有限层Langmuir-Blodgett类晶型薄膜微观结构与超分子结构的小角X-射线散射研究 I: 硬脂酸镉盐膜系

本文应用小角X-射线散射,参考方介石与硬脂酸结晶结构,为硬脂酸镉盐膜系设计了七种可能的分子链模型,在微机上进行拟合研究。结果指出:链倾角Ach～24-27°，与β-硬脂酸结晶相近;碳键角Acc～115°,比正四面体模型有所扩张;链端羧酸镉属离子键结构,而非文献习用的共价键结构;堆砌缺陷d约0.156nm,小于文献值约0.1nm;酸/皂剂量比x=0.8-1.0,因制膜条件变化而不同;界面对链堆砌有明显影响。总之,小角X-射线散射可对超薄L-B薄膜(<10nm)的精细结构进行有效的研究。     

有限层Langmuir-Blodgett类晶型薄膜微观结构与超分子结构的小角X-射线散射研究 I: 硬脂酸镉盐膜系

本文应用小角X-射线散射,参考方介石与硬脂酸结晶结构,为硬脂酸镉盐膜系设计了七种可能的分子链模型,在微机上进行拟合研究。结果指出:链倾角Ach～24-27°，与β-硬脂酸结晶相近;碳键角Acc～115°,比正四面体模型有所扩张;链端羧酸镉属离子键结构,而非文献习用的共价键结构;堆砌缺陷d约0.156nm,小于文献值约0.1nm;酸/皂剂量比x=0.8-1.0,因制膜条件变化而不同;界面对链堆砌有明显影响。总之,小角X-射线散射可对超薄L-B薄膜(<10nm)的精细结构进行有效的研究。     

有限层Langmuir-Blodgett类晶型薄膜微观结构与超分子结构的小角X-射线散射研究——Ⅰ.硬脂酸镉盐膜系

本文应用小角 X-射线散射,参考方介石与硬脂酸结晶结构,为硬脂酸镉盐膜系设计了七种可能的分子链模型,在微机上进行拟合研究.结果指出:链倾角也 A_(ch)～24—27°,与β-硬脂酸结晶相近;碳链键角 A_(cc)～115°,比正四面体模型有所扩张;链端羧酸镉属离子键结构,而非文献习用的共价键结构;堆砌缺陷 d 约0.156nm,小于文献值约0.1nm;酸/皂剂量比 x=0.8—1.0,因制膜条件变化而不同;界面对链堆砌有明显影响.总之,小角 X-射线散射可对超薄 L-B 薄膜(<10 nm)的精细结构进行有效的研究.     

拉伸热历史对取向聚对苯二甲酸乙二酯膜在热处理过程中收缩和伸长的影响

弄清取向非晶态聚合物在热处理过程中的收缩和伸长的变化规律,以及所对应的结构变化,有较大的实用意义和科学意义。 对于取向聚对苯二甲酸乙二酯的热收缩和热伸长已有很多研究,但对于拉伸热历史对取向PET在热处理过程中的尺寸变化的影响尚缺乏系统的研究。在热拉伸的过程中发生分子链的取向、热弛豫和结晶三个相互竞争的过程。因此,改变拉伸条件可以得到具有各种不同取向和结晶的PET试样。当非晶态PET膜片在80-105℃以较低     

由N—催化剂催化聚合的聚丙烯结晶行为研究

用小角X-射线散射法(SAXS),广角X-射线衍射法(WXAD)和差示扫描量热法(DSC)对由N-催化剂催化聚合的聚丙烯结晶行为进行探讨。发现这种聚丙烯结晶中有β晶型存在,且其含量随结晶时间增加而增加随结晶温度升高而降低;β晶含量增加,聚合物的长周期也会增加,β晶对长周期的影响比α晶更大。乙烯共聚改性后的聚丙烯因分子链规整性下降而阻止了β晶的形成。在熔融状态下结晶时,β晶的形成要求聚丙烯的分子链具有更高的规整性。这些实验结果均从分子链段结晶机理得到了解释。     

聚对苯二甲酸乙二酯非晶态膜片单轴热——拉伸中的结晶与松弛

用动态力学损耗温度谱作为测试手段,研究了非晶态PET膜片在78—112℃温度范围内的单轴拉伸。实验结果说明,在较低温度下所得结晶的拉伸试样,完全由于应变诱发结晶,发生在应力-应变曲线的屈服后应力开始上升的阶段。在较高温度下(90℃或更高)拉伸可得非晶态而且光学各向同性的试样,是由于分子链的小尺度取向在拉伸过程中已完全热松弛所致,而分子链的大尺度取向要通过高弹态流动而松弛,其速率较慢,用拉伸后试样两端固定时的应力松弛进行了观察。在较低温度下应力松弛后仍为非晶态,在较高温度下应力松弛到起始应力的1O％下才开始结晶。FTIR研究表明在这种状态下的结晶有一结晶诱导期,其时间尺度与应力松弛阶段相当。     

取向态聚对苯二甲酸乙二酯膜热弛豫过程的偏振红外光谱研究

用升温在位偏振红外光谱测量方法，研究了不同取向态的聚对苯二甲酸乙二酯（ＰＥＴ）膜在热弛豫过程中的尺寸变化以及分子链构象和取向的变化．结果说明，ＰＥＴ小尺度取向链段的热弛豫较大尺度取向分子链的热弛豫在较低的温度下发生，取向ＰＥＴ膜的热收缩主要与分子链大尺度取向的弛豫有关，而其后的自发伸长是结晶过程引起的，分子链的取向程度对结晶伸长的幅度有着重要影响．     

试样两端固定或松弛态结晶对取向非晶态聚对苯二甲酸乙二酯膜结晶的影响

<正> 在研究聚合物的结晶过程中,有时(如在同步辐射法、X-衍射法和红外法的测定中)须将试样两端固定,有时(如研究热处理过程中取向聚合物的尺寸和结构变化)须将试样处于松弛状态。因而研究两端固定或松弛状态对取向聚合物结晶速率和结构的影响引起了人们的兴趣。一些研究结果得出,与松弛状态结晶相比,试样两端固定态结晶使取向聚合物的结晶速率变慢,但有时也出现相反的结果。此外,在上述文献中所用的原始试样都已具有较高的结晶度。为了弄清这一问题,我们用密度、双折射和应力测量等方法对取向程度不同的非晶态PET膜进行了深入和系统的研究。结果表明,试样两端固定与否对结晶速率的影响与试样原始的取向程度有关。     

氰乙基纤维素/二甲基乙酰胺液晶溶液的取向态织构

本文用偏光显微镜、小角光散射和消偏振光法对受切应力后取向的氰乙基纤维素/二甲基乙酰胺液晶溶液的织态结构进行了研究。证明在取向的液晶溶液中,分子链沿切应力方向高度取向。相邻条纹间的分子链取向稍有不同。     

聚偏氟乙烯取向薄膜的结晶形态

本文用小角激光散射法研究了聚偏氟乙烯薄膜在拉伸取向过程中晶体形态及结构的变化。拉伸使球晶形变为椭球,同时伴随着局部熔融与重结晶过程,散射图案由原来的四叶瓣发展为八叶瓣。红外测量及X-射线衍射分析表明,拉伸引起分子链构象改变,使晶型发生了转变。     

Orientation of platelets in multilayered nanocomposite polymer films

The orientation of platelets in micro-meter-thick polymer-clay nanocomposite films was investigated with small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD). The films with various clay contents (15–60% by mass fraction) were prepared by a layer-by-layer approach from polymer-clay solutions that led to the formation of a high degree of orientation in both polymer and clay platelets. Shear-induced orientation of polymer-clay solutions is compared with the orientation of polymer-clay films. SANS, SAXS, and WAXD, with beam configurations in and perpendicular to the spread direction of the film, were used to determine the structure and orientation of platelets. In all films, the clay platelets oriented preferentially in the plane of the film. The observed differences in semidilute solutions, with clay surface normal parallel to the vorticity direction, versus bulk films and with clay surface normal parallel to the shear gradient direction at clay mass fractions of 40 and 60%, were attributed to the collapses of clay platelet during the drying process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3237–3248, 2003     

Highly oriented structure formed in a lamella-forming diblock copolymer with high molar mass

Highly oriented films were prepared simply by annealing a lamella-forming block copolymer, poly(ethylene oxide-b-styrene) (PEO-b-PS), with high molar mass under a pressure of 0.2 MPa. The oriented structures were characterized by small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). The SAXS measurements showed that the lamellar layers of the block copolymer are highly oriented parallel in the film plane. The WAXD images showed that the c-axis of PEO crystals was oriented normal to the film plane. The Hermans-Stein orientation functions for the lamellar layer and the crystal axis are 0.954 and −0.466, respectively, and are close to the values of perfect orientation. It was considered that the highly oriented structure was formed by the combined effects of shear flow and self-organization of the block copolymer during annealing under stress. The high degree of orientation both for the lamellar layer and crystal planes also suggested that the crystallization in the confined domains results in a high degree of orientation of PEO crystals with respect to the lamellar interface of the block copolymer.     

Study of crystalline orientation in drawn ultra-high–molecular weight polyethylene films

A wide-angle x-ray diffraction (WAXD) study of the development of molecular orientation in the crystalline phase of ultra-high–molecular weight polyethylene films prepared by the gelation–crystallization method is presented. WAXD scans of the undrawn films show that the lamellae are oriented in the plane of the films. Upon drawing at 130°C, the orientation of the molecular chains changes from the direction normal to the film surface (ND) to the elongation direction. The decrease of the 200/020 intensity ratio at low draw ration (λ <10) indicates that double orientation develops during the transformation from the lamellar to the fibrillar morphology, with the a-axis oriented parallel to ND. The orientation distributions of the 110, 200, 020, and 002 planes of the orthorhombic unit cell of polyethylene were studied and characterized by the coefficients of a Legendre polynomial series. At a draw ratio of 4.5, the second-order coefficient, 〈P₂(cos χ〉, already gets close to its limiting value, but it is shown that higher order coefficients of the polynomial series can be used to describe the evolution of the orentation, even up to λ = 50. The coefficients relative to the molecular chain orientation, 〈P_n(cos χ)〉_c, can be calculated from different crystalline reflections. Curve-fitting calculations were made in order to improve the correlation between the results obtained from the orientation distribution of the 110, 020, and 002 planes. A Person VII function was found to give a better fit of the experimental curves than Gaussian or Lorentzian equations. © 1993 John Wiley & Sons, Inc.     

Orientation and mechanical properties of laser‐induced photothermally drawn fibers composed of multiwalled carbon nanotubes and poly(ethylene terephthalate)

This study presents a novel photothermal drawing of poly(ethylene terephthalate) (PET)/multiwalled carbon nanotube (MWCNT) fibers. The photothermal drawing was carried out using the near infrared laser‐induced photothermal properties of MWCNTs. An uniform fiber surface was obtained from a continuous necking deformation of the undrawn fibers, particularly at a draw ratio of 4 and higher. The breaking stress and modulus of the photothermally drawn PET/MWCNT fibers were significantly enhanced, in comparison to those of hot drawn fibers at the same draw ratio. The enhanced mechanical properties were ascribed to the increased orientation of PET chains and MWCNTs as well as PET crystallinity due to photothermal drawing. In particular, a significantly higher degree of orientation of the MWCNTs along the fiber axis was obtained from photothermal drawing, as shown in polarized Raman spectra measurements. The photothermal drawing in this study has the potential to enhance the mechanical properties of fibers containing MWCNTs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 603–609     

The effect of melt processing conditions on the hydrogen-bonded sheet orientation and polarization of nylon 11 films

It is known that melt-quenched, cold-drawn, and then annealed nylon 11 films possess a particular doubly oriented hydrogen-bonded sheet structure: the hydrogen-bonded sheets being in the plane of the film and the molecular chain direction being in the direction of draw. These films have been shown to be ferroelectric. In order to clarify the role of this special double orientation on polarization mechanisms and, in addition, provide insight into the reasons for this unique orientation, a systematic study was undertaken. Nylon 11 was melted at 210°C in a hot press for different melting times (ranging from 30 s to 20 min) prior to quenching into an ice-water bath. The resulting orientation of the hydrogen-bonded sheet structure in these films was examined using wide-angle X-ray diffraction and FTIR spectroscopy. For undrawn, melt-quenched films with short times in the melt, a degree of preferred orientation of the hydrogen-bonded sheets in the plane of the film was observed. As time in the melt increased, this preferred orientation in the plane decreased. This was also observed for films which were cold drawn before annealing. However, following cold drawing and several cycles of polarization using a maximum field of 150 MV/m at room temperature, the uniaxially drawn films with different times in the melt possessed the same remanent polarization and the same final orientation of the hydrogen-bonded sheets in the film thickness direction. © 1996 John Wiley & Sons, Inc.     

Biaxial Orientation in Triple Centrifuged Natural Rubber

Natural rubber (NR) latex was purified through triple centrifugation process and film samples were prepared. The strain-induced crystallization was studied during the uniaxial elongation of the NR samples at room temperature. Crystalline orientation was detected by wide angle x-ray diffraction (WAXD) measuring the intensity of 200 and 120 reflections. The WAXD patterns were compared with the aspect ratio (width/length) of the original NR films. The results indicate that the induced crystals have a biaxial orientation (BO), where the c-axis is parallel to the draw direction and the a-axis is parallel to the film surface. Using the WAXD through patterns, we distinguish the highly oriented BO region in the samples. In order to analyze the structure and properties of the NR, the effect of BO is an essential factor.     

Fiber structure development in high‐speed melt spinning of poly(trimethylene terephthalate) (PTT)—On‐line measurement of birefringence

To investigate the mechanism of fiber structure development for poly(trimethylene terephthalate) (PTT) in high‐speed spinning, the PTT fiber was spun with take‐up speeds from 1 to 8 km/min and simultaneously birefringence and diameter in spin‐line were measured by on‐line measurement system. The orientation‐induced crystallization of PTT fiber started to be developed at 3–4 km/min, where an abrupt decrease in diameter and an increase in birefringence appeared. The birefringence increased up to 4 km/min, decreased suddenly, and then increased gradually. The sudden decrease of birefringence at 4–5 km/min might be caused by an increase of crystalline fraction due to the fact that the intrinsic crystalline birefringence of PTT is over 10 times as low as that of PET. In WAXD images, crystalline diffraction emerged faintly at 3 km/min and distinct diffraction arcs were observed at 4–5 km/min and above. The diffraction intensity increased and the tilting angle also increased with take‐up speed. The long period structure observed in SAXS pattern started to emerge at 6 km/min, and its scattering intensity increased with take‐up speed. The long period structure was ～11–12 nm long. The cold crystallization temperature in DSC thermogram shifted to lower temperature and diminished due to the orientation‐induced crystallization as take‐up speed increased, but the melting temperature hardly increased unlike PBT and PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 847–856, 2008     

MOLECULAR AND SUPRAMOLECULAR ORDERING IN CONFINED ENVIRONMENTS

Crystal and phase morphologies and structures determined by self-organization of crystalline-amorphous diblockcopolymers, crystallization of the crystallizable blocks, and vitrification of the amorphous blocks are reviewed through asystematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base ofcompetitions among these three processes, molecular and supramolecular ordering in confined environments can beinvestigated. In a concentration-fluctuation-induced disordered (D_(CF)) diblock copolymer, the competition between crystalli-zation of the PEO blocks and vitrification of the PS blocks is momtored by time-resolved simultaneous small angle X-rayscattering (SAXS) and wide angle X-ray diffraction (WAXD) techniques. In the case of T_c相似文献