【作者】 彭孟军；

【导师】 廖永贵； 解孝林；

【作者基本信息】 华中科技大学 ， 化学工艺， 2011， 硕士

【摘要】 在多相多组分高分子体系中,相结构及界面层的微观结构往往决定着材料的宏观性能（如力学、电学、光学、渗透性等）并影响其最终用途。而在高分子界面的形成过程中,扩散起着至关重要的作用。相比小分子之间的扩散行为,高分子/高分子界面扩散则复杂得多,已难以用简单的Fick扩散模型来加以描述。因此,针对高分子/高分子界面扩散行为的理论和实验方法研究显得尤为必要。迄今为止,科学家们先后提出的研究理论包括“蛇行”理论、“慢模式”理论、“快模式”理论、“快慢杂化”理论等。与此同时,虽然已有不少实验技术成功应用于此行为的研究,例如中子反射、二次离子质谱、振动光谱（包括拉曼光谱和红外光谱）、透射电子显微镜等,但由于受到各种因素的限制,特别是仪器分辨率的限制,只有一些倒空间技术（如中子反射）能在扩散运动基本单元——高分子链尺寸上来研究此行为,目前尚缺乏在正空间分子尺度上研究此行为动力学的方法。本论文首先借助差示扫描量热仪（DSC）和万能电子拉力仪分别研究了聚甲基丙烯酸正丁酯/聚氯乙烯（PnBMA/PVC）共混体系的相容性和拉伸性能。最后用原子力显微镜（AFM）着重研究了PnBMA/PVC层压体系的界面扩散动力学行为。（1）通过溶液浇铸法制备了一系列不同PVC含量的共混体系薄膜,DSC结果表明所有共混体系均仅显示出一个玻璃化温度（T_g）,说明PVC和PnBMA具有良好的相容性。随着PVC含量的增加,共混体系的T_g逐渐增加。实验值在一定程度上可由Fried、Fox和Gordon-Taylor方程来描述,其中在没有拟合参数k的情况下,Fox方程稍优于Fried方程;但拟合最好的还属k=0.99±0.10的Gordon-Taylor方程,即T_g与PVC的质量分数几乎呈线性关系。采用改良的浊点法得到了共混体系的相图,该体系表现为下临界共溶温度（LCST）行为,其下临界共熔点的组成和温度分别为90wt%的PVC和192℃。（2）共混物薄膜的拉伸性能结果显示:随着PVC含量的增加,共混体系的比模量和屈服应力逐渐增加,而断裂伸长率则逐渐下降。（3）通过层压法制备了75℃下退火16h、37h和96h、以及110℃下退火0.5h、1h和4h的层压体系。使用超薄切片技术得到面积约为0.2×0.4mm2的扩散横截面的超平平面。采用轻敲式AFM（tapping mode,TM-AFM,即DFM）进行测量,同时得到了扩散界面的形貌图（topography image）和相位图（phase image）。结合这些图形,获得了界面的相对浓度分布及其厚度、以及界面层厚度与退火时间的标度关系。退火温度为75℃时,由于PnBMA需对PVC先进行塑化,扩散速度相当缓慢,PnBMA在界面处堆积,界面层厚度与退火时间成正比,遵守非Fick扩散的Case-Ⅱ行为,渗透速率v_p=4.36×10^-13m/s。退火温度为110℃时,界面层厚度与退火时间的平方根成正比,遵守典型的Fick扩散Case-I行为,相互扩散系数D_m=2.04×10^-19m²/s,与Dlubek等人用DSC法( 2.0×10^-18m²/s)和PALS法( （ 2.5³.5）×10^-17m²/s)得到的结果一致。结果表明,AFM可在高分子链尺寸水平上观察高分子/高分子界面相互扩散及聚集行为。更多还原

【Abstract】 The properties of multi-phase and multi-component polymers, such as mechanical, electronic, optical, and permeable properties, are dependent on the microstructures of domain and interface. Diffusion plays a key role on the formation of interface. However, polymer/polymer interdiffusion is much more complicated than the diffusion between small molecules which can be described by a simple Fickian model well. Therefore, theoretical and experimental methods for polymer/polymer interdiffusion are particularly important. So far, lots of theories have been used to describe polymer/polymer interdiffusion, including reptation theory, slow-mode theory, fast-mode theory and fast-slow hybrid theory. Meanwhile, many kinds of experimental methods, such as neutron reflectivity （NR）, secondary ion mass spectrometry （SIMS）, vibration scpectroscopies （Raman spectroscopy and infrared spectroscopy）, transmission electron microscopy （TEM）, have been successfully used for the study of polymer/polymer interfusion. However, to the best of our knowledge, the investigation on this interdiffusion kinetics at a level of molecular size in real space has not been reported yet.In this work, the miscibility of poly（n-butyl methacrylate）/poly（vinyl chloride） （PnBMA/PVC） blend and the interdiffusion of PnBMA/PVC laminates have been investigated by differential scanning calorimetery （DSC） and atomic force microscopy （AFM）, respectively. The tensile property of PnBMA/PVC blends has been studied also.（1） A series of PnBMA/PVC blend films with different PVC mass were prepared by casting their mixture solution. DSC results showed each blend appeared only a single glass transition temperature （T_g） which increased with PVC mass, indicating that PVC and PnBMA were miscible well. These T_gs were be described by Fried equation, Fox equation and Gordon-Taylor equation well. Without the fitting parameter k, Fox equation was better than Fried equation; but with the parameter k=0.99±0.10, Gordon-Taylor equation was the best suitable one, where T_gs almost presented a linear relation with PVC mass. This blend exhibited a lower critical solution temperature （LCST） behavior with a critical composition of 90wt% PVC and a critical temperature of 192℃, respectively.（2） The tensile properties of PnBMA/PVC blend films showed that the specific modulus and yield stress increased but elongation at break decreased with the increase of PVC mass.（3） PnBMA/PVC laminates were annealed at 110℃for 0.5 h, 1 h, 4 h and at 75℃for 16 h, 37 h, 96 h, respectively. An ultra-smooth cross-section across interface was then prepared by ultramicrotoming. Combined with topography and phase images of tapping mode atomic force microscopy （TM-DFM）, the relative concentration profile, interface width and the relationship between interface width and annealing time could be obtained. At 75℃, the diffusion followed a typical Case-Ⅱdiffusion behavior where the interface width was proportional to annealing time. The penetration velocity was 4.36×10^-13 m/s. However, at 110℃, the diffusion obeyed a typical Fickian diffusion behavior where the interface width was proportional to the square root of annealing time. The mutual diffusion coefficient was 2.04×10^-19 m²/s which was in good agreement with those obtained from DSC (2.0×10^-18 m²/s) and positron annihilation lifetime spectroscopy (2.5³.5×10^-17 m²/s). These results imply that AFM is a reliable and powerful tool for the investigation of polymer/polymer interdiffusion at a level of polymer chain size.更多还原