P4VP Block Research Articles

Multilevel Hollow-Structured Particles through Halogen-Bond Regulated Polymer Assembly under 3DConfinement.

Engineering of hollow particles with tunable internal structures often requires complicated processes and/or invasive cleavage. Halogen-bond driven 3D confined-assembly of block copolymers has shed light on the engineering of polymer organization along with the fabricating of unique nanostructures. Herein, a family of multilevel hollow-structured particles (e.g., fully porous, multi-chamber, multi-shell, and concentric multi-layer architectures) is reported via halogen-bond regulated 3Dconfined-assembly of amphiphilic polymer networks. To do so, polystyrene-b-poly(2-vinyl pyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) amphiphilic triblock copolymer is selected, where P2VP blocks act as halogen acceptor. Meanwhile, poly(3-(2,3,5,6-tetrafluoro-4-iodophenoxy) propyl acrylate) (PTFIPA) is employed as halogen donor. Halogen-bond driven donor-acceptor linking between PTFIPA and P2VP block presented in PS-b-P2VP-b-PEO, can lead to the formation of supramolecular polymeric networks, along with the increased P2VP domain and tunable hydrophobic volume. Therefore, an adjustable packing parameter (p) is thus anticipated, which can enable the morphology transformation sequence until an equilibrium state is reached. Moreover, computer simulations are further utilized as the tool to interpret such morphologies transition and identify the precise distribution of each component. Benefiting from the tunable hollow structure and a substantial surface for transporting purpose, these structurally novel particles open perspectives toward promising applications including encapsulation, nanoreactor, and catalyst support.

Nanoscopic catalyst-loaded porous metal oxide hollow frameworks using porous block copolymer templates for high performance formaldehyde sensors

Porous and hollow nanostructures functionalized with nanoscopic catalysts have attracted considerable interest in a wide range of applications depending on surface reactions. In this study, we present an efficient and versatile synthetic strategy of porous metal oxide hollow frameworks (HFs) decorated with noble metal nanoparticles (NPs). The key lies in the use of porous and bicontinuous polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) microparticles as templates, which feature pores on the order of several hundred nanometers in size. Homogeneous Pt loading on the surface of the porous microparticles is achieved through the preferential adsorption of Pt precursors onto the P4VP block via electrostatic interactions. Subsequent SnO2 thin film deposition and calcination ultimately yield honeycomb-like SnO2 HFs with macropores and uniform distribution of Pt NPs. The Pt NP-loaded SnO2 HFs exhibit exceptional formaldehyde (HCHO) sensing capabilities, characterized by remarkable sensitivity (31.4 at 5 ppm), rapid response time (4.7 s at 5 ppm), ultra-low detection limit of 10 ppb, and remarkable cross-selectivity. These outstanding features result from their high surface area, gas permeability within porous hollow structures, and well-dispersed Pt NPs, which catalytically activate the sensor. Our study provides great promise for advancing surface catalytic reactions due to their exceptional surface area and gas permeability, paving the way for future applications.

Light-Responsive Shape- and Color-Changing Block Copolymer Particles with Fast Switching Speed.

Polymer particles capable of dynamic shape changes in response to light have received substantial attention in the development of intelligent multifunctional materials. In this study, we develop a light-responsive block copolymer (BCP) particle system that exhibits fast and reversible shape and color transitions. The key molecular design is the integration of spiropyran photoacid (SPPA) molecules into the BCP particle system, which enables fast and dynamic transformations of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) particles in response to light. The SPPA photoisomerization, induced by 420 nm light irradiation, lowers the pH of the aqueous surroundings from 5.5 to 3.3. The protonated P4VP block substantially increases in domain size from 14 to 39 nm, resulting in significant elongation of the BCP particles (i.e., an increase in the aspect ratio (AR) of the particles from 1.8 to 3.4). Moreover, SPPA adsorbed onto the P4VP surface induces significant changes in the luminescent properties of the BCP particles via photoisomerization of SPPA. Notably, the BCP particles undergo fast, dynamic shape and color transitions within a period of 10 min, maintaining high reversibility over multiple light exposures. Functional dyes are selectively incorporated into different domains of the light-responsive BCP particles to achieve different ranges of color responses. Thus, this study showcases a light-responsive hydrogel display capable of reversible and multicolor photopatterning.

Photonic Crystal Reflectors with Ultrahigh Sensitivity and Discriminability for Detecting Extremely Low-Concentration Surfactants.

Developing a facile, intuitive, ultrahigh-sensitive sensor to detect harmful substances in water is critical. Here, an ultrahigh-sensitive sensor is fabricated using a quaternized lamellae-structured polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer (BCP), capable of detecting the heavily used surfactants including sodium dodecyl sulfate (SDS) and sodium methyl sulfate (SMS) through direct visualization of the structural color change. Two distinct detecting mechanisms, including unexpected blue-shifting and red-shifting reflectance wavelengths, are found for low and high concentrations of the SDS surfactant, respectively, due to concentration-dependent compatibility between the quaternized P2VP (QP2VP) block chains and SDS molecules. As the SDS concentration is low (0-1 mM), the QP2VP chains undergo the counter anionic exchange with the hydrophobic alkyl chains of the SDS, resulting in a blue shift toward colorlessness. In contrast, as the SDS concentration is high (>1 mM), the nanoaggregation of the SDS molecules in the layered QP2VP microdomain leads to enhanced hydration nature and increased lamellar periodicity with the red-shifting reflectance wavelength. In contrast, SMS with weaker hydrophobicity results in unchanged and red-shifting reflectance wavelengths at low and high concentrations. Inspired by this, detecting the extremely low-concentration SDS surfactant (0.01 mM) by direct visualization is achieved. The structural color change for surfactant detection also exhibits excellent reversibility and discriminability, providing a straightforward method of detecting anionic surfactants.

High‐Efficiency Structural Coloration Enabled by Defect‐Free Block Copolymer Self‐Assembly for a Solar Cell Distributed Bragg Reflector

AbstractSolar cell coloration with minimum optical loss is increasingly required for building‐integrated photovoltaics (BIPV) in modern urban areas because of its importance in harmonizing the exterior of zero‐energy buildings and surroundings. A simple strategy for developing a distributed Bragg reflector (DBR) is designated with 1D lamella‐forming polystyrene‐b‐poly(2‐vinylpyridine) (PS‐b‐P2VP) films. An optimized thermal annealing process produces defect‐free lamellar microdomains oriented parallel to the substrate throughout the film. The selective crosslinking in the P2VP block and swelling of these films in a methanol solution with methanesulfonic acid facilitate the formation of highly asymmetric gigantic lamellae, enabling the entire visible‐wavelength spectrum of DBR structural colors. Three representative red (R), green (G), and blue (B) DBR films are produced on a Si solar cell. Coloration from high‐reflectance and narrow‐width DBR films results in vividly colored Si solar cells with a minor or negligible reduction in power conversion efficiency. The approach for photovoltaics, in terms of both the attractive esthetic and technical aspects of BIPV application, offers a viable method for fabricating high‐performance DBR films based on block copolymer self‐assembly.

Assembly of P2VP and PS-b-P2VP composite helical nanowire arrays at the liquid/liquid interface

The nanostructures based on polymers have attracted much research interest because of their rich morphologies, unique properties and potential applications in various fields. In particular, helical nanostructures have been research hotspots in recent years. In this work, composite non-helical and helical nanowire arrays of atactic poly(2-vinylpyridine) (P2VP), and block copolymers polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) were fabricated successfully with inorganic species such as HAuCl4 through a liquid/liquid interfacial adsorption and self-assembly approach without addition of any chiral inducers. The formation process of the helical nanowires of P2VP includes the following steps, i.e. adsorption of the polymer molecules and HAuCl4 at the interface, the following protonation of pyridine groups, straightening of the P2VP chains by mutual repulsion between the protonated pyridine groups, aggregation of the P2VP chains due to the hydrophobic interactions between the backbones, and ordered organization of the pyridine groups through π-π interactions. The helical nanowires of PS-b-P2VP are worm-like micelles with a PS core and a P2VP shell, which are formed through the self-assembly of the block copolymer molecules with HAuCl4 within the interfacial phase with the help of hydrophobic interaction between the PS blocks and orderly stacking of the P2VP blocks. The different formation mechanisms reflected the effects of molecular structure on the self-assembly of polymers. In addition, the formed nanowires further self-organize into ordered arrays due to the increasing interfacial pressure during the generation of the nanowires. The results of this study expand the scope of research on polymer self-assembly and the application of liquid/liquid interfacial self-assembly techniques to acquire highly ordered supramolecular nanostructures.

PH-Mediated Size-Selective Adsorption of Gold Nanoparticles on Diblock Copolymer Brushes.

Precise control of nanoparticles at interfaces can be achieved by designing stimuli-responsive surfaces that have tunable interactions with nanoparticles. In this study, we demonstrate that a polymer brush can selectively adsorb nanoparticles according to size by tuning the pH of the buffer solution. Specifically, we developed a facile polymer brush preparation method using a symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer deposited on a grafted polystyrene layer. This method is based on the assembly of a PS-b-P2VP thin film oriented with parallel lamellae that remains after exfoliation of the top PS-b-P2VP layer. We characterized the P2VP brush using X-ray reflectivity and atomic force microscopy. The buffer pH is used to tailor interactions between citrate-coated gold nanoparticles (AuNPs) and the top P2VP block that behaves like a polymer brush. At low pH (∼4.0) the P2VP brushes are strongly stretched and display a high density of attractive sites, whereas at neutral pH (∼6.5) the P2VP brushes are only slightly stretched and have fewer attractive sites. A quartz crystal microbalance with dissipation monitored the adsorption thermodynamics as a function of AuNP diameter (11 and 21 nm) and pH of the buffer. Neutral pH provides limited penetration depth for nanoparticles and promotes size selectivity for 11 nm AuNP adsorption. As a proof of concept, the P2VP brushes were exposed to various mixtures of large and small AuNPs to demonstrate selective capture of the smaller AuNPs. This study shows the potential of creating devices for nanoparticle size separations using pH-sensitive polymer brushes.

Organic-Inorganic Phenolic/POSS Hybrids Provide Highly Ordered Mesoporous Structures Templated by High Thermal Stability of PS-b-P4VP Diblock Copolymer.

Anionic living polymerization was used to prepare a diblock copolymer of poly(styrene-b-4-vinyl pyridine) (PS-b-P4VP), and a phenolic resin with a double-decker silsesquioxane (DDSQ) cage structure was used to form a phenolic/DDSQ hybrid (PDDSQ-30 with 30 wt.% DDSQ). Strong intermolecular hydrogen bonding could be confirmed through the hydroxyl (OH) groups of PDDSQ hybrid with the pyridine group of the P4VP block in PDDSQ-30/PS-b-P4VP blends based on Fourier transform infrared spectroscopy analyses, where increasing PDDSQ concentrations resulted in a higher proportion of hydrogen-bonded pyridine groups. After thermal polymerization at 180 °C, the self-assembled structures of these PDDSQ/PS-b-P4VP blends were revealed by data from small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), where the d-spacing increased with raising PDDSQ concentration. Because relatively higher thermal stability of the PDDSQ hybrid than pure phenolic resin and PS-b-P4VP template, we can obtain the long ranger order of mesoporous PDDSQ hybrids after removing the PS-b-P4VP template, which reveals the high surface area and high pore volume with cylindrical and spherical structures corresponding to the PDDSQ compositions that are rarely observed by using pure phenolic resin as the matrix and could be used in supercapacitor application.

PH-Responsive Poly(ethylene glycol)-b-poly(2-vinylpyridine) Micelles for the Triggered Release of Therapeutics

The use of pH-responsive polymeric micelles is a promising approach to afford the targeted, pH-mediated delivery of hydrophobic drugs within the low-pH tumour milieu and intracellular organelles of cancer cells. However, even for a common pH-responsive polymeric micelle system-e.g., those utilising poly(ethylene glycol)-b-poly(2-vinylpyridine) (PEG-b-PVP) diblock copolymers-there is a lack of available data describing the compatibility of hydrophobic drugs, as well as the relationships between copolymer microstructure and drug compatibility. Furthermore, synthesis of the constituent pH-responsive copolymers generally requires complex temperature control or degassing procedures that limit their accessibility. Herein we report the facile synthesis of a series of diblock copolymers via visible-light-mediated photocontrolled reversible addition-fragmentation chain-transfer polymerisation, with a constant PEG block length (90 repeat units (RUs)) and varying PVP block lengths (46-235 RUs). All copolymers exhibited narrow dispersity values (Đ ≤ 1.23) and formed polymeric micelles with low polydispersity index (PDI) values (typically <0.20) at physiological pH (7.4), within a suitable size range for passive tumour targeting (<130 nm). The encapsulation and release of three hydrophobic drugs (cyclin-dependent kinase inhibitor (CDKI)-73, gossypol, and doxorubicin) were investigated in vitro at pH 7.4-4.5 to simulate drug release within the tumour milieu and cancer cell endosome. Marked differences in drug encapsulation and release were observed when the PVP block length was increased from 86 to 235 RUs. With a PVP block length of 235 RUs, the micelles exhibited differing encapsulation and release properties for each drug. Minimal release was observed for doxorubicin (10%, pH 4.5) and CDKI-73 exhibited moderate release (77%, pH 4.5), whereas gossypol exhibited the best combination of encapsulation efficiency (83%) and release (91% pH 4.5) overall. These data demonstrate the drug selectivity of the PVP core, where both the block molecular weight and hydrophobicity of the core (and accordingly the hydrophobicity of the drug) have a significant effect on drug encapsulation and release. These systems remain a promising means of achieving targeted, pH-responsive drug delivery-albeit for select, compatible hydrophobic drugs-which warrants their further investigation to develop and evaluate clinically relevant micelle systems.

Stimuli-Responsive Triblock Terpolymer Conversion into Multi-Stimuli-Responsive Micelles with Dynamic Covalent Bonds for Drug Delivery through a Quick and Controllable Post-Polymerization Reaction

Stimuli-responsive copolymers are of great interest for targeted drug delivery. This study reports on a controllable post-polymerization quaternization with 2-bromomethyl-4-fluorophenylboronic acid of the poly(4-vinyl pyridine) (P4VP) block of a common poly(styrene)-b-poly(4-vinyl pyridine)-b-poly(ethylene oxide) (SVE) triblock terpolymer in order to achieve a selective responsivity to various diols. For this purpose, a reproducible method was established for P4VP block quaternization at a defined ratio, confirming the reaction yield by 11B, 1H NMR. Then, a reproducible self-assembly protocol is designed for preparing stable micelles from functionalized stimuli-responsive triblock terpolymers, which are characterized by light scattering and by cryogenic transmission electron microscopy. In addition, UV-Vis spectroscopy is used to monitor the boron-ester bonding and hydrolysis with alizarin as a model drug and to study encapsulation and release of this drug, induced by sensing with three geminal diols: fructose, galactose and ascorbic acid. The obtained results show that only the latter, with the vicinal diol group on sp2-hybridized carbons, was efficient for alizarin release. Therefore, the post-polymerization method for triblock terpolymer functionalization presented in this study allows for preparation of specific stimuli-responsive systems with a high potential for targeted drug delivery, especially for cancer treatment.

In situ synthesis of the Fe3O4@poly(4-vinylpyridine)-block-polystyrene magnetic polymer nanocomposites via dispersion RAFT polymerization

This work presents a facile strategy for the generation of Fe3O4@poly(4-vinylpyridine)-block-polystyrene (Fe3O4@P4VP-b-PS) magnetic polymer nanocomposites. P4VP-b-PS nanoparticles prepared by dispersion RAFT polymerization of styrene in methanol/water in the presence of macro-P4VP chain transfer agent was employed as templates to grow Fe3O4 on polymeric network templates. With the following addition of FeCl3 into the above polymer colloids, pyridyl moieties in P4VP block of nanoparticles could further react with Fe3+ through a coordination reaction to generate Fe3+@P4VP-b-PS nanoparticles. After the subsequent addition of FeCl2 and NH3⋅H2O, the co-precipitation reaction occurred on the surface of the polymeric nanoparticle to form Fe3O4@P4VP-b-PS magnetic polymer nanocomposites. Herein, FT-IR, XRD, TGA, XPS, TEM and VSM were applied to characterize the morphology, structure and magnetism performance of the synthesized magnetic polymeric nanocomposites.

Uniform π‐Conjugated‐Co‐Oligomer‐Based Nanofibers of Controlled Length with Near‐Infrared Emission, Photodynamic and Photothermal Activities

Abstractπ‐Conjugated‐polymer‐based nanofibers (CPNFs) have attracted considerable interest in the community of nanomedicine owing to their high‐aspect‐ratio architecture and inherent photo‐imaging, photothermal, photodynamic, and photoacoustic properties. However, the preparation of uniform CPNFs of controlled length and composition with near‐infrared emission (NIR), photothermal and photodynamic activity remains in its infancy. A novel block copolymer consisting of a donor‐acceptor‐donor (D‐A‐D) π‐conjugated co‐oligomer with a diketopyrrolopyrrole (DPP) unit as electron‐deficient acceptor flanked by oligo(p‐ phenylene ethynylene) (OPE) as an electron‐rich donor and a poly(2‐vinylpyridine) (P2VP) block (OPE4‐DPP‐OPE4‐b‐P2VP44, the subscripts describe the extra and average number of repeat units for π‐conjugated OPE segment and P2VP block, respectively) is designed and synthesized. By using the self‐seeding approach of living crystallization‐drive self‐assembly (CDSA), uniform CPNFs containing a D‐A‐D OPE4‐DPP‐OPE4 core and a P2VP corona with tunable length from 31 to 611 nm are generated. The resulting CPNFs exhibit NIR emission with a peak at 837 nm. The CPNFs also can serve as a photosensitizer to efficiently produce single oxygen and show a photothermal effect upon 660 nm irradiation. To the author's best knowledge, it is the first report on the generation of uniform CPNFs of controlled length with NIR emission, and photodynamic and photothermal activities by living CDSA.

Control on Pt-containing ordered honeycomb mesoporous nanostructures via self-assembly of block copolymer

Control on the mesoporous nanostructures with uniform-sized and well-arranged mesopores can provide enhanced surface areas and mechanical properties, which are preferred for the development of energies, sensors, and electro-optical devices. Herein, Pt-containing ordered honeycomb (Pt/OHC) nanocomposites with regularly arranged mesopores were synthesized via self-assembly of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers (BCPs), following mechanism study of morphological evolution, concept of structural control, potential in catalyst application, and exploration of various metals. Particularly, it was found that the self-assembly of BCP directed the ordered arrangement of the mesopores, whereas the P4VP blocks incorporated Pt and precisely positioned it on the pore walls and on the outer surface of the honeycomb matrix. Mono- to multi-layered Pt/OHCs could be generated by controlling the thicknesses of the self-assembled pristine templates, and the average diameters of the mesopores could be varied from 12 nm to 40 nm by tuning the PS:P4VP block mass ratios. The obtained Pt/OHC demonstrated promising application as electrocatalysts in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), for which an overpotential of 39 mV at current density of 10 mA/cm2 (η10) and a high half wave potential (E1/2) of 0.87 V (vs. RHE), respectively, were observed in acidic media. In addition, the strategy developed here could be expanded for other metals, such as Au and Ir, to be incorporated into the ordered honeycomb matrix, providing a robust method to synthesize metal-containing mesoporous nanomaterials. With this work, we aim to offer an insight of designing ordered mesoporous nanocomposites, a concept of control over the mesoporous nanostructures, and a potential for their application in electrocatalysts.

3D spiderweb-like nanowire networks loading single-atom catalysts in capillary array as high-efficiency microreactor

Rapid fluid transport and high reaction efficiency are known as irreconcilable indicators for designing high-performance monolithic microreactors. Here, proceeding from microstructure design and single-atom catalysts (SACs) utilization simultaneously, we developed 3D spiderweb-like nanowire networks in wood capillary array owning high permeability integrated with successfully synthesized SACs as high-efficiency microreactor for organic pollutant removal from water. The 3D spiderweb-like nanowire networks could be obtained by noncovalent and physical entanglement interactions of ultralong and flexible PEG113-b-P4VP104 worm-like micelles forming loosened micro-aerogel in the wood capillary. Abundant nanowire networks in straight microchannels array allow vast quantities of catalyst active component loading sites and greatly increase contact reaction efficiency. Meanwhile, the grid-like porous structure of the nanowire networks preferably maintains good permeability of the wood capillary array. Furthermore, strong coordination interaction of pyridine in P4VP block and confinement effect from core-shell structured worm-like micelles afford uniformly distributed SACs with high density. As a proof of concept, we demonstrate an integration of unique microstructure from 3D spiderweb-like nanowire networks in wood capillary array and well dispersed Pd-N4/Fe-N4 SACs enables high removal efficiency for methylene blue and fast mass transfer for water. Importantly, this work provides a facile and scalable method for atomically dispersed catalysts, paving the way for designing high-performance microreactors in other potentially important reactions.

PH-responsive crosslinked vesicles and micelles based on poly(2-ethyl-2-oxazoline-b-4-vinylpyridine)

Crosslinked vesicles have raised significant interest in the last decade as structures that mimic cells, organelles, and nanoreactors. Herein, the use of 1,4-dibromobutane (DBB) and Cu2+ to crosslink pH-responsive poly(2-ethyl-2-oxazoline-b-4-vinylpyridine) - P(EtOx-b-4VP) - vesicles, or alternatively a vesicles + micelles mixture, whose external layer is composed of the biocompatible and stealth PEtOx is discussed. DBB-crosslinked and Cu2+-crosslinked P(EtOx-b-4VP) aggregates were stable against hydrolytic degradation in the pH range that was studied (2–10) except for Cu2+-crosslinked aggregates at pH = 2. The swelling of the DBB-crosslinked aggregates in an aqueous medium was modulated by the pH-responsiveness of the P4VP block. Freeze-dried DBB-crosslinked aggregates could be dispersed in water and maintained their morphology, which is an advantage for storage and property preservation. Hydrophobic Nile red and Reichardt’s dye induced the self-assembly of the non-crosslinked copolymers in an aqueous medium, forming inverse structures with an external layer of P4VP. On the other hand, these hydrophobic molecules were loaded by the crosslinked aggregates even in acidic conditions where both PEtOx and P4VP blocks are swollen by water, and the PEtOx block played an important role in this process. Moreover, the hydrophilic macromolecule rhodamine isothiocyanate-dextran could be encapsulated inside the vesicles. While the external layer of the aggregates composed of PEtOx sorbs hydrophobic molecules, the transport through the polymeric bilayer of the vesicles may be pH-controlled by the P4VP block. Overall, these results indicate that crosslinked P(EtOx-b-4VP) aggregates are feasible candidates in the development of nanoreactors and cell/organelle mimics.

Effect of Molecular Structure of Photoswitchable Surfactant on Light-Responsive Shape Transition of Block Copolymer Particles

Photoactive shape-changing particles offer a promising platform for smart materials with tunable properties at high spatiotemporal resolutions. Herein, a series of spiropyran-based surfactants with different alkyl spacer lengths are developed to achieve photoactive, shape-changing particles through confined self-assembly of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) within an evaporative emulsion. The length of the alkyl chain spacer between the spiropyran headgroup and ionic chain-end is modulated from hexyl to ethyl decanoate to provide surfactants with tunable amphiphilicity. Under UV light, the hydrophilic ring-opened merocyanine surfactants produce onion-like microspheres with a P4VP surface. Conversely, by exposure to visible light, the ring-closure reaction of the spiropyran moieties shifts their hydrophobicity and yields striped ellipsoids with axially stacked PS and P4VP blocks. This sphere-to-ellipsoid transition is observed only for surfactants that contain spacers longer than or equal to octyl. The effects of photoswitchable surfactants on their interfacial properties and corresponding morphological evolution of the particles are investigated to elucidate the mechanism of the shape transition of the photoactive particles.

WITHDRAWN:Control on Pt-Containing Ordered Honeycomb Mesoporous Nanostructures via Self-Assembly of Block Copolymer

Control on the mesoporous nanostructures with uniform-sized and well-arranged mesopores can provide enhanced surface areas and mechanical properties, which are preferred for the development of energies, sensors, and electro-optical devices. Herein, Pt-containing ordered honeycomb (Pt/OHC) nanocomposites with regularly arranged mesopores were synthesized via self-assembly of polystyrene- block -poly(4-vinylpyridine) (PS- b -P4VP) block copolymers (BCPs), following mechanism study of morphological evolution, concept of structural control, potential in catalyst application, and exploration of various metals. Particularly, it was found that the self-assembly of BCP directed the ordered arrangement of the mesopores, whereas the PVP blocks incorporated Pt and precisely positioned it on the pore walls and on the outer surface of the honeycomb matrix. Mono- to multi-layered Pt/OHCs could be generated by controlling the thicknesses of the self-assembled pristine templates, and the average diameters of the mesopores could be varied from 12 nm to 40 nm by tuning the PS:P4VP block mass ratios. The obtained Pt/OHC demonstrated promising application as electrocatalysts in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), for which an overpotential of 39 mV at current density of 10 mA/cm 2 (η 10 ) and a high half wave potential ( E 1/2 ) of 0.87 V (vs. RHE), respectively, were observed in acidic media. In addition, the strategy developed here could be expanded for other metals, such as Au and Ir, to be incorporated into the ordered honeycomb matrix, providing a robust method to synthesize metal-containing mesoporous nanomaterials. With this work, we aim to offer an insight of designing ordered mesoporous nanocomposites, a concept of control over the mesoporous nanostructures, and a potential for their application in electrocatalysts. Pt-containing ordered honeycomb (Pt/OHC) nanocomposites were synthesized via self-assembly of PS- b -P4VP block copolymers (BCPs), following mechanism study of morphological evolution, concept of structural control, potential in electrocatalyst application, and exploration of various metals. With this work, we aim to offer some insights in designing and controlling on the mesoporous nanostructures and to provide a facile method to synthesize mesoporous metallic nanocomposites with advanced performance for potential application in electrocatalysts.

Thermodynamic understanding the phase behavior of fully quaternized poly(ethylene oxide)-b-poly(4-vinylpyridine) block copolymers

In this study, the poly(ionic liquid)s (PILs)-based block copolymers (BCPs) with a high charge density, poly(ethylene oxide)-b-quaternized poly(4-vinylpyridinium) with X− as counterion (PEO-b-QP4VP-X), were prepared by full quaternization of the poly(4-vinylpyridine) (P4VP) block in neutral PEO-b-P4VP BCP. The complete quaternization of P4VP block was confirmed by NMR and FT-IR. The phase separation behavior of PEO-b-QP4VP-X BCPs was examined, which was found to be strongly dependent on the counterion species. Specifically, as compared with the neutral PEO-b-P4VP, PEO-b-QP4VP-Br exhibits a stronger segregation strength, while the other three PEO-b-QP4VP-X (X = PF6, TFO and TFSI) BCPs show a weaker phase separation ability. The phase behavior of PEO-b-QP4VP-X was explained using the thermodynamic mechanism originally applied for salt-doped BCPs of low charge density. The variation of the Flory-Huggins parameter (Δχ) can be divided into three terms: Δχ1 due to the change in monomer identity after quaternization, ΔχBorn from the Born energy of counterions and χΓ arising from the local charge cohesion. For PEO-b-QP4VP-X BCPs, both Δχ1 and ΔχBorn are negative, but χΓ is positive, and they vary with counterion size in different ways. The competition of these three terms dominates the change tendency of phase behavior, among which Δχ1 plays an important role at high level of charge density. The rationality of the aforementioned thermodynamic mechanism of Δχ was also verified by the phase behavior of salt-doped PEO-b-QP4VP-X.

Gold/Pentablock Terpolymer Hybrid Multifunctional Nanocarriers for Controlled Delivery of Tamoxifen: Effect of Nanostructure on Release Kinetics.

Here, we describe the preparation and characterization of organic/inorganic hybrid polymer multifunctional nanocarriers. Novel nanocomposites of gold nanoparticles using pH-responsive coordination pentablock terpolymers of poly(ε-caprolactone)-b-poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide)-b-poly(ε-caprolactone), bearing or not bearing partially quaternized vinylpyridine moieties, were studied. The template morphology of the coordination pentablock terpolymer at physiological pH ranges from crew-cut to multicompartmentalized micelles which can be tuned by chemical modification of the central block. Additionally, the presence of 2VP groups allows the coordination of gold ions, which can be reduced in situ to construct gold@polymer nanohybrids. Furthermore, the possibility of tuning the gold distribution in the micelles, through partial quaternization of the central P2VP block, was also investigated. Various morphological gold colloidal nanoparticles such as gold@core-corona nanoparticles and gold@core-gold@corona nanoparticles were synthesized on the corresponding template of the pentablock terpolymer, first by coordination with gold ions, followed by reduction with NaBH4. The pentablock and gold@pentablock nanoparticles could sparingly accommodate a water-soluble drug, Tamoxifen (TAX), in their hydrophobic micellar cores. The nanostructure of the nanocarrier remarkably affects the TAX delivery kinetics. Importantly, the hybrid gold@polymer nanoparticles showed prolonged release profiles for the guest molecule, relative to the corresponding bare amphiphilic pentablock polymeric micelles. These Gold@pentablock terpolymer hybrid nanoparticles could act as a multifunctional theranostic nanoplatform, integrating sustainable pH-controlled drug delivery, diagnostic function and photothermal therapy.

Effect of Hofmeister Salts on the LCST of Poly(diethyl vinylphosphonate) and Poly(2‐vinylpyridine‐block‐diethyl vinylphosphonate)

AbstractHerein, the effect of Hofmeister anions on the cloud point of poly(diethyl vinylphosphonate) (PDEVP) homopolymers and poly(2‐vinylpyridine‐block‐diethyl vinylphosphonate) (P(2VP‐b‐DEVP)) block copolymers using their sodium salts is reported. The change in the cloud point temperature (TCP) of these two polymers upon the addition of coordinating transition metal salts is investigated. The TCP of the different solutions is determined by ultraviolet–visible spectroscopy at different temperatures. Additionally, dynamic light scattering (DLS) is applied to investigate the behavior of the block copolymer below and above the TCP. Both polymers follow the trend of the Hofmeister series using the different sodium salts. This indicates that the P2VP block of the copolymer does not affect the TCP when noncoordinating cations are used. In contrast, a linear increase in the TCP is observed when the block copolymer is used in the presence of copper(II) or iron(III), whereas the TCP of the homopolymer in the same concentration range remains unchanged. The cloud point is increased due to an increase in hydrophilicity and electrostatic repulsion, resulting from the transition metal ion coordination. The coordination to the P2VP units is confirmed by the DLS. These findings can lead to potential applications as sensors or in wastewater purification.