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Ferroelectric polymers are a family of crystalline polymers with reversible remanent polarization originating from their unique chemical structures and molecular packing. As an important ferroelectric polymer, poly(vinylidene fluoride) (PVDF) and its copolymers have been exploited for various applications, including nonvolatile memories, energy harvesters, and piezoelectric/pyroelectric sensors. To achieve better performance in PVDF-based devices, crystallization manipulation and controllable nanostructure formation are unavoidable and are of crucial importance. For this review, recent exploitation of the control of PVDF ferroelectric polymer crystallization at the nanoscale was specifically examined and summarized to provide insight into the future development of ferroelectric polymer nanomaterials. Ferroelectric polymers, poly(vinylidene fluoride) (PVDF), and its copolymers have been exploited for various applications, including nonvolatile memories, energy harvesters, and piezoelectric/pyroelectric sensors. To achieve better performance in PVDF-based devices, crystallization manipulation and controllable nanostructure formation are unavoidable and are of crucial importance. For this review, recent exploitation of the control of PVDF ferroelectric polymer crystallization at the nanoscale was specifically examined and summarized to provide insight into the future development of ferroelectric polymer nanomaterials.

Facile preparation of poly(vinylidene fluoride) (PVDF) homopolymer nanoparticles (NPs) with monodispersed size distribution and predominant ferroelectric phases was done in an interfacial nonsolvent (water/methanol)-solvent (dimethylformamide (DMF))-polymer (PVDF) ternary system using two interfacial nanoassembly methods. First, a fluidic liquid-liquid interface consisting of two miscible solvents was created by introducing nonsolvent (water) under the PVDF solution. After the interface was created, the interface moved up to the DMF phase direction; PVDF NPs were produced through nonsolvent-induced phase separation. As the water content decreased in the nonsolvent by mixing with methanol, PVDF structures changed from nanoparticles with 252 nm average diameter (PVDF NP-1) to a porous membrane through membrane-wrapped NPs. The phenomena were found to be related to the mutual affinity of solvent, nonsolvent, and PVDF. When an additional external force was introduced to the water-DMF-PVDF system through magnetic stirring (reprecipitation method), smaller PVDF NPs with 61.4 nm diameter were obtained (PVDF NP-2). Both the as-prepared PVDF NPs were demonstrated with the predominant ferroelectric (electroactive (EA)) phase up to 97-98% among crystalline phases, which is apparently the highest value ever reported for PVDF homopolymer NPs. It is noteworthy that PVDF NP-2 showed a higher β phase ratio than that of PVDF NP-1, as proved using Fourier transform infrared (FT-IR) spectroscopy. Also, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements revealed that PVDF NP-1 exhibited higher crystallinity and that PVDF NP-2 underwent a well-separated two-step phase transition under heating. Results suggest that controlling interface formation with DMF and water plays a crucial role in manipulating ferroelectric PVDF nanostructures in terms of crystallinity and the ferroelectric β phase-to-γ phase ratio.

We synthesized polycyclosiloxanes with varying catechol substitution ratios (CFPSs) and investigated silver nanoparticles (AgNPs) adsorption ability on their self-assembled nanofilm. The nanopartic...

We synthesized pyrene-containing amphiphilic fluorinated copolymers p(C7F15MAA/PyMMA)s through free radical polymerization. The pyrene composition ratio was readily tuned from 0.6 to 3 mol% with di...

High-energy storage in polymer dielectrics is limited by two decisive factors: low-electric breakdown strength and high hysteresis under high fields. Poly(vinylidene fluoride) (PVDF), as a well-known ferroelectric polymer having a high-breakdown strength (700 MV/m) and a high dielectric constant, is suitable for use as a dielectric capacitor film, but ferroelectric hysteresis from the crystalline phase has prevented its practical application. In our previous study, the ferroelectric switching of crystalline PVDF is suppressed effectively in PVDF-based Langmuir–Blodgett (LB) nanofilms because of its large interfacial effect, even in an extremely high electric field. This study investigated the ferroelectricity and energy storage behaviors of PVDF LB nanofilms at sub-50 nm thicknesses. The ferroelectric hysteresis loops were measured using a Sawyer–Tower circuit in different electric fields. An energy density of 6.0 J/cm3 at 500 MV/m was demonstrated for the 12-nm-thick PVDF LB nanofilm device. Polar polymers with permanent dipoles such as poly(vinylidene fluoride) (PVDF) are suitable for use as high-energy storage density dielectrics because of their high permittivity. This study investigated the ferroelectricity and energy storage behaviors of PVDF Langmuir–Blodgett (LB) nanofilms at sub-50 nm thicknesses. The ferroelectric hysteresis loops were measured using a Sawyer–Tower circuit in different electric fields. An energy density of 6.0 J/cm3 at 500 MV/m was demonstrated for the 12-nm-thick PVDF LB nanofilm device.

This report describes the synthesis of highly carboxylated cellulose nanocrystals (CNCs) from jute fiber by facile oxidation with ammonium persulfate (APS). The oxidation time effects on microstructure, surface chemistry, crystal structure, and thermal properties were investigated. Crystal-like morphology was obtained with 5.2 nm average particle diameter and 300–500 nm length, depending on the oxidation time. The degree of oxidation (DO) was found to be 0.27: the highest among APS-oxidized CNCs. The carboxylic group amount of 1550 mmol kg−1 was achieved for 16 h oxidation treatment, resulting in high surface charge with the absolute zeta potential value of 40 mV. The DO value was well correlated with the peak intensity of carbonyl group ascertained from FT-IR studies: 0.12 + 0.38(I1730/I1060). As-prepared CNCs showed improved dispersibility in organic solvents up to 15 h. The APS oxidized CNCs showed good thermal stability: the onset decomposition temperature was 240 °C. Using X-ray diffraction method the crystalline index was ascertained as more than 67%. Surface modification of APS-oxidized cellulose nanofibers (CNFs) was confirmed using FT-IR and XPS. Modified CNFs were dispersed in organic solvents such as toluene and THF. Jute is a good candidate material for obtaining highly pure and crystalline CNCs through APS oxidation, exhibiting great potential as a functional material for use in diverse fields.

The paper describes facile synthesis of boronic ester-containing polycyclosiloxane (pCS-ABPE) through a one-pot-two-step hydrosilylation reaction that allows control of the functionalization efficiency stoichiometrically from zero to 100%. The combination of cyclosiloxane and boronic acid groups is expected to benefit from excellent thermal properties, flexible polymer backbone, and chemical resistance of the polycyclosiloxane part and the dynamic chemical properties of the boronic acid part to generate novel and functional hybrid polymers. Results showed that the hydrolysis of pCS-ABPE gave rise to a boronic-acid-containing polycylcosiloxane (pCS-AB) with good self-assembly nanofilm formation (6 nm film thickness) on plastic substrates through dip-coating method, mainly because of its low surface free energy (∼20 mN m−1). In addition, the dynaminc characteristics of boronic acid groups in the pCS-AB film were demonstrated through water soluble dye Alizarin Red S (ARS) coating. The film surface underwent reversible coating through the boronic acid equilibrium: formation of the dynamic covalent bonding (pCS-AB-ARS) and bond deformation with Zn ions for ARS-Zn complex formation. The performance makes the self-assembly nanofilm promising for chemical sensor applications.

Ferroelectric poly(vinylidene fluoride)/semiconductive polythiophene (P3CPenT) blend monolayers were developed at varying blend ratios using the Langmuir-Blodgett technique. The multilayered blend nanosheets show much improved surface roughness that is more applicable for electronics applications than spin-cast films. Because of the precisely controllable bottom-up construction, semiconductive P3CPenT were well dispersed into the ferroelectric PVDF matrix. Moreover, the ferroelectric matrix contains almost 100% β crystals: a polar crystal phase responsible for the ferroelectricity of PVDF. Both the good dispersion of semiconductive P3CPenT and the outstanding ferroelectricity of the PVDF matrix in the blend nanosheets guaranteed the success of ferroelectric organic non-volatile memories based on ferroelectricity-manipulated resistive switching with a fresh high ON/OFF ratio and long endurance to 30 days.

Complex flower-shaped superstructures (FSSs) have rarely been reported in pure organic systems with a single soft organic molecule without rigid skeletons. Herein, simple self-assembled complex FSSs using amphiphilic organic cyclosiloxane amphiphiles are obtained through a drop-casting solution process. The synergetic effect of amide–amide hydrogen bonding/alkyl hydrophobic interactions can be tuned to generate “flower petals” with either straight ligulate or curved-plate rosaceous corolla shapes. The step-wise petal formation process is also investigated using scanning electron microscopy. Furthermore, FSSs with different petal shapes with varying surface “wettabilities” are demonstrated. The ligulate-like structure forms a networked porous surface that can suspend water droplets with a non-wet contact mode, i.e., a slippery superhydrophoborphobic surface. The surface of the rosaceous corolla petals exhibits a wet-contact mode with respect to the water droplet with sticky superhydrophobicity. The results play a significant role in understanding the structure and properties of self-assembled FSSs, thereby shedding new light on developing new hierarchical materials from soft organic amphiphiles in the future.

We describe a systematic approach for producing cellulose nanofiber (CNF) nanosheets using the Langmuir-Blodgett (LB) technique. The CNFs were obtained from sulfuric acid hydrolysis of commercially available microfibrillated cellulose. Needle-like CNFs, negatively charged by grafted sulfate groups, were maintained at the air-water interface, assisted by amphiphilic polymer, poly( N-dodecyl acrylamide) (pDDA). The CNFs produced a stable monolayer. The surface pressure increased steadily with a high collapse pressure of 50 mN m-1 when spread with formic acid and pDDA. The composite monolayers were transferred onto solid substrates as Y-type LB films using a vertical dipping method. Upstroke and downstroke transfer ratios of the films were, respectively, unity and 0.88, indicating that full coverage was achieved by the monolayer even for more than 200 layers. Results obtained using atomic force microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy showed that CNF nanosheets possess well-defined layer structures with average monolayer thickness of 5.3 nm. The relative amount of CNFs in the nanosheets was calculated as 62.6 wt % using the quartz crystal microbalance technique. The as-prepared nanosheets are optically transparent to visible light and have high hydrophobicity. In fact, the nanosheet transparency was higher than 88% at 600 nm wavelength for 24 layers. A miniscule amount of pDDA enables demonstration of free-standing CNF nanosheets with 1 cm width and 45.6 nm thickness (23 layers).

A Cellulose nanofiber (CNF) is an amazing nanomaterial produced from ubiquitous sources with outstanding mechanical, chemical, and barrier properties. This report describes facile functionalization of CNF with trichloro(1H,1H,2H,2H-heptadecafluorodecyl)silane (THFS). The paste form CNF was solvent exchanged from initial water to AK-225 (a mixture of 3,3-dichloro-1,1,1,2,2-pentafluoropropane and 1,3-dichloro-1,1,2,2,3-pentafluoropuropane) before surface modification with THFS. The modified CNFs were dispersed uniformly in AK-225. The CNF film, which was prepared using simple drop casting, showed a superhydrophobic surface with a water contact angle of 160° and oleophilicity with a hexane contact angle of less than 35°. The modified CNF assembly is thermally stable, optically transparent and resistant to corrosive environment (acidic, basic and seawater solutions). The separation of oil and water mixtures was demonstrated using steel mesh coated with modified CNF. Separation efficiency greater than 99% was achieved by simple gravitational force for hydrocarbons and organic solvents. The as-prepared mesh can be used repeatedly more than 50 times with the same efficiency as the initial state.

A crystalline tetramethylcyclotetrasiloxane (TMCS)-derived amphiphile was regioselectively synthesized with eight peripheral hydrophilic amide groups and hydrophobic dodecyl chains by Pt(0)-catalyzed hydrosilylation and amidation reactions. The as-synthesized materials showed ordered lamellar structure formation in the powder form. It also exhibits superior two-dimensional (2D) monolayer formation properties at the air–water interface with unexpectedly high collapse surface pressure and elastic modulus. The monolayers act as two-dimensional building blocks with finely controllable thickness on a several nanometer scale irrespective of the substrate type and properties. The amphiphile forms nanofibers spontaneously by good–poor solvent strategies, which contributes to porous three-dimensional (3D) structures possessing superhydrophobic surface wettability.

As-deposited poly(vinylidene fluoride) (PVDF) Langmuir–Blodgett (LB) nanofilms with a complete β phase show a remarkably high remanent polarization (Pr), about 6.6 μC cm−2 at 81 nm. Extrinsic switching characteristics of the nanofilms are demonstrated. Results also show that highly oriented PVDF homopolymer LB nanofilms down to 12 nm with no post-treatment retain robust room-temperature ferroelectric polarization switching that is greater than 105 operation cycles, with longer standing fatigue endurance than those of PVDF copolymer nanofilms.

Poly(vinylidene fluoride) (PVDF) was used as an organic spacer to fabricate spin-valve devices for the first time. Their magnetoresistance (MR) effects with different layer numbers of PVDF were investigated at both room and low temperatures. The device resistances and MR ratios increase with decreasing measurement temperature. It is noted that the MR ratios at room temperature are over 2% and 0.5% for devices with 3 layers and 13 layers of PVDF, respectively.

The present work addresses the solvent-dependent properties of Langmuir films of poly(vinylidene fluoride) (PVDF) and amphiphilic poly(N-dodecylacrylamide) (pDDA) at different mixing ratios. After introducing pDDA nanosheets, PVDF Langmuir films obtain a tremendously enhanced modulus as well as high transfer ratios using the vertical dipping method caused by the support of the pDDA two-dimensional hydrogen bonding network. Brewster angle microscopy (BAM) was used to investigate PVDF monolayers at the air–water interface in situ. Spreading from different solvents, the PVDF molecules take completely different aggregation states at the air–water interface. The PVDF molecules aggregate to become large domains when spread from N-methyl-2-pyrrolidone (NMP). However, the volatile and low-polarity methylethyl ketone (MEK) made the PVDF molecules more dispersive on the water surface. This study also discovers a versatile crystallization control of PVDF homopolymer from complete β phase (NMP) to complete α phase (MEK) at the air–water interface, thereby eliciting useful information for further manipulation of film morphologies and film applications.

Fluorinated polymer nanoparticle films were prepared by dissolving amphiphilic fluorinated polymer, poly (N-1H, 1H-pentadecafluorooctylmethacrylamide) (pC7F15MAA) in two miscible solvents (AK-225 and acetic acid). A superhydrophobic and porous film was obtained by dropcasting the solution on substrates. With higher ratios of AK-225 to acetic acid, pC7F15MAA was densified around acetic acid droplets, leading to the formation of pC7F15MAA nanoparticles. The condition of the nanoparticle film preparation was investigated by varying the mixing ratio or total concentration. A highly sensitive dissolved oxygen sensor system was successfully prepared utilizing a smart surface of superhydrophobic and porous pC7F15MAA nanoparticle film. The sensitivity showed I0/I40 = 126 in the range of dissolved oxygen concentration of 0 ~ 40 mg L-1. The oxygen sensitivity was compared with that of previous reports.

Our earlier research prepared ferroelectric poly(vinylidene fluoride) (PVDF) homopolymer monolayers at the air–water interface using amphiphilic poly(N-dodecylacrylamide) (pDDA) nanosheets with Langmuir–Blodgett (LB) technique. However, the miscibility of solvent for PVDF with the water sub-phase in the Langmuir trough makes the film composition unclear in spite of the feeding ratio of ( ). In this study, angle-resolved X-ray photoelectron spectroscopy (AR-XPS) was used to investigate the surface chemical composition and the depth profile of the PVDF/pDDA LB nanofilms. The X-ray photoelectron spectroscopy (XPS) spectra confirmed by the detection of fluorine atoms that PVDF molecules were deposited successfully onto the substrate. The constant chemical composition with increasing takeoff angle from 15 to 75° reflects a well-regular layer structure of the PVDF LB nanofilm. The mixing ratio of is , which contributes 89.8 wt % PVDF and 10.2 wt % in the PVDF/pDDA LB nanofilms.