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Structural Fluctuations and Crystal Growth in Ultra-thin Polymer Films

超薄聚合物薄膜中的结构波动和晶体生长

基本信息

批准号：
06452069
负责人：
MIYAJI Hideki
金额：
$ 4.74万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452069/
关键词：
Polymer Ultra-thin Film Crystal Growth Structural fluctuation Diffusion

项目摘要

1.Ultra-thin polystirene films from 20 to several hundreds of nm in thickeness were prepared by a water casting method. Since the radius of gyration is given to be 0.03*M^<1/2> nm for a poly-stirene chain with molecular weight of M,the chains with molecular weight of more than 100,000 are to be squeezed in the ultra-thin films ; accordingly chains shows structures and dynamics different from those in bulk. 2.The X-ray amorphous halo observed with use of PSPC has shown no difference between the thin film and bulk ; the structure of the most of chains in the film has the same structure as in bulk. 3.Atomic force microscopy shows that the fluctuation of height on the surface of the amorphous film is about 1 nm. The fluctuation was observed also on the crystal surface after crystallization of the film, and hence crystais are coverd with amorphous layr. 4.The effect of substrate are conspicuous on primary nucleations. Above 210ﾟC of crystallization temperature, lemellar crystals perpendicular to a carbon substrate were observed at the center of grown crystals ; a screw dislocation was at the center for mica substrate. Below 150ﾟC,observed were 2-dimensional spherulites with branched lemellae perpendicular to the substrate. 5.Film thckness dependence of lateral growth rates wrere measured as a function of molecular weight M,crystallization temperature T_C and substrate materials. For the lamellar crystals parallel to the substrate, the growth rate G decease linearly with the inverse of the thickness D : G/G_*=1-a/D where G_* is the growth rate in bulk, a is a constant of about 5 nm, independent of T_C, M and substrate materials. For the 2-D spherulites, G remains unchanged with decreasing D.We therefore conclude that the part of a polymer chain at a distance less than 5 nm from a substrate "feels" the absorption of chain segments on the substrate, and hence suffers the delay of diffusion for crystallization to give rise to G decreasing linearly with 1/D.

1.采用水铸法制备了厚度从20 nm到几百nm的聚苯乙烯超薄薄膜。由于分子量为M的聚苯乙烯链的回转半径为0.03*M^<1/2> nm，分子量大于100，000的链在超薄膜中受到挤压，因此链表现出不同于本体的结构和动力学。2.用PSPC观察到的X射线非晶晕表明薄膜和体相没有区别，薄膜中大部分链的结构与体相相同。3.原子力显微镜观察表明，非晶薄膜表面的高度起伏约为1 nm。在薄膜晶化后的晶体表面也观察到这种波动，因此晶体表面覆盖着非晶层。4.基体对初生形核有显著的影响。在结晶温度高于210 ° C时，在生长的晶体中心观察到垂直于碳基底的片状晶体;云母基底的中心是螺旋位错。在150 ℃以下，观察到二维球晶，其具有垂直于基底的支化的球粒。5.测量了薄膜厚度对横向生长速率的影响，它们是分子量M、晶化温度T_C和衬底材料的函数。对于平行于衬底的片状晶体，生长速率G与厚度D的倒数成线性关系：G/G *=1-a/D，其中G * 为体生长速率，a为约5 nm的常数，与T_C、M和衬底材料无关。对于2-D球晶，G保持不变，随着D的减少。因此，我们得出结论，在距离小于5 nm的聚合物链的一部分，从基板上的链段的吸收“感觉”，因此遭受延迟的扩散结晶，以引起G与1/D线性下降。