Anisotropic Polyethylene Nanocrystals Labeled with a Single Fluorescent Dye Molecule: Toward Monitoring of Nanoparticle Orientation

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• 作者：Benjamin Scheinhardt ; Justyna Trzaskowski ; Moritz C. Baier ; Beate Stempfle ; Alex Oppermann ; Dominik W枚ll ; Stefan Mecking
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：October 8, 2013
• 年：2013
• 卷：46
• 期：19
• 页码：7902-7910
• 全文大小：421K
• 年卷期：v.46,no.19(October 8, 2013)
• ISSN：1520-5835

文摘

The three-dimensional orientation monitoring of anisotropic nanoparticles during dynamic processes is a fundamental issue. Herein we show that incorporation of a single fluorescent reporter molecule is a promising concept toward this goal. As a model system, shape anisotropic single lamella polyethylene (PE) nanocrystals bearing one single fluorescent reporter molecule were prepared via ring-opening metathesis polymerization (ROMP) of highly ring-strained trans-cyclooctene (^trCOE) using a mixture of a dye-functionalized ruthenium-based initiator (1; perylene diimide (PDI) substituted Hoveyda鈥揋rubbs second generation Ru alkylidene) and an appropriate excess of the unlabeled analogue (2; Hoveyda鈥揋rubbs second generation Ru alkylidene) in aqueous microemulsion as a key step and subsequent exhaustive hydrogenation (>99.9%) of the main-chain unsaturated polymer in the nanoparticles to yield nanocrystals of high molecular weight, strictly linear PE (M_n = 8 脳 10⁵ g mol^鈥?; M_w/M_n = 1.4). TEM and AFM show a particle thickness of ca. 12 nm with a lateral extension of typically 45 nm. Comparable initiation kinetics of both complexes 1 and 2, which is a key requirement for this approach, were revealed by fluorescence spectroscopy studies (螖H^{鈥?/sup> = 57.4 kJ mol鈥?, 螖S鈥?/sup> = 鈭?3.0 J mol鈥? K鈥? for 1 vs 螖H鈥?/sup> = 63.6 kJ mol鈥?, 螖S鈥?/sup> = 鈭?0.8 J mol鈥? K鈥? for 2 for the initiation with n-butyl vinyl ether, respectively). The labeled nanocrystals were characterized by means of single molecule fluorescence spectroscopy. Orientational analysis via defocused wide-field fluorescence microscopy (DWFM) revealed a fixed orientation of the chromophores within the nanocrystals, with their long molecular axis predominantly oriented parallel to the polar axis of the nanoparticles.}