Anti-reflective effect of transparent polymer by plasma treatment with end-hall ion source and optical coating

The surface of poly(methyl methacrylate) (PMMA) was treated by plasma with an end-Hall ion source in vacuum in order to enhance its anti-reflectivity. The cone-shaped bumps induced by the plasma etching have shown an antireflective effect. Moreover, PMMA has poor thermal durability due to its low melting point; therefore, the etched PMMA was further coated by a 5 nm thick SiO₂ film after 900 and 1300 s plasma etching. Samples after SiO₂ coating were thermally annealed at temperature of 70°C for 1 h. Experiments show that transmittance was increased after 5 nm thick SiO₂ coating. The of transmittance of PMMA after both sides treated by 900 s plasma etching and 5 nm SiO₂ coating was not changed after thermal annealing. However, without SiO₂ coating the transmission was reduced 1% after annealing. Atomic force microscope (AFM) demonstrated that the nano-structures of cone-shaped bumps were formed on the PMMA after plasma etching and a smoother nano-structured pattern preserved the transmittance of the PMMA after both sides treated by 900 s plasma etching and 5 nm SiO₂ coating. Three dimensional photonic crystal formed by uniformly distributed cone-shaped bumps was assumed to result in the reduction of the anti-reflectivity of treated PMMA.     

Fluorination of polymethylmethaacrylate with tetrafluoroethane using DC glow discharge plasma

Fluorination of polymer surfaces has technological applications in various fields such as microelectronics, biomaterials, textile, packing, etc. In this study PMMA surfaces were fluorinated using DC glow discharge plasma. Tetrafluoroethane was used as the fluorinating agent. On the fluorinated PMMA surface, static water contact angle, surface energy, optical transmittance (UV-vis), XPS and AFM analyses were carried out. After the fluorination PMMA surface becomes hydrophobic with water contact angle of 107° without losing optical transparency. Surface energy of fluorine plasma-treated PMMA decreased from 35 mJ/cm² to 21.2 mJ/cm². RMS roughness of the fluorinated surface was 4.01 nm and XPS studies revealed the formation of C-CF_x and CF₃ groups on the PMMA surface.     

Vacuum ultraviolet smoothing of nanometer-scale asperities of Poly(methyl methacrylate) surface

Smoothing of the nanometer-scale asperities of a poly(methyl methacrylate) (PMMA) film using vacuum ultraviolet (VUV) with the wavelength λ = 123.6 nm was studied. The exposure time and the residual air pressure in an working chamber were varied during the process of VUV treatment. A nanostructured surface of PMMA film is used as a sample to be exposed. The nanostructured surface of the PMMA film was obtained by treating the initially smooth spin-coated film in oxygen radio-frequency plasma. The degree of VUV exposure is estimated using changes in the morphology and roughness of the nanostructured surface, which were determined by atomic-force microscopy (AFM). Recognition of morphological surface features on the AFM-images and determination of main geometrical characteristics of these features are performed by using virtual feature-oriented scanning method. It is discovered by morphology and Fourier spectra that the nanostructured surface of the PMMA film is partially ordered. The developed VUV smoothing procedure can be used to treat the electron-beam, UV, and X-ray sensitive PMMA resists, PMMA elements of microelectromechanical systems, biomedical PMMA implants, as well as to certify nanotechnological equipment incorporating UV radiation sources.     

Modification of hydrophobic acrylic intraocular lens with poly(ethylene glycol) by atmospheric pressure glow discharge: A facile approach

To improve the anterior surface biocompatibility of hydrophobic acrylic intraocular lens (IOL) in a convenient and continuous way, poly(ethylene glycol)s (PEGs) were immobilized by atmospheric pressure glow discharge (APGD) treatment using argon as the discharge gas. The hydrophilicity and chemical changes on the IOL surface were characterized by static water contact angle and X-ray photoelectron spectroscopy to confirm the covalent binding of PEG. The morphology of the IOL surface was observed under field emission scanning electron microscopy and atomic force microscopy. The surface biocompatibility was evaluated by adhesion experiments with platelets, macrophages, and lens epithelial cells (LECs) in vitro. The results revealed that the anterior surface of the PEG-grafted IOL displayed significantly and permanently improved hydrophilicity. Cell repellency was observed, especially in the PEG-modified IOL group, which resisted the attachment of platelets, macrophages and LECs. Moreover, the spread and growth of cells were suppressed, which may be attributed to the steric stabilization force and chain mobility effect of the modified PEG. All of these results indicated that hydrophobic acrylic IOLs can be hydrophilic modified by PEG through APGD treatment in a convenient and continuous manner which will provide advantages for further industrial applications.     

UV laser ablation of intraocular lenses: SEM and AFM microscopy examination of the biomaterial surface

Several new materials and patterns are studied for the formation and etching of intraocular lenses (IOLs), in order to improve their optical properties, to reduce the diffractive aberrations and to decrease the incidence of posterior capsular opacification. The aim of this study is to investigate the use of UV (λ = 266 nm) laser pulses to ablate the intraocular lenses materials, and thus to provide an alternative to conventional surface shaping techniques for IOLs fabrication. Ablation experiments were conducted using various polymer substrates of hydrophobic acrylic IOLs and PMMA IOLs. We investigated the ablation efficiency and the morphology of the ablated area by imaging the surface modification with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The morphological appearance of IOL samples reveals the effect of a photochemical and photothermal ablation mechanism.     

Preparation and Characterization of PMMA/ZnO Nanocomposites via In‐Situ Polymerization Method

Poly(methyl methacrylate) zine oxide (ZnO) (PMMA/ZnO) nanocomposites were successfully prepared by the solution radical copolymerization of the monomer, methyl methacrylate (MMA), and the oleic acid–modified ZnO nanoparticles (OA‐ZnO) with 2,2′‐azobis(isobutylonitrile) (AIBN) as initiator in toluene. The products were characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FT‐IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Ultraviolet ‐variable (UV‐Vis) analysis showed that the composites had high absorption in the ultraviolet region and low absorption in the visible region. The absorption in the ultraviolet region depended on the content of ZnO nanoparticles in the nanocomposites. It is expected that they can be used as UV‐filters in optical materials.     

Ultrashort laser ablation of PMMA and intraocular lenses

The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials, techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular lenses, and thus provide an alternative to conventional techniques. Ablation experiments were conducted using various polymer substrates (PMMA samples, hydrophobic acrylic IOL, yellow azo dye doped IOL, and hydrophilic acrylic IOL consist of 25% H₂O). The irradiation was performed using 100 fs pulses of 800 nm radiation from a regeneratively amplified Ti:sapphire laser system. We investigated the ablation efficiency and the phenomenology of the ablated patterns by probing the ablation depth using a profilometer. The surface modification was examined using a high resolution optical microscope (IOLs) or atomic force microscope—AFM (PMMA samples). It was found that different polymers exhibited different ablation characteristics, a result that we attribute to the differing optical properties of the materials. In particular, it was observed that the topography of the ablation tracks created on the hydrophilic intraocular lenses was smoother in comparison to those created on the PMMA and hydrophobic lens. The yellow doped hydrophobic intraocular lenses show higher ablation efficiency than undoped hydrophobic acrylic lenses.     

铜铟硫纳米晶/PMMA复合薄膜的制备与光学性质表征

铜铟硫(CuInS₂)纳米晶具有发射光谱宽、波长易于调控、量子产率高、合成成本低、容易与封装材料复合等优点,在远程白光LED结构中具有广阔的应用前景。远程白光LED结构是针对LED散热问题提出的一种新型封装结构,在这种结构中复合荧光涂层(复合薄膜)与蓝光芯片进行隔离封装,这种结构对复合薄膜中纳米晶的热稳定性的要求大大降低。首先合成出了不同发光波长的CuInS₂纳米晶荧光材料,然后将其封装到PMMA基质中制备了系列的CuInS₂纳米晶/PMMA复合薄膜。通过荧光光谱和紫外可见光谱的方法,针对纳米晶复合薄膜出现的发光波长红移以及不同发光波长纳米晶/PMMA复合薄膜透过率不一致的现象进行了详细研究。     

Posterior capsular opacification and intraocular lens surface micro-roughness characteristics: an atomic force microscopy study

ObjectiveSurface roughness parameters of various intraocular lenses (IOLs) biomaterials using atomic force microscopy (AFM) are compared. Variation, if any, in the micro-roughness properties of different IOLs made up of the same biomaterial is also explored. Retrospective analysis of posterior capsular opacification (PCO) incidence has been followed up for a period of four years post IOL implantation to evaluate the correlation of PCO formation with surface roughness of IOLs.DesignExperimental materials study.Materials and participantsSurface characteristics of 20 different IOL models were assessed using AFM. These IOL models were made up of PMMA or HEMA or acrylic hydrophobic or acrylic hydrophilic or silicone. Retrospective analysis of PCO incidence in 3629 eyes of 2656 patients implanted with the same IOL models was performed.MethodsTopological characteristics of 20 different IOLs made up of 5 different biomaterials including (i) PMMA, (ii) HEMA, (iii) acrylic hydrophobic, (iv) acrylic hydrophilic and (v) silicone were evaluated using AFM in the tapping mode. Images were acquired with a resolution of 256 × 256 data points per scan at a scan rate of 0.5 Hz per line and a scan size of 10 × 10 μm. Rate of PCO formation in 3629 eyes of 2656 patients implanted with the five different IOL biomaterials was retrospectively analyzed.ResultsAFM images of IOL optic surfaces showed a collection of pores, grooves, ridges and surface irregularities. Surface roughness parameters of the IOL optics were significantly different on comparing lenses of different materials. Acrylic hydrophobic IOLs had minimum surface roughness while acrylic hydrophilic IOLs showed the highest surface roughness. Different IOL models of the same biomaterial showed varied topological roughness characteristics. Retrospective analyses of PCO formation rate after IOL implantation was carried out, which revealed that rate of PCO incidence, was directly proportional to the increase in surface micro-roughness of IOLs.ConclusionsAFM is a powerful technique for the topological characterization of IOLs. Acrylic hydrophobic IOLs showed minimum surface roughness properties as well as minimum PCO incidence over a period of four years post implantation. It is, therefore, tempting to consider acrylic hydrophobic IOLs over other IOL biomaterials as the ideal biocompatible material for lowering PCO incidence. These results suggest an urgent need for manufacturers to optimize the various steps involved in the fabrication of IOLs.     

改进的SILAR法制备ZnO薄膜及其表征

采用一种改进的液相成膜技术——连续离子层吸附与反应(SILAR)法, 用锌氨络离子\[Zn(NH3)4\]2+ 溶液作为独立的前驱体溶液, 以载玻片为衬底, 在(125±5) ℃的温度下沉积出致密、 透明的ZnO薄膜。 分别用冷场发射型扫描电镜(FESEM)和X射线衍射(XRD)分析了薄膜样品的表面形貌和结晶状态, 用紫外可见分光光度计(UV-Vis spectroscopy)研究了薄膜样品的发光性能。 结果表明: 获得样品为六角纤锌矿结构的多晶薄膜材料沿\[002\]方向择优生长; 样品表面均匀、 致密, 厚度约为550 nm;在可见光波段具有高的透射率(＞80％)。 A modified solution method,successive ionic layer adsorption and reaction(SILAR),was applied to prepare transparent zinc oxide(ZnO) film on glass substrate at (125±5) ℃ in mixed ion precursor solution. The surface morphology and crystallizations of films were analyzed by field emission scanning microscopy(FESEM) and X ray diffraction(XRD), respectively. The optical properties of the films were studied by ultraviolet visible(UV Vis)spectroscopy. The results show that the obtained samples are polycrystalline films of hexagonal wurtzite structure,with the preference of [002\] orientation. The as deposited films exhibit uniform and compact surface morphology, with the film thickness of 550 nm, and have high transmittance in the visible band(＞80％).     

Surface composition and electronic properties of indium tin oxide and oxynitride films

The surface properties of indium tin oxynitride films prepared by rf-sputtering in nitrogen atmosphere were investigated by X-ray and ultraviolet photoelectron spectroscopy as well as electron energy loss spectroscopy and Auger electron spectroscopy depth profiling. The results are compared to reference measurements on conventional rf-sputtered indium tin oxide films. The incorporated nitrogen is present in different chemical environments. Employing these different spectroscopic techniques, it was found that desorption of nitrogen from the ITON structure upon annealing is the origin of the observed drastical changes in the surface composition and electronic structure. The formation of oxygen vacancies and Sn surface segregation upon annealing is linked to improvements in the physical properties (larger spectral range of transmittance and higher conductivity) of the films.     

Reversible UV degradation of PMMA plastic optical fibers

Laser-induced fluorescence, Raman and absorption spectroscopy are used to investigate reversible degradation of transmission in PMMA optical fibers. When exposed to 254 nm UV light, optical transmission of PMMA plastic optical fiber in 400-800 nm range shows a significant increase in attenuation for shorter wavelengths. Over a period of 10 days following UV exposure, the transmittance of the plastic fiber recovers to a significant fraction of its pre-exposure value. UV-exposed fiber exhibits strong laser-induced fluorescence with 488 nm argon-ion laser. This fluorescence spans a spectral region between 450 nm and 750 nm with a peak around 580 nm. The fluorescence intensity decreases over several days following UV exposure. Likewise, Raman is also used to investigate degradation process. Freshly UV-exposed fiber shows total absence of Raman spectrum of PMMA. Following UV exposure, recovery of Raman signal over several days is correlated to the recovery of fiber transmittance as well as the decay of laser-induced fluorescence. A widely believed plausible explanation for UV-induced increase of attenuation involves formation of different macro radicals which recombine progressively after UV is stopped. Laser-induced fluorescence over several days is reported here providing direct evidence for molecular-level deterioration and recovery of PMMA.     

Surface modification of PMMA/O-MMT composite microfibers by TiO2 coating

In the present work, poly(methyl methacrylate) (PMMA)/organically modified montmorillonite (O-MMT) composite microfibers were firstly prepared by emulsion polymerization combined with electrospinning, and then coated by nanosize titanium dioxide (TiO₂) using RF magnetron sputter technique. The modified surfaces of PMMA/O-MMT composite microfibers were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), UV-vis spectroscopy and drop shape analyzer. Finally, the photocatalytic properties of TiO₂ coated PMMA/O-MMT composite microfiber membranes were evaluated by degradation of methylene blue(MB) under UV illumination. The experimental results revealed that anatase-TiO₂ and rutile-TiO₂ nanoparticles were well spread and physically deposited on the surface of PMMA/O-MMT microfibers, and the wettability of the PMMA/O-MMT composite microfibers was improved after surface modification by sputter coating. Furthermore, the PMMA/O-MMT microfibers membrane coated with TiO₂ performed well in photocatalytic degradation of MB.     

Mg–Al LDH reinforced PMMA nanocomposites: a potential material for packaging industry

Poly-methylmethacrylate/Mg–Al layered double hydroxide (PMMA/LDH) based nanocomposites have successfully been synthesised with varying LDH content by in situ polymerisation technique and systematically studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT IR), UV-Visible spectroscopy and microscopic (FE SEM and HR TEM) analysis. In particular, thermogravimetric analysis (TGA) and gas barrier properties measurement were carried out to assess the suitable application of these materials. The thermal property of PMMA/LDH composites was compared with neat PMMA and an enhancement in thermal stability was noticed with gradual increase in LDH content in the composite. Gas permeability measurement data showed significant decrease in oxygen permeability value of the PMMA/LDH nanocomposites in comparison to the pristine PMMA. Enhancement in thermal stability along with significant reduction in oxygen permeability of PMMA upon composite formation indicate the possible application of these materials in packaging industries.     

磁控溅射法制备钛掺杂WO3薄膜结构和性能的研究

采用中频孪生非平衡磁控溅射技术制备钛掺杂WO_3薄膜。运用X射线衍射(XRD),拉曼光谱、紫外分光光度计、计时安培分析仪和原子力显微镜(AFM)等测试手段分析了钛掺杂WO_3薄膜的结构和光学性能。实验结果表明,掺杂后的薄膜在相同的热处理条件下晶化程度降低,晶粒细化,离子抽出和注入的通道大大增多,钛掺杂原子数分数0．051的着色响应速度提高,循环寿命提高了4倍以上,但着色后透射率下降。     

Surface modification of polyethylene film by acrylamide graft and alcoholysis for improvement of antithrombogenicity

To improve antithrombogenicity of polyethylene (PE) films, the films pretreated by Ar plasma were radiated by ultraviolet light to initiate grafting polymerization with acrylamide (AAm) in absence of photo-initiator, then the AAm-grafted PE films (PE-g-AAm) were alcoholized with octadecyl alcohol. Effects of Ar plasma composite parameter (W/FM), pretreated time, AAm monomer concentration, and UV irradiation time on grafting rate were investigated systematically. AAm-grafted PE film and alcoholized PE film (PE-g-SAAm) were characterized by contact angle, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transfer infrared (ATR-FT-IR) spectroscopy and atomic force microscope (AFM), respectively. The results indicated that the moieties of AAm and stearyl were successively immobilized onto the PE surface. The platelet adhesion experiment showed that antithrombogenicity of the modified PE films was improved in comparison with PE films. The change in antithrombogenicity is attributed to the surface of the modified film in presence of tail-like structure which consists of polyacrylamide as spacer and stearyl as end groups.     

Improvement in mechanical and optical properties of vapour chopped vacuum evaporated PANI/PMMA composite thin film

PANI/PMMA composite was synthesized by emulsion polymerization pathway and the composite thin film was obtained by vacuum evaporation. The effect of vapour chopping and varying PMMA concentration was also studied. The FTIR spectra showed that the PANI/PMMA composite thin film deposited as a short chain oligomers. Increase in transmittance and decrease in refractive index was obtained with increasing concentration of PMMA, which further increased the adhesion and decreased intrinsic stress. The vapour chopping improved its optical as well as mechanical properties and produced smoother surface morphology. Increase of PMMA made the film more amorphous and does not change its band gap.     

衬底温度对HfO_2薄膜结构和光学性能的影响

采用直流磁控反应溅射法,分别在室温,200,300,400和500℃下制备了HfO2薄膜。利用X射线衍射(XRD)、椭圆偏振光谱(SE)和紫外可见光谱(UVvis)研究了衬底温度对HfO2薄膜的晶体结构和光学性能的影响。XRD研究结果显示:不同衬底温度下制备的HfO2薄膜均为单斜多晶结构;随衬底温度的升高,(-111)面择优生长更加明显,薄膜中晶粒尺寸增大。SE和UVvis研究结果表明:随衬底温度升高,薄膜折射率增加,光学带隙变小;制备的HfO2薄膜在250～850nm范围内有良好的透过性能,透过率在80%以上。     

Properties of ZnO thin films deposited by DC reactive magnetron sputtering under different plasma power

ZnO thin films were prepared by DC reactive magnetron sputtering under various values of the plasma power at room temperature. The samples were characterized with X-ray diffraction (XRD), optical transmittance, photoluminescence (PL), and atomic force microscopy (AFM), respectively. The results show that samples change from ZnO (110) dominant crystal orientation to ZnO (002) dominant crystal orientation with the increase of plasma power. The samples also exhibit compressive intrinsic stresses. The coherent domain size of the film crystallite along with the root mean square (RMS) of the surface roughness increases with the increase of the plasma power. Optical transmittance spectra reveal that all samples have excellent optical properties. With the increase of plasma power, slight optical transmittance decreasing and fundamental absorption edge red shifting were observed. Films prepared under higher plasma powers show weaker emission intensities, which may be related to substoichiometric composition.     

Solid electrolyte membranes from semi-interpenetrating polymer networks of PEG-grafted polymethacrylates and poly(methyl methacrylate)

Solid polymer electrolyte membranes were prepared as semi-interpenetrating networks by photo-induced polymerization of mixtures of poly(ethylene glycol) (PEG) methacrylate macromonomers in the presence of poly(methyl methacrylate) (PMMA) and lithium bis(trifluoromethanesulfonyl)imide salt. The composition of the membranes was varied with respect to the PMMA content, the degree of cross-linking, and the salt concentration. Infrared analysis of the membranes indicated that the lithium ions were coordinated by the PEG side chains. Calorimetry results showed a single glass transition for the blend membranes. However, dynamic mechanical measurements, as well as a closer analysis of the calorimetry data, revealed that the blends were heterogeneous systems. The ionic conductivity of the membranes increased with the content of PEG-grafted polymethacrylate, and was found to exceed 10^− 5 S cm^− 1 at 30 °C for membranes containing more than 85 wt.% of this component in the polymer blend.