P4VP Block Research Articles

Nonvolatile organic field-effect transistors memory devices using supramolecular block copolymer/functional small molecule nanocomposite electret.

Organic field-effect transistors (OFETs) memory devices based on hybrid nanocomposite electret were fabricated by cooperative supramolecular polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with two different block compositions (asymmetric L1 and symmetric L2) that contain hydroxyl-functionalized ferrocene small molecules (FMs). Because of the selective hydrogen interaction between the hydroxyl groups of FM and pyridine groups in P4VP block, the small FMs can preferentially disperse in the P4VP nanodomain, which can be used as nanostructured charge-trapping nanocomposite electret (L1-FMX and L2-FMX) under solvent-annealing process. The charge-storage functionalities can be easily tailored by morphologies of the hybrid nanocomposite thin film and spatial distribution of the FM molecules in which the relative molecular mass of block copolymers and the FM loading ratio can further control both of them. These block copolymer nanocomposite thin film electrets with charge-controlling guest FM for OFETs memory devices exhibit significant features including the ternary bits storage, high-density trapping sites, charge-carrier trapping of both polarities (ambipolar trapping), and solution processing that can make important progress for future advanced storage and memory technology.

Preparation and thermal characterization of poly(2‐vinylpyridine) copolymers coordinated to Cr nanoparticles

In this study, polystyrene‐block‐poly(2‐vinylpyridine), PS‐b‐P2VP, polyisoprene‐block‐poly(2‐vinylpyridne), PI‐b‐P2VP and poly(methyl metacrylate)‐block‐poly(2‐vinylpyridine), PMMA‐b‐P2VP, coordinated to Cr metal were synthesized and characterized by Fourier transform infrared, transmission electron microscopy and direct pyrolysis mass spectrometry techniques. Both thermal degradation mechanism and thermal stability of P2VP blocks were affected by the coordination of Cr nanoparticles to nitrogen of pyridine rings. Thermal decomposition of P2VP blocks was started by loss of pyridine units leaving an unsaturated and/or crosslinked polymer backbone that degraded at relatively high temperatures. Incorporation of Cr metal did not noticeably influence thermal behavior of PS and PI blocks. However, increase in thermal stability of PMMA block was detected and associated with inhibition of the interactions between carbonyl groups of MMA chains with nitrogen atom of pyridine ring as a consequence of coordination to metal. Copyright © 2015 John Wiley & Sons, Ltd.

Flower like micellar assemblies in poly(styrene)-block-poly(4-vinyl pyridine)/poly(acrylic acid) complexes

The formation of rare flower like micelles in poly(styrene)-block-poly(4-vinyl pyridine)/poly(acrylic acid) (PS-b-P4VP/PAA) diblock copolymer/homopolymer complexes is reported. The self-assembly as well as the morphological changes in the complexes were induced by the addition of a high molecular weight PAA/ethanol solution into the PS-b-P4VP solution in dimethyl formamide followed by dialyses. The composition-dependent micelles were varying in size and shape with increase in PAA concentration in solution. The complex aggregates in solution were characterized by dynamic light scattering (DLS) whereas morphologies in the solid complexes were observed using transmission electron microscopy (TEM). Flower like micelles are formed in complexes at 20wt% PAA concentration followed by ‘spikey’ micellar assemblies at 40wt% PAA. The size of the micelles was found to be increased upon the addition of PAA into the block copolymer solution. Infrared studies revealed the intermolecular hydrogen bonding interactions between the complementary binding sites on PAA and the P4VP block of the block copolymer. Finally, a model was proposed to explain the self-assembly and morphological transitions in these complexes based on the experimental results obtained.

Tunable Photonic Band Gap of PS-b-P2VP Lamellar Film Using Metal Ions and pH Gradation.

Optical properties of photonic crystal film were investigated by tuning photonic band gap (PBG). The lamellar-forming photonic films were prepared by nearly symmetric poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) block copolymers. Molecular weight of PS block and P2VP block is 52 kg/mol, and 57 kg/mol, respectively. When submerged in water, the lamellar films were swollen and show Bragg reflection in visible light region. We observed that the reflection color can be tuned by ion concentration (e.g., hydrogen or metal ion) in water. The higher concentration of hydrogen ion in solution, the longer reflectance wavelength shifted (from 537 nm to 743 nm). In addition, max-reflectance wavelength is dependent on both metal ion and the concentration. The max-reflectance wavelength is shifted from 653 nm (i.e., in water without ion) to 430 nm, 465 nm, and 505 nm for 120 mM of Ca2+, Fe2+, and Cu2+, respectively. Therefore, we can control the photonic band gap of photonic devices by changing the condition of swelling solution.

Tailor-made dimensions of diblock copolymer truncated micelles on a solid by UV irradiation.

We investigated the structural evolution of truncated micelles in ultrathin films of polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP, of monolayer thickness on bare silicon substrates (SiOx/Si) upon UV irradiation in air- (UVIA) and nitrogen-rich (UVIN) environments. The structural evolution of micelles upon UV irradiation was monitored using GISAXS measurements in situ, while the surface morphology was probed using atomic force microscopy ex situ and the chemical composition using X-ray photoelectron spectroscopy (XPS). This work provides clear evidence for the interpretation of the relationship between the structural evolution and photochemical reactions in PS-b-P2VP truncated micelles upon UVIA and UVIN. Under UVIA treatment, photolysis and cross-linking reactions coexisted within the micelles; photolysis occurred mainly at the top of the micelles, whereas cross-linking occurred preferentially at the bottom. The shape and size of UVIA-treated truncated micelles were controlled predominantly by oxidative photolysis reactions, which depended on the concentration gradient of free radicals and oxygen along the micelle height. Because of an interplay between photolysis and photo-crosslinking, the scattering length densities (SLD) of PS and P2VP remained constant. In contrast, UVIN treatments enhanced the contrast in SLD between the PS shell and the P2VP core as cross-linking dominated over photolysis in the presence of nitrogen. The enhancement of the SLD contrast was due to the various degrees of cross-linking under UVIN for the PS and P2VP blocks.

Aligned silicon nanofins via the directed self-assembly of PS-b-P4VP block copolymer and metal oxide enhanced pattern transfer

'Directing' block copolymer (BCP) patterns is a possible option for future semiconductor device patterning, but pattern transfer of BCP masks is somewhat hindered by the inherently low etch contrast between blocks. Here, we demonstrate a 'fab' friendly methodology for forming well-registered and aligned silicon (Si) nanofins following pattern transfer of robust metal oxide nanowire masks through the directed self-assembly (DSA) of BCPs. A cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) (PS-b-P4VP) BCP was employed producing 'fingerprint' line patterns over macroscopic areas following solvent vapor annealing treatment. The directed assembly of PS-b-P4VP line patterns was enabled by electron-beam lithographically defined hydrogen silsequioxane (HSQ) gratings. We developed metal oxide nanowire features using PS-b-P4VP structures which facilitated high quality pattern transfer to the underlying Si substrate. This work highlights the precision at which long range ordered ∼10 nm Si nanofin features with 32 nm pitch can be defined using a cylindrical BCP system for nanolithography application. The results show promise for future nanocircuitry fabrication to access sub-16 nm critical dimensions using cylindrical systems as surface interfaces are easier to tailor than lamellar systems. Additionally, the work helps to demonstrate the extension of these methods to a 'high χ' BCP beyond the size limitations of the more well-studied PS-b-poly(methyl methylacrylate) (PS-b-PMMA) system.

Encapsulation of Au Nanoparticles by Poly(4-Vinylpyridine)-Block-Polystyrene-Block-Poly(4-Vinylpyridine) for Controlled Chain Assembly

We report a facile method to encapsulate Au nanoparticles (NPs) in an amphiphilic ABA triblock copolymer, poly(4-vinylpyridine)-block-polystyrene-block-poly(4-vinylpyridine) (P4VP-b-PS-b-P4VP), forming Au@P4VP-b-PS-b-P4VP core–shell nanostructures. On the basis of the hydrophobically funcationalized Au surface, we propose that the P4VP-b-PS-b-P4VP is folded into a U shape, so that the hydrophobic PS block attach to the Au surface and the hydrophilic P4VP blocks are dissolved in the solution facing outwards. As the polymer micelles transform from spheres to cylinders and vesicles, the embedded Au NPs are brought along in the process and end up in the complex polymer nanostructures. Driven by the tendency of the polymer to form cylindrical micelles, the positively charged core–shell NPs can assemble into chains, where the method was only demonstrated previously exploiting the negatively charged amphiphilic polystyrene-block-poly(acrylic acid) shells.

Physical Hydrogels via Charge Driven Self-Organization of a Triblock Polyampholyte – Rheological and Structural Investigations

We investigate the conformational properties of stimuli-responsive hydrogels from triblock polyelectrolytes PtBA-b-P2VP-b-PtBA (PtBA and P2VP are poly(tert-butyl acrylate) and poly(2-vinylpyridine)) and the corresponding polyampholytes PAA-b-P2VP-b-PAA (PAA is poly(acrylic acid)), the latter with nonquaternized or quaternized P2VP blocks. The block lengths are the same in all three polymers with relatively short end blocks and long middle blocks. The mechanical properties of the hydrogels have previously been found to depend strongly on the pH value and on the nature of the blocks (Polymer 2008, 49, 1249). Here, we present results from rheological studies and small-angle neutron scattering revealing the underlying hydrogel structures. The hydrogel structure of the polyampholyte depends on the charge asymmetry, controlled by the pH value, and reveals several transitions with increasing charge ratio. A low charge asymmetry causes the collapse of the chains into large globular structures due to the fluctuati...

A New Strategy To Synthesize Temperature- and pH-Sensitive Multicompartment Block Copolymer Nanoparticles by Two Macro-RAFT Agents Comediated Dispersion Polymerization

Multicompartment block copolymer nanoparticles (MCBNs) arouse great interest due to their special structure and wide application. However, synthesis of MCBNs suffers from great inconvenience and difficulty. In this contribution, an efficient strategy to prepare well-defined temperature- and pH-sensitive MCBNs constructed with two diblock copolymers of poly(4-vinylpyridine)-b-polystyrene (P4VP-b-PS) and poly(N-isopropylacrylamide)-b-polystyrene (PNIPAM-b-PS) through the two macro-RAFT agents comediated dispersion polymerization is proposed. In this two macro-RAFT agents comediated dispersion polymerization, two macro-RAFT agents having similar polymerization degree are simultaneously adopted, and onset micellization of PNIPAM-b-PS and P4VP-b-PS occurs simultaneously to form mixed corona–core nanoparticles containing a PNIPAM/P4VP mixed corona and a PS core. In neutral water at room temperature, the corona-forming P4VP block deposits on the PS core to form MCBNs, which contain a solvophobic PS core, discrete P4VP nodules on the PS core, and a solvophilic PNIPAM corona. The parameters affecting the MCBNs structure are investigated. It is found that the higher percent of the poly(4-vinylpyridine) trithiocarbonate (P4VP-TTC) macro-RAFT agent and the shorter PS block, the larger the size of the P4VP nodules on MCBNs. The synthesized MCBNs are temperature- and pH-responsive. Through the phase transition of the temperature-responsive PNIPAM block and the pH-responsive P4VP block, the morphology of MCBNs can be changed. Our strategy of the two macro-RAFT agents comediated dispersion polymerization is believed sufficiently to overcome the inconvenience and difficulty in synthesis of well-defined MCBNs.

Effect of molecular architectures in photoinduced birefringence in films of azo-modified diblock copolymers

Langmuir films of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with an azo dye, 4-[4-(phenylazo)-1-naphthylazo]phenol (Disperse Orange 13, DO13), hydrogen-bonded to the pyridine group of P4VP blocks were investigated. The surface pressure isotherms were considerably different for the copolymer dissolved in a nonselective (chloroform) and selective (toluene) solvents. The Langmuir–Blodgett (LB) and Langmuir–Schaefer (LS) films produced with PS-b-P4VP(DO13) copolymers displayed higher optically induced birefringence than the cast films owing to their nanostructured nature. The photoinduced birefringence properties were particularly enhanced when toluene was used owing to the confinement of azo chromophores in micelles consisting of a P4VP core and a PS corona.

Directing the Interfacial Morphology of Hierarchical Structures of Dendron-Jacketed Block Copolymers via Liquid Crystalline Phases

Interfacial morphologies of hierarchically phase-separated domains in supramolecular dendron-jacketed block copolymers (DJBCP) are directed via liquid-crystalline (LC) phases of the dendronized blocks. The DJBCP is formed with a dendron 4′-(3,4,5-trioctyloxybenzoyloxy)benzoic acid (TOB), selectively incorporated into the P4VP block of poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP). Revealed from small- and wide-angle X-ray scattering as well as transmission electron microscopy, the hexagonally packed columnar LC phase (HEXcol) of the dendronized blocks P4VP(TOB) can substantially decrease the curvature of the intermaterial dividing surfaces (IMDS) of the DJBCP. Consequently formed are hierarchically structured DJBCP with hexagonally packed hexagon PS cylinders. As the locally two-dimensionally (2D)-ordered HEXcol phase reduces to 1D ordered smectic (Sm) phase with weakened LC packing strength, the planar IMDS of the DJBCP relaxes into curved IMDS for circular PS cylinders. IMDS flattening effect im...

Synthesis of hollow silica nanosphere with high accessible surface area and their hybridization with carbon matrix for drastic enhancement of electrochemical property

Hollow silica nanospheres with high accessible surface area have been synthesized by using core-shell-corona polymeric micelle of poly (styrene-b-2-vinyle pyridine-b-ethylene oxide) (PS45kPVP26k-PEO82k) as a template. The size of the template polymeric micelle depends on the pH of the solution, i.e. approximate to 100 nm at pH 7 whereas. approximate to 300 nm at pH 4. The enlarged size of the micelle is possibly due to the protonation of the PVP block, which also serves as reaction sites for silica precursor. The size of the obtained silica nanosphere measured with transmission electron microscope (TEM) is around approximate to 70 nm and shell thickness is approximate to 20 nm. Fourier transformed infrared spectroscopy (FTIR) data confirms that the polymer template is completely removed during calcination. Conductive carbon is doped into the silica nanosphere through glucose solution followed by hydrothermal treatment and pyrolysis. It is found that the electrochemical performance and stability of the silica nanosphere is dramatically enhanced after carbon doping. The combined strategy of the core-shell-corona micelle as template and carbon doping could represent a new platform for the researchers to develop functional nanomaterials.

Spatial Organization of Nanoparticles in Thin Film Block Copolymer/Homopolymer Hosts

Polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymers (BCP) form spherical micelles, wherein each micelle is composed of an inner core of the P2VP block and an outer corona of the PS block of BCP, within thin film PS homopolymer hosts. The spatial distribution of PS-grafted gold nanoparticles (PS-Au NPs) within this thin film BCP/homopolymer system is characterized by a morphological diagram of the curvature of the Au cores 1/RC vs the degree of polymerization N of the grafted PS chains. Five basic morphological regimes, largely dictated by competing entropic and enthalpic intermolecular interactions, characterize the distribution of nanoparticles. The NP distributions include one case wherein the NPs reside primarily at the external interfaces (free surface and substrate) and another where the nanoparticles preferentially “decorate” the surfaces of the micelles. The existence of these different regimes is rationalized in terms of various competing short- and long-range intermolecular interac...

Kinetics of Preferential Adsorption of Amphiphilic Star Block Copolymers that Tether by Their Corona Blocks at the Solid/Fluid Interface

The kinetics of preferential adsorption of a series of amphiphilic star block copolymers having cores made of polystyrene, PS, and coronas made of poly(2-vinylpyridine), PVP, have been studied using in situ phase modulated ellipsometry. The stars have, on average, either 26 or 40 PS-b-PVP diblock copolymer arms with PS/PVP molecular weight ratios (S/V) of 1/1, 5/1, or 9/1. Preferential adsorption from dilute toluene solutions onto silicon surfaces tethers these topologically complex star copolymers through their PVP blocks, yielding an interfacial structure resembling a dome. The adsorption kinetics are concentration dependent and show two distinct regimes: an initial rapid adsorption is followed by a slow approach toward equilibrium that is dominated by relaxations and rearrangements. For all PS/PVP ratios studied, star copolymers having 40 arms exhibit greater final adsorbed amounts compared to those having 26 arms. A kinetics model that considers diffusion of molecules at the solid/fluid interface as well as surface relaxation/reorganization events is used to characterize the adsorption process. In general, while both processes are necessary to describe the kinetics of preferential adsorption of these materials, surface rearrangements dominate for the two stars having the largest size and number of arms. It is also found that star block copolymers having symmetric arms (PS/PVP = 1/1) approach adsorption equilibrium in agreement with random sequential adsorption (RSA) model kinetics, attaining final adsorbed amounts that are close to those predicted for RSA processes. In contrast, the asymmetric stars having PS/PVP = 9/1 and 5/1 are able to rearrange on the surface, reaching final adsorbed amounts that are greater than those predicted for RSA processes, suggesting surface relaxation/reorganization and possible stretching due to confinement occurring at the solid/fluid interface. The results reported provide key insights as to how composition and connectivity of highly branched soft materials impact their self-assembly and interfacial structure.

Nanoparticle directed domain orientation in thin films of asymmetric block copolymers

We investigated the thin film morphology of two different asymmetric block copolymers (BCP), polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and poly(n-pentyl methacrylate)-block-poly(methyl methacrylate) (PPMA-b-PMMA), loaded with pre-synthesized iron oxide nanoparticles (NP). The chemical composition of the BCP constituents determines the strength of the interaction between polymer chains and nanoparticles. In the case of NP/PS-b-P4VP system, the nanoparticles interact preferentially with the P4VP block and hence localize selectively in the P4VP cylindrical microdomains. However, for the NP/PPMA-b-PMMA system, the nanoparticles have no significant preference for the copolymer blocks and segregate at the polymer/substrate interface. Interestingly, this changes the effective substrate surface energy and hence leads to a remarkable change in domain orientation from parallel to perpendicular with respect to the substrate. These results clearly demonstrate the importance of both enthalpic and entropic factors which determine spatial distribution of NP in BCP films and influence domain orientation.

Water in Oil Emulsion Stabilized by Tadpole-like Single Chain Polymer Nanoparticles and Its Application in Biphase Reaction

In this study, tadpole-like single chain polymer nanoparticles (TSCPNs) were efficiently synthesized by intramolecularly cross-linking P4VP block of commercial block polymer of PMMA2250-b-P4VP286 in N,N-dimethylformamide using propargyl bromide as cross-linking agent. The intramolecular cross-linking reaction led to the production of TSCPNs with a linear tail and a cross-linked head. The as-prepared TSCPNs were then applied as emulsifier to stabilize water in chlorobenzene emulsion, and an extremely stabilized water in oil (W/O) emulsion was generated at a low TSCPNs concentration. The TSCPNs concentration was as low as 0.0075 wt % versus total weight of water and chlorobenzene for emulsion formation. The emulsifying performance of TSCPNs was better than that of low molecular surfactant, such as Span-80. The generated W/O emulsion provided an ideal medium for the reduction of oil-soluble p-nitroanisole by water-soluble sulfide to p-anisidine, an effective contact problem between the two reactants with different solubility was well solved through interfacial reaction.

Protonation-Induced Microphase Separation in Thin Films of a Polyelectrolyte-Hydrophilic Diblock Copolymer.

Block copolymers composed of poly(oligo ethylene glycol methyl ether methacrylate) and poly(2-vinylpyridine) are disordered in the neat state but can be induced to order by protonation of the P2VP block, demonstrating a tunable and responsive method for triggering assembly in thin films. Comparison of protonation with the addition of salts shows that microphase separation is due to selective protonation of the P2VP block. Increasing acid incorporation and increasing 2-vinylpyridine content for P2VP minority copolymers both promote increasingly phase-separated morphologies, consistent with protonation increasing the effective strength of segregation between the two blocks. The self-assembled nanostructures formed after casting from acidic solutions may be tuned based on the amount and type of acid incorporation as well as the annealing treatment applied after casting, where both aqueous and polar organic solvents are shown to be effective. Therefore, POEGMA-b-P2VP is a novel ion-containing block copolymer whose morphologies can be facilely tuned during casting and processing by controlling its exposure to acid.

Precise Control of Quantum Dot Location within the P3HT-b-P2VP/QD Nanowires Formed by Crystallization-Driven 1D Growth of Hybrid Dimeric Seeds

Herein, we report a simple fabrication of hybrid nanowires (NWs) composed of a p-type conjugated polymer (CP) and n-type inorganic quantum dots (QDs) by exploiting the crystallization-driven solution assembly of poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) rod-coil amphiphiles. The visualization of the crystallization-driven growth evolution of hybrid NWs through systematic transmission electron microscopy experiments showed that discrete dimeric CdSe QDs bridged by P3HT-b-P2VP polymers were generated during the initial state of crystallization. These, in turn, assemble into elongated fibrils, forming the coaxial P3HT-b-P2VP/QDs hybrid NWs. In particular, the location of the QD arrays within the single strand of P3HT-b-P2VP can be controlled precisely by manipulating the regioregularity (RR) values of P3HT block and the relative lengths of P2VP block. The degree of coaxiality of the QD arrays was shown to depend on the coplanarity of the thiophene rings of P3HT block, which can be controlled by the RR value of P3HT block. In addition, the location of QDs could be regulated at the specific-local site of P3HT-b-P2VP NW according to the surface characteristics of QDs. As an example, the comparison of two different QDs coated with hydrophobic alkyl-terminated and hydroxyl-terminated molecules, respectively, is used to elucidate the effect of the surface properties of QDs on their nanolocation in the NW.

Defects, Solvent Quality, and Photonic Response in Lamellar Block Copolymer Gels

Stimuli-responsive photonic gels are made from the lamellar block copolymer (BCP) poly(styrene-b-2-vinylpyridine) (PS–P2VP), where the photonic responses are triggered by swelling/deswelling of the P2VP block with a selective solvent. When compared to isotropic swelling in chemically cross-linked homopolymer gels, the P2VP block in the lamellar BCP shows significantly lower degrees of swelling in alcohol–water cosolvents. The glassy PS layers completely constrain the lateral expansion of the P2VP gel layers and the dislocation defect network that develops during BCP self-assembly provides a counter force to vertical swelling. A model based on Flory–Huggins mixing and dislocation network strain energy is proposed to capture the swelling behavior of the BCP and is then used to estimate the dislocation network density in the lamellar BCP. This work establishes the quantitative relationship between the reflective color of the photonic gel, the effective χ parameter of the swellable block and the solvent, and ...

Light responsive thin films of micelles of PS-b-PVP complexed with diazophenol chromophore

We have incorporated push–pull azobenzene units into diblock-copolymer micelles by supramolecular assembly. Specifically, we encapsulated a phenol-functionalized chromophore, DO13, within PS-b-P4VP micelles in toluene by means of H-bond interactions developed between DO13 molecules and pyridine groups of P4VP block. The solutions were spin-coated onto glass substrates resulting in multi- or mono-layered thin films of micelles with P4VP(DO13) core and PS corona. We show that the use of DO13 as a building block of micellar aggregates allowed us to manipulate the developed nanostructures. Spherical to cylindrical micellar transition was found when we increased the degree of chromophore complexation. Also, it was found that the polymer concentration in the solution plays an important role in determining the micellar nanostructures. The chain extension and change in composition of the P4VP core in the presence of the chromophore may be responsible for the structural changes observed in the micelles. The optical properties of the thin films have been investigated focusing on the effect of the micellar morphology over the photoinduced birefringence. The optical anisotropy (Δn) increased with respect to the analogous homogeneous system P4VP(DO13), indicating that the protective micelle environment can enhance the optical properties of the embedded chromophores significantly. Furthermore, we show very interesting new results in which we have related changes in optical properties to the film morphology (spheres to cylinders). This can be exploited for producing optical devices having improved optoelectronic properties and stability.