Surface characterization of polyimide films

 Various kinds of poly(amide acid)s were prepared by the reaction of four kinds of acid dianhydride and three kinds of diamine in N,N-dimethylacetamide (DMAc). Polyimide films were prepared by casting the poly(amide acid) solution on soda glass substrates, followed by thermal imidization at various temperatures. Contact angles of polyimide films for the sides in contact both with air and with glass substrate (air side and glass side, respectively) were measured to evaluate the dispersive component (γ^D _S) and the nondispersive component (γ^P _S) of surface free energy (γ_S) of polyimide films. It was shown that, for the air side, γ^P _S value decreased greatly and γ^D _S values increased slightly with the development of imidization. Values of γ^P _S for the glass side were much higher than those for the air side. Poly(amide acid) solution was also cast on quartz glass and silicone rubber, and was thermally imidized. The γ^P _S for the quartz glass side was almost the same as that for the soda glass side. But the γ^P _S for the silicone rubber side was as low as the γ^P _S for the air side. Attenuated total reflection infrared spectroscopy of polyimide films showed that the degree of imidization for the glass side surface was not as high as that for the air side surface, and that the amount of polar groups for the glass side surface was higher than that for the air side surface. Among the various kinds of polyimides, there is a slight but clear difference in the values of γ_S and its components, which can be rationalized from the difference in the chemical structure. It was also found that thermal degradation and oxidation can be easily detected from the change of surface free energy and its components for the polyimide films after being treated at high temperatures in both air and vacuo. Received: 22 January 1998 Accepted: 10 March 1998     

Properties of polyimide films doped with copper complexes

Polyimide films based on either 3, 3′, 4, 4′-benzophenone tetracarboxylic acid dianhydride or pyromellitic dianhydride with 4,4′-oxydianiline have been doped with copper(I) and copper(II) complexes. High-quality, flexible, glass-cast films have been obtained which exhibit increased softening temperatures and lower polymer decomposition temperatures. The atmosphere and glass sides of the films are quite different. The copper(I) dopant is oxidized on the air side of the film, while the glass side contains predominantly copper (I). In the copper(II) case most of the copper appears on the air side as a silvery substance in the Cu(II) state. Chemical as well as ion etching can remove this material. Electrical resistivity of the copper(II)-doped films is decreased by three to five orders of magnitude relative to the polymer alone.     

X-ray reflectivity investigations of glass surfaces produced by float and draw techniques

Surfaces of soda-lime glass and borosilicate glass have been investigated by grazing incidence X-ray reflectivity (GIXR). Characteristic differences are obtained in dependence on the fabrication procedure, the composition and the cleaning procedure. Strong variation is recorded between the two soda-lime float glass surfaces while minor differences are analysed between the top and bottom side of borosilicate float glass. This is attributed to the reduced amount of tin diffused into the bottom side of the borosilicate glass surface. Different cleaning procedures generate characteristic changes on the glass surfaces which can be verified by GIXR. The results indicate that borosilicate float glass combines the merits of the good surface quality of float glass with the high chemical resistivity of borosilicate glass.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

主链玻璃化转变区在室温附近的梳形聚合物电解质

主链玻璃化转变区在室温附近的梳形聚合物电解质＊齐力林云青夏永姚王佛松（中国科学院长春应用化学研究所长春１３００２２）关键词梳状高分子，固体电解质，离子导电性，玻璃化转变，分子运动＊１９９４－１０－３０收稿；１９９５－１２－１０修稿７３２高分子固体电解...     

Forensic comparative glass analysis by laser-induced breakdown spectroscopy

Glass samples of four types commonly encountered in forensic examinations have been analyzed by laser-induced breakdown spectroscopy (LIBS) for the purpose of discriminating between samples originating from different sources. Some of the glass sets were also examined by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Refractive index (RI) measurements were also made on all glass samples and the refractive index data was combined with the LIBS and with the LA-ICP-MS data to enhance discrimination. The glass types examined included float glass taken from front and side automobile windows (examined on the non-float side), automobile headlamp glass, automobile side-mirror glass and brown beverage container glass. The largest overall discrimination was obtained by employing RI data in combination with LA-ICP-MS (98.8% discrimination of 666 pairwise comparisons at 95% confidence), while LIBS in combination with RI provided a somewhat lower discrimination (87.2% discrimination of 1122 pairwise comparisons at 95% confidence). Samples of side-mirror glass were less discriminated by LIBS due to a larger variance in emission intensities, while discrimination of side-mirror glass by LA-ICP-MS remained high.     

环氧树脂/玻璃纤维复合界面的电子能谱化学分析

采用化学分析用电子能谱技术分别对机械剥离后的玻璃纤维布和短切玻璃纤维增强环氧树脂试样的玻璃纤维面作了对比分析,发现树脂残留物表面上有富裕的环氧基,证明剥离不是发生在树脂／玻璃纤维（布）粘结界面上,而是发生在粘结界面附近的树脂层里;环氧树脂／玻璃纤维布界面比环氧树脂／短切玻璃纤维界面有更强的界面增强效应。     

Multiple Transitions in Polyvinyl Alkyl Ethers at Low Temperatures

Abstract

A series of polyvinyl alkyl ethers, with the ether side chain ranging in length from methyl to n-decyl, has been studied from ～60°K to above the glass transition. A linear variable differential transformer was used to measure the linear expansion coefficient, α, complemented by mechanical loss measurements with a freely oscillating torsion pendulum and dielectric loss measurements. In addition to the glass transition, two low-temperature transitions have been observed in these systems. The first below T_g, T_gg(1), follows the same trend as the glass transition, i.e., as the side chain length increases the temperature at which the transition occurs decreases, until n-octyl, where side chain crystallization is manifested. The second transition below T_g, T_gg(2), occurs at ～100°K irrespective of side chain length. Because of their analagous dependence on side chain length, T_gg(1) is thought to be similar to the glass transition, i.e., due to main chain motion. Δα' at T_gg(2) is of greater magnitude than Δα' at T_gg(1) and is thought to be a result of reorientation of the side chain.     

Atomic force microscopy of coated glasses

Atomic force microscopy has been used to investigate the topology of alkoxide gel dip coatings on different substrates. Results of SiO(2) - TiO(2) - ZrO(2) (STZ) coatings are presented on float glass, on polished fused silica, on commercially coated insulating flat glass, and on PtRh. Consolidated STZ coatings display the so-called glass pattern with ripples equal or less than 2 nm high. The same pattern is seen on partially dense STZ coatings, as soon as the surface is stiff enough for scanning, and also on the bottom of a 50 nm deep sputtering crater in the consolidated coating. The vitreous STZ coating on the fire side of the float glass is as flat as the float glass itself. It has the same tendency to contamination. 100 nm wide and 50 nm deep polishing grooves on fused silica have been filled up with the 80 nm thick coating, only dips of a few nm remain. The trenches between the SnO(2) crystallites on the insulating flat glass were filled up and the roughness of the substrate was partially reduced. PtRh sheet remained rough even after the coating. On the partially densified STZ coating, sputtering generates a grained surface.     

Properties and chain flexibility of poly(dl-isobornyl methacrylate)

The glass transition temperature and characteristic ratio of poly(dl-isobornyl methacrylate) have been determined. The results indicate that in the case of certain polymethacrylates the chain flexibility depends mostly on the bulkiness of the side group, while the glass transition temperatures depend mostly on side-group rigidity.     

Glass transition of atactic polystyrene probed at the submolecular level by dynamic infrared linear dichroism (DIRLD) spectroscopy

Dynamic infrared linear dichroism (DIRLD) spectroscopy is a rheo-optical characterization technique developed specifically to probe the submolecular dynamics of polymer segments. The technique combines the measurement of submolecular orientation based on the directionally selective absorption of polarized IR light with a small-amplitude oscillatory tensile deformation used in dynamic mechanical analysis. A DIRLD spectroscopic study of atactic polystyrene reveals that a dramatic change in the reorientation behavior of aromatic side groups is observed around the glass transition temperature of 100 °C. The transition point for the main chain backbone, on the other hand, is observed at a much higher temperature around 125 °C. Thus, the macroscopically observable glass transition of polystyrene seems to be dominated by the dynamics of side groups rather than that of the coordinated motions of polymer segments along the backbone. This result suggests a fundamental similarity between the glass transition phenomena of polymers and those of small-molecule inorganic glasses.     

Molecular level structures of poly(n-alkyl methacrylate)s with different side chain lengths at the polymer/air and polymer/water interfaces

Sum frequency generation (SFG) vibrational spectroscopy has been successfully applied to study molecular structures of several poly(n-alkyl methacrylate)s (PAMAs) with different side chain lengths at the PAMA/air and PAMA/water interfaces. We have observed that the ester side chains from all PAMAs always dominate the interface, but the orientation information of the methyl end group on the side chains varies, depending on the length of the side chain. The contributions from methylene groups on the side chains have been evaluated, and the surface structures have been related to the surface tension of these polymers. Different water restructuring behaviors have been observed for different PAMAs. This phenomenon and its reversibility are strongly dependent on the glass transition temperature of each polymer, which is influenced by the side chain length. Detailed data fitting and analysis has been discussed.     

Tailored adhesion at polymer/nonpolymer interfaces

In this investigation, block copolymers of deuterated polystyrene (dPS) and poly (2-vinylpyridine) (PVP) have been used to modify the adhesion at polystyrene/soda lime glass interfaces. The fracture energy, G_s of these interfaces was measured using an asymmetric double cantilever beam specimen. The failure mechanism was investigated using forward recoil spectrometry (FRES) and Rutherford backscattering spectrometry (RBS). The areal density, ∑ of the dPS-PVP block copolymer at the two fracture surfaces, as well as the fraction of the dPS block on the PS side of the fractured sample are measured directly by FRES. The fraction of the PVP block on the glass side of the interface can be found by quaternizing the PVP with methyl iodide and then using RBS to measure the amount of iodine on each fracture surface. Short dPS blocks (N_dPS < 175) do not entangle effectively with the PS homopolymer and only very small increases in G_c can be achieved as the dPS block pulls out of the interface. If the dPS block is long (N_dPS ? 175) and if ∑ is large, crazes can develop in the PS ahead of the crack. The crazed interface fails at low ∑ by breaking the block copolymer close to the styrene/vinylpyridine link. At higher ∑, if the PVP block is relatively short (N_PVP = 95), the crazed interface fails by the PVP block being pulled off the glass. If both the PVP and dPS blocks are long (? 175), the G_c increases rapidly with increases in ∑, but the interface becomes so strong that the glass on the thinner side of the test specimen breaks. The dPS block and the PVP block are found on opposite sides of the fracture surface with most of the PVP on the glass and most of the dPS on the PS side of the interfaces. Finally, if the glass surface is modified by coating it with a self-assembled hydrophobic monolayer produced from chlorodimethyloctadecylsilane (CDMOS), the interface becomes very weak and fails by pull-off of the PVP from the CDMOS-coated glass. Using these results it is possible to tailor the interfacial adhesion to produce a desired G_c within a wide range of possible values. © 1994 John Wiley & Sons, Inc.     

含mPEG侧链的水溶性梳状聚合物的合成及其侧链受限结晶行为研究

采用大单体与小单体共聚的技术,通过自由基引发溶液聚合,合成了一系列水溶性梳状聚合物———聚丙烯酸接枝聚乙二醇单甲醚(PAA-g-mPEG).制备过程分两步进行,首先合成大单体聚乙二醇单甲醚丙烯酸酯,然后将大单体与丙烯酸单体共聚,合成了梳状聚合物.通过控制反应条件,获得了一系列主链和支链组成比不同的接枝共聚物.用傅立叶变换红外光谱(FT-IR)和核磁共振氢谱(1H-NMR)表征了共聚物的结构,并对其侧链的结晶行为进行了研究.采用差热扫描量热法(DSC)表征并分析了不同侧链长度的mPEG的热性能及其结晶情况.利用相差显微镜和原子力显微镜(AFM)观察薄膜的结晶形貌,表明梳状聚合物的侧链mPEG在受限条件下的薄膜结晶形貌为高度支化的晶体,初步分析了mPEG链长及其在共聚物中的重量百分含量对晶体形貌的影响.     

N-烷基壳聚糖玻璃化转变温度的研究

采用差示扫描量热(DSC)法和热释电流(TSC)法研究了N-烷基壳聚糖的玻璃化转变行为. DSC法中采用二次扫描以消除溶剂和热历史的影响, 并利用物理老化方法来增强N-烷基壳聚糖在DSC曲线上的玻璃化转变区域的热焓吸热峰, 以克服DSC法的不灵敏性. 两种研究方法的结果一致表明, 三种N-烷基壳聚糖的玻璃化转变均发生在110～150 ℃温区内；取代的柔性烷基越大, 玻璃化转变温度(Tg)越低；但N-甲基壳聚糖例外, 其Tg略高于壳聚糖, 空间阻碍在这里起决定的作用.     

Polymer Structures and Glass Transition: A Molecular Dynamics Simulation Study

Full atomistic molecular dynamics (MD) simulations on five polymers with different chain backbone (C—C, Si—O, and C—O) and different side groups (—H, one —CH₃, and two —CH₃) are performed to study the effects of chain flexibility and side groups on the glass transition of polymers. Molecular dynamics simulations of NPT (constant pressure and constant temperature) dynamics are carried out to obtain specific volume as a function of temperature for polyethylene (PE), poly(propylene) (PP), polyisobutylene (PIB), poly(oxymethylene) (POM), and poly(dimethylsiloxane) (PDMS). The volumetric glass transition temperature has been determined as the temperature marking the discontinuity in slope of the plots of V–T simulation data. Various energy components at different temperatures of the polymers are investigated and their roles played in the glass transition process are analyzed. In order to understand the polymer chain conformations above and below the glass transition temperature, dihedral angle distributions of polymer chains at various temperatures are also studied.     

Synthesis and evaluation of a series of novel 2-substituted poly(allylalcohol) side chain liquid crystalline oligomers exhibiting ferroelectricity

The recently published Baylis-Hillman methodology has been used to prepare a number of side chain liquid crystalline poly(allylalcohols) incorporating a ferroelectric mesogenic side chain. These poly(allylalcohols) exhibited wide range S*_C phases and, in the case of two of these materials, low glass transition temperatures. The transition temperatures and phase behaviour of the SCLC poly(allylalcohols) were compared to acrylate and methacrylate SCLC oligomers containing a similar mesogenic side chain. The response times for two poly(allylalcohols) exhibiting low glass transition temperatures were also measured over a wide temperature range. Although the poly(allylalcohols) had comparable response times to the analogous acrylate and methacrylate SCLCP, they showed the greater temperature dependence of the response time. However, at 39°C one of the SCLC poly(allylalcohols) showed a response time of 65 ms.     

Dynamic mechanical investigations of different substituted cellulose o-silyl ethers

In contrast to many cellulose derivatives, the cellulose O-silyl ethers with bulky side groups exhibit scarcely a change in glass transition temperature by a variation of the degree of substitution (DS) or degree of polymerization (DP) or by introducing phenyl carbamate groups for the remaining hydroxyls along the main chain. However, a substitution of these hydroxyls by flexible acetate groups lowers the glass transition temperature considerably. The secondary dispersion (relaxation) behavior is strongly influenced by the various substituents and can be correlated to specific motions of the molecules. The dynamic mechanical properties are also dependent on the kind of preconditioning of the samples.     

Molecular mobility of substituted poly(p-phenylenes) characterized by a range of polymer relaxation techniques

The free volume and related mobility properties of substituted poly(p-phenylene) polymers are examined. The techniques used range from positron annihilation, dielectric relaxation, and dynamic mechanical spectroscopy to thermally stimulated currents. Fractional free volume is determined for the samples with different substituted side groups and related to the glass transition temperature. Bulkier groups lead to a greater fractional free volume and lower glass transition temperatures. Comparison of molecular relaxation times using the different characterization techniques demonstrates that there is strong coupling between motion of the main chain and the side groups, on which the dipoles reside. Intermolecular coupling between the main chains at the primary relaxation is shown in this work to be related to the nature of the side chains and resultant free volume, as are the temperature locations of local, secondary relaxations. A qualitative model describing the effect of regiochemistry on the motions and packing of these materials is also proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1465–1481, 1998     

Characterization of tunneling systems in molecular versus polymer glasses by high-pressure photon echo spectroscopy

Intrinsic differences between tunneling two-level systems (TLSs) in molecular versus polymeric glasses are revealed by studying the effect of compression on TLS dynamics. Photon echo studies under variable low-temperature (1.1-2.3 K) and high-pressure (0-30 kbar) conditions have been performed to contrast the effect of compression on molecular [2-methyl-tetrahydrofuran (2MTHF)] versus polymer [Polymethylmethacrylate (PMMA)] glasses. The pressure-induced reduction in the magnitude of the optical dephasing rate of rhodamine 640 in a molecular glass (2MTHF) is found to be comparable to the volume decrease of the glass (e.g., approximately 20% at 30 kbar), indicating that TLSs in 2MTHF are associated with void space or low-density regions of the glass. In contrast, the relative pressure insensitivity observed for organic polymer glasses (PMMA) supports the idea that these TLSs are associated with side chain defects. The power-law exponent for the temperature-dependent dephasing in 2MTHF also decreased significantly at high pressure, suggesting a change in the form of the TLS density of states upon compression of the molecular glass.     

Synthesis and evaluation of a series of novel 2-substituted poly(allylalcohol) side chain liquid crystalline oligomers exhibiting ferroelectricity

Abstract

The recently published Baylis-Hillman methodology has been used to prepare a number of side chain liquid crystalline poly(allylalcohols) incorporating a ferroelectric mesogenic side chain. These poly(allylalcohols) exhibited wide range S?_C phases and, in the case of two of these materials, low glass transition temperatures. The transition temperatures and phase behaviour of the SCLC poly(allylalcohols) were compared to acrylate and methacrylate SCLC oligomers containing a similar mesogenic side chain. The response times for two poly(allylalcohols) exhibiting low glass transition temperatures were also measured over a wide temperature range. Although the poly(allylalcohols) had comparable response times to the analogous acrylate and methacrylate SCLCP, they showed the greater temperature dependence of the response time. However, at 39°C one of the SCLC poly(allylalcohols) showed a response time of 65 ms.