浅色可溶含氟聚酰亚胺的合成与性能研究

利用含氟二胺2,2一双[4-(4-氨基-2-三氟甲基苯氧基)苯基]六氟丙烷分别与1,2,3,4-环丁烷四酸二酐、均苯四甲酸二酐、3,3,,4,4'-联苯四酸二酐、3,3',4,4'-二苯醚四酸二酐和3,3',4,4'-二苯酮四酸二酐进行低温缩聚反应,经热酰亚胺化制备出5种含氟聚酰亚胺(PI)薄膜,均表现出优良的综合性能.其中,含脂环PI薄膜在可见光波长范围内(400～700nm)具有优异的光学透明性,450nm处的透光率为84.6%,紫外截止波长为307.2nm,近乎无色透明,且5种含氟PI在光通讯波段(1.30μm和1.55μm)无明显吸收;这些含氟PI均具有良好的溶解性;除含脂环PI的热稳定性稍差外,4种芳香PI薄膜的5%热失重温度均超过519℃,具有良好的热稳定性.     

6FAPE基含氟聚酰亚胺的结构与性能研究

利用含氟二胺单体4,4'-双(4-氨基-2-三氟甲基苯氧基)二苯醚(6FAPE),分别与1,2,3,4-环丁烷四酸二酐(CBDA)、3,3',4,4'-二苯醚四酸二酐(ODPA)、3,3',4,4'-联苯四酸二酐(BPDA)、3,3',4,4'-二苯甲酮四羧酸二酐(BTDA)和均苯四甲酸二酐(PMDA)进行低温缩聚反应,经热酰亚胺化制备出5种聚酰亚胺(PI)薄膜,考察了其光学透明性和热性能,研究了聚酰亚胺分子结构与性能的关系.结果表明,CBDA基含氟PI薄膜在可见光波长范围内(400～700nm)具有优异的光学透明性,450nm处的透光率为84.6%,且5种含氟PI薄膜在光通讯波段(1.30μm和1.55μm)均无明显吸收;除CBDA外,含氟PI薄膜均具有良好的热稳定性,5%热失重温度超过530℃;5种含氟PT薄膜的玻璃化转变温度Tg均在200℃以上,且CBDA基舍氟PI薄膜的Tg最高,达到265.5℃.     

可溶性透明含氟聚酰亚胺薄膜的合成与性能

利用3种二胺单体1,4-双(4-氨基-2-三氟甲基苯氧基)苯、4,4’-双(4-氨基-2-三氟甲基苯氧基)二苯醚和4,4’-双(4-氨基-2-三氟甲基苯氧基)六氟丙烷分别与3种二酐单体1,2,3,4-环丁烷四酸二酐(CBDA)、均苯四甲酸二酐(PMDA)和3,3’,4,4’-二苯醚四酸二酐(ODPA)进行低温溶液缩聚反应,再经热酰亚胺化制备出9种聚酰亚胺(PI)薄膜。结果表明,这些PI具有较好的溶解性,可溶解于氨型强极性溶剂,在弱极性溶剂中也有一定的溶解性;CBDA和ODPA基PI在450 nm处的透光率超过80%,且CBDA基PI的紫外截止波长为310 nm,更接近无色,但其热稳定性最差,5%热分解温度在420℃左右,而PMDA和ODPA基PI的热稳定性较好。     

砜基取代高折射率高透明性聚酰亚胺的合成与性能

首先合成了同时含有砜基与硫醚键的二胺单体,4,4′-双(4-胺基苯硫基)二苯砜(BADPS).采用BADPS分别与4种二酐单体,3,3′,4,4′-联苯四羧酸二酐(BPDA)、3,3′,4,4′-二苯醚四羧酸二酐(ODPA)、4,4′-双(3,4-二羧基苯硫基)二苯硫醚二酐(3SDEA)以及1,2,3,4-环丁烷四羧酸二酐(CBDA)通过两步聚合工艺制备了一系列聚酰亚胺(PI).制备的PI薄膜具有优良的综合性能,包括良好的热稳定性、可见光波长范围内优良的透明性以及高折射率与低双折射.10mm厚的PI薄膜在450nm处的透光率超过80%.全芳香族PI(PI-1～PI-3)的折射率＞1.70,双折射＜0.02.     

无色透明耐高温聚酰亚胺薄膜的制备与性能研究

分别采用两种联苯型二酐单体,对称结构的3,3',4,4'-联苯四甲酸二酐(s-BPDA)以及不对称结构的2,3,3',4'-联苯四甲酸二酐(a-BPDA)与含氟芳香族二胺1,4-双(4'-氨基-2'-三氟甲基苯氧基)联苯(TFDAB)通过两步缩聚法制备了两种聚酰亚胺材料PI-1(s-BPDA/TFDAB)与PI-2(a-BPDA/TFDAB).研究结果表明,不对称结构可以显著增加PI薄膜在可见光区的透明性.25μm厚的PI-2薄膜在450nm处的透光率达到93%,而同样厚度的PI-1薄膜的透光率只有67%.此外,在PI分子结构中引入不对称结构不会牺牲材料的耐热稳定性、力学性能与介电性能.     

共聚物链结构对共聚型含氟聚酰亚胺薄膜性能的影响

以4,4'-二氨基-2,2'-双三氟甲基联苯(TFMB)、4,4'-(六氟异丙烯)二酞酸酐(6FDA)和3,3',4,4'-联苯四甲酸二酐(BPDA)为反应单体,改变非含氟BPDA单体在二酐中的配比和加料方式制备出一系列共聚型含氟聚酰亚胺(PI)薄膜并表征和分析其性能,研究了共聚物链结构对其性能的影响。结果表明,BPDA单体的加料方式及其在二酐单体中的比例均影响薄膜的性能。共聚型含氟PI薄膜在室温下均溶于非质子极性溶剂,且在可见光范围内有较高的透光率。随着非含氟二酐单体BPDA含量的提高薄膜的光学性能略有降低而其热性能和力学拉伸性能提高。非含氟二酐单体占二酐单体的比例为68.97%的共聚型PI薄膜,在500 nm处的透过率达到96.01%;非含氟二酐单体占二酐单体比例为35.71%的共聚型PI薄膜失重10%的热分解温度为595.23℃,拉伸强度为100.98 MPa。同时,BPDA加料方式的改变对共聚型PI薄膜的光学性能、热学性能和力学拉伸性能均有不同程度的影响。     

含螺环结构的二胺及其聚酰亚胺的合成与性能

首先,以双酚A和甲磺酸反应合成出3,3,3',3'-四甲基-6,6'-二羟基-1,1'-螺旋双茚满,然后与2-氯-5-硝基三氟甲苯反应得到3,3,3',3'-四甲基-6,6'-双[4-硝基-2-三氟甲基苯氧基]-1,1'-螺旋双茚满,最后在Pd/C-水合肼还原作用下得到3,3,3',3'-四甲基-6,6'-双[4-氨基-2-三氟甲基苯氧基]-1,1'-螺旋双茚满。采用上述二胺单体分别与1,2,3,4-环丁烷四酸二酐、均苯四甲酸二酐、联苯二酐、3,3',4,4'-二苯醚四酸二酐、3,3',4,4'-二苯酮四酸二酐和六氟二酐通过两步法制备出6种含螺环结构的聚酰亚胺(PI)。采用核磁、红外光谱、X射线衍射、紫外-可见光谱、热重分析、差示扫描量热分析和溶解性测试等手段表征了所得化合物和PI的结构与性能。研究结果表明,这些含螺环的PI主要表现为非晶结构和较大的分子链间距离,且具有良好的溶解性、光学性能和热性能。     

环丁烷基聚酰亚胺液晶取向膜的制备及光控取向研究

采用1,2,3,4-环丁烷四酸二酐(CBDA)分别与芳香族二胺单体,包括4,4′-二氨基二苯甲烷(MDA)、3,3′-二甲基-4,4′-二氨基二苯甲烷(DMDA)、3,3′,5,5′-四甲基-4,4′-二氨基二苯甲烷(TMMDA)、3,3′-二甲基-5,5′-二乙基-4,4′-二氨基二苯甲烷(DMDEDA)、1,1-双(4-氨基-3,5-二甲基苯基)-1-苯基甲烷(PTMDA)以及1,1-双(4-氨基-3,5-二甲基苯基)-1-(3′-三氟甲基苯基)甲烷(TFMDA)通过低温溶液缩聚法制备了聚酰胺酸(PAA)型液晶取向剂。采用该系列PAA取向剂装配了液晶盒。测试结果显示,PAA高温固化后形成的聚酰亚胺(PI)取向膜具有良好的耐热稳定性,5%失重温度均超过了450℃。经过波长为254 nm的线性偏振紫外光(LPUV)辐照后,该系列PI取向膜对液晶分子具有良好的取向效果,预倾角(θ_p)为0.28～0.47°。装配的液晶盒的残余直流电压(RDC)最低可达364 mV。     

2,5-双(4-氨基-2-三氟甲基苯氧基)叔丁基苯及其聚酰亚胺的制备和性能研究

通过两步反应制备得到2,5-双(4-氨基-2-三氟甲基苯氧基)叔丁基苯,将其分别与均苯四甲酸二酐(PM-DA)、3,3’,4,4’-四羧酸二苯醚二酐(ODPA)、3,3’,4,4’-二苯酮四酸二酐(BTDA)、3,3’,4,4’-联苯四酸二酐(BPDA)、双酚A二酐(BPADA)通过缩聚和热亚胺化制备得到5种性能优异的聚酰亚胺薄膜。结果表明薄膜的玻璃化转变温度(Tg)高于210℃,起始分解温度高于510℃;吸水率低于0.9%;介电常数介于2.90～3.15之间;杨氏模量在1.48～2.27GPa之间。     

一类含双叔丁基苯结构聚酰亚胺的合成与性能

通过分子设计制备一种含双叔丁基结构的刚性芳香二胺单体——4,4′-二氨基苯基-3″,5″-二叔丁基甲苯,将该二胺单体分别与3种不同的商品化芳香二酐(3,3′,4,4′-联苯四酸二酐(BPDA)、3,3′,4,4′-二苯醚酐(ODPA)、3,3′,4,4′-二苯酮四酸二酐(BTDA))采用一步高温缩聚制备了3种新型聚酰亚胺NPI(3a～3c)。该类聚酰亚胺具有优异的溶解成膜性能,在室温可溶解于N-甲基-2-吡咯烷酮、N,N-二甲基乙酰胺、间甲酚等高沸点溶剂中,在加热时还能溶解于CHCl_3,CH_2Cl_2,THF等低沸点溶剂,并可通过其聚合物溶液浇铸得到柔韧的薄膜;所制聚酰亚胺薄膜具有优良的热性能,玻璃化转变温度(T_g)范围为262～303℃,在N_2中质量损失10%的温度超过523℃;具有优异的光学性能,所制薄膜还具有较浅的颜色和良好的光学透过性,在450 nm波长光下的透光率为69%～76%,截止波长为341～353 nm。     

Transparent polyimide/graphene oxide nanocomposite with improved moisture barrier property

Colorless and organo-soluble polyimide (PI) films have been synthesized from an alicyclic dianhydride BCDA and aromatic diamine 3,4′-ODA in the cosolvent of DMAc and GBL via one-step process. The graphene oxide (GO) was mixed with the above PI in DMAc solution to fabricate the PI/GO nanocomposite films. With the addition of only 0.001 wt% of GO in PI matrix, the resultant nanocomposite (PI/GO-0.001) exhibits not only the enhanced resistance to moisture but also retains superior visible light transmission, enhanced mechanical strength, and excellent dimensional stability, simultaneously. The water-vapor-transmission-rate (WVTR) significantly reduced to 30 g mil m⁻² day⁻¹ for this nanocomposite compared to 181 g mil m⁻² day⁻¹ for pure PI. Notably, the PI/GO-0.001 nanocomposite also exhibits low coefficient of thermal expansion (CTE) of 41 ppm °C⁻¹, which is benefited from the homogeneous distribution of ultrathin GO nanosheets in PI matrix.     

Stability of NiO membranes on photostructurable glass substrates for micro solid oxide fuel cells

NiO thin films with thicknesses in the range of 100 to 900 nm were deposited by spray pyrolysis onto photostructurable glass substrates and, ultimately, free-standing membranes with diameters of 100, 200 and 300 µm were fabricated using these thin films. The membranes are intended to act as simplified anodes or anode current collectors in micro solid oxide fuel cells (µSOFCs) and their differential pressure and thermal stability were characterized. The membranes tolerated a differential pressure between 13,700 and 158,600 Pa. Smaller membranes showed more pressure tolerance than larger membranes. A membrane diameter of 100 µm and a film thickness of 400-500 nm turned out to be a promising geometry for µSOFC membranes. All membranes survived temperatures higher than the intended operating temperature of µSOFCs (350-600 °C). We attribute the good thermal stability to the match of the thermo-mechanical properties of the substrate and the NiO thin films for the lower temperature regime and the substrate softening at higher temperatures releasing stresses in the thin films. Furthermore, the thermal expansion of the substrate is close to thermal expansion of materials used in SOFCs and circular geometries can be realized using wet etching.     

Growth regimes of CdTe deposited by close-spaced sublimation for application in thin film solar cells

We have systematically investigated the growth of CdTe thin films by Close Spaced Sublimation (CSS). Thin films of CdTe were deposited onto CdS substrates held at temperatures in the range 250 to 550 °C. The effect of substrate temperature and evaporation rate on structure and surface morphology of CdTe films were investigated. Up to 450 °C substrate temperature the growth rate was almost constant and decreased exponentially for higher temperatures. The structures of the CdTe films were determined by XRD and a strong (111) orientation was observed within the temperature range 250 °C-470 °C. Above 470 °C the texture changed to mostly (311) and (220) orientations. Surface morphology and grain size of CdTe growth was determined with AFM and SEM. The morphology of the layers showed three major modes: Columnar grains with a diameter of 0.2 μm and a length of 6 μm for temperatures from 250 °C to 350 °C, pyramidal grains with a diameter of 0.5-1.5 μm up to 470°C and irregular shaped grains with a diameter of 5-10 μm for temperatures up to 550 °C. The roughness increased linearly from 15 nm to 220 nm within the substrate temperature range.     

Thermal,optical, electrochemical,and electrochromic characteristics of novel polyimides bearing the Acridine Yellow moiety

A series of novel polyimides and copolyimides were obtained by combining 2,7-dimethylacridine-3,6-diamine with one of three aromatic dianhydrides: 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-(4,4′-isopropylidene-diphenoxy)bis(phthalic anhydride) and 4,4′-tetraphthaloyl-bis(1,8-naphthalene dicarboxylic)dianhydride. The resultant polymers showed glass transition temperatures (T_g) in the range 209–331 °C and decomposition temperature (T_d) in the range of 370–475 °C. The optical properties, absorption and photoluminescence (PL) of the obtained polymers were investigated in solution and in the solid state as blends with inert poly(methyl methacrylate). The polymers dissolved in NMP emitted blue or green light with the maximum emission wavelength in the range of 438–512 nm, while emitting blue light in the solid state. The electrochemical behavior of the polyimides was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). They exhibited electrochemical band gap in the range of 1.36–2.94 eV.     

High organosolubility and optical transparency of novel polyimides derived from 2′,7′-bis(4-amino-2-trifluoromethylphenoxy)-spiro (fluorene-9,9′-xanthene)

A novel spiro(fluorene-9,9′-xanthene) skeleton bis(ether amine) monomer, 2′,7′-bis(4-amino-2-trifluoromethylphenoxy)-spiro(fluorene-9,9′-xanthene), was prepared through a simple acid-catalyzed condensation reaction of 9-fluorenone with resorcinol to form the spiro framework through an sp³ carbon atom. Subsequent nucleophilic substitution reaction of spiro[fluorene-9,9′-(2′,7′-dihydroxyxanthene)] with 2-chloro-5-nitrobenzotrifluoride in the presence of potassium carbonate in N,N-dimethylacetamide, was followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of new polyimides were synthesized from the diamine with various commercially available aromatic tetracarboxylic dianhydrides via a conventional two-stage process with the thermal or chemical imidization of the poly(amic acid) precursors. Most of the polyimides obtained from both routes were soluble in many organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide and m-cresol. All the polyimides could afford transparent, flexible, and strong films with low moisture absorptions of 0.35–0.64% and low dielectric constants of 2.63–3.09 at 1 kHz. Thin films of these polyimides showed an UV–vis absorption cutoff wavelength at 356–384 nm, and those of polyimides from 4,4′-oxydiphthalic dianhydride and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) were essentially colorless. The polyimides exhibited excellent thermal stability, with decomposition temperatures (at 10% weight loss) above 540 °C in both air and nitrogen atmospheres and glass transition temperatures (T_g) in the range of 274–323 °C.     

Porous nanostructured ZnO films deposited by picosecond laser ablation

Porous nanostructured polycrystalline ZnO films, free of large particulates, were deposited by picosecond laser ablation. Using a Zn target, zinc oxide films were deposited on indium tin oxide (ITO) substrates using a picosecond Nd:YVO₄ laser (8 ps, 50 kHz, 532 nm, 0.17 J/cm²) in an oxygen atmosphere at room temperature (RT). The morpho-structural characteristics of ZnO films deposited at different oxygen pressures (150–900 mTorr) and gas flow rates (0.25 and 10 sccm) were studied. The post-deposition influence of annealing (250–550 °C) in oxygen on the film characteristics was also investigated. At RT, a mixture of Zn and ZnO formed. At substrate temperatures above 350 °C, the films were completely oxidized, containing a ZnO wurtzite phase with crystallite sizes of 12.2–40.1 nm. At pressures of up to 450 mTorr, the porous films consisted of well-distinguished primary nanoparticles with average sizes of 45–58 nm, while at higher pressures, larger clusters (3.1–14.7 μm) were dominant, leading to thicker films; higher flow rates favored clustering.     

Colorless and transparent polyimide nanocomposite films containing organoclay

A series of colorless and transparent polyimide (PI) nanocomposite films was synthesized from 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and bis(3-aminophenyl) sulfone (APS) with various organoclay contents via solution intercalation polymerization to poly(amic acid)s, followed by thermal imidization. Varying the organoclay loading in the range of 0 to 1.00 wt% produced variations in the thermal properties, morphologies, and optical transparencies of the hybrids. The hybrid films exhibited high optical transparencies and almost no color, with cut-off wavelengths between 330 and 346 nm and very low yellow index (YI) values of 1.78-3.80. The hybrid PI films showed good thermal properties with glass transition temperatures of 236-245 degrees C. Most films did not show significant thermal decomposition below 450 degrees C. It was found that the addition of only a small amount of organoclay was sufficient to improve the thermal properties of the PI films, with maximum enhancements being observed at 0.50 wt% organoclay. Moreover, these PI hybrids also showed low coefficients of thermal expansion (CTE).     

Preparation of wide gap Cu(In,Ga)S2 films on ZnO coated substrates

We have prepared Cu(In,Ga)S₂ films at growth temperatures from 300 °C to 580 °C with a homogeneous gallium depth distribution (estimated band gap 1.67 eV) onto soda lime glass (SLG) substrates with one of three different kinds of back contact: Mo(1000 nm), ZnO(500 nm), and Mo(30 nm)/ZnO(500 nm), respectively. We have also investigated the depth profiles of Zn and Na (diffused from SLG) in Cu(In,Ga)S₂ films by secondary ion mass spectroscopy (SIMS). The efficiency of solar cells on Mo increases with increasing growth temperature. It is higher on Mo/ZnO than on ZnO, and increases from 350 °C to 450 °C, then decreases above 450 °C. It was observed by SIMS that the amount of Zn in Cu(In,Ga)S₂ on Mo/ZnO is lower than it is on ZnO up to 450 °C, and a large amount of Zn diffuses into absorbers over 450 °C, which contributes to decreasing efficiency. The amount of Na in the back contact increases with growth temperature. The depth distribution of Na in Cu(In,Ga)S₂ films on Mo is almost constant in the order of 10¹⁷-10¹⁸ cm^− 3, on ZnO and Mo/ZnO the Na concentration increases towards the surface and is in the range of 10¹⁵-10¹⁷ cm^− 3.     

Thermal treatment effect on the optical properties of ZrO2 thin films deposited by thermionic vacuum arc

This paper shows the ex situ thermal treatment effects of the ZrO₂ thin films obtained by TVA (thermionic vacuum arc) technique on the optical properties (e.g., transmittance, refractive index and band-gap energy) of ZrO₂ thin films. The crystal structure, surface and optical properties were investigated for ZrO₂ thin films deposited on glass substrates by thermionic vacuum arc (TVA) method. The thermal treatment effect on the optical properties of the thin films was determined. The XRD analysis showed that the deposited ZrO₂ thin films have baddeleyite (monoclinic) and zirconium (hexagonal) structures. The thicknesses and refractive index were determined by interferometric measurements. The thin films were thermal treated at different temperatures (350 °C, 450 °C and 550 °C), and the analysis showed that the optical properties of ZrO₂ deposited thin films were improved by thermal treatment at 450 °C.