聚(ε-己内酯)薄膜结晶形貌及分子取向研究

用匀胶机通过溶液铸膜方法在硅片和铝箔基板上分别制备具有不同厚度的聚(ε-己内酯)(PCL)薄膜. 通过原子力显微镜(AFM)和偏光衰减全反射傅里叶红外光谱(ATR-FTIR)对薄膜中PCL的结晶形貌、 片晶生长方式及分子链取向进行了研究. AFM结果表明, 在200 nm或更厚的薄膜中, PCL主要以侧立(edge-on)片晶的方式生长; 对于厚度小于200 nm的薄膜, PCL片晶更倾向于以平躺(flat-on)的方式生长. 这种片晶生长方式的改变在硅片和铝箔基板上都表现出同样的倾向. 此外, 在15 nm或更薄的薄膜中, PCL结晶由通常的球晶结构变为树枝状晶体. 偏光ATR-FTIR结果表明, 当膜厚小于200 nm时, 薄膜结晶中PCL分子链沿垂直于基板表面方向取向, 并且膜越薄, 取向程度越高, 与AFM的观测结果一致.     

基板受限条件下聚合物薄膜厚度对结晶的影响研究

通过溶液铸膜方法,用匀胶机(spin-coater)在铝箔基板上制备出一系列具有不同厚度的结晶聚合物聚羟基丁酸酯(PHB)和聚ε-己内酯(PCL)超薄膜.经退火处理后,用差热扫描量热仪(DSC)测试了薄膜厚度对其结晶熔点T_m和结晶温度T_c的影响.结果表明,结晶熔点T_m随超薄膜厚度的减小逐渐减小;在减至一定的厚度时,熔点有突升,至极大值后,随膜厚继续减小熔点又会骤降.而结晶温度T_c则一直随膜厚的减小而逐渐降低.可以认为,结晶聚合物的分子在基板受限作用下,主要是熔融熵的变化导致了熔点的上述变化,而受限条件下的扩散控制结晶使结晶温度降低.     

基板界面对PS/PMMA共混物薄膜相逆转组成比的影响

近年来高分子共混体系中的界面、表面效应逐渐引起了越来越多研究者的兴趣 .人们发现 ,当共混物薄膜厚度减至一定程度时 ,聚合物共混物薄膜中的相形态、相容性及相分离动力学与本体中有较大的不同[1～ 3] .基板界面作用对共混薄膜体系的热力学、动力学行为产生很大的影响 .我们以往的研究 [4 ,5]也发现 ,PP/EVAc(70 /30 )共混体系退火过程中 ,基板界面 (如玻璃 )作用可大大加速分散相(EVAc)粒子的粗化凝聚过程 .本研究用聚甲基丙烯酸甲酯和聚苯乙烯共混物的四氢呋喃溶液在不同基板介质 (如玻璃基板 ,PP基板 )上成膜 ,用相差显微镜观测了…     

热处理对聚偏氟乙烯-酰胺类溶剂所制薄膜结晶行为的影响

使用红外光谱和偏光显微镜对PVDF(聚偏氟乙烯)-DMF(N,N-二甲基甲酰胺)和PVDF-DMAc(N,N-二甲基乙酰胺)体系结晶行为的研究表明,PVDF薄膜的结晶受制备溶剂,后期热处理温度和膜厚度等因素的影响;升高温度,β相含量减小;当温度低于90℃时,PVDF-DMF体系的F(β)值较DMAc体系大,在90~160℃之间则相反,且两种体系的F(β)值分别在约90℃和80℃发生“突变”;同时,结晶还明显受到薄膜厚度的影响,厚度大,结晶较完善.     

热致液晶含氯侧基聚芳醚酮的单晶状条带织构

通常主链液晶高分子在受到剪切作用时 ,分子微纤呈周期性锯齿状排列 ,其光学效应表现为在偏光显微镜下可观察到相互平行且与剪切方向垂直的条带织构 [1] .而厚度适中的主链液晶聚合物薄膜经过热处理 ,即使没有受到剪切取向的作用 ,介晶微区的尺寸发展到一定大小时也会形成条带织构 ,即所谓结晶诱导[2 ] 和固化诱导 [3,4 ] 的条带织构 .在所报道的条带织构中 (包括剪切和非剪切 ) ,分子链均平行于膜平面 .本文研究发现 ,热致液晶氯代聚芳醚酮的薄膜样品在其高有序液晶温区经热处理 ,可形成结晶诱导的单晶状条带织构 ,其分子链垂直于膜平面 .…     

薄膜高分子结晶形态及其生长机理研究进展

由于高分子薄膜和超薄膜的空间效应和界面效应显著,其结晶行为与本体相比具有很大的差别。本文综述了近年来关于高分子在薄膜和超薄膜中特殊结晶行为的研究进展,重点介绍了晶体取向与薄膜厚度的关系。随着膜厚的减小,界面吸附作用对侧立片晶的抑制作用增强,导致晶体取向由侧立转变为平躺。超薄膜中晶体生长受扩散机理控制,其形态不稳定,变为树枝状晶体。在超薄膜中晶体的生长速率随着膜厚的减小而减小,当膜厚小于片晶厚度时,减小的趋势变缓。     

退火过程中聚乳酸中间相的形成和结构演化

采用淬火法制备聚乳酸(PLA)非晶薄膜,并利用原位显微红外光谱在线研究PLA非晶薄膜在不同退火温度下的结构演化.结果表明,PLA非晶薄膜存在一个临界结晶温度,当退火温度高于临界结晶温度时,PLA非晶薄膜可以通过分子链的局部调整实现冷结晶,反之,不能发生冷结晶;在冷结晶过程中先出现中间相,随后发生中间相-晶体相的转变;中间相是通过分子链的构象调整和分子链间的堆砌调整产生的,退火温度越高,中间相出现得越早,最终得到的晶体结构越规整.     

不同链长二元混合自组装薄膜的制备及其微观摩擦性能研究

采用分步组装的方法,将正己酰氯、正癸酰氯、正十四碳酰氯和硬脂酰氯按不同比例混合,接枝到3-(三甲氧基硅烷基)丙基乙烯基二胺(DA)氨基自组装膜表面,制备出一系列不同链长二元混合自组装薄膜;通过调节溶液中二元组分的相对比例,得到一系列不同厚度和不同表面润湿性的纳米有机薄膜;对薄膜进行了接触角测量、椭圆偏光测厚以及原子力形貌分析,并用摩擦力显微镜考察了其摩擦学性能.没有发现相分离现象,而且研究发现,随着长碳链分子所占比例的增大,薄膜的致密度增加,表面疏水性能增强,微观摩擦系数也随之减小.     

硫醇在Au(111)上SA单分子层膜研究

采用自组装(SA)技术制备了正丁硫醇、正十二硫醇及两种硫醇等摩尔混合物的SA单分子层膜。用椭圆偏振仪、接触角测量仪、扫描电子显微镜(SEM)、X-射线光电子能谱仪(XPS)和原子力显微镜(AFM)对3种SA膜进行了分析表征。结果表明SA膜是取向有序的纳米级超薄膜,分子链长、基片表面的晶格取向和表面的洁净度等对膜有一定的影响,长链分子膜表面是疏水性的。用椭圆偏光、XPS和AFM3种方法测定3种单分子层膜的厚度分别为0.59～0.67nm,1.60～1.69nm,1.23～1.32nm。AFM图象进一步证实了混合单分子层膜是由两种不同厚度的微畴组成。     

OTS自组装单层膜诱导定向生长SrTiO3功能陶瓷薄膜

采用自组装单层膜技术,以三氯十八烷基硅烷(octadecyl-trichioro-silane,OTS)为模版,在玻璃基片上成功制备了钛酸锶晶态薄膜.改性基板的亲水性测定与金相显微镜测试表明,紫外光照射使基板由疏水转变为亲水,OTS单分子膜对薄膜的沉积具有诱导作用:X射线衍射(XRD)与扫描电镜(SEM)表征显示,制备成功的钛酸锶薄膜结晶良好,样品表面均匀,在垂直基板表面方向上呈花状生长:EDS能谱测试为钛酸锶薄膜的化学组成提供了有力的证据;同时探讨了白组装单层膜和钛酸锶薄膜的形成机理.     

AFM研究PCL薄膜的结晶形态

利用原子力显微镜 (AFM)详细研究了聚己内酯 (PCL)超薄膜及其在特殊限制环境下的结晶形态 .AFM的观察表明 ,PCL在石英基板上的结晶形态呈现典型的球晶及比较少见的树枝状晶两种形态 .认为主要是超薄膜结晶过程中由于几何受限及基板吸附导致分子链扩散移动速度大大降低 ,由此形成的扩散控制结晶过程从而导致最终形成树枝状的分形结构 .将聚合物限制在间距为 10 μm的凹槽内 ,发现PCL的结晶有比较规整的排列 ,而且沿着凹槽的方向结晶排列取向优先 .当在凹槽两侧铝条上施加强电场后 ,发现在静电场作用下 ,PCL的结晶取向生长方向发生改变 ,沿着电场方向排列生长的结晶增多     

Temperature-driven surface morphology evolution of poly(3-hydroxybutyrate) single layer and poly(3-hydroxybutyrate)/poly(vinyl phenol) bilayer on Si wafers

 The specular and off-specular X-ray reflectivities were efficiently employed to study the evolution of surface morphology as a function of temperature in a single layer of poly(3-hydroxybutyrate) (PHB) and a bilayer of PHB/poly(vinyl phenol) (PVPh) on Si substrates. The results indicate that the changes of thickness and surface roughness caused by pre-melting of PHB crystals are not obvious for the single layer, whereas the surface roughness of the PHB layer and the intensity of the off-specular X-ray reflectivity for the bilayer exhibit a remarkable non-monotonic change in the temperature range of 100-150℃; the roughness parameter evaluated by the specular X-ray reflectivity reaches its maximum at 120℃. The interaction at the interface between PVPh and PHB certainly contributes to the non-monotonic changes. Such interaction also affects the crystallization and melting behavior of PHB thin film greatly. The crystallization of PHB thin film is inhibited even on the glassy surface of PVPh sublayer. In the melting process, the PHB crystals on PVPh sublayer feature a three-section melting curve separated by a plateau region of 120-140℃.     

Enantioselective crystallization of histidine on chiral self-assembled films of cysteine

In this paper, the preparation and use of chiral surfaces derived from enantiomerically pure crystals of amino acids are described. For this purpose, a self-assembly process to grow thin chiral films of (+)-L- or (-)-D-cysteine on gold surfaces was chosen. These chiral films were utilized as crystallization catalysts in the crystallization of enantiomers from solutions. To demonstrate the chiral discrimination power of the chiral surfaces in crystallization processes, the crystallization of racemic histidine onto the chiral films was investigated. Our study demonstrates the potential application of chiral films to control chirality throughout crystallization, where one enantiomer crystallizes onto the chiral surfaces with relative high enantiomeric excess. In addition, crystallization of pure histidine enantiomers onto chiral films results in strong crystal morphology modification with preferred orientation.     

Thickness-dependent molecular chain and lamellar crystal orientation in ultrathin poly(di-n-hexylsilane) films

The molecular chain and lamellar crystal orientation in ultrathin films (thickness < 100 nm) of poly-(di-n-hexylsilane) (PDHS) on silicon wafer substrates have been investigated by using transmission electronic microscopy, wide-angle X-ray diffraction, atomic force microscopy, and UV absorption spectroscopy. PDHS showed a film thickness-dependent molecular chain and lamellar crystal orientation. Lamellar crystals grew preferentially in flat-on orientation in the monolayer ultrathin films of PDHS, i.e., the silicon backbones were oriented along the surface-normal direction. By contrast, the orientation of lamellar crystals was preferentially edge-on in ultrathin films thicker than ca. 13 nm, i.e., the silicon backbones were oriented parallel to the substrate surface. We interpret the different orientations of molecular chain and lamellar crystal as due to the reduction of the entropy of the polymer chain near the substrate surface and the particularity of the crystallographic (001) plane of flat-on lamellae, respectively. A remarkable influence of the orientations of the silicon backbone on the UV absorption of these PDHS ultrathin films was observed due to the one-dimensional nature of sigma-electrons delocalized along the silicon backbone. With the silicon backbones perpendicular or parallel to the surface of the substrate, the UV absorbance increased or decreased with an increase of the angle between the incident UV beam direction and direction normal to the thin film, respectively.     

聚β-羟基丁酸酯和聚ε-己内酯的酯交换反应

以辛酸亚锡为催化剂 ,研究了聚 β 羟基丁酸酯 (PHB)与聚ε 己内酯 (PCL)在液相条件下的酯交换反应 .讨论了反应时间 ,反应温度和催化剂浓度对酯交换反应的影响 .采用1 3C NMR ,FTIR ,DSC ,WAXD和TGA等方法对PHB和PCL共聚酯 (PHB co PCL)的结构进行了表征 ,并对其结晶行为、晶体结构和热稳定性进行了研究 .结果表明 ,通过酯交换反应 ,所得到的共聚酯为嵌段共聚物 .提高反应温度和延长反应时间有利于酯交换反应的发生 .随着酯交换量的增加 ,PHB co PCL的结晶行为发生很大的变化 .但是 ,PHB co PCL晶体结构并没有因为PCL链段的引入而发生变化 ,而且它的热稳定性在空气气氛中略有提高     

分级聚丙烯的取向结晶过程

聚丙烯熔体在剪切或应变应力作用下 ,分子链发生取向形成伸直链纤维晶 ,这些先取向形成的纤维晶成为其后结晶的晶核 .这种线形排列的特殊自晶核被称作排核 ( Row nuclei) [1] .排核诱导的结晶温度高于异相核和均相核 .折叠链片晶在排核上附生生长 ,形成具有柱状对称性的超分子结构 ,称为柱状晶 ( Cylindrite) [2 ,3] .聚合物的分子量 ,剪切温度和剪切速度等因素对柱状晶的生成有很大影响 [4 ,5] .本文选用不同级分的聚丙烯样品 ,利用高分子 (特别是取向结晶 )的记忆效应 [6,7] ,研究了剪切后薄膜试样在熔融重结晶过程中柱状晶的形成和发展…     

In situ ATR-FTIR studies on MgCl2-diisobutyl phthalate interactions in thin film Ziegler-Natta catalysts

To study the surface structure of MgCl(2) support and its interaction with other active components in Ziegler-Natta catalyst, such as electron donors, we prepared a thin film analogue for Ziegler-Natta ethylene polymerization catalyst support by spin-coating a solution of MgCl(2) in ethanol, optionally containing a diester internal donor (diisobutyl-ortho-phthalate, DIBP) on a flat Si crystal surface. The donor content of these films was quantified by applying attenuated total internal reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Changes in the interaction of DIBP with MgCl(2) at various temperatures were monitored by in situ ATR-FTIR. Upon increasing the temperature, a shift in the (C═O) band toward lower wavenumbers was observed together with the depletion of (O-H) stretching band due to the desorption of residual ethanol. We assign this shift to gradual redistribution of adsorbed DIBP from adsorption sites on the MgCl(2) (104) surface toward the more acidic MgCl(2) (110) surface. The morphologies of MgCl(2) and MgCl(2)/DIBP films were studied by transmission electron microscopy (TEM) revealing a preferential orientation of ClMgCl layers (001) parallel to the lateral film dimensions. This orientation becomes more pronounced upon annealing. In the absence of donor, the MgCl(2) grow in to large crystals aligned in large domains upon annealing. Both crystal growth and alignment is impeded by the presence of donor.