权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

High-resolution electron microscopy of shish-kebab structure in uniaxially oriented polyesters.

单轴取向聚酯中的烤串结构的高分辨率电子显微镜。

基本信息

批准号：
16550174
负责人：
TSUJI Masaki
金额：
$ 2.3万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Because the specimen thickness should be smaller than 50nm for direct observation by transmission electron microscopy (TEM), uniaxially oriented thin films of various polyesters were made by applying "shear strain (shear rate= about 4 x 10^6 /sec)" to the respective melts. Electrospinning was also employed for producing nanofibers of the polyesters and of regenerated silk fibroin. There are still several problems to be solved, for example, in the methods for fixing/supporting specimens on the specimen grids for TEM as well as in that the resultant nanofibers are too thick for TEM observation. Although expected high-resolution observation could not be carried out, main results for three years are as follows :1) When poly(butylene terephthalate) (PBT) is crystallized from the melt under a static condition, usual-positive spherulites are formed above 200ーC and unusual ones below 200゜C. For each of the three kinds (usual-positive, usual-negative and unusual types) of 2- dimensional spherul … More ites, which were made by isothermal crystallization from the melt or by solution-cast method, the growth direction of crystalline lamellae in the corresponding spherulite and the origin of its optical property (namely, birefringence) were discussed on the basis of morphological studies.2) Uniaxially oriented thin films were prepared by applying shear strain to the respective melts of poly(ethylene terephthalate) (PET), poly(ethylene naphthalate) PEN and PBT, which are aromatic polyesters. In particular, stacked-lamellar structure was undoubtedly recognized in the films of PEN and PBT, and thus we concluded that shish-kebab structure is formed even in polyesters.3) In order to clarify the structure of melt-spun fibers of poly(p-dioxanone) (PPDX) which is a biodegradable aliphatic polyester, the fibers were investigated by X-ray diffraction and morphlogical observation. PPDX nanofibers were prepared by electrospinning as model specimens for TEM observation. Uniaxially oriented thin films of PPDX and electrospun nanofibers of regenerated silk fibroin were prepared, and morphology of the films and that of the nanofibers were studied.4) Electrospun nanofibers were made for each of aromatic polyesters (PET, PEN, and PBT). The average diameter of PBT nanofibers was about 100nm and the smallest of all the polymers utilized in this project. Average nanofiber-diameters of other all polymers are much greater than 100nm. We found that it is necessary to develop new procedures/methods for making electrospun nanofibers with their average diameters being smaller than 50nm, and then to improve their degrees of chain orientation and of crystallinity. Less

由于通过透射电子显微镜（TEM）直接观察，试样厚度必须小于50nm，因此通过对各自的熔体施加“剪切应变（剪切速率约为4 × 10^6 /sec）”来制备各种聚酯的单轴定向薄膜。静电纺丝还可用于涤纶和再生丝素纳米纤维的制备。目前仍有几个问题需要解决，例如，在TEM的样品网格上固定/支撑样品的方法，以及由此产生的纳米纤维太厚而无法进行TEM观察。虽然无法进行预期的高分辨率观测，但三年的主要结果如下：1)在静态条件下从熔体中结晶聚对苯二甲酸丁二酯（PBT）时，在200℃以上形成正常正球晶，在200℃以下形成异常正球晶。对熔体等温结晶和液铸法制备的三种（常正型、常负型和异常型）2维球晶，分别从形态学上讨论了相应球晶中晶片的生长方向及其光学性质（即双折射）的来源。2)分别对芳香族聚酯——聚对苯二甲酸乙酯（PET）、聚萘二甲酸乙酯（PEN）和PBT熔体施加剪切应变，制备了单轴取向薄膜。特别是在PEN和PBT薄膜中，我们无疑发现了堆叠层状结构，因此我们得出结论，即使在聚酯中也形成了羊肉串结构。3)为了明确可生物降解脂肪族聚酯聚对二氧环酮（PPDX）熔融纺丝纤维的结构，采用x射线衍射和形貌观察对纤维进行了研究。采用静电纺丝法制备PPDX纳米纤维作为模型试样，进行TEM观察。制备了单轴定向PPDX薄膜和静电纺再生丝素纳米纤维，并对薄膜和纳米纤维的形貌进行了研究。4)分别制备了芳香族聚酯（PET、PEN和PBT）的静电纺丝纳米纤维。PBT纳米纤维的平均直径约为100nm，是本项目中使用的所有聚合物中最小的。其他聚合物的平均纳米纤维直径都远远大于100纳米。我们发现有必要开发新的工艺/方法来制备平均直径小于50nm的电纺纳米纤维，从而提高其链取向度和结晶度。少