A Real-Time Study of Homogeneous Nucleation, Growth, and Phase Transformations in Nanodroplets of Low Molecular Weight Isotactic Polypropylene Using AFM

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• 作者：Lekshmi Kailas ; Cvetelin Vasilev ; Jean-Nicolas Audinot ; Henri-Noë ; l Migeon ; Jamie K. Hobbs
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：October 2, 2007
• 年：2007
• 卷：40
• 期：20
• 页码：7223 - 7230
• 全文大小：1155K
• 年卷期：v.40,no.20(October 2, 2007)
• ISSN：1520-5835

文摘

Nanodroplets of isotactic polypropylene (iPP) were observed using temperature-controlled AFMin order to study the polymer's crystallization behavior. The nucleation, growth, and transformation of iPP crystalson heating have been directly imaged. The strong confinement of the polymer into nanoscale droplets has allowedthe controlled observation of polymer nucleation as well as access to crystal growth at exceptionally highsupercooling in iPP. Different modes of crystal growth were observed depending on the film thickness, includingthe formation of multiple independent homogeneous nuclei within single droplets. The temperature at which theonset of nucleation was observed in individual droplets was found to be dependent on the thickness as well asthe volume of the droplets. For droplets with smaller thicknesses (<5 nm), the thickness of the droplets wasfound to be the dominating factor influencing the nucleation temperature. This is the first real-space, real-timeobservation of homogeneous nucleation in iPP, almost 125 C below its melting point, which could signify crystalgrowth in the smectic form, and of the subsequent reorganization into the -form.