Dr. Chiara Gstrein

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Chiara graduated in June 2016.

Currently at:

Trüb Emulsions Chemie AG, Ramsen, Switzerland

Chiara Gstrein
Chiara Gstrein

Research Interests

My project focusses on dendronized polymers (DPs), which are macromolecules that carry dendrons at every backbone repeat unit. Due to the branched architecture and steric demand of the dendrons, DPs adopt a cylindrical shape. Below a certain dendron generation, g, DPs will still be flexible and have 'free' volume. This makes them interesting candidates for host-guest studies as well as enzyme mimicking nanoreactors.
The goal of my work is to gain information about the interior of DPs such as local polarity and accessible free volume for solvents and guest uptake. Therefore a new series of DPs which carry a solvatochromic probe (p-nitroaniline) covalently fixed at the branch point of g=1 was designed. By UV-Vis spectroscopy measurements of the DP series in different solvents it is possible to acquire information on changes in packing density as well as intrinsic polarity of the DPs.
These studies are complemented by loading experiments with various guests.

DPs with different g
Representation of DPs with different g with a solvatochromic probe (yellow) attached at g=1 (left). Chemical structure of one repeat unit of a g=4 DP (right).

Publications

Solvatochromism of dye-labeled dendronized polymers of generation numbers 1-4: comparison to dendrimers
Chiara Gstrein, Baozhong Zhang, Mona A. Abdel-Rahman, Oscar Bertran, Carlos Alemán, Gerhard Wegner and A. Dieter Schlüter
Chemical Science, vol. 7, pp. 4644-4652, Cambridge: Royal Society of Chemistry, 2016.

Two series of dendronized polymers (DPs) of generations g = 1-4 with different levels of dendritic substitution (low and high) and a solvatochromic probe at g = 1 level are used to study their swelling behavior in a collection of solvents largely differing in polarity as indicated by the Kamlet-Taft parameters. This is done by measuring the UV-Vis spectra of all samples in all solvents and determining the longest wavelength absorptions (λmax). The λmax values fall into a range defined by the extreme situations, when the solvatochromic probe is either fully surrounded by solvent or completely shielded against it. The former situation is achieved in a model compound and the latter situation is believed to be reached when in a poor solvent the dendritic shell around the backbone is fully collapsed. We observe that solvent penetration into the interior of the DPs decreases with increasing g and does so faster for the more highly dendritically substituted series than for the less highly substituted one. Interestingly, the swelling of the more highly substituted DP series already at the g = 4 level has decreased to approximately 20% of that at the g = 1 level which supports an earlier proposal that high g DPs can be viewed as nano-sized molecular objects. Furthermore, when comparing these two DP series with a g = 1-6 series of dendrimers investigated by Fréchet et al. it becomes evident that even the less substituted series of DPs is much less responsive to solvent changes as assessed by the solvatochromic probe than the dendrimers, suggesting the branches around the (polymeric) core in DPs to be more densely packed compared to those in dendrimers, thus, establishing a key difference between these two dendritic macromolecules.

Shielding effects in spacious macromolecules: a case study with dendronized polymers
Chiara Gstrein, Peter Walde, A. Dieter Schlüter and Thomas Nauser
Photochemical & Photobiological Sciences, vol. 15: no. 8, pp. 964-968, Cambridge: Royal Society of Chemistry, 2016.
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