图  1  简化的晶态聚合物多尺度分级结构模型^[19]

Figure  1.  Simplified model of hierarchical structures of the crystalline polymer^[19]

图  2  高温高压条件下聚合物的状态方程和结构研究采用的实验技术：(a) DAC加载的基于同步辐射光源的X射线衍射实验的实验系统^[22]，其中，ID为插入件（insertion device），包括扭摆器（wiggler）和波荡器（undulator），(b) 美国阿贡国家实验室APS光源的DCS实验站（该实验站建有基于轻气炮加载的同步辐射X射线衍射实验系统^[29]，其中，HDPE为高密度聚乙烯（high-density polyethylene），PDV（photon Doppler velocimetry）为光子多普勒测速），(c) 基于激光冲击加载和XFEL的聚合物结构测量实验光路（包括X射线广角衍射和小角散射等^[16]，其中，LCLS（Linac Coherent Light Source）是位于斯坦福的XFEL装置，VISAR为任意面反射激光干涉测速系统（velocity interferometer system for any reflector））

Figure  2.  Experimental techniques for research of equation of state and phase transition of polymers at high pressures and high temperatures: (a) schematic of synchrotron-based X-ray diffraction beamline with diamond anvil cell, which generates high pressure and high temperature conditions^[22], in which ID is insertion device, including wigglers and undulators; (b) synchrotron-based X-ray diffraction beamline combined with gas-gun driven compression at Dynamic Compression Sector of Advanced Photon Source, Argonne National Laboratory^[29], in which HDPE is high-density polyethylene, and PDV is photon Doppler velocimetry; (c) structure determination of laser-shocked polymer using X-ray free electron laser, including X-ray wide-angle diffraction and small angle scattering techniques^[16], in which LCLS is linac coherent light source

图  3  (a) 聚合物的Hugoniot状态方程^[8]，(b) PEEK的Hugoniot状态方程在低压段的数据，图中的实线是采用二次函数的拟合结果：u_s = c₀+s₁u_p+$s_2 u_{\mathrm{p}}^2$，(c) PEEK的Hugoniot状态方程^[30–32]（图中的实线是一次函数拟合结果，u_s-u_p关系需分4段进行拟合）

Figure  3.  (a) Hugoniot equation of states of polymers^[8]; (b) Hugoniot equation of states of PEEK at low pressures (Solid line show the quadratic fitting result: u_s = c₀+s₁u_p+$s_2 u_{\mathrm{p}}^2$); (c) Hugoniot equation of states of PEEK^[30–32] (Solid lines show the linear fitting results, which are made up of four distinct lines in different regimes. )

图  4  (a) Kel-F800（chlorotrifluoroethylene-co-vinylidene fluoride）在0～18.5 GPa压力范围内的状态方程^[39]（Kel-F800在低压段的压缩趋势（绿色数据点）与高压段（蓝色数据点）明显不同，实线为采用三阶Birch-Murnaghan状态方程拟合整个压力范围内的数据的结果)，(b) Kel-F800在高压下的典型布里渊散射谱

Figure  4.  (a) Equation of state of Kel-F800 up to 18.5 GPa^[39], which indicates the different compressive behaviors of Kel-F800 at low pressures (green points) and high pressures (blue points) (Solid line is the fitting result of all the experimental data points using 3rd order Birch-Murnaghan equation of state); (b) the typical Brillouin spectra of Kel-F800 at high pressures

图  5  Fedotenko等^[45]发展改进的可见光成像状态方程测量方法：(a) 可见光成像状态方程测量系统（DM（dichroic mirror）为二色镜，FO （focusing optics）为聚焦光学器件，BS为50/50分光镜，CMOS是用于图像观察的相机，VIS（visible）表示可见光，NIR（near-infrared）表示近红外光），(b) 利用FIB聚焦离子束切割的规则形状的样品，(c) 样品尺寸的判读方法，(d) 可见光成像测量获得的金属Ti的状态方程与X射线衍射实验测量结果的对比，其中，${K_0}$和${{{K}}_0 '}$分别为体积模量及体积模量在环境压力下的压力导数

Figure  5.  Optical equation of state measurement method developed by Fedotenko et al.^[45]: (a) optical equation of state measurement system, in which DM is the long-pass dichroic mirror, FOs are the focusing optics, BS is the 50/50 beam splitter, and CMOS is the camera for image observation, VIS is visible light, NIR is near-infrared light; (b) the sample with sharp edges manufactured by focused ion beam technique; (c) linear size measurement; (d) comparison of the equation of states of metallic Ti measured by the optical method and X-ray diffraction technique, in which ${K_0}$ and ${{{K}}_0 '}$ are the bulk modulus and its pressure derivative at ambient pressure, respectively

图  6  不同方法测量的VCE的状态方程^[46]（即使在12 GPa较低的压力范围内，不同方法测量的VCE的状态方程表现出很大的差异，实验数据的分散性很大）

Figure  6.  Equation of states of VCE measured by different techniques^[46] (The results measured by different techniques present large discrepancy even in the very low pressure condition of 12 GPa. Furthermore, the experimental data pointes are quite scattered.)

图  7  (a)～(c)不同压力下PE的典型衍射谱^[47]（绿色为理论模拟的正交的Pnma结构的衍射谱，红色为单斜的P2₁/m结构的衍射谱，蓝色为单斜的A2/m结构的衍射谱），（d）不同压力下PE的拉曼谱^[48]（1340 cm⁻¹附近的强峰是金刚石的拉曼峰）

Figure  7.  (a)–(c) Typical X-ray diffraction spectra of PE at high pressures^[47] (The green, red and blue spectra are the ab initio simulated patterns of the orthorhombic Pnma, monoclinic P2₁/m, and the monoclinic A2/m structures, respectively.); (d) Raman spectra of PE at selected pressures^[48] (The broad and strong peak at about 1340 cm⁻¹ is the Raman peak from diamond anvils.)