P4VP Block Research Articles

Uniform Nanorods with Regioselective Distribution of Inorganic Nanoparticles Templated by 2D Block Copolymer Nanosheets.

The inorganic/organic hybrid materials with regioselective distribution of functional inorganic nanoparticles (NPs) have received constant interest attributed to fascinating integrated properties. However, there remains a formidable challenge in realizing the regioselective distribution of NPs for the specific hybrid nanorods. Herein, we report the construction of uniform core-shell hybrid nanorods with the regioselective distribution of inorganic NPs by selectively disassembling the prepared NPs/polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) hybrid nanosheets. Moreover, through precisely adjusting the parameters, such as complexation ability between the metal precursor and P4VP blocks, the protonation degree of P4VP blocks and complexation time, the NPs/polymer core-shell hybrid nanorod with the uniform distribution of NPs, and dumbbell-like hybrid nanorods with selective distribution of NPs at both ends can be obtained. This finding reveals a unique insight into the design of the anisotropic functional hybrid materials with the regioselective distribution of inorganic NPs.

Competitive hydrogen bonding induced phase separation in supramolecular comb-shaped diblock copolymer

In this study, a route to prepare nanostructure in miscible diblock copolymers by utilization of competitively intermolecular hydrogen-bonding interactions is demonstrated. Block copolymers poly(4-vinylpyridine-b-4-hydroxybutyl acrylate) (P4VP-b-P4HBA) with various block ratios were synthesized and they were demonstrated to be miscible due to the intramolecular hydrogen bonding. By combination of P4VP-b-P4HBA and 3-pentadecylphenol (PDP), the miscible block copolymer forms comb-shaped di-block copolymer complexes through the competition interactions between the hydroxyl groups of PDP (proton donors) and the nitrogen of the pyridine rings of the P4VP blocks (proton acceptors). Upon blending with PDP, we observed morphology change from sphere structure to cylindrical, and lamellar, in a manner strongly dependent on the P4HBA fraction. The microstructure of this special comb-shaped di-block copolymer shows a strong sensitivity to the temperature. The results from the in situ small angle X-ray scattering experiments have demonstrated that, even below the order-disorder temperature, the size of the phase domain decreases with increasing temperature due to decrease of the strength of the hydrogen bond upon heating.

Morphological transition and transformation of 2D nanosheets by controlling the balance of π-π stacking interaction and crystalline driving forces.

Nanoscale organic two-dimensional (2D) materials of block polymers (BCPs) have attracted interest on account of their wide potential applications in a range of fields. Herein, we design a new poly(p-phenylenevinylene) (PPV) based BCP that contains a triisopropylsilyl side chain and poly (2-vinyl pyridine) (P2VP) corona, which could assemble into a series of 2D square and rectangular micelles in isopropanol. The aspect ratios and the scales of the 2D micelles can be tuned in two ways, including altering the ratios of the P2VP and PPV-TIPS blocks and their concentrations. By precisely controlling the aspect ratios, micro-scale rod-like micelles are also obtained. From in depth studies of the morphology transition from rectangular micelles to rod-like or square micelles, it is found that the BCPs initially organize into fibers and then assemble into final micelles by the combined forces of π-π interactions and the crystalline force from TIPS side chains. Based on the balance of the two interactions, 2D circle-like micelles are also achieved by heterogenous co-assembly of two kinds of polymers with different cores.

Influence of Salt Doping on the Entropy‐Driven Lower Disorder‐to‐Order Transition Behavior of Poly(ethylene oxide)‐b‐Poly(4‐vinylpyridine)

AbstractPoly(ethylene oxide)‐b‐poly(4‐vinylpyridine) (PEO‐b‐P4VP) block copolymers (BCPs) exhibiting lower disorder‐to‐order transition (LDOT) phase behavior are doped with different salts (LiCl, CuCl2, and FeCl3), in which both blocks can competitively associate with the metal ions. It is found that the entropy‐driven LDOT phase behavior of PEO‐b‐P4VP can be bi‐directionally adjusted by enthalpic interactions, depending on the complexation selectivity of metal ions toward two blocks and doping ratio (r). At low rs, Li+ ions preferentially interact with PEO block, leading to a decreased disorder‐to‐order transition temperature (TDOT). Cu2+ ions selectively complex with the P4VP block, and the TDOT first increases with increasing r, followed by a decrease. By contrast, Fe3+ ions interact strongly with both blocks, resulting in increase of TDOT. At high rs, the complexation selectivity becomes weaker, leading to reduced immiscibility and increased TDOT, as compared with the hybrids with low rs. The effects of metal cation and r on the LDOT phase behavior are qualitatively explained by the change of the Flory–Huggins parameter.

Antithrombotic and hemocompatible properties of nanostructured coatings assembled from block copolymers

We describe the antithrombotic properties of nanopatterned coatings created by self-assembly of poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) with different molecular weights. By changing the assembly conditions, we obtained nanopatterns that differ by their morphology (size and shape of the nanopattern) and chemistry. The surface exposition of P2VP block allowed quaternization, i.e. introduction of positive surface charge and following electrostatic deposition of heparin. Proteins (albumin and fibrinogen) adsorption, platelet adhesion and activation, cytocompatibility, and reendothelization capacity of the coatings were assessed and discussed in a function of the nanopattern morphology and chemistry. We found that quaternization results in excellent antithrombotic and hemocompatible properties comparable to heparinization by hampering the fibrinogen adhesion and platelet activation. In the case of quaternization, this effect depends on the size of the polymer blocks, while all heparinized patterns had similar performance showing that heparin surface coverage of 40 % is enough to improve substantially the hemocompatibility.

Photonic Particles Made by the Confined Self-Assembly of a Supramolecular Comb-Like Block Copolymer.

Approaches that enable the preparation of robust polymeric photonic particles are of interest for the development of nonfading and highly reflective pigments for applications such as paints and display technologies. Here, the preparation of photonic particles that display structural color in both, aqueous suspension and the dry solid state is reported. This is achieved by exploiting the confined self-assembly of a supramolecular comb-like block copolymer (BCP) that microphase separates into a well-ordered lamellar morphology with dimensions that promote a photonic bandgap in the visible range. The comb-like BCP is formed by robust ionic interactions between poly(styrene-b-4-vinyl-pyridine) (PS-b-P4VP) BCP and dodecylbenzene sulfonic acid (DBSA), which selectively interacts with P4VP blocks. The components are combined in chloroform, and an aqueous emulsion is prepared. Evaporation of the organic solvent leads to the formation of solid microparticles with an onion-like 3D morphology. These photonic pigments display brilliant colors with reflectance spectra featuring pronounced optical bandgaps across the entire visible wavelength range with a peak reflectivity of 80-90%.

Highly Tunable Nanostructures in a Doubly pH‐Responsive Pentablock Terpolymer in Solution and in Thin Films

AbstractMultiblock copolymers with charged blocks are complex systems that show great potential for enhancing the structural control of block copolymers. A pentablock terpolymer PMMA‐b‐PDMAEMA‐b‐P2VP‐b‐PDMAEMA‐b‐PMMA is investigated. It contains two types of midblocks, which are weak cationic polyelectrolytes, namely poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(2‐vinylpyridine) (P2VP). Furthermore, these are end‐capped with short hydrophobic poly(methyl methacrylate) (PMMA) blocks in dilute aqueous solution and thin films. The self‐assembly behavior depends on the degrees of ionization α of the P2VP and PDMAEMA blocks, which are altered in a wide range by varying the pH value. High degrees of ionization of both blocks prevent structure formation, whereas microphase‐separated nanostructures form for a partially charged and uncharged state. While in solutions, the nanostructure formation is governed by the dependence of the P2VP block solubility of the and the flexibility of the PDMAEMA blocks on α, in thin films, the dependence of the segregation strength on α is key. Furthermore, the solution state plays a crucial role in the film formation during spin‐coating. Overall, both the mixing behavior of the 3 types of blocks and the block sequence, governing the bridging behavior, result in strong variations of the nanostructures and their repeat distances.

Electrolysis on a Chip with Tunable Thin Film Nanostructured PGM Electrocatalysts Generated from Self-Assembled Block Copolymer Templates.

Self-assembled block copolymers are promising templates for fabricating thin film materials with tuned periodic feature sizes and geometry at the nanoscale. Here, a series of nanostructured platinum and iridium oxide electrocatalysts templated from poly(styrene)-block-poly(vinyl pyridine) (PSbPVP) block copolymers via an incipient wetness impregnation (IWI) pathway is reported. Both nanowire and nanocylinder electrocatalysts of varying feature sizes are assessed and higher catalyst loadings are achieved by the alkylation of the pyridine moieties in the PVP block prior to IWI. Electrocatalyst evaluations featuring hydrogen pump and water electrolysis demonstrations are carried out on interdigitated electrode (IDE) chips flexible with liquid supporting electrolytes and thin film polymer electrolytes. Notably, the mass activities of the nanostructured electrocatalysts from alkylated block copolymer templates are 35%-94% higher than electrocatalysts from non-alkylated block copolymer templates. Standing cylinder nanostructures lead to higher mass activities than lamellar variants despite their not having the largest surface area per unit catalyst loading demonstrating that mesostructure architectures have a profound impact on reactivity. Overall, IDE chips with model thin film electrocatalysts prepared from self-assembled block copolymers offer a high-throughput experimental method for correlating electrocatalyst nanostructure and composition to electrochemical reactivity.

Synthesis and self-assembly of star multiple block copolymer of poly(4-vinylpyridine)-block-polystyrene

Star multiple block copolymer of poly (4-vinylpyridine)-block-polystyrene (s-P4VP-b-PS) is synthesized via initial synthesis of linear poly (4-vinylpyridine)-block-polystyrene (l-P4VP-b-PS) by dispersion RAFT polymerization to form l-P4VP-b-PS nano-assemblies and then cross-linking within the l-P4VP-b-PS nano-assemblies. The synthesized s-P4VP-b-PS has a high molecular weight and exists 25–47 nm nanospheres in the common solvent of N,N-dimethylformamide. The self-assembly of s-P4VP-b-PS in two block selective solvents, e.g., toluene and methanol, is investigated, and great difference from l-P4VP-b-PS is demonstrated. In methanol, s-P4VP-b-PS forms core-corona nanospheres. In toluene, s-P4VP-b-PS forms dispersed nanoparticles or nanoparticle clusters dependent on polymer concentration. In the s-P4VP-b-PS nanoparticle clusters, poly (4-vinylpyridine) forms dispersed nano-domains, the size of which is firmly dependent on the degree of polymerization of the P4VP block. It is thought that the great difference between s-P4VP-b-PS and l-P4VP-b-PS will arouse new interest on self-assembly of block copolymers.

Self-Assembly Behavior of PS-b-P2VP Block Copolymers and Carbon Quantum Dots at Water/Oil Interfaces

The interfacial assembly of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer and carboxylated carbon quantum dots (c-CQDs) at the water/oil interface and the morphology of the resu...

Conductive Thin Films over Large Areas by Supramolecular Self-Assembly.

We report a "one-step" method for preparing conductive thin films with cylindrical microdomains oriented normal to the surface over large areas using the supramolecular assembly of poly(styrene-block-4-vinylpyridine) (PS19-b-P4VP5) and 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine (HOTPP). HOTPP interacts with the P4VP block by hydrogen bonding between the hydroxyl group of HOTPP and pyridine ring of PS19-b-P4VP5, forming cylindrical P4VP(HOTPP) domains having an average diameter of ∼17 nm in a PS matrix. Dynamic light scattering, contact angle, and in situ grazing incidence small-angle X-ray scattering measurements show a morphological transition from spherical micelles in solution to cylindrical microdomains oriented normal to the substrate surface during the drying process. From the dependence of current on voltage, an average current of ∼4.0 nA is found to pass through a single microdomain, pointing to a promising route for organic semiconductor device applications.

Precisely Controlled Two-Dimensional Rhombic Copolymer Micelles for Sensitive Flexible Tunneling Devices

Nanoscale two-dimensional (2D) organic materials have attracted significant interest on account of their unique properties, which result from their ultrathin and flat morphology. Supramolecular 2D ...

When a pH-triggered nanopatterned shape transition drives the wettability of a hierarchically self-organized film: A bio-inspired effect of “sea Anemone”

HypothesisHierarchically structured surfaces including sensitive materials presents the advantage to exalt wettability variation due to the combination of micro structure effect directed by Cassie Baxter and/or Wenzel behaviour which is tuned by the surface energy variation of sensitive polymer films. ExperimentsHerein is reported the synthesis and the hierarchical structuration of a pH sensitive diblock copolymer P(S-stat-MMA)-b-P4VP with a pH-sensitive Poly 4-vinylpyridine P4VP block. Applying the Breath Figure method casting (minute time scale process), this diblock copolymer allows to obtain a micro porous honeycomb film while a wall nano-structuration due to self-assembly of diblock copolymer is observed. FindingsThe pH-triggered wettability is studied and correlated with the morphology evolution of P4VP nano-domains investigated by AFM in a liquid cell. Indeed, a nano-dots to nano-rings/donuts transition is highlighted when decreasing the pH below the pKa of the P4VP. This nano “sea Anemone” shape transition induces the macroscopic changes of the wettability of a hierarchically self-organized honeycomb film, explained by the protonation of P4VP chains inducing electrostatic repulsion and then hydrophilic surface.

Tunable Photonic Microspheres of Comb-Like Supramolecules.

Photonic crystals (PCs) are ideal candidates for reflective color pigments with high color purity and brightness due to tunable optical stop band. Herein, the generation of PC microspheres through 3D confined supramolecular assembly of block copolymers (polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP) and small molecules (3-n-pentadecylphenol, PDP) in emulsion droplets is demonstrated. The intrinsic structural colors of the PC microspheres are effectively regulated by tuning hydrogen-bonding interaction between P2VP blocks and PDP, where reflected color can be readily tuned across the whole visible spectrum range. Also, the effects of both PDP and homopolymer (hPS) on periodic structure and optical properties of the microspheres are investigated. Moreover, the spectral results of finite element method (FEM) simulation agree well with the variation of structural colors by tuning the periodicity in PC microspheres. The supramolecular microspheres with tunable intrinsic structural color can be potentially useful in the various practical applications including display, anti-counterfeit printing and painting.

Feature size control using surface reconstruction temperature in block copolymer lithography for InAs nanowire growth

Here we present a method to control the size of the openings in hexagonally organized BCP thin films of poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) by using surface reconstruction. The surface reconstruction is based on selective swelling of the P4VP block in ethanol, and its extraction to the surface of the film, resulting in pores upon drying. We found that the BCP pore diameter increases with ethanol immersion temperature. In our case, the temperature range 18 to 60 °C allowed fine-tuning of the pore size between 14 and 22 nm. A conclusion is that even though the molecular weight of the respective polymer blocks is fixed, the PS-b-P4VP pore diameter can be tuned by controlling temperature during surface reconstruction. These results can be used for BCP-based nanofabrication in general, and for vertical nanowire growth in particular, where high pattern density and diameter control are of importance. Finally, we demonstrate successful growth of indium arsenide InAs vertical nanowires by selective-area metal-organic vapor phase epitaxy (MOVPE), using a silicon nitride mask patterned by the proposed PS-b-P4VP surface reconstruction lithography method.

Janus Colloidal Dimer by Intramolecular Cross-Linking in Concentrated Solutions

We propose a new method to large-scale synthesize polymeric colloidal dimers by electrostatically-mediated intramolecular cross-linking of an example di-block copolymer of poly(isoprene)-b-poly(vinylpyridine) (PI-b-P4VP) in highly concentrated solutions. The synthesis is orthogonally performed in a highly polar solvent such as DMSO. The first colloid is achieved by intramolecular cross-linking of the PI block with 1,6-hexanediisothiocyanate after modification with 2-mercaptoethylamine hydrochloride to introduce an electrostatic interaction. The Janus single-chain nanoparticle of cPI-P4VP is derived. In the sequential step, the other colloid is achieved by intramolecular cross-linking the P4VP block of cPI-P4VP with 1,5-diiodopentane after modification with iodoethane. The polymer colloidal dimer of cPI-cP4VP is thus achieved. The Janus cPI-cP4VP dimer is composed of two different domains: the cPI containing residual amine and cyanate groups and the cP4VP containing residual pyridine and quaternized groups. The dimer can be synthesized at a higher concentration of 100 mg/mL. A huge family of functional colloidal dimers is expected after selectively loading materials within the desired colloidal domains.

Core-Cross-Linked Micelles Made by RAFT Polymerization with a Polycationic Outer Shell Based on Poly(1-methyl-4-vinylpyridinium)

A convergent synthesis of amphiphilic polymers with a polystyrene (PS) core and a polyelectrolytic poly(1-methyl-4-vinylpyridinium iodide) (P4VPMe+I–) shell is reported. The polymers were obtained by reversible addition–fragmentation chain transfer (RAFT) polymerization in water using a trithiocarbonate chain transfer agent [R0-SC(S)SPr, R0 = −C(Me)(CN)CH2CH2COOH]. Two types of particle structure, both having a spherical morphology and diameters in the 85–150 nm range, have been obtained as stable latexes with polymer content up to 10% in weight. The first structure consists of core-cross-linked micelles (CCMs), where amphiphilic P4VPMe+I–-b-PS arms are cross-linked at the hydrophobic end by the use of diethylene glycol dimethacrylate. The Coulombic repulsion between the outer shells of the precursor micelles ensures the absence of macrogelation during the cross-linking step. The second structure consists of nanogels (NGs), where the entire hydrophobic core is cross-linked during the last step of simultaneous chain extension and cross-linking of a P4VPMe+I–-b-PS intermediate with a short PS block. The lack of radical polymerization for the 4VPMe+I– monomer and the lack of chain extension with styrene for a R0-P4VPMe+I–-SC(S)SPr intermediate were circumvented by the synthesis of R0-P4VP-b-PS-SC(S)SPr containing a short PS block by sequential RAFT polymerization of 4-vinylpyridine (4VP) and styrene, followed by quantitative cationization of the P4VP block by MeI and subsequent sequential (for the CCMs) or simultaneous (for the NGs) chain extension and cross-linking.

Three-Dimensional Nanoporous Metal Structures from Poly(2-vinylpyridine)-block-Poly(4-vinylpyridine) Copolymer Thin Film.

We fabricated 3D nanoporous metal structures from poly(2-vinylpyridine)-block-poly(4-vinylpyridine) copolymer (P24VP) thin film with vertically oriented lamellar nanodomains by coordinating corresponding metal precursors followed by reduction to metals. Although metal precursors are coordinated with both P2VP and P4VP blocks, the metal coordination power toward P4VP block is much greater than that toward P2VP block. Thus, most of the metal precursors are located in the P4VP block, while a few exist in the P2VP block. After the metal precursors were reduced to corresponding metals by reactive ion etching, metals located in P4VP regions became continuous main frames. However, metals in P2VP regions could not be continuous because of smaller amounts, resulting in nanoporous structures. Using these 3D nanoporous structures, we measured the electrocatalytic activity for hydrogen evolution reaction. 3D nanoporous platinum (Pt) showed enhanced catalytic activity compared with Pt flat film due to the large surface area. Moreover, 3D nanoporous Pt/cobalt bimetallic structures showed better catalytic activity than 3D nanoporous Pt structures.

Europium based coordination polyelectrolytes enable core-shell-corona micelles as luminescent probes.

Core-shell-corona (CSC) micelles have multiple layers, which can serve as separate compartments. This property allows them to combine multiple functionalities in a single nanoparticle, with obvious application potential. Here, we propose a new type of CSC micelles with an apolar core and a polyelectrolyte complex shell incorporating coordination polymers. We obtain these particles by using a poly(styrene)-b-poly(vinyl pyridine)-b-poly(ethylene oxide) (PS-b-PVP-b-PEO) triblock copolymer with quaternized PVP blocks. This polymer leads to well-defined CSC micelles with a cationic shell, which allows us to entrap anionic coordination polymers without disturbing the micellar structure. Useful properties can be imported in this way, e.g., europium (Eu)-based coordination polymers endow the CSC micelles with strong luminescence. Moreover, copper ions (Cu2+) can quench the luminescence because they disturb the Eu-ligand coordination. Upon adding sulfide ions (S2-), copper ions precipitate as CuS and the Eu-ligand bond as well as the corresponding luminescence are restored. This effect is highly specific for Cu2+ and S2-: other cations or anions hardly interfere with this "on-off-on" luminescence response towards Cu2+ and S2-, demonstrating the selectivity of these CSC micelles as detectors of copper and sulfide ions.

Organic-Inorganic Nanocomposite Film for High-Performance Stretchable Resistive Memory Device.

A compatible organic/inorganic nanocomposite film for a stretchable resistive memory device with high performance is demonstrated using poly(4-vinylpyridine)-block-poly(propyl methacrylate) (P4VP-b-PPMA) with zinc oxide (ZnO) nanoparticle. The PPMA soft segment is designed for reducing the rigidity of the active layer, while the P4VP block serves as a charge-trapping component to induce conductive filament and also a compatible moiety for inorganic nanoparticles through hydrogen bonding. The experimental results show that the P4VP-b-PPMA-based electrical memory device exhibits write-once-read-many-times memory behavior and an excellent ON/OFF current ratio of over 105 with a stable turn-on voltage (Vset ) around -2.0 V and stable memory behavior upon stretching up to 60% strain. On the other hand, P4VP-b-PPMA/ZnO nanocomposite film switches the memory characteristic to the dynamic random access memory behavior. The stretchable memory device prepared from the nanocomposite film can have a stretching durability over 40% strain and up to 1000 times cycling stretch-relaxation test. This work demonstrates a new strategy using nanocomposite films with tunable electrical characteristics and enhanced mechanical properties for stretchable electrical devices.