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

Abstract

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 ( tr COE) using a mixture of a dye-functionalized ruthenium-based initiator (1; perylene diimide (PDI) substituted Hoveyda−Grubbs second generation Ru alkylidene) and an appropriate excess of the unlabeled analogue (2; Hoveyda−Grubbs 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 × 10 5 g mol −1 ; 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 (ΔH ‡ = 57.4 kJ mol −1 , ΔS ‡ = −73.0 J mol −1 K −1 for 1 vs ΔH ‡ = 63.6 kJ mol −1 , ΔS ‡ = −80.8 J mol −1 K −1 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.

Dye-functionalized polymers via ring opening metathesis polymerization: principal routes and applications

“…In addition, there is a potential interference between the initiator and the pending dye due to sterical hindrance or functional groups of the dye which could alter the polymerization kinetics, especially of the initiation step. Consequently, this route has not been used very often and only relatively innocuous dyes like perylenebisimides [8], pyrene [9], or phenanthroimidazole [11] have been employed whereas fluorescein [10] could be only used after protecting the O-H functionalities, see Fig. 2.…”

Fast and Efficient Microwave‐Assisted Synthesis of Perylenebisimides

“…The final products were characterized by 1 HNMR, 13 CNMR, MALDI-MS, FT-IR, UV/Vis absorption and fluorescence spectroscopy. 13 C-NMR analysis was not possible for all compounds, due to their poor solubility in standard deuterated solvents.…”

“…13 C-NMR analysis was not possible for all compounds, due to their poor solubility in standard deuterated solvents.…”

“…All spectra were recorded at 298 K. 1 H NMR spectroscopic data are reported as follows: chemical shift in parts per million (ppm) on the δ scale, integration, multiplicity, coupling constants (Hz), and assignments. 13 C NMR spectroscopic data are reported as follows: chemical shifts in parts per million on the δ scale and carbon environments determined from DEPT spectra. The 1,6,7,12-tetrabromo-and 1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylic bisanhydride were prepared according to the literature.…”

“…The 1,6,7,12-tetrabromo-and 1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylic bisanhydride were prepared according to the literature. [13] Synthesis of Perylenebisimides with Alkylamine. General Procedure for 1-6: 100 mg of perylene-3,4,9,10-tetracarboxylic bisanhydride were suspended in dry DMF (5 mL) with 2 equiv.…”