Xinping Wang

• Tottori University

Triazoliums are a family of five-membered heterocyclic cations that contain three nitrogen and two carbon atoms. In contrast to the widely studied imidazolium cations, triazoliums are less explored. In terms of the chemical structure, triazolium replaces a carbon atom in the imidazolium cation ring with an electron-withdrawing nitrogen atom, which...

Using angle-resolved X-ray photoelectron spectroscopy, sum-frequency generation vibrational spectroscopy, contact angle measurements, and molecular dynamics simulations, we verify that the glass transition temperature ( T g ) of polymer glass is lower near the free surface. However, the experimental T g -gradients showed a linear variation with dep...

Herein, the adsorption of polystyrene (PS) on phenyl-modified SiO2–Si substrates was investigated. Different from those on neat SiO2–Si substrate, the growth rate (vads) in the linear regime and hads/Rg (hads,...

The polymer/substrate interface plays a significant role in the dynamics of nanoconfined polymers because of its suppression on polymer mobility and its long-range propagation feature, while the molecular origin of the long-range substrate effect in unentangled polymer material is still ambiguous. Herein, we investigated the propagation distances o...

Herein, the desorption of the adsorbed chains (including two regions of flattened chains and loosely adsorbed chains) was examined by monitoring the chain exchange kinetics between the adsorbed chains and the top-free chains in a bilayer system by using fluorine-labeled polystyrene (PS). The results indicated that the exchange behavior of PS-flatte...

Cyclic polymers have recently attracted more and more attention due to their unique structures and performance, but their synthesis still presents great challenges. The commonly used ring-closure strategy to synthesize...

Surface glass transition temperature (Tgsurf) and transition width (W) within 1 nm of the surface were measured by monitoring a qualitative change in the contact angle or density of end-groups (by Time-of-Flight Secondary Ion Mass Spectrometry) with temperature. Polystyrene (PS) films with various thicknesses (h) and molecular weights were studied....

The spatially heterogeneous dynamics in supported ultrathin polymer films are widely recognized to explain their unique thickness-dependent physical properties. In this paper, the surface dynamics of supported poly(ethylene terephthalate) films were scaled by the surface crystallization rate to investigate the variations of the spatially heterogene...

Dry polymer brushes have attracted great attention because of their potential utility in regulating interface properties. However, it is still unknown whether dry polymer brushes will exhibit degrafting behavior as a result of thermal annealing. Herein, a study of the conformational entropy effect on thermal degrafting of dry polystyrene (PS) brush...

Due to the stepwise crystallization behavior of polymorphous poly(l-lactide) (PLLA) films, the surface crystalline structures of thin PLLA films supported on Si/SiOx substrates with various thicknesses of both the film and adsorbed layer were investigated separately by grazing incidence wide-angle X-ray diffraction (GIWAXD). An unusual highly packe...

The lamellar membranes have been considered as one of the most promising candidates for seawater desalination owing to their well-defined 2D nanochannels for fast water permeation and excellent ions rejection. However, it was difficult to directly determine the influence of different functional groups on the desalination performance through experim...

Confinement alters polymer dynamics and results in a marked Tg confinement effect, i.e., a reduction in the glass-transition temperature (Tg) of a polymer under confinement. The Tg confinement effect is related to dynamic enhancement at the air interface caused by reductions in intermolecular cohesion forces at the interface. Thus, tuning molecular...

Bacterial keratitis (BK) and related inflammatory diseases causes irreversible damage to the corneal tissue. In this study, a novel polyacrylamide semi-interpenetrating network hydrogel including quaternized chitosan and tannic acid (PAM-QCS-TA) were used to construct a novel antibacterial and antioxidant contact lens. The obtained hydrogels showed...

The adsorbed layer on a solid surface plays a crucial role in the dynamics of nanoconfinement polymer materials. However, the influence of the adsorbed layer is complex, and clarifying this influence on the dynamics of confined polymers remains a major challenge. In this paper, SiO2-Si substrates with various thicknesses and adsorbed layers of PS w...

Rational functionalization plays an important role to push forward graphene applications in multifarious cutting-edge technologies. A key topic that how to program the regular distribution of functional groups, however, remains a big challenge. Herein, we developed a very simple, high-throughput graphite reduction methodology to attain the negative...

Water-based polymer coatings usually exhibit poor adhesion performance compared to their solvent-based counterparts. Unveiling the difference in interface structures between water-based and solvent-based polymer coatings will help to improve the adhesion performance of water-based polymer coatings. Herein, sum frequency generation (SFG) vibrational...

Many emerging materials, such as ultrastable glasses1,2 of interest for phone displays and OLED television screens, owe their properties to a gradient of enhanced mobility at the surface of glass-forming liquids. The discovery of this surface mobility enhancement3,4,5 has reshaped our understanding of the behaviour of glass formers and of how to fa...

Thermally sensitive polymers have attracted tremendous interest in the design of stimulus-responsive surfactants. In this article, poly(propylene oxide)-b-poly(N-isopropylacrylamide) (PPO-b-PNIPAm) with different block lengths of PNIPAm was synthesized through atom transfer radical polymerization (ATRP). Different from commercial Pluronic surfactan...

Low energy density is the major obstacle for the practical all-solid-state supercapacitors, which may be raised by the combination of the pseudocapacitance with the electrochemical double-layer capacitance. Although graphene and polyaniline have been demonstrated two effective materials, the synthetic route of graphene and their hybrid mode largely...

It has been demonstrated that tailoring the properties of semiconductor/dielectric interfaces with fluorinated polymers yields better performance for organic field-effect transistors (OFETs). However, it remains a challenge to fabricate bottom-gate OFET devices on fluorinated dielectrics using solution-processed methods due to the poor wettability...

The film thickness and substrate interface are the two most common parameters to tune the dynamics of supported thin films. Here, we investigated the glass transition temperature (Tg) and thermal expansion of thin poly(methyl methacrylate) (PMMA) films with various thicknesses and different interfacial effects. We showed that, although the Tg of th...

Tethering a quaternary ammonium (QA)-based poly(ionic liquid) (PIL) onto substrate surfaces appears to be an attractive strategy for the development of antibacterial surfaces. In this work, N-alkyl QA-type PIL brushes were prepared via surface-initiated atom transfer radical polymerization, and their antibacterial activities against E. coli and S....

Intermolecular crowding of densely-tethered polymers promotes chain extension and anisotropy that induces many unique properties. In this study, we used conformation-sensitive infrared spectroscopy to determine that chain extension in a polymer brush is associated with local conformation rearrangements, i.e., contraction of side groups and increase...

Over the past few decades, global paper consumption has continued to increase. The growing demand for paper has aggravated the negative impact on the environment. Therefore, the development of erasable ink or rewritable paper seems to be an ideal way to alleviate this crisis. In this work, a hydrophilic anthracene derivative with nucleophilic subst...

The interfacial orientation of aromatic groups plays a crucial role in determining the properties of graphene-based aromatic polymer nanocomposites. Here, the interfacial orientation of the polystyrene (PS) phenyl groups in contact with graphene is revealed by sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra showed that the...

The thickness of the surface layer on both poly(methyl methacrylate) (PMMA) and polystyrene (PS) films was investigated by monitoring the surface reorganization of fluorinated tracer-labeled PMMA and PS. Three different surface-sensitive techniques with various analytical depth capabilities were used, including contact angle (CA) measurements, sum-...

Highly sensitive and selective detection of trace Cu²⁺ over fourteen kinds of metal ions in aqueous solutions was achieved by the use of a novel contrast-enhancing fluorescent microgels. The microgels were prepared by the use of N-isopropylacrylamide and 1-vinylimidazole as monomers and fluorescent tetraphenylethene (TPE) derivatives as cross-linke...

To overcome the low energy density bottleneck of graphene‐based supercapacitors and to organically endow them with high‐power density, ultralong‐life cycles, etc., one rational strategy that couple graphene sheets with multielectron, redox‐reversible, and structurally‐stable organic compounds. Herein, a graphene‐indanthrone (IDT) donor–π–acceptor h...

A method based on the PeakForce QNM atomic force microscopic (AFM) adhesion measurement is employed to investigate the glassy dynamics of polystyrene (PS) single-chain particles end-grafted to SiO2—Si substrates with different diameters, D0, of 3.4 nm–8.8 nm and molar masses, Mn, of 8–123 kg/mol. As temperature was increased, the adhesion force, Fa...

A high-density poly(methyl methacrylate) (PMMA) brush (σ = 0.77 chain/nm2) with a lower molecular weight distribution was prepared onto a silicon wafer by surface-initiated atom transfer radical polymerization. The surface of the PMMA brush chains was characterized upon the process of the environmental change, from air to water, using contact angle...

Graphite fluoride‐launched graphene functionalization has attracted increasing interest in recent years. Highly basic nucleophiles are normally employed for ultrastrong CF bonding. However, frequently, an appreciable majority of C–F units of graphite fluoride are reductively eliminated, leading to low functionalization degrees. It is hypothesized t...

In this paper, the interfacial π–π interactions of polystyrene (PS) chains next to aromatic-modified substrates were investigated. The results show that the glass transition temperature (Tg) and the modulus of the supported thin PS films increased gradually from phenyl-, naphthyl- to anthracenyl-modified substrates with an increasing number of π el...

In this study, we designed and synthesized the hybrid microgels with positively charged cross-linking network and embedded gold nanoparticles. The hybrid microgels presented reversible thermo-sensitive behavior and the volume transition temperature of ~37 oC, which was close to body temperature. These microgels were successfully applied as vectors...

Interfaces play an important role in modifying the dynamics of polymers confined to the nanoscale. We demonstrate that the distance over which an interface suppresses molecular mobility in poly(styrene) thin films can be systematically increased by tens of nanometers by controlling the chain of conformation, i.e., the height of the loops in irrever...

Degradable and thermo-sensitive microgels were successfully prepared via simultaneous quaternization and siloxane condensation during surfactant-free emulsion polymerization with N-vinylcaprolactam (NVCL) as main monomer, and 1-vinylimidazole (VIM) as co-monomer in the presence of (3-bromopropyl)trimethoxysilane (BPTMOS). The formation mechanism of...

The surface average conformation of poly(ethylene terephthalate) (PET) films was modulated by adjusting the water content in corresponding trifluoroacetic acid (TFA) spin-coating solutions, which was confirmed by surface-sensitive sum frequency generation (SFG) vibrational spectroscopy. Molecular dynamics simulation results showed that the added wa...

Poly(ionic liquid)s (PILs) can self-assemble into polymeric nanoparticles with highly ordered inner structures, which make them potential candidates for antibacterial agents because of their highly concentrated local charges. However, investigation on the antibacterial application of self-assembled PIL nanoparticles has seldom involved. Here, alkyl...

We demonstrated, using grazing incidence wide-angle X-ray diffraction (GI-WAXD), sum frequency generational spectroscopy (SFG), and atomic force microscopy (AFM), that the aggregation state and molecular ordering of polymer brushes with crystalline side groups (i.e., poly(n-octadecyl methacrylate)) can be well controlled by their grafting densities...

Ultrathin polymer films exhibit a liquidlike mobile surface layer near the free surface, which plays an important role in the size-dependent physical properties of polymer nanomaterials. Most research has focused on the thickness of the surface layer related to segmental relaxation, while few studies have focused on that related to large-scale segm...

In order to investigate protein-resistant surfaces with heterogeneous nanopatterns, V-shaped polymer brushes composed of a hydrophilic methoxypoly(ethylene glycol) (mPEG) arm and a hydrophobic polystyrene (PS) or fluorinated poly(methyl methacrylate) (PMMA-b-PFMA) arm were prepared in which the surface structure and phase-separation behavior were c...

The local conformation of poly(styrene-co-butadiene) rubber (SBR) chains in direct contact with a quartz substrate was examined by interface-sensitive sum-frequency generation (SFG) spectroscopy. SFG signals, which could be obtained from functional groups only oriented at the interface, were clearly observed for SBR in a film at room temperature wh...

Thin polymer films with well-assembled fluorinated groups on their surfaces are not easily achieved via spin-coating film-fabrication methods, because the solution solidifies very rapidly during spin-coating, which hinders the fluorinated moieties from segregating and organizing on the film surface. In this contribution, we have proposed a comprehe...

The segmental relaxation dynamics of the core and the corona in a single dry spherical micelle comprising a polystyrene (PS) or poly(methyl methacrylate) (PMMA) core and a poly(acrylic acid) (PAA) corona, along with the effects of the micelle density and the chain length of the core-forming and corona-forming polymers, were investigated by AFM. The...

The question of how to scale the mobility gradient of polymer chains near a substrate in supported ultrathin polymer films is a great challenge. In this paper, a mobility gradient of poly(ethylene terephthalate) (PET) chains near a substrate is characterized by cold crystallization. We found that either decreasing the PET film thickness or increasi...

A facile method was developed to measure the utmost distance of polymer dynamics suppressed by a solid substrate by investigating the diffusion of a fluorinated tracer-labeled polymer in the bottom layer of bilayer samples. Here, a labeled layer of fluorinated tracer-labeled at the polymer chain end of variable thickness was supported on a substrat...

Thin amorphous poly(ethylene terephthalate) (PET) films covered with/without a crystallized surface layer were prepared onto silicon wafers. In the former and latter cases, the surface mobility in the film was depressed and enhanced, respectively. The glass transition temperature (T-g) of the amorphous PET film decreased with the reduction of the f...

Thin amorphous poly(ethylene terephthalate) (PET) films covered with/without a crystallized surface layer were prepared onto silicon wafers. In the former and latter cases, the surface mobility in the film was depressed and enhanced, respectively. The glass transition temperature (Tg) of the amorphous PET film decreased with the reduction of the fi...

The effects of the grafting densities (σp), molecular weights (Mn) and thicknesses of dry polystyrene (PS) brushes on their glass transition temperature (T) were investigated by ellipsometry. The results show that T strongly depends on the grafting density of the PS brushes. The T of the PS brushes with σp > 0.30 increases with decreasing Mn (or br...

To elucidate the mechanism underlying the effect of polymer/solid interfacial interactions on the dynamics of thin polymer films, the glass transition of thin end-functionalized polystyrene films supported on SiO2-Si, such as proton-terminated PS (PS-H), α,ω-dicarboxy-terminated PS (PS-COOH), and α,ω-dihydroxyl-terminated PS (PS-OH), was investigat...

Despite its importance in the processing of nanomaterials, the rheological behavior of thin polymer films is poorly understood, partly due to the inherent measurement challenges. Herein, we have developed a facile method for investigating the rheological behavior of supported thin polymeric films by monitoring the growth of the "wetting ridge"-a mi...

Crystallization is an important property of polymeric materials. In conventional viewpoint, the transformation of disordered chains into crystals is usually a spatially homogeneous process (i.e., it occurs simultaneously throughout the sample), that is, the crystallization rate at each local position within the sample is almost the same. Here, we s...

In this article, the fluorinated amphiphilic V-shaped brushes with two highly incompatible arms of mPEG42 and PMMA38-b-PFMAy were produced by reacting COOH in the PAA segment in methoxypoly(ethylene glycol)-b-poly(acrylic acid)-b-poly(methyl methacrylate)-b-poly(2-perfluoro-octylethyl methacrylate) (mPEG42-b-PAA11-b-PMMA38-b-PFMAy) with an epoxy g...

Although poly(vinyl acetate) (PVAc) differs from poly(methyl acrylate) (PMA) only in the reversed position of the ester group, a large difference in the concentration dependence of the casting solution on the corresponding surface structure of the cast films of PVAc, PMA and poly(methyl methacrylate) (PMMA) was observed. The hydrophobicity of both...

A novel method was previously reported for detecting the glass transition of thin polystyrene (PS) films by correlating the relationships between the temperature-dependent viscoelasticity of the PS films and stick-slip behavior on their surfaces during dynamic wetting of liquid droplets. In the present study, the frequency dependence of the stick-s...

Acrylate block polymer brushes (Au-PMMA65-b-PODMAy -ec-FMA2 ) with two 2-perfluorooctylethyl methacrylate units at the brush end were successfully prepared on a Au substrate by a “grafting to” method. Characterization by XPS, contact angle measurement, ellipsometry and nanomechanical measurement showed that a well-ordered and perpendicularly orient...

The effects of the properties of casting solution on the surface structure of poly(methyl methacrylate) (PMMA) films were systematically investigated. It was observed that the hydrophobicity of PMMA films increased with increasing viscosity of the corresponding polymer solution regardless of the film-forming techniques that were utilized. The ratio...

The effect of the concentration of casting solutions on the surface dynamics of the corresponding spin-coated poly(methyl methacrylate) (PMMA) film was investigated by measuring the surface reorganization of fluorine tracer-labeled PMMA. The onset temperature of fluorinated PMMA chain end reorganization (T) was identified and is shown to depend on...

We present an experimental investigation of the segmental relaxation behavior of polystyrene (PS) chains that are confined in a micellar core tethered by a poly(acrylic acid) (PAA) block corona on the dry film surface, along with various core density and molecular weight of PS block from below to well above the entanglement molecular weight. The re...

A new kind of composite membrane for the pervaporaLion dehydration of acetic acid was prepared by casting sodium alginate (NaAlg) solution onto a microporous polypropylene membrane (MPPM) which possessed well-controlled porosity and excellent solvent resistance. The MPPM surface was modified by N-2 plasma prior to the fabrication of the correspondi...

The dynamic wetting of water droplets on ultrathin poly(vinyl acetate) (PVAc) films supported by substrates with tunable surface hydroxyl group content was investigated at room temperature. The jumping angle of water droplets on the ultrathin PVAc films decreased with increasing hydroxyl content on the substrate surface, while a smooth evolution of...

We investigated the segmental mobility distribution at the poly(methyl methacrylate) film surface within the depth of 9.0 nm, by measuring the surface reorganization of fluorinated tracer-labeled PMMA using three different surface-sensitive techniques with various analytical depth capabilities, including contact angle measurements, sum frequency ge...

The effect of chain constraint on the surface dynamic of poly(methyl methacrylate) (PMMA) was investigated in the context of polymer tethering to a micelle core. Film surfaces dominated by either poly(methyl methacrylate) (PMMA) tethered by a poly(2-perfluorooctylethyl methacrylate) (PFMA) micelle core or non-micellized free PMMA chains are fabrica...

A novel method was developed to detect the glass transition of thin and ultrathin polystyrene (PS) films by correlating the relationships between the temperature-dependent viscoelasticity of the PS films and stick–slip behavior on their surfaces during dynamic wetting of glycerol or oligo-poly(ethylene glycol) droplets. The peak temperature (Tjm) o...

The surface structures of poly(vinyl alcohol) (PVA) films with four different degrees of hydrolysis after immersion in ethanol were investigated using sum frequency generation (SFG) vibrational spectroscopy and contact angle (CA) goniometry. The result showed that the surface chemical structure of the PVA films was strongly dependent on the degree...

In this paper, the relationship between the surface structures of spin-coated fluorinated polymer films and their corresponding film-formation solution/air interface structures was investigated. Film-forming poly(n-alkyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate (FMA; PFMAy-ec-PnAMAx-ec-PFMAy) was synthesized via a controlled...

In this paper, the relationship between the surface structure of fluorinated polymers and their protein-resistant property was studied by preparing films of poly(n-alkyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate (FMA) (PFMA(y)-ec-PnAMA(x)-ec-PFMA(y)) with various ordered structures of perfluorinated alkyls. These fluorinated...

Poly(vinyl alcohol)-based membranes with controllable surface structures and bulk characteristics were prepared by casting PVA/poly(acrylic acid) (PAA) solutions onto different substrates. Four kinds of surfaces, namely the air-side 1 and glass-side surface (a glass plate used as substrate), the air-side 2 and PTFE-side surface (a polytetrafluoroet...

Previously, we developed several methods to use sum frequency generation (SFG) vibrational spectroscopy to probe buried polymer/metal interfaces in situ by depositing polymer films with different thicknesses on metal surfaces or sandwiching a polymer thin film between a metal surface and a fused silica window. In this study, we developed a new and...

The surface chemical structure development in solution-cast styrene(S)/butadiene(B) block copolymer films as a function of solvent evaporation time was investigated using sum frequency generation vibrational spectroscopy (SFG). The surface structure formation of the styrene(S)/butadien(B) block copolymer (30 wt% PS) films during the solution-to-fil...

In this paper, a series of poly(styrene-b-isoprene-b-styrene) triblock copolymers (SIS), with different chemical components, was synthesized by anionic polymerization. The relationships between surface structures of these block copolymers and their stick-slip phenomena were investigated. There is a transition from stick-slip to a closely smooth mot...

Monolayer detection on metal surface requires ultra high sensitivity. Sum Frequency Generation Spectroscopy (SFG) and Surface Enhanced Raman Spectroscopy (SERS) are regarded as two powerful techniques with submolecular sensitivity to detect adsorbents on metal surface. However, in some cases it's still challenge to characterize molecules or groups...

New fluorinated copolymers of poly(methyl methacrylate)-b-poly(butyl methacrylate) or poly(n-octadecyl methacrylate) end-capped with 2-perfluorooctylethyl methacrylate (PMMA(x)-b-PBMA(y)-ec-PFMA(z) or PMMA(x)-b-PODMA(y)-ec-PFMA(z)) were synthesized by living atom transfer radical polymerization. Thin films made of PMMA(230)-b-PODMA(y)-ec-PFMA(1) we...