P4VP Block Research Articles

Orientation control of high-χ triblock copolymer for sub-10 nm patterning using fluorine-containing polymeric additives

Directed self-assembly (DSA) of block copolymers (BCPs) is one of the most promising techniques to tackle the ever-increasing demand for sublithographic features in semiconductor industries. BCPs with high Flory–Huggins parameter (χ) are of particular interest due to their ability to self-assemble at the length scale of sub-10 nm. However, such high-χ BCPs typically have imbalanced surface energies between respective blocks, making it a challenge to achieve desired perpendicular orientation. To address this challenge, we mixed a fluorine-containing polymeric additive with poly(2-vinylpyridine)-<italic>block</italic>-polystyrene-<italic>block</italic>-poly(2-vinylpyridine) (P2VP-<italic>b</italic>-PS-<italic>b</italic>-P2VP) and successfully controlled the orientation of the high-χ triblock copolymer. The additive selectively mixes with P2VP block through hydrogen bonding and can reduce the dissimilarity of surface energies between PS and P2VP blocks. After optimizing additive dose and annealing conditions, desired perpendicular orientation formed upon simple thermal annealing. We further demonstrated DSA of this material system with five times density multiplication and a half-pitch as small as 8.5 nm. This material system is also amenable to sequential infiltration synthesis treatment to selectively grow metal oxide in P2VP domains, which can facilitate the subsequent pattern transfer. We believe that this integration-friendly DSA platform using simple thermal annealing holds the great potential for sub-10 nm nanopatterning applications.

Disassembly of Crystalline Platelets of an Amphiphilic Triblock Copolymer Mediated by Varying pH and Organic Diacids

AbstractRegulation of crystalline micelles is difficult to achieve because of the strong solidification of crystallization. In this present work, an amphiphilic triblock copolymer poly(ethylene oxide)‐b‐poly(ε‐caprolactone)‐b‐poly(4‐vinylpyridine) (PEO‐b‐PCL‐b‐P4VP) is prepared, in which the P4VP block serves as an H‐bonding acceptor. It is originally self‐assembled into crystalline lamellar micelles in aqueous solution. Subsequently, the effect of varying pH and organic diacids on morphological transition is investigated in detail. Lamellae‐to‐cylinder‐to‐sphere transitions are observed after decreasing the pH or with the addition of organic diacids with different chain spacers. The decreasing pH causes increasing hydrophilicity of the P4VP block, while adding organic diacids results in an increasing corona swelling of the P4VP segment, both of which lead to a decreasing crystallinity of the poly(ε‐caprolactone) core. Consequently, morphological variety changing from lamellar to worm‐like to spherical micelles can be achieved.

Photocontrol of Supramolecular Azo-Containing Block Copolymer Thin Films during Dip-Coating: Toward Nanoscale Patterned Coatings

Dip-coating allows nanostructured block copolymer (BCP) thin film fabrication in a fast and facile one-step process. It can also be coupled with external controls, such as illumination. Herein, we expose several design principles that enable photocontrol of the nanostructured surface pattern and thickness of supramolecular BCP thin films. This is done using a polystyrene–poly(4-vinylpyridine) (PS-P4VP) BCP and two hydroxy-functionalized small-molecule (SM) azo derivatives that have different photochemical characteristics and that hydrogen bond to the P4VP block. We show how the film preparation concept provides tunability through the chemical structure of the photoactive SM, the relative amount of SM in the dip-coating solution, and the choice of solvent. It was found that the film thickness and SM uptake in the films are increased by illumination when THF is used but are unchanged when toluene is used as solvent, which is attributed to an optical heating effect observable with volatile solvents. The phot...

Hydrogen bonding induces unusual self-assembled structures from mixtures of two miscible disordered diblock copolymers

We synthesized two miscible disordered diblock copolymers, poly(methyl methacrylate–b–vinylphenol) (PMMA-b-PVPh) and poly(4-vinylpyridine–b–ethylene oxide) (P4VP-b-PEO), through anionic living and reversible addition fragmentation chain transfer polymerizations, respectively; together, these polymers contained one hydrogen bond donor (PVPh) and three hydrogen bond acceptors (P4VP, PEO, PMMA). The inter-association equilibrium constants (KA) for the three different hydrogen bonded pairs followed the order PVPh/P4VP (KA = 1200) > PVPh/PEO (KA = 280) > PVPh/PMMA (KA = 47.1), suggesting that the PVPh units prefer to hydrogen bond with P4VP block, rather than PEO and PMMA blocks. Nevertheless, the excluded PMMA and PEO segments experienced weak intermolecular dipole–dipole interactions, such that the PMMA-b-PVPh/P4VP-b-PEO blends exhibited two-phase behavior, forming miscible PVPh/P4VP and PMMA/PEO phases, as evidenced using transmission electron microscopy.

Fabrication of Hybrid Polymeric Micelles Containing AuNPs and Metalloporphyrin in the Core.

Multi-structure assemblies consisting of gold nanoparticles and porphyrin were fabricated by using diblock copolymer, poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP). The copolymer of PEG-b-P4VP was used in the formation of core-shell micelles in water, in which the P4VP block serves as the core, while the PEG block forms the shell. In the micellar core, gold nanoparticle and metalloporphyrin were dispersed through the axial coordination. Structural and morphological characterizations of the complex micelle were carried out by transmission electron microscopy, laser light scatting, and UV-visible spectroscopy. Metalloporphyrin in the complex micelle exhibited excellent photostability by reducing the generation of the singlet oxygen. This strategy may provide a novel approach to design photocatalysts that have target applications in photocatalysis and solar cells.

Synthesis of P4VP-b-PBLG Diblock Copolymers and Their Self-Assembly Behavior

Well-defined P4VP-b-PBLG diblock polymer composed of poly (4-vinylpyridine) (P4VP) and poly (γ-benzyl-L-glutamate) (PBLG) was synthesized by click reaction with alkyne- and azide-functionalized homopolymers. Besides, P4VP blocks were synthesized by copper-mediated atom transfer radical polymerization (ATRP) with a chlorine-containing alkyne bifunctional initiator, and the azido-terminated PBLG homopolymers were synthesized by ring-opening polymerization (ROP) of γ-benzyl-L-glutamate with an amine-containing azide initiator. In addition, the synthesized P4VP-b-PBLG with different block ratios has been characterized by proton nuclear magnetic resonance (1H NMR), Gel permeation chromatograph (GPC) and fourier transform infrated spectroscopy (FT-IR). Then, the self-assembly behaviors of P4VP-b-PBLG have been studied by changing parameters like dripping speed and block ratio. The morphologies of self-assembly of spherical, disk-like and ellipsoid-like shape particles have been observed and analyzed by scanning electron microscopy (SEM). These results have provided guidelines for the design of macromolecular self-assembly.

Core-Shell Interface-Oriented Synthesis of Bowl-Structured Hollow Silica Nanospheres Using Self-Assembled ABC Triblock Copolymeric Micelles.

Hollow porous silica nanospheres (HSNs) are emerging classes of cutting-edge nanostructured materials. They have elicited much interest as carriers of active molecule delivery due to their amorphous chemical structure, nontoxic nature, and biocompatibility. Structural development with hierarchical morphology is mostly required to obtain the desired performance. In this context, large through-holes or pore openings on shells are desired so that the postsynthesis loading of active-moleculeonto HSNs via a simple immersion method can be facilitated. This study reports the synthesis of HSNs with large through-holes or pore openings on shells, which are subsequently termed bowl-structured hollow porous silica nanospheres (BHSNs). The synthesis of BHSNs was mediated by the core-shell interfaces of the core-shell corona-structured micelles obtained from a commercially available ABC triblock copolymer (polystyrene- b-poly(2-vinylpyridine)- b-poly(ethylene oxide) (PS-P2VP-PEO)). In this synthesis process, polymer@SiO2 composite structure was formed because of the deposition of silica (SiO2) on the micelles' core. The P2VP block played a significant role in the hydrolysis and condensation of the silica precursor, i.e., tetraethylorthosilicate (TEOS) and then maintaining the shell's growth. The PS core of the micelles built the void spaces. Transmission electron microscopy (TEM) images revealed a spherical hollow structure with an average particle size of 41.87 ± 3.28 nm. The average diameter of void spaces was 21.71 ± 1.22 nm, and the shell thickness was 10.17 ± 1.68 nm. According to the TEM image analysis, the average large pore was determined to be 15.95 nm. Scanning electron microscopy (SEM) images further confirmed the presence of large single pores or openings in shells. These were formed as a result of the accumulated ethanol on the PS core acting to prevent the growth of silica.

Behavior of ATRP-derived styrene and 4-vinylpyridine-based amphiphilic block copolymers in solution

The reaction sequence of (i) styrene (St) and (ii) 4-vinylpyridine (4VP) employing atom transfer radical polymerization (ATRP) with Cu(I)Cl/Me6TREN as the catalyst is known to lead to poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymers with narrow molecular weight distributions and is well-controlled for both the styrene and the successive 4VP polymerization. Block copolymers derived by this reaction sequence can easily be converted to amphiphilic species by quarternization of the P4VP block. It was found that the behavior of ATRP-derived PSn-b-P4VPm+⋅MeI− ionomers in solution is similar to the behavior of anionically derived ionomers. This indicates that the minor difference in polydispersity and chain termini in particular does not influence the colloidal characteristics significantly. Thus, ATRP was proven to be a valuable alternative to sensitive anionic polymerization technique to produce amphiphilic block copolymer systems. Additionally, it was found that PSn-b-P4VPm+⋅MeI− ionomers with short P4VPm+⋅MeI− and long PS blocks self-assemble in dioxane to “inverse” amphiphilic micelles and undergo a morphological transition to “regular” micelles upon slow addition of ethanol.

Control on the Morphology of ABA Amphiphilic Triblock Copolymer Micelles in Dioxane/Water Mixture Solvent

This work offers a typical understanding of the factors that govern the nanostructures of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine) (P4VP-b-PS-b-P4VP) block copolymers (BCs) in dioxane/water, in which water is a selective solvent for the P4VP block. It is achieved through an investigation of the amphiphilic triblock copolymer micelles by variation of three different factors, including water content (above CWC but under the immobile concentration), temperature (ranging from 20 °C to 80 °C), and copolymer composition (low and high PS block length). Transition of bead-like micelles to vesicles is observed with the increase of water content due to the increase of interfacial energy between the copolymer and the solvent. Effect of temperature superposed on that of water content results in various morphologies, such as beads, fibers, rods, capsules, toroids, lamellae, and vesicles. The interfacial tension between the BC and the solvent increases with the increase of water content but decreases with the increase of temperature, indicating that the micellar morphologies are resulted from the competitive interplay between the temperature and the water content and always change in a direction that decreases the interfacial energy. Based on the micellar structures obtained in this work and the effects of temperature superposed on water concentration, a diagram of phase evolution of different micellar morphologies is illustrated here, covering the temperature range from 20 °C to 80 °C and the water content changing from 20 vol% to 35 vol%. For the investigation of BC composition, morphological transition of vesicle-to-fiber, for high PS length, is observed as compared with bead-to-capsule for low PS length, as the temperature changes from 20 °C to 80 °C. Our research complements the protocols to control over the morphologies and the phase diagram describing P4VP-b-PS-b-P4VP micellar nanostructures in aqueous solution.

Enhanced electrochemical response of a modified glassy carbon electrode by poly(2-vinlypyridine-b-methyl methacrylate) conjugated gold nanoparticles for detection of nicotine.

Poly(2-vinylpyridine-b-methylmethacrylate) coated gold nanoparticles [P(2VP-MMA)-AuNPs] were prepared and characterized by UV-Vis, FTIR, AFM, and zetasizer analysis. Investigation of the potential of the synthesized poly(2-vinylpyridine-b-methylmethacrylate) coated gold nanoparticles [P(2VP-MMA)-AuNPs] for detection of nicotine is the main focus of the current study. P(2VP-MMA)-AuNPs were coated on a glassy carbon electrode (GCE) for electrochemical detection of nicotine by cyclic voltammetry. The effect of molar mass of individual P2VP blocks and total molar mass of the block copolymer is evaluated in the context of an enhanced electrochemical response of the modified GCE for its sensing ability of nicotine in both aqueous and organic media. The electrochemical detection of nicotine is significantly enhanced by modification of the GCE with P(2VP-MMA)-AuNPs.

ELECTROCHEMICAL CHARACTERIZATION OF POLYLACTIC ACID-BLOCK-POLY(2-VINYLPYRIDINE)/GOLD NANOPARTICLE COMPOSITES FOR GLUCOSE BIOSENSOR DEVELOPMENT

Nanocomposites that consist of diblock copolymer (BCP) and gold nanoparticles (AuNPs) can be applied as a matrix to immobilize enzymes or other molecules based on the well-defined core/shell nanostructures of these composites. In this research, polylactic acid-block-poly(2-vinylpyridine) (PLA-b-P2VP)/hydrogen tetrachloroaurate(III) hydrate (HAuCl4.3H2O) composites were hybridized and then reduced in dichloromethane (DCM) solution. The hybridizations between gold precursors and the P2VP domain were prepared with different ratios of gold to P2VP block (1:1, 1:5, 1:10, 5:1, 10:1) by taking advantage of the association between the long-pair nitrogen of the pyridine group of P2VP. The reduction of the Au3+/PLA-b-P2VP composite was accomplished by hydrazine solution in order to get gold nanoparticle/PLA-b-P2VP composites, which was visually confirmed by a direct color change from bright yellow to purple. In this work, ultraviolet–visible (UV-vis) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to confirm the association between gold precursors and pyridine groups as well as the synthesis of gold nanoparticles.The composite which labeled as R3 (Au3+: P2VP = 10:1) showed the highest peak current based on the cyclic voltammetry (CV) measurment. Furthermore, graphene oxide (GO) was added into R3 to prepare BCP/AuNPs/GO composite and reduced to BCP/AuNPs/rGO through electrochemical reduction. The resulting BCP/AuNPs/rGO showed high potential to be used in amperometric biosensor.

Gyroid Structures at Highly Asymmetric Volume Fractions by Blending of ABC Triblock Terpolymer and AB Diblock Copolymer

We investigated, via small-angle X-ray scattering and transmission electron microscopy, the morphologies of binary blend of polyisoprene-b-polystyrene-b-poly(2-vinylpyridine) (ISP) triblock terpolymer and polyisoprene-b-polystyrene (IS) diblock copolymer. An asymmetric ISP with volume fractions (f) of 0.12, 0.75, and 0.13 for PI, PS, and P2VP blocks, respectively, showed a new morphology: coexistence of spheres and cylinders with tetragonal packing. Asymmetric IS with fI = 0.11 and fS = 0.89 showed conventional body-centered cubic spherical microdomains. Very interestingly, a binary blend of ISP and IS with overall volume fractions of fI = 0.12, fS = 0.79, and fP = 0.09 exhibited core–shell double gyroid (CSG: Q230 space group), where PI consists of thin core and PS forms thick shell, while P2VP becomes thin matrix. It is very unusual to form CSG even at highly asymmetric volume fractions.

Synthesis by ATRP of Polystyrene-b-Poly(4-vinylpyridine) and Characterization by Inverse Gas Chromatography

A linear diblock copolymer [Polystyrene-b-Poly(4-vinyl-pyridine)] (PS-b-P4VP) was successfully prepared through Atom Transfer Radical Polymerization (ATRP). This synthesis is performed in two successive steps: using the (1-bromoethyl) benzene as initiatorand and Hexamethyl tris [2(dimethylamino)ethyl] amine as ligands in a protic solvent. The first step of the synthesis allows the realization of block polystyrene having a terminal function; however, Bromine (Br) permits the grafting of the second successive block P4VP. RMN -1H demonstrates that the P4VP block has been grafted onto the PS block. The molecular weight of PS-b-P4VP is determined by size exclusion chromatography, and its thermal stability is examined by TGA. The surface and the thermodynamic properties of this copolymer are studied by inverse gas chromatography (IGC). The new Hamieh Model shows that the synthesized copolymer PS-P4VP has an amphoteric behavior with rather very basic character that is six times stronger than acidic character (in Lewis terms), reflected the presence of acidic and basic groups in the structure of the PS-P4VP copolymer, more particularly the presence of benzenic, methyl and vinylpyridine groups.

Emulsion Solvent Evaporation-Induced Self-Assembly of Block Copolymers Containing pH-Sensitive Block.

A simple yet efficient method is developed to manipulate the self-assembly of pH-sensitive block copolymers (BCPs) confined in emulsion droplets. Addition of acid induces significant variation in morphological transition (e.g., structure and surface composition changes) of the polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) assemblies, due to the hydrophobic-hydrophilic transition of the pH-sensitive P4VP block via protonation. In the case of pH > pKa(P4VP) (pKa (P4VP) = 4.8), the BCPs can self-assemble into pupa-like particles because of the nearly neutral wetting of PS and P4VP blocks at the oil/water interface. As expected, onion-like particles obtained when pH is slightly lower than pKa(P4VP) (e.g., pH = 3.00), due to the interfacial affinity to the weakly hydrophilic P4VP block. Interestingly, when pH was further decreased to ∼2.5, interfacial instability of the emulsion droplets was observed, and each emulsion droplet generated nanoscale assemblies including vesicles, worm-like and/or spherical micelles rather than a nanostructured microparticle. Furthermore, homopolymer with different molecular weights and addition ratio are employed to adjust the interactions among copolymer blocks. By this means, particles with hierarchical structures can be obtained. Moreover, owing to the kinetically controlled processing, we found that temperature and stirring speed, which can significantly affect the kinetics of the evaporation of organic solvent and the formation of particles, played a key role in the morphology of the assemblies. We believe that manipulation of the property for the aqueous phase is a promising strategy to rationally design and fabricate polymeric assemblies with desirable shapes and internal structures.

Inorganic‐Macroion‐Induced Formation of Bicontinuous Block Copolymer Nanocomposites with Enhanced Conductivity and Modulus

AbstractA facile and electrostatically driven approach has been developed to prepare bicontinuous polymer nanocomposites that is based on the polyoxometalate (POM) macroion induced phase transition of PS‐b‐P2VP from an initial lamellar phase to a stable bicontinuous phase. The multi‐charged POMs can electrostatically cross‐link P2VP blocks and give rise to bicontinuous phases in which the POM hybrid conductive domains occupy a large volume fraction of more than 50 %. Furthermore, the POMs can give rise to high proton conductivity and serve as nanoenhancers, endowing the bicontinuous nanocomposites with a conductivity of 0.1 mS cm−1 and a Young's modulus of 7.4 GPa at room temperature; these values are greater than those of pristine PS‐b‐P2VP by two orders of magnitude and a factor of 1.8, respectively. This approach can provide a new concept based on electrostatic control to design functional bicontinuous polymer materials.

Inorganic-Macroion-Induced Formation of Bicontinuous Block Copolymer Nanocomposites with Enhanced Conductivity and Modulus.

A facile and electrostatically driven approach has been developed to prepare bicontinuous polymer nanocomposites that is based on the polyoxometalate (POM) macroion induced phase transition of PS-b-P2VP from an initial lamellar phase to a stable bicontinuous phase. The multi-charged POMs can electrostatically cross-link P2VP blocks and give rise to bicontinuous phases in which the POM hybrid conductive domains occupy a large volume fraction of more than 50 %. Furthermore, the POMs can give rise to high proton conductivity and serve as nanoenhancers, endowing the bicontinuous nanocomposites with a conductivity of 0.1 mS cm-1 and a Young's modulus of 7.4 GPa at room temperature; these values are greater than those of pristine PS-b-P2VP by two orders of magnitude and a factor of 1.8, respectively. This approach can provide a new concept based on electrostatic control to design functional bicontinuous polymer materials.

Asymmetric supramolecular double-comb diblock copolymers: From plasticization, to confined crystallization, to breakout

The combination of asymmetric P4VP-b-PAPI diblock copolymers (i.e. fP4VP≠fPAPI) and 3-NDP surfactants in hydrogen-bonded [poly(4-vinylpyridine)-block-poly(N-acryloylpiperidine)](3-nonadecylphenol)x (P4PA(3-NDP)x) supramolecular double-comb diblock copolymers could potentially result in rather interesting morphologies. However, plasticization of the copolymer and the ability of 3-NDP to crystallize were found to affect their self-assembly significantly. In general, for high comb densities x, the complex's tendency to crystallize and its preference to form a flat interface dominated microphase separation. Lower values of x on the other hand gave uneven distribution of 3-NDP, resulting in a higher glass transition temperature of the P4VP block. Crystallization of 3-NDP's aliphatic tails was therefore in most cases restricted to the preferential PAPI microdomains, thereby maintaining the large length scale block copolymer morphology that was already present in the melt. Such behavior is identical to self-assembly of linear semicrystalline diblock copolymers, as in these type of systems structure formation depends on the segregation strength and relative magnitude of the order-disorder transition (TODT), Tg and Tc, leading to mechanisms like confined crystallization or breakout.

Regioregularity-Driven Morphological Transition of Poly(3-hexylthiophene)-Based Block Copolymers

Conjugated polymer-based block copolymers (BCPs) offer great potential to provide beneficial nanostructures for efficient organic optoelectronics. However, their complicated self-assembly behavior, which is attributed to the strong crystallization of conjugated blocks, is still not well understood due to the lack of a model BCP system. Herein, we develop a series of novel conjugated polymer-based BCPs, poly(3-hexylthiophene)-block-poly(2-vinylpyridine) (P3HT-b-P2VP), in which the regioregularity (RR) of the P3HT block was varied from 95 to 73%. The tunable RR content allows for precise regulation of P3HT crystallization with minimal influence on the microphase-separation force between the P3HT and P2VP blocks. When RR is high (i.e., 95 or 85%), structure formation is controlled by crystallization of P3HT, and the ultimate structure is characterized by nanoscale P3HT fibrils in an amorphous matrix. In contrast, as RR decreases to 78 and 73%, P3HT crystallization is suppressed. The self-assembly is controll...

Synthesis of Hybrid Silica Nanoparticles Densely Grafted with Thermo and pH Dual-Responsive Brushes via Surface-Initiated ATRP

This work introduces a synthesis of well-defined thermo and pH dual-responsive poly(N-isopropylacrylamide)-b-poly(4-vinylpyridine)-grafted silica nanoparticles (SNPs-g-PNIPAM-b-P4VP) via surface-initiated atom transfer radical polymerization (ATRP). ATRP initiators were attached onto the surfaces of silica nanoparticles followed by ATRP of N-isopropylacrylamide (NIPAM). During the surface-initiated ATRP, free sacrificial initiator and halogen exchange were utilized to render the polymerization in a controlled manner. Because of the retention of the polymer chain’s end-group functionality, chain extension with 4-vinylpyridine (4VP) from the obtained PNIPAM-grafted SNPs (SNPs-g-PNIPAM) was successfully conducted. Kinetics of the chain extension was studied in detail, showing the livingness of this reinitiation process. Subsequent quaternization of the outer P4VP block with methyl iodide led to the synthesized hybrid nanoparticles being well dispersed in aqueous solution. This well dispersibility affords the...

Complexation induced by weak interaction between DNA and PEO-b-P4VP below the CMC of the polymer

The complexation between circular DNA and individual chains of PEO-b-P4VP with a relatively long PEO block and a short P4VP block is highly controllable when the interaction between DNA and the polymer is weak enough. When one circular DNA chain is taken into consideration, and the polymer concentration is far below its critical micelle concentration (CMC), polymer chains are absorbed by DNA chain due to the interaction between the negatively charged DNA chain and the slightly positively charged P4VP block chains. After the adsorption/complexation, the DNA chain is converted into a nanoring (type 1). In the nanoring, the DNA chain is sufficiently wrapped by the polymer and adopts a fully stretched conformation, so that the DNA compact ratio in the nanorings is close to 1. When the polymer concentration is close to but lower than the CMC, the free polymer chains in the solution are adsorbed not only by the DNA chain but also by the polymer chains that have already been adsorbed on the DNA chain. As a result, the circular DNA chain adsorbs more polymer chains, and thus the resultant nanoring (type 2) has a larger width. In the type 2 nanoring, the DNA chain is slightly compressed; the DNA compact ratio is only about 2−3. Therefore, complexation induced by the weak interaction between DNA and PEO-b-P4VP below the CMC can produce narrow-disperse and large nanorings with a perimeter of micrometers, which are difficult to prepare by existing methods.