Dendronized polymers (DPs) are macromolecules that carry dendrons at every backbone repeat unit. Dendrons can be developed to higher generations g. Due to the branched architecture and steric demand of the dendrons, DPs will adopt a cylindrical shape and internally be densely packed at higher g, particularly when g approaches gmax. Beyond gmax the attachment of a defectless next g is not possible anymore.[1] The goal of this work is to gain g-dependent information about the interior of DPs such as local polarity and accessible volume for guests and solvents. Our method is based on a new series of DPs with g=1-4 which carry a solvatochromic probe (p-nitroaniline) covalently fixed at the branch point of g=1. The λmax values of these samples are determined by UV/Vis spectroscopy for solvents with 2&lt;εr&lt;47 and most of them show clear g-dependence. While in all other solvents λmax with increasing g seems to converge near 395 nm,[2] in toluene (at 65 °C) a much stronger g-dependence is observed resulting in λmax= 410 nm for g=4. Thus, in all solvents the branches are in fact increasingly shielding the probe but except for in toluene the probe remains somewhat solvent accessible. Toluene is a poor solvent for our DPs[3] and our results suggest that the branches collapse, with the toluene molecules being largely squeezed out of the interior resulting in a λmax which reflects the intrinsic polarity of the branches. Our studies are flanked by MD-simulations performed by Prof. C. Alemán, Barcelona, which provide numbers for how many solvent molecules are incorporated into the various g DPs. [1] Schlüter A. D.; Halperin A.; Kröger M.; Vlassopoulos D.; Wegner G.; Zhang B. ACS Macro Lett. 2014, 3, 991-998. [2] Hawker C. J.; Wooley K. L.; Fréchet J. M. J. J. Am. Chem. Soc. 1993, 115, 4375-4376. [3] Kröger A.; Zhang B.; Rosenauer C.; Schlüter A. D.; Wegner G. Colloid Polym Sci 2013, 291, 2879-2892.

Probing the interior of dendronized polymers with solvatochromic p-nitroanilino groups

249th National Meeting (2015)

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