碳纳米管/二硒化钼有机玻璃的非线性吸收、非线性散射和光限幅特性

MoSe₂的禁带宽度较窄（1.1–1.5 eV）,且具有可调谐的激子光电效应,这样使其在光致发光、光电晶体管、太阳能电池和光学非线性等方面具有潜在的应用价值.然而,纯的MoSe₂的光生电子空穴复合率较高,限制了其在某些光学领域中的应用.通过设计MoSe₂的复合材料,可以降低材料的光生电子空穴复合率,从而扩展其应用领域.首先,通过热溶剂法合成CNT/MoSe₂复合材料;然后,通过浇铸法将其分散在甲基丙烯酸甲酯（MMA）中制备成有机玻璃,其中MMA会聚合成聚甲基丙烯酸甲酯（PMMA）,并利用改进的Z-扫描技术首次对CNT/MoSe₂/PMMA有机玻璃的非线性吸收、非线性散射和光限幅特性进行了研究.研究表明,随着输入能量的变化,通过调节输入能量,CNT/MoSe₂/PMMA有机玻璃表现出饱和吸收（SA）和从SA到反饱和吸收的转变.结合材料特性及应用条件要求,可以得到CNT/MoSe₂/PMMA有机玻璃在光学设备,如光学限制器和锁模/调Q激光器等方向具有较好的应用前景.     

Chiral organic glass and its infrared spectrum property

Chiral molecules griseofulvin were disseminated homogeneously in poly methyl metahcrylate (PMMA) host, which agglomerate from methyl metahcrylate and N, N-dimethyl formamide dimethyl acetal, using benzoyl peroxide as a catalyst. So the chiral organic glass has been manufactured successfully. Its optical rotatory were investigated from a solution state to a solid state. The results of measurement show that the chiral parameter of the chiral organic glass is 2.65×10^{-7} and its specific rotation has increased compared with its solution condition. Its infrared spectra property has been measured by Fourier transformation infrared spectrometer. The results show that the chiral molecules fill in the pore of the network structure in the organic glass, which hardly link with the host.     

Bump formation on a glass surface with a transparent coating using femtosecond laser processing

The morphology of a glass surface having a transparent coating processed with focused femtosecond laser pulses is investigated. The transparent coating is formed of poly-methyl methacrylate (PMMA). When the glass was coated with a PMMA film with a thickness of 2.8 μm, bumps were formed over a wide range of axial focus positions. The same laser pulse energy produced cavities when processing bare glass with no coating. The bumps were formed as a result of suppressing material emission from the glass surface by a shielding effect of plasma generated by ablation of the PMMA film and by physical blocking of the PMMA film. A thinner film with a thickness of 0.7 μm produced a reduced shielding effect, forming an exploded bump with a small pit at its center and debris around the periphery. PACS 44.10.+i; 61.80.Ba; 79.20.Ds     

The application of conventional photolithography to microscale organic resistive memory devices

We demonstrate the application of conventional photolithography to fabricate organic memory devices in an array structure with a cell area of 4 × 4 μm² without damaging the underlying organic memory layer. Applying photolithography to organic electronic devices is not trivial because the solvents used during lithography may dissolve and damage the previously coated organic layers. The application of photolithography to our organic devices was possible because of the introduction of polymethyl methacrylate (PMMA)/polyvinyl alcohol (PVA) onto the memory active layer, where PMMA functions as a buffer layer to prevent dissolution of the PVA layer during developing process, and PVA acts as a striped layer during metal lift-off process. Embedded Al bottom electrodes were particularly constructed to minimize the switching failure. The completed organic memory devices exhibited typical unipolar switching behavior and excellent memory performance in terms of their statistical memory parameters (ON and OFF currents and threshold voltages), ON/OFF ratio (>10²), endurance (>230 cycles), and retention (>10⁴ s). This convenient photolithography patterning technique is applicable for the further scaling of many types of organic devices.     

Molecular dynamics simulation studies of the miscibility and thermal properties of PMMA/PS polymer blend

This investigation is an attempt to improve our understanding of the thermal properties of PMMA (Polymethyl methacrylate) by using PS(Polystyrene); the miscibility of PMMA/PS polymer blend is studied. Our work aims to study the impact of the percentage of PMMA/PS polymer blend on the simulated values of the glass transition temperature (Tg) using the dilatometric method. Compass was chosen as the force field (second category force field). The results reveal a single value of the glass transition temperature Tg that is found for all the curves of the PMMA/PS blend system (molar ratio: (50:50, 60:40, 54:46 and 80:20)); this could be a good criterion for predicting the miscibility. Additionally, the solubility parameters of PMMA and PS are calculated and used to obtain the Flory–Huggins parameter, and the morphology of our polymer blend is simulated using the dissipative particle dynamics method (DPD). Our results exhibit an increase in the Tg of PMMA whenever PS is added; hence, we can confirm the miscibility of the PMMA/PS polymer system.     

The effect of polymer type on electric breakdown strength on a nanosecond time scale

Based on the concepts of fast polarization,effective electric field and electron impact ionization criterion,the effect of polymer type on electric breakdown strength(E BD) on a nanosecond time scale is investigated,and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived.According to this formula,it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers.By calculating the effective relative dielectric constants for different types of polymers,the theoretical relation for the electric breakdown strengths of common polymers is predicted.To verify the prediction,the polymers of PE(polyethylene),PTFE(polytetrafluoroethelene),PMMA(organic glass) and Nylon are tested with a nanosecond-pulse generator.The experimental result shows E BD(PTFE) > E BD(PMMA) > E BD(Nylon) > E BD(PE).This result is consistent with the theoretical prediction.     

Hologram Recording in Various Glass Plates by Corona Charging

We propose techniques of hologram replication in glass plates and reconstruction on another film by corona charging. A surface relief hologram on an azobenzene polymer film was recorded in the form of electric polarization in glass plates that include alkali cations by corona charging at high temperature. The hologram recorded in the glass plate is stable for more than 1 month at room temperature. After removal of the azobenzene polymer film from the plate, poly(methyl methacrylate) (PMMA) film was spin-coated onto the plate. The hologram recorded in the plate was reconstructed with the same surface relief structure on the PMMA film by corona charging again at 110°C.     

喷雾工艺制备的高性能有机光敏薄膜晶体管

以聚3-己基噻吩(P3HT)为有机层、价格低廉的聚甲基丙烯酸甲酯(PMMA)为绝缘层制备了底栅顶接触型结构的有机薄膜晶体管(OTFT)。采用一种新型喷雾工艺来制备器件的有机薄膜层,通过测量有机薄膜晶体管的电学特性,可得出应用喷雾制备的器件有较好的性能。在100 mW/cm2标准模拟太阳光照下,测量基于P3HT的有机薄膜晶体管器源漏电流随时间的变化特性,结果表明基于P3HT的有机光敏薄膜晶体管,不仅具有明显的响应特性,而且具有很好的恢复特性。同时,对比黑暗和光照1,2,4 min下的OTFT特性转移曲线,得到器件的阈值电压随时间的变化曲线。     

Interaction of Domains in Ternary Polymer Melt Blends with Separate Dispersions of the Inner Phases

The morphology evolution in three immiscible ternary polymer systems characterized by separate dispersions of the dispersed phases (i.e., no encapsulation phenomena takes place) was characterized. The components used were three of the following: commercial atactic poly(methyl methacrylate) (PMMA) and polystyrene (PS), crystallizable poly(butylene terephthalate) (PBT) and isotactic polypropylene (PP) and glass microspheres (GMS). In System I PMMA/PS/PP (primary dispersed phase/matrix/secondary, or minor, dispersed phase), all of the components were liquid on blending at 190°C. In System II PP/PS/PBT and System III PP/PSyGMS, at 190°C, the minor PBT and GMS dispersed phases were nondeformable. It was shown that small portions (0.5–1.0 wt%) of the PP minor dispersed phase added to the binary PMMA/PS blend produced a dual action: (a) transition of the PMMA dispersed phase to a cocontinuous one and (b) simultaneous substantial (up to a 6-fold) growth of the degree of dispersion of the blend. Moreover, these effects were accompanied by about a three-fold reduction of the threshold PMMA concentration (C*) at which it formed its own co-continuous phase in the ternary blend compared to that in the PMMA/PS binary mixture. The observed phenomena took place regardless of whether the domains of the minor dispersed phase were liquid (System I) or solid (Systems II and III), and was strongly related to the domain sizes of this phase and blend composition. A mechanism underlying the outlined behavior is proposed.     

Dielectric relaxations in ultrathin isotactic PMMA films and PS-PMMA-PS trilayer films

The local and cooperative dynamics of supported ultrathin films ( L = 6.4 - 120 nm) of isotactic poly(methyl methacrylate) (i-PMMA, Mn = 118 x 10(3) g/mol) was studied using dielectric relaxation spectroscopy for a wide range of frequencies (0.1 Hz to 10(6) Hz) and temperatures (250 - 423 K). To assess the influence of the PMMA film surfaces on the glass transition dynamics, two different sample geometries were employed: a single layer PMMA film with the film surfaces in direct contact with aluminum films which act as attractive, hard boundaries; and a stacked polystyrene-PMMA-polystyrene trilayer film which contains diffuse PMMA-PS interfaces. For single layer films of i-PMMA, a decrease of the glass transition temperature T(g) by up to 10 K was observed for a film thickness L < 25 nm (comparable to R(EE)), indicated by a decrease of the peak temperature T(alpha) in the loss epsilon(")(T) at low and high frequencies and by a decrease in the temperature corresponding to the maximum in the apparent activation energy E(a)(T) of the alpha-process. In contrast, measurements of i-PMMA sandwiched between PS-layers revealed a slight (up to 5 K) increase in T(g) for PMMA film thickness values less than 30 nm. The slowing down of the glass transition dynamics for the thinnest PMMA films is consistent with an increased contribution from the less mobile PMMA-PS interdiffusion regions.     

Glass transition temperature and thermal stability of ZnS/PMMA nanocomposites

In this article, ZnS nanoparticles were prepared by wet chemical precipitation method using zinc sulphate (ZnSO₄), sodium sulphide (Na₂S) and thio-glycerol. These nanoparticles were characterized through X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The solution-based processing was used to prepare Poly methyl methacrylate (PMMA) nanocomposites with different weight percents (0, 2, 4, 6 and 8) of ZnS nanoparticles. The obtained ZnS/PMMA nanocomposites were characterized through XRD, scanning electron microscope and TEM measurements. The dynamic mechanical analyzer was used to obtain the storage modulus and glass transition temperature (T _g) of the nanocomposites. The apparent activation energy of the glass transition region was also determined using the Vogel–Fulcher–Tammann equation. The results indicated that the thermal stability of ZnS/PMMA nanocomposites was higher than PMMA and 6 wt. % of ZnS nanoparticles in PMMA matrix showed the maximum activation energy, which indicated that this nanocomposite had higher thermal stability than other composites.     

Parametric Studies on the Grafting of Poly(Methyl Methacrylate) onto Organophilic Montmorillonite Using Silylated Clay Platelets

Poly(methyl methacrylate) (PMMA)/organophilic montmorillonite (Cloisite 30B) nanocomposites were synthesized by the chemical grafting of PMMA onto Cloisite 30B via solution polymerization of methyl methacrylate (MMA) with vinyl-modified organoclay. The effects of different parameters such as clay weight percent (CWP), solvent per monomer volume ratio, and dispersion time on the properties of the PMMA grafted Cloisite 30B were investigated using the Taguchi experimental design method. This method gives a much-reduced variance for the experiments with optimum setting of control parameters and provides a set of minimum experiments compared to the conventional methods. Qualitative evidence for the chemical grafting of the PMMA onto Cloisite 30B was confirmed by Fourier transform infrared spectroscopy (FT-IR). X-ray diffraction (XRD) was used to investigate interlayer changes of the clay in the grafted nanoplatelets. The exfoliated/intercalated morphology of the nanocomposites was confirmed by XRD. Furthermore, thermal properties were measured by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). Statistical analysis of results revealed that clay weight percent and solvent per monomer ratio had significant effects on the properties of final products. The percent of grafted PMMA and storage modulus of PMMA/30B nanocomposites decreased with increasing clay content due to better dispersion of the clay at lower loadings. On the other hand, because of a tendency to formation of homopolymer and oligomers at higher solvent loadings; the percent of grafted PMMA, storage modulus and glass transition temperature of PMMA/30B nanocomposites decreased with an increase in solvent per monomer volume ratio. However, the obtained PMMA/30B nanocomposites at the optimum conditions, was exhibited a higher glass transition temperature, higher storage modulus and better thermal stability than the pure PMMA.     

The role of adsorption of sodium bis(2-ethylhexyl) sulfosuccinate in wetting of glass and poly(methyl methacrylate) surface

Advancing contact angles, θ, for aqueous solutions of the anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) were measured on glass and poly(methyl methacrylate) (PMMA) surface. Using the obtained results we determined the properties of aqueous AOT solutions in wetting of these surfaces. It occurs that the wettability of glass and PMMA by these solutions depends on the concentration of AOT in solution. There is almost linear dependence between the contact angle (θ) and concentration of AOT (log C) in the range from 5 × 10⁻⁴ to 2.5 × 10⁻³ M/dm³ (value of the critical micelle concentration of AOT—CMC) both for glass and PMMA surface. For calculations of AOT adsorption at solid (glass, PMMA)-solution drop-air system interfaces the relationship between the adhesion tension (γ_LV cos θ) and surface tension (γ_LV) and the Gibbs and Young equations were taken into account. From the measurement and calculation results the slope of the γ_LV cos θ − γ_LV curve was found to be constant and equal 0.7 for glass and −0.1 for PMMA over the whole range of AOT concentration in solution. From this fact it can be concluded that if Γ_SV is equal zero then Γ_SL > 0 for the PMMA-solution and Γ_SL < 0 for glass-solution systems. It means that surfactant concentration excess at PMMA-solution interface is considerably lower than at solution-air interface, but this excess of AOT concentration at glass-solution interface is lower than in the bulk phase. By extrapolating the linear dependence between the adhesion and surface tension the value of the critical surface tension (γ_c) of wetting for glass and PMMA was also determined, that equaled 25.9 and 25.6 mN/m for glass and PMMA, respectively. Using the value of the glass and PMMA surface tension as well as the measured surface tension of aqueous AOT solutions in Young equation, the solid-liquid interface tension (γ_SL) was found. There was a linear dependence between the γ_SL and γ_LV both for glass and PMMA, but there were different slope values of the curves for glass and PMMA, i.e. −0.7 and 0.1, respectively. The dependence between the work of adhesion (W_A) and surface tension (γ_LV) was also linear of different slopes for glass and for PMMA surface.     

氰基团修饰的苯腙类有机分子掺杂极化聚合膜光学非线性的研究

采用实时测量光学二次谐波产生（ＳＨＧ）和吸收光谱的方法对苯腙类有机分子ＮＤＡ及一种新合成的经氰基团修饰的有机分子ＣＮＤＡ掺杂ＰＭＭＡ极化聚合膜的非线性光学性质进行了研究。实验中发现两种掺杂极化聚合膜的最佳电晕极化温度均低于它们的玻转温度,ＣＮＤＡ／ＰＭ－ＭＡ极化掺杂聚合膜的χ（２）较ＮＤＡ／ＰＭＭＡ极化聚合膜的大。结合极化前和极化后吸收峰强度的变化,得到ＣＮＤＡ分子的非线性极化率β约为１４６×１０－３０ｅｓｕ。在撤离极化场后,ＣＮＤＡ／ＰＭＭＡ的二次谐波强度的弛豫也比ＮＤＡ／ＰＭＭＡ的慢     

有机盐掺杂聚合物微腔的受激发射特性研究$lt;font color="#ff0000"$gt;（已撤稿）$lt;/font$gt;

采用新型有机吡啶盐trans-4-［p-（N-hydroxyethyl-N-methylamino）styryl］-N-methylpyridinium iodide （ASPI）与有机小分子８-羟基喹啉铝（Alq₃）组成能量传递体系,掺杂于惰性聚合物聚甲基丙烯酸脂（PMMA）薄膜中作为增益介质,利用分布布拉格反射镜（DBR）和金属Ag层作为反射镜,制备了垂直微腔结构的有机半导体固体激光器.在纳秒脉冲激光抽运下研究了该有机微腔的受激发射特性,观测到峰值位于600 nm处谱半高全宽为243 nm的单模激光出射;同时观察到明显的激光能量阈值特性,单脉冲的受激发射能量阈值为8?μJ.-----------------2009年《物理学报》第58卷第4期第2781-2784页一文,由于作者的责任,故撤销该文。 关键词： 有机盐 能量转移 微腔 受激发射     

不同绝缘层上生长的并五苯薄膜及其OTFT器件性能的研究

分别以SiO₂和PMMA为绝缘层材料制备了底栅顶接触结构的OTFT器件,得到以PMMA为绝缘层的器件具有更好的性能,其场效应迁移率为0.207 cm2·Vs-1,开关电流比为4.93×103,阈值电压为-4.3 V;而以SiO₂为绝缘层的器件,其场效应迁移率仅为0.039 cm2·Vs-1,开关电流比为5.98×102,阈值电压为-5.4 V。为分析器件性能差异的原因,测得了SiO₂和PMMA薄膜表面的AFM图谱及其上沉积并五苯薄膜后的AFM和XRD图谱。通过AFM图谱发现PMMA表面较SiO₂表面粗糙度小,其表面粗糙度的均方根值为0.216 nm,而二氧化硅薄膜表面粗糙度的均方根值为1.579 nm;且发现在PMMA上生长的并五苯薄膜的成膜质量优于在SiO₂,具有较大的晶粒尺寸和较少的晶粒间界。通过XRD图谱发现在PMMA上生长的并五苯薄膜具有明显的衍射峰,进一步证明了在PMMA上生长的并五苯薄膜具有更好的结晶状况,将更有利于载流子的传输。     

Yielding behavior of glassy polymers. I. Free-volume model

Rigid, glassy polymers show a diversity of tensile behavior-ranging from apparently brittle to ductile. To delineate some of the factors that control the toughness or impact resistance of these polymers, the yielding behavior of poly (methyl methacrylate) (PMMA) was studied. Results of other workers have shown that the cold flow exhibited by many glassy polymers can be explained qualitatively by a free-volume model. The treatment assumes that molecular flow is permitted when the free volume increase, resulting from the dilatational component of the applied stress, is sufficient to bring the total free volume to that characteristic of the polymer liquid. The present study refines this approach by introducing an “effective temperature,” defined as that hypothetical temperature at which the glass would have an equilibrium free volume equal to the total free volume of the nonequilibrium glass at temperature T. Equations are derived which more satisfactorily describe the temperature and strain-rate dependences of the tensile yield strain of PMMA glass from -10° to 90°C at rates between 0.015 and 120%/sec.     

塑料光纤相位调制灵敏度的研究

研究了压电涂层PMMA纤芯塑料光纤中的相位调制.射频信号通过对光纤外层的压电涂层作用,使纤芯中产生应变,从而对光纤中的光信号进行相位调制.数值计算结果表明,与传统的石英光纤相比,PMMA塑料光纤的相位调制的灵敏度要高数十倍以上.     

Modulation of refractive index and thickness of poly(methyl methacrylate) thin films with UV irradiation and heat treatment

This paper reports changes in refractive index and thickness of spin-coated poly(methyl methacrylate) (PMMA) thin films upon irradiation by a conventional high-pressure mercury UV lamp. Significant increase in refractive index and reduction in thickness are detected. Index modulations of greater than 0.01 are achieved in the thin films after 4 min of irradiation. The thickness reduction of an irradiated PMMA film is consistent with its weight loss. This is caused by the escape of the volatile molecules generated during the irradiation process. A slight increase in the refractive index is also found in the film, heat-treated above its glass transition temperature (Tg). This thermal effect is detected in the UV irradiation process. We propose three possible aliphatic structures that are formed during the photochemical reaction and may exist in the main chain of irradiated PMMA after the irradiation. Their refractive indices in aggregate state are greater than that of PMMA based on an evaluation using the Lorentz-Lorenz equation. This is suggested to be an important reason for the refractive index increase in the UV-irradiated PMMA films. A UV-irradiated film, heat-treated above its Tg, has a rough surface with many tiny holes as illustrated by atomic force microscopy. These holes are attributed to the evaporation of the small molecules generated during the irradiation process.