The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer (GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on ...The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer (GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on plasma characteristics diagnosis. The composition and ion energy distributions of a multi-carbon (CaHs/H2) plasma mixture at different working pressures were diagnosed by an energy-resolved mass spectrometer (MS) during the GDP film deposition process. The Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (SEM) and white-fight interferometer (WLI) results were obtained to investigate the structure, morphology and roughness characterization of the deposited films, respectively. It was found that the degree of ionization of the C4H8/H2 plasma reduces with an increase in the working pressure. At a low working pressure, the C-H fragments exhibited small-mass and high ion energy in plasma. In this case, the film had a low CH3/CH2 ratio, and displayed a smooth surface without any holes, cracks or asperities. While the working pressure increased to 15 Pa, the largest number of large-mass fragments led to the deposition rate reaching a maximum of 2.11 #m h-1, and to hole defects on the film surface. However, continuing to increase the working pressure, the film surface became smooth again, and the interface between clusters became inconspicuous without etching pits.展开更多
Coarse-grained molecular dynamics simulations were carried out to investigate the dewetting behavior of a polymer thin film on partial wetting solid surface at the early stage of the dewetting process. Spontaneous dew...Coarse-grained molecular dynamics simulations were carried out to investigate the dewetting behavior of a polymer thin film on partial wetting solid surface at the early stage of the dewetting process. Spontaneous dewetting is initiated by removing a band of strip from both the ends of the liquid polymer film which has achieved equilibrium. The solid-liquid interaction and temperature were varied to show their influence on the dewetting dynamics during dewetting as well as the shape evolution of the liquid polymer film. As is consistent with the results obtained in previous researches, the liquid film recedes at a constant speed initially with different solid-liquid couplings and tempe- ratures. Furthermore, smaller coupling parameters or higher temperatures tend to accelerate the recession speed of the liquid film and shorten the constant-speed recession duration. Obvious rims were not always observed. Both coupling parameter and temperature can influence the emergence of the rims.展开更多
In order to perform data acquisition and avoid unwanted over-current damage to the power supply, a convenient and real-time method of experimentally investigating repetitive nanosecond-pulse breakdown in polymer diele...In order to perform data acquisition and avoid unwanted over-current damage to the power supply, a convenient and real-time method of experimentally investigating repetitive nanosecond-pulse breakdown in polymer dielectric samples is presented. The measurement-acquisition and control system not only records breakdown voltage and current, and time-to-breakdown duration, but also provides a real-time power-off protection for the power supply. Furthermore, the number of applied pulses can be calculated by the product of the time-to-breakdown duration and repetition rate. When the measured time-to-breakdown duration error is taken into account, the repetition rate of applied nanosecond-pulses should be below 40kHz. In addition, some experimental data on repetitive nanosecond-pulse breakdown of polymer films are presented and discussed.展开更多
When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of ...When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of liquid crystal film were successfully performed without disturbing the surface morphology.展开更多
Dielectric polymer films are energy storage materials that are used in pulse power operations, power electronics and sustainable energy applications. This paper reviews energy storage devices with focus on dielectric ...Dielectric polymer films are energy storage materials that are used in pulse power operations, power electronics and sustainable energy applications. This paper reviews energy storage devices with focus on dielectric film capacitors. Two prominent examples of polymer dielectrics Polyetherimide (PEI) and Poly (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) (THV) have been discussed. Polyetherimide (PEI) is an amorphous polymer recognized for its high-temperature capability, low dielectric loss and high dielectric strength. THV is a semi-crystalline polymer with high dielectric constant, high-temperature capability and charge-discharge efficiency. The primary focus of this paper is to introduce the reader to the fabrication procedures and characterization techniques used in research labs for processing of dielectric polymers. The fabrication and characterization process of both polymers has been discussed in detail to shed the light on experimental process in this area of research.展开更多
The optical properties of the pure polymer film and polymer films doped with Phenol Red dye at different concentrations were investigated. The films were prepared using the casting technique. Poly (methyl-methacrylate...The optical properties of the pure polymer film and polymer films doped with Phenol Red dye at different concentrations were investigated. The films were prepared using the casting technique. Poly (methyl-methacrylate) (PMMA) polymer was doped with the Phenol Red dye dissolved in a mixture of chloroform and little quantity of methanol, used as suitable solvent for both the dye and the polymer. The spectral absorption measurements of these films were carried out at different dye concentrations using UV-Vis double-beam spectrophotometer in the wavelength range 300 - 800 nm. The optical parameters of the prepared Phenol Red dye doped polymer films, absorption coefficient (α), extinction coefficient (κ), refractive index (n), optical and electrical conductivities (σ<sub>opt</sub> and σ<sub>elect</sub>), and optical energy band gap (E<sub>g</sub>), were determined. The results showed that the Phenol Red dye doped polymer film is a good candidate for photonic applications such as, solar cells, optical sensors, and other photonic devices.展开更多
It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or hetero...It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneousnucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defectsof the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by acharateristic wavevector, q, independent of the density of rubbing-induced defects. Heterogeneous nucleation, on the otherhand, is identified for those with q increasing with increasing density of defects. Our result shows that PS films on oxidecoated silicon with thickness less than ≈ 13 nm are dominated by spinodal dewetting, but the thicker films are dominated bynucleation dewetting. We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in thedewetting film, contrary to the classic theory of Cahn.展开更多
Locust is a common flying insect. Locust wings were used as biomimetic templates to fabricate multi-functional polymer(polydimethylsiloxane, PDMS) films by soft lithography. The microstructure and wettability of the...Locust is a common flying insect. Locust wings were used as biomimetic templates to fabricate multi-functional polymer(polydimethylsiloxane, PDMS) films by soft lithography. The microstructure and wettability of the natural and artificial locust wing surfaces were investigated by means of a scanning electron microscope(SEM) and a video-based contact angle meter. The natural locust wing surface exhibits complicated hierarchical structures and high adhesive superhydrophobicity(contact angle 152°). The prepared polymer film faithfully reproduces the surface microstructures of the bio-template, and displays a good hydrophobicity and high adhesion(contact angle 144°). The complex wettability of the natural and artificial locust wing surfaces ascribes to the cooperative effect of hydrophobic composition and multi-dimensional rough microstructures. This work not only promotes our understanding of the wetting mechanism on bio-surfaces, but offers an inexpensive and effective approach for biomimetic fabrication of multi-functional interfacial materials.展开更多
We have investigated the influence of the adsorption process on the dewetting behavior of the linear polystyrene film (LPS), the 3-arm star polystyrene film (3SPS) and the ring polystyrene film (RPS) on the sila...We have investigated the influence of the adsorption process on the dewetting behavior of the linear polystyrene film (LPS), the 3-arm star polystyrene film (3SPS) and the ring polystyrene film (RPS) on the silanized Si substrate. Results show that the adsorption process greatly influences the dewetting behavior of the thin polymer films. On the silanized Si substrate, the 3SPS chains exhibit stronger adsorption compared with the LPS chains and RPS chains; as a result, the wetting layer forms more easily. For LPS films, with the decrease of annealing temperature, the kinetics of polymer film changes from exponential behavior to slip dewetting. As a comparison, the stability of 3SPS and RPS films switches from slip dewetting to unusual dewetting kinetic behavior. The adsorbed nanodroplets on the solid substrate play an important role in the dewetting kinetics by reducing the driving force of dewetting and increase the resistant force of dewetting. Additionally, Brownian dynamics (BD) simulation shows that the absolute values of adsorption energy (ε) gradually increase from linear polymer (-0.3896) to ring polymer (-0.4033) and to star polymer (-0.4264), which is consistent with the results of our adsorption experiments.展开更多
In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a c...In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal (Ch-LC) monomers mixture containing a photopolymerizable chiral H-bonded assembly (PCHA). The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green/yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Additionally, the selective reflection band (SRB) of the cholesteric polymer film in solution with pH 〉 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH 〈 7 hardly changed. This pH sensitivity in solutions with pH 〉 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by --OH- and --K+ ions in the alkaline solution. In contrast, it couldn't happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical/photonic papers, optical sensors and LCs displays, etc.展开更多
The stability of ultrathin polymer films plays a crucial role in their technological applications.Here,we systematically investigated the influence of interfacial adsorption in physical aging and the stability of thin...The stability of ultrathin polymer films plays a crucial role in their technological applications.Here,we systematically investigated the influence of interfacial adsorption in physical aging and the stability of thin polymer films in the solvent-induced process.We further identify the stability mechanism from the theory of thin film stability.Our results show that the aging temperature and film thickness can strongly influence the stability of thin PS films in acetone vapor.Physical aging can greatly improve the stability of thin polymer films when the aging temperature T_(aging1)>T_(g).A thinner PS film more quickly reaches a stable state via physical aging.At short aging time,the formation of the adsorbed layer can reduce the polar interaction;however,it slightly influences the stability of thin polymer films in the solvent-induced process.At later aging stage,the conformational rearrangement of the polymer chains induced by the interfacial effect at the aging temperature Taging1 plays an important role in stabilizing the thin polymer films.However,at T_(aging2)<T_(g),the process of physical aging slightly influences the stability of the thin polymer films.The formation of the adsorbed layer at Taging2 can reduce the short-range polar interaction of the thin film system and cannot suppress the instability of thin polymer films in the solvent-induced process.These results provide further insight into the stable mechanism of thin polymer films in the solvent-induced process.展开更多
A true single-step process suitable for fabrication of micro-periodic structure in polymer films by twophoton initiated photopolymerization and laser ablation is presented. By the right choice of the irradiation energ...A true single-step process suitable for fabrication of micro-periodic structure in polymer films by twophoton initiated photopolymerization and laser ablation is presented. By the right choice of the irradiation energy, the irradiated zone is modified or ablated in the 1.44-μm-thick film. The mechanism of grating generation and the potential application of the gratings in integrated optics are discussed.展开更多
Water-based polymer films can be readily deposited onto a wide range of metallic materials as an environmentally friendly coating through the demulsification-induced fast solidification(DIFS)method.However,there is st...Water-based polymer films can be readily deposited onto a wide range of metallic materials as an environmentally friendly coating through the demulsification-induced fast solidification(DIFS)method.However,there is still a lack of in-depth understanding of the demulsification process of the water-based emulsions and their deposition processes.Herein,we demonstrate that the build-up process of the commercial water-based micron-scale waterborne polyurethane,polyvinyl acetate,polyurethane acrylate,and natural rubber polymer films is affected by the collective effect of electric field and ion diffusion exerted by anode-cathode electrode pairs,applied voltage,conduction time,electrode distance,and emulsion species.A structural investigation of as-prepared polymer films allows us to propose two new structure build-up models.During a flat film deposition,isolated islands are formed first and grow on the substrate surface,and eventually,their mutual coalescence forms the final layer.Whereas,for a convex layer formation,the layer is first formed in the middle of the substrate and then grows toward the sides of the convex structure of the substrate.The results presented in this work expand the understanding of the mechanism of the DIFS process and may provide some new insights into structure-oriented multifunctional material design.展开更多
Isocyanate-treated graphite oxides (iGOs) were well-dispersed into the polystyrene (PS) thin films and formed a novel network structure. With control in fabrication, an iGOs-web layer was horizontally embedded nea...Isocyanate-treated graphite oxides (iGOs) were well-dispersed into the polystyrene (PS) thin films and formed a novel network structure. With control in fabrication, an iGOs-web layer was horizontally embedded near the surface of the films and thus formed a composite slightly doped by iGOs. This work demonstrated that the iGOs network can remarkably depress the dewetting process in the polymer matrix of the composite, while dewetting often leads to rupture of polymer films and is considered as a major practical limit in using polymeric materials above their glass transition temperatures (Tg). Via annealing the 50-120 nm thick composite and associated neat PS films at temperatures ranging from 35℃ to 70 ℃ above Tg, surface morphology evolution of the films was monitored by atomic force microscopy (AFM). The iGOs-doped PS exhibited excellent thermal stability, i.e., the number of dewetting holes was greatly reduced and the long-term hole growth was fairly restricted. In contrast, the neat PS film showed serious surface fluctuation and a final rupture induced by ordinary dewetting. The method developed in this work may pave a road to reinforce thin polymer films and enhance their thermal stability, in order to meet requirements by technological advances.展开更多
We describe a simple and cost-effective holographic method for the fabrication of surface-relief zone plates. The zone plate is inscribed by interference between the first-and second-order diffracted waves from an ion...We describe a simple and cost-effective holographic method for the fabrication of surface-relief zone plates. The zone plate is inscribed by interference between the first-and second-order diffracted waves from an ion-etched Fresnel zone plate. The inscribed surface-relief zone plates are observed by atomic force microscope (AFM). The formation process of the surface grating and the mass diffusion in azo polvmer are analvzed.展开更多
The development of solid-state smart materials, in particular those showing photoresponsive luminescence, is highly desirable for their cutting edge applications in displays, sensors, data-storage, and anticounterfeit...The development of solid-state smart materials, in particular those showing photoresponsive luminescence, is highly desirable for their cutting edge applications in displays, sensors, data-storage, and anticounterfeiting. However, to achieve both excellent photoresponsive performance and bright luminescence in solid state remains challenge. Herein, we integrate a novel photochromic fluorophore YL into flexible polymer chains, thereby enabling the resultant polymer PYL with reversible photoisomerization upon aggregation. Remarkably, the polymer PYL possesses excellent photochromic properties and aggregationinduced emission(AIE) activity, which can be attributed to the photoactive YL moiety. Upon light exposure, its film exhibits reversibly off-to-on fluorescent modulation with quick response, high emission efficiency and signal contrast, sharply different from the weak emission in solution. The novel photoresponsive AIE polymer with invisible/visible color and fluorescence transformation allows for advanced anti-counterfeiting applications. This work provides an efficient platform for constructing solid-state photocontrollable luminescent materials.展开更多
A full-field finite element method (FEM) analysis combined with electronic speckle pattern interferometry (ESPI) measurement was developed to investigate defect evolution in polymer films. Different from the previ...A full-field finite element method (FEM) analysis combined with electronic speckle pattern interferometry (ESPI) measurement was developed to investigate defect evolution in polymer films. Different from the previous reports, which only compare the ESPI experimental and FEM simulated results at several points or lines, herein the full-field FEM results were exported, subtracted with a continuous distribution. By choosing proper parameters and number of substeps, the simulated and experimental results showed excellent correspondence. Furthermore, the displacement fields vertical to the tensional direction were also presented, and the strain field was preliminarily evaluated. The current method of combination of ESPI and FEM allows for capturing the experimental fringe maps to validate and optimize FEM results simulated, and would give a higher security to structural and mechanical analysis of polymeric materials.展开更多
Nano porous polymer film with a hexagonal colum nar(Coln)structure was fabricated by templated hydroge n-bonding discotic liquid crystals containing methacrylate functional group.The supramolecular hydrogen-bonded com...Nano porous polymer film with a hexagonal colum nar(Coln)structure was fabricated by templated hydroge n-bonding discotic liquid crystals containing methacrylate functional group.The supramolecular hydrogen-bonded complex T3Ph-L is composed of a 1,3/5-tris(1Hbenzo[d]imidazol-2-yl)benzene(T3Ph)core molecule as the hydrogen-bonding acceptor and 3,4,5-tris((11-(methacryloyloxy)undecyl)oxy)benzoic acid(L)peripheral molecules as donors.And the Colh structure is always retained after self-assembly,photo-crosslinking,and removal of the template T3Ph.The nanoporous polymer film can retain the Colh phase even under the dry condition,which indicates more possibilities for practical applicati ons.After chemical modificati on of the inner wall of the nano pores,the nan oporous polymer film with pores of about 1 nm selectively adsorbs ionic dyes,and the adsorption process is spontaneous and exothermic in nature.Homeotropic alignment can be obtained when the blend complex was sandwiched between two modified glasses after annealing by slow cooling,which shows that the nanoporous polymer film has potential in applications such as nanofiltration.展开更多
The fluorescently labelled polymers including pyrene-labelled polystyrene(PyPS) and pyrene-labelled poly(methyl methacrylate)(PyPMMA) with narrow molecular weight distributions were synthesized by the atom transfer ra...The fluorescently labelled polymers including pyrene-labelled polystyrene(PyPS) and pyrene-labelled poly(methyl methacrylate)(PyPMMA) with narrow molecular weight distributions were synthesized by the atom transfer radical copolymerization(ATRCP) of styrene or methyl methacrylate with 1-pyrenemethyl methacrylate(PyMMA). The ultrathin PyPS and PyPMMA films with the thickness ranging from 30 nm to 400 nm supported on the quartz slides were prepared by spin-coating. The fluorescent quantum yield(QY) of the pyrene probe in the ultrathin polymer films was investigated by the photoluminescence spectrometer using an integrating sphere detector. The QY decreased with the reduction of film thickness in the sub-200 nm range.展开更多
基金financially supported by National Natural Science Foundation of China (No. 51401194)
文摘The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer (GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on plasma characteristics diagnosis. The composition and ion energy distributions of a multi-carbon (CaHs/H2) plasma mixture at different working pressures were diagnosed by an energy-resolved mass spectrometer (MS) during the GDP film deposition process. The Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (SEM) and white-fight interferometer (WLI) results were obtained to investigate the structure, morphology and roughness characterization of the deposited films, respectively. It was found that the degree of ionization of the C4H8/H2 plasma reduces with an increase in the working pressure. At a low working pressure, the C-H fragments exhibited small-mass and high ion energy in plasma. In this case, the film had a low CH3/CH2 ratio, and displayed a smooth surface without any holes, cracks or asperities. While the working pressure increased to 15 Pa, the largest number of large-mass fragments led to the deposition rate reaching a maximum of 2.11 #m h-1, and to hole defects on the film surface. However, continuing to increase the working pressure, the film surface became smooth again, and the interface between clusters became inconspicuous without etching pits.
基金Supported by the National Natural Science Foundation of China(Nos.20774036 50930001+1 种基金 20933001)the Program for New Century Excellent Talents in University of China and Fok Ying Tung Education Foundation(No.114018)
文摘Coarse-grained molecular dynamics simulations were carried out to investigate the dewetting behavior of a polymer thin film on partial wetting solid surface at the early stage of the dewetting process. Spontaneous dewetting is initiated by removing a band of strip from both the ends of the liquid polymer film which has achieved equilibrium. The solid-liquid interaction and temperature were varied to show their influence on the dewetting dynamics during dewetting as well as the shape evolution of the liquid polymer film. As is consistent with the results obtained in previous researches, the liquid film recedes at a constant speed initially with different solid-liquid couplings and tempe- ratures. Furthermore, smaller coupling parameters or higher temperatures tend to accelerate the recession speed of the liquid film and shorten the constant-speed recession duration. Obvious rims were not always observed. Both coupling parameter and temperature can influence the emergence of the rims.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50707032 and 50437020)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KGCX2-YW-339)the State Key Laboratory of Controland Simulation of Power System and Generation Equipment in Tsinghua University (Grant No. SKLD09KZ05)
文摘In order to perform data acquisition and avoid unwanted over-current damage to the power supply, a convenient and real-time method of experimentally investigating repetitive nanosecond-pulse breakdown in polymer dielectric samples is presented. The measurement-acquisition and control system not only records breakdown voltage and current, and time-to-breakdown duration, but also provides a real-time power-off protection for the power supply. Furthermore, the number of applied pulses can be calculated by the product of the time-to-breakdown duration and repetition rate. When the measured time-to-breakdown duration error is taken into account, the repetition rate of applied nanosecond-pulses should be below 40kHz. In addition, some experimental data on repetitive nanosecond-pulse breakdown of polymer films are presented and discussed.
基金support by the Visiting Scholar Foundation of the Key Lab in Nankai University, and to financial support by the National Natural Science Foundation of China (No. 29974014).
文摘When colloidal silver particles were chemically deposited onto polymer film as an over-coating layer, surface-enhanced Raman scattering (SERS) spectra could be collected for the surface analysis. SERS measurements of liquid crystal film were successfully performed without disturbing the surface morphology.
文摘Dielectric polymer films are energy storage materials that are used in pulse power operations, power electronics and sustainable energy applications. This paper reviews energy storage devices with focus on dielectric film capacitors. Two prominent examples of polymer dielectrics Polyetherimide (PEI) and Poly (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) (THV) have been discussed. Polyetherimide (PEI) is an amorphous polymer recognized for its high-temperature capability, low dielectric loss and high dielectric strength. THV is a semi-crystalline polymer with high dielectric constant, high-temperature capability and charge-discharge efficiency. The primary focus of this paper is to introduce the reader to the fabrication procedures and characterization techniques used in research labs for processing of dielectric polymers. The fabrication and characterization process of both polymers has been discussed in detail to shed the light on experimental process in this area of research.
文摘The optical properties of the pure polymer film and polymer films doped with Phenol Red dye at different concentrations were investigated. The films were prepared using the casting technique. Poly (methyl-methacrylate) (PMMA) polymer was doped with the Phenol Red dye dissolved in a mixture of chloroform and little quantity of methanol, used as suitable solvent for both the dye and the polymer. The spectral absorption measurements of these films were carried out at different dye concentrations using UV-Vis double-beam spectrophotometer in the wavelength range 300 - 800 nm. The optical parameters of the prepared Phenol Red dye doped polymer films, absorption coefficient (α), extinction coefficient (κ), refractive index (n), optical and electrical conductivities (σ<sub>opt</sub> and σ<sub>elect</sub>), and optical energy band gap (E<sub>g</sub>), were determined. The results showed that the Phenol Red dye doped polymer film is a good candidate for photonic applications such as, solar cells, optical sensors, and other photonic devices.
基金This work was supported by the Institute of Nano Science and Technology and the Hong Kong University of Science and Technology through the Postdoctoral Matching Fund.
文摘It has been a long-standing question whether dewetting of polymer film from non-wettable substrate surfaceswherein the bicontinuous morphology never forms in the dewetting film is due to spinodal instability or heterogeneousnucleation. In this experiment, we use a simple method to make the distinction through introduction of topographical defectsof the films by rubbing the sample surface with a rayon cloth. Spinodal dewetting is identified for those films that dewet by acharateristic wavevector, q, independent of the density of rubbing-induced defects. Heterogeneous nucleation, on the otherhand, is identified for those with q increasing with increasing density of defects. Our result shows that PS films on oxidecoated silicon with thickness less than ≈ 13 nm are dominated by spinodal dewetting, but the thicker films are dominated bynucleation dewetting. We also confirm that spinodal dewetting does not necessarily lead to a bicontinuous morphology in thedewetting film, contrary to the classic theory of Cahn.
基金Supported by the National Natural Science Foundation of China(No.50875108) and the Natural Science Foundation of Science and Technology Department of Jilin Province, China(No.201115162).
文摘Locust is a common flying insect. Locust wings were used as biomimetic templates to fabricate multi-functional polymer(polydimethylsiloxane, PDMS) films by soft lithography. The microstructure and wettability of the natural and artificial locust wing surfaces were investigated by means of a scanning electron microscope(SEM) and a video-based contact angle meter. The natural locust wing surface exhibits complicated hierarchical structures and high adhesive superhydrophobicity(contact angle 152°). The prepared polymer film faithfully reproduces the surface microstructures of the bio-template, and displays a good hydrophobicity and high adhesion(contact angle 144°). The complex wettability of the natural and artificial locust wing surfaces ascribes to the cooperative effect of hydrophobic composition and multi-dimensional rough microstructures. This work not only promotes our understanding of the wetting mechanism on bio-surfaces, but offers an inexpensive and effective approach for biomimetic fabrication of multi-functional interfacial materials.
基金financially supported by the National Natural Science Foundation of China (Nos.51473168,21234007,21674114,51503048,51573131 and 21374077)the grant of Guizhou Education University (No.107003001455)the Natural Science Foundation of Guizhou Province (No.QKHJC[2017]1137)
文摘We have investigated the influence of the adsorption process on the dewetting behavior of the linear polystyrene film (LPS), the 3-arm star polystyrene film (3SPS) and the ring polystyrene film (RPS) on the silanized Si substrate. Results show that the adsorption process greatly influences the dewetting behavior of the thin polymer films. On the silanized Si substrate, the 3SPS chains exhibit stronger adsorption compared with the LPS chains and RPS chains; as a result, the wetting layer forms more easily. For LPS films, with the decrease of annealing temperature, the kinetics of polymer film changes from exponential behavior to slip dewetting. As a comparison, the stability of 3SPS and RPS films switches from slip dewetting to unusual dewetting kinetic behavior. The adsorbed nanodroplets on the solid substrate play an important role in the dewetting kinetics by reducing the driving force of dewetting and increase the resistant force of dewetting. Additionally, Brownian dynamics (BD) simulation shows that the absolute values of adsorption energy (ε) gradually increase from linear polymer (-0.3896) to ring polymer (-0.4033) and to star polymer (-0.4264), which is consistent with the results of our adsorption experiments.
基金supported by the National Natural Science Foundation of China (No. 50903004)
文摘In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal (Ch-LC) monomers mixture containing a photopolymerizable chiral H-bonded assembly (PCHA). The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green/yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Additionally, the selective reflection band (SRB) of the cholesteric polymer film in solution with pH 〉 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH 〈 7 hardly changed. This pH sensitivity in solutions with pH 〉 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by --OH- and --K+ ions in the alkaline solution. In contrast, it couldn't happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical/photonic papers, optical sensors and LCs displays, etc.
基金supported by the Science Challenge Project(No.TZ2018004)the Fundamental Research Funds for the Central Universities(No.2232019D3-10)+1 种基金the National Natural Science Foundation of China(Nos.51473168,21674113,21334007,21790340)the Programs of Chinese Academy of Sciences(Nos.QYZDY-SSW-SLH027,YJKYYQ20190084).
文摘The stability of ultrathin polymer films plays a crucial role in their technological applications.Here,we systematically investigated the influence of interfacial adsorption in physical aging and the stability of thin polymer films in the solvent-induced process.We further identify the stability mechanism from the theory of thin film stability.Our results show that the aging temperature and film thickness can strongly influence the stability of thin PS films in acetone vapor.Physical aging can greatly improve the stability of thin polymer films when the aging temperature T_(aging1)>T_(g).A thinner PS film more quickly reaches a stable state via physical aging.At short aging time,the formation of the adsorbed layer can reduce the polar interaction;however,it slightly influences the stability of thin polymer films in the solvent-induced process.At later aging stage,the conformational rearrangement of the polymer chains induced by the interfacial effect at the aging temperature Taging1 plays an important role in stabilizing the thin polymer films.However,at T_(aging2)<T_(g),the process of physical aging slightly influences the stability of the thin polymer films.The formation of the adsorbed layer at Taging2 can reduce the short-range polar interaction of the thin film system and cannot suppress the instability of thin polymer films in the solvent-induced process.These results provide further insight into the stable mechanism of thin polymer films in the solvent-induced process.
基金This work was supported by the State Key Program of China (No.2004CB719803)the National Natural Science Foundation of China (No.50173015.50218001,and 60377041).
文摘A true single-step process suitable for fabrication of micro-periodic structure in polymer films by twophoton initiated photopolymerization and laser ablation is presented. By the right choice of the irradiation energy, the irradiated zone is modified or ablated in the 1.44-μm-thick film. The mechanism of grating generation and the potential application of the gratings in integrated optics are discussed.
基金supported by the Science and Technology Development Planning Project of Jilin Province,China (No.20200401037GX)the National Natural Science Foundation of China (No.21504008).
文摘Water-based polymer films can be readily deposited onto a wide range of metallic materials as an environmentally friendly coating through the demulsification-induced fast solidification(DIFS)method.However,there is still a lack of in-depth understanding of the demulsification process of the water-based emulsions and their deposition processes.Herein,we demonstrate that the build-up process of the commercial water-based micron-scale waterborne polyurethane,polyvinyl acetate,polyurethane acrylate,and natural rubber polymer films is affected by the collective effect of electric field and ion diffusion exerted by anode-cathode electrode pairs,applied voltage,conduction time,electrode distance,and emulsion species.A structural investigation of as-prepared polymer films allows us to propose two new structure build-up models.During a flat film deposition,isolated islands are formed first and grow on the substrate surface,and eventually,their mutual coalescence forms the final layer.Whereas,for a convex layer formation,the layer is first formed in the middle of the substrate and then grows toward the sides of the convex structure of the substrate.The results presented in this work expand the understanding of the mechanism of the DIFS process and may provide some new insights into structure-oriented multifunctional material design.
基金the start-up fund of Y.G.from both University of Michigan-Shanghai Jiao Tong University Joint InstituteSchool of Materials Science and Engineering at SJTU+4 种基金the National Science Foundation of China for financial support through the General Program(No.2157408)the foundation of Shanghai Sailing Plan(No,16YF1406100)the National Youth 1000 Talent Program of Chinathe Shanghai 1000 Talent Planthe Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China
文摘Isocyanate-treated graphite oxides (iGOs) were well-dispersed into the polystyrene (PS) thin films and formed a novel network structure. With control in fabrication, an iGOs-web layer was horizontally embedded near the surface of the films and thus formed a composite slightly doped by iGOs. This work demonstrated that the iGOs network can remarkably depress the dewetting process in the polymer matrix of the composite, while dewetting often leads to rupture of polymer films and is considered as a major practical limit in using polymeric materials above their glass transition temperatures (Tg). Via annealing the 50-120 nm thick composite and associated neat PS films at temperatures ranging from 35℃ to 70 ℃ above Tg, surface morphology evolution of the films was monitored by atomic force microscopy (AFM). The iGOs-doped PS exhibited excellent thermal stability, i.e., the number of dewetting holes was greatly reduced and the long-term hole growth was fairly restricted. In contrast, the neat PS film showed serious surface fluctuation and a final rupture induced by ordinary dewetting. The method developed in this work may pave a road to reinforce thin polymer films and enhance their thermal stability, in order to meet requirements by technological advances.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 90206002.
文摘We describe a simple and cost-effective holographic method for the fabrication of surface-relief zone plates. The zone plate is inscribed by interference between the first-and second-order diffracted waves from an ion-etched Fresnel zone plate. The inscribed surface-relief zone plates are observed by atomic force microscope (AFM). The formation process of the surface grating and the mass diffusion in azo polvmer are analvzed.
基金financially supported by the National Natural Science Foundation of China for Science Center Program (No. 21788102)Creative Research Groups (No. 21421004)+4 种基金Key Project (No. 21636002)Shanghai Pujiang Program (No. 20PJ1402900)National key Research and Development Program (No. 2016YFA0200300)Shanghai Municipal Science and Technology Major Project (No. 2018SHZDZX03)Program of Introducing Talents of Discipline to Universities (No. B16017)。
文摘The development of solid-state smart materials, in particular those showing photoresponsive luminescence, is highly desirable for their cutting edge applications in displays, sensors, data-storage, and anticounterfeiting. However, to achieve both excellent photoresponsive performance and bright luminescence in solid state remains challenge. Herein, we integrate a novel photochromic fluorophore YL into flexible polymer chains, thereby enabling the resultant polymer PYL with reversible photoisomerization upon aggregation. Remarkably, the polymer PYL possesses excellent photochromic properties and aggregationinduced emission(AIE) activity, which can be attributed to the photoactive YL moiety. Upon light exposure, its film exhibits reversibly off-to-on fluorescent modulation with quick response, high emission efficiency and signal contrast, sharply different from the weak emission in solution. The novel photoresponsive AIE polymer with invisible/visible color and fluorescence transformation allows for advanced anti-counterfeiting applications. This work provides an efficient platform for constructing solid-state photocontrollable luminescent materials.
文摘A full-field finite element method (FEM) analysis combined with electronic speckle pattern interferometry (ESPI) measurement was developed to investigate defect evolution in polymer films. Different from the previous reports, which only compare the ESPI experimental and FEM simulated results at several points or lines, herein the full-field FEM results were exported, subtracted with a continuous distribution. By choosing proper parameters and number of substeps, the simulated and experimental results showed excellent correspondence. Furthermore, the displacement fields vertical to the tensional direction were also presented, and the strain field was preliminarily evaluated. The current method of combination of ESPI and FEM allows for capturing the experimental fringe maps to validate and optimize FEM results simulated, and would give a higher security to structural and mechanical analysis of polymeric materials.
基金the National Key R&D Program of China(No.2018YFB0703702)the National Natural Science Foundation of China(No.51725301).
文摘Nano porous polymer film with a hexagonal colum nar(Coln)structure was fabricated by templated hydroge n-bonding discotic liquid crystals containing methacrylate functional group.The supramolecular hydrogen-bonded complex T3Ph-L is composed of a 1,3/5-tris(1Hbenzo[d]imidazol-2-yl)benzene(T3Ph)core molecule as the hydrogen-bonding acceptor and 3,4,5-tris((11-(methacryloyloxy)undecyl)oxy)benzoic acid(L)peripheral molecules as donors.And the Colh structure is always retained after self-assembly,photo-crosslinking,and removal of the template T3Ph.The nanoporous polymer film can retain the Colh phase even under the dry condition,which indicates more possibilities for practical applicati ons.After chemical modificati on of the inner wall of the nano pores,the nan oporous polymer film with pores of about 1 nm selectively adsorbs ionic dyes,and the adsorption process is spontaneous and exothermic in nature.Homeotropic alignment can be obtained when the blend complex was sandwiched between two modified glasses after annealing by slow cooling,which shows that the nanoporous polymer film has potential in applications such as nanofiltration.
基金financially supported by the National Natural Science Foundation of China(Nos.21174167 and 51573212)the Natural Science Foundation of Guangdong Province(Nos.S2013030013474 and 2014A030313178)
文摘The fluorescently labelled polymers including pyrene-labelled polystyrene(PyPS) and pyrene-labelled poly(methyl methacrylate)(PyPMMA) with narrow molecular weight distributions were synthesized by the atom transfer radical copolymerization(ATRCP) of styrene or methyl methacrylate with 1-pyrenemethyl methacrylate(PyMMA). The ultrathin PyPS and PyPMMA films with the thickness ranging from 30 nm to 400 nm supported on the quartz slides were prepared by spin-coating. The fluorescent quantum yield(QY) of the pyrene probe in the ultrathin polymer films was investigated by the photoluminescence spectrometer using an integrating sphere detector. The QY decreased with the reduction of film thickness in the sub-200 nm range.