ceramic-forming precursors to templating agents such as self-assembled surfactants or organic block copolymers (BCPs) has thus far been the primary route to forming ordered nanoporous oxides1,2,3,4,5 and nanostructured non-oxide ceramics6,7,8,9. In spite of its viability, however, this approach has several intrinsic shortcomings, including: (1) stringent requirements for amphiphilicity between template and precursor, lack of which may lead to macro-phase separation and loss of nano-scale order; (2) morphologies that can change uncontrollably with varying amounts of added ceramic precursor. Here we report a novel single-source ceramic precursor, based on a hybrid organic–inorganic BCP of polynorbornene–decaborane, that enables the formation of ordered ceramic nanostructures with tunable morphology and composition. In particular, we describe the synthesis of nanostructured boron carbonitride and mesoporous boron nitride, the latter of which exhibits the highest reported surface area for this material to date.