报告内容摘要

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Halogen bonding is a rather exotic yet emerging noncovalent interaction for constructing supramolecular assemblies. It is in many ways similar to the more familiar hydrogen bonding, nevertheless it is the several important differences between these two interactions that render halogen bonding a unique tool for molecular recognition and the design of functional materials [1]. In terms of photoresponsive materials design, the most important characteristics of halogen bonding are its directionality and tunable interaction strength, which we have used to design azobenzene-based supramolecular polymers and liquid crystals for photoalignment and photoinduced surface-relief grating (SRG) formation [2,3].

The supramolecular liquid crystal, shown in Fig. 1a, comprises of two nonmesogenic constituents that are complexed via halogen bonding. This spacerless complex uniquely combines efficient photoalignment (order parameters as high as 0.55 were induced into initially isotropic spin coated thin films upon irradiation with polarized light) and SRG formation (gratings with modulation depth of 600 nm were inscribed onto films with 250 nm thickness; Fig. 1b) [1]. On the other hand, halogen-bonded polymer-azobenzene complexes have allowed us to probe the dependence of SRG formation efficiency on the nature and strength of noncovalent interaction between the polymer host and the azobenzene units [2]. This is important in view of gaining fundamental understanding on the light-induced mass transport process, which is not yet comprehensively understood. These results comprise the very first examples of halogen-bond-based photoresponsive materials, and serve to demonstrate that halogen bonding makes a difference!

Figure 1. (a) Halogen-bond-driven self-assembly of the nonmesogenic constituents yields a supramolecular complex with monotropic nematic LC phase. (b) Spin-coated (crystalline) thin films of the complex have the unique ability of combining efficient photoalignment and efficient light-induced surface-relief grating formation.

References

1.         A. Priimagi, G. Cavallo, P. Metrangolo, G. Resnati, Acc. Chem. Res. 2013, 46, 2686-2695.

2.         A. Priimagi, M. Saccone, G. Cavallo, A. Shishido, T. Pilati, P. Metrangolo, G. Resnati, Adv. Mater. 2012, 24, OP345-OP352.

3.         A. Priimagi, G. Cavallo, A. Forni, M. Leben, M. Kaivola, P. Metrangolo, R. Milani, A. Shishido, T. Pilati, G. Resnati, G. Terraneo, Adv. Funct. Mater. 2012, 22, 2572-2579.

 

报告人简介

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Professor  Arri Priimagi

Department of Chemistry and Bioengineering, Tampere University of Technology, Finland

E-mail: arri.priimagi@tut.fi

Professional Experiences

09.2014– Assistant Professor (Tenure Track), Department of Chemistry and Bioengineering,

Tampere University of Technology, Finland.

12.2013–08.2014 International Research Fellow, Department of Chemistry, Materials, and Chemical Engineering, Politecnico di Milano, Italy.

08.2010–11.2013 Aalto Post-Doctoral Fellow, Department of Applied Physics, Aalto University,

12.2010–12.2012 Post-Doctoral Fellow of the Japanese Society for the Promotion of Science,

Chemical Resources Laboratory, Tokyo Institute of Technology, Japan.

10.2009–07.2010 Post-Doctoral Researcher, Department of Applied Physics, Aalto University,

10.2004–11.2009 Doctor of Science and Technology, Helsinki University of Technology

Dissertation: "Polymer–azobenzene complexes: from supramolecular concepts

to efficient photoresponsive polymers" (Tutors Profs. M. Kaivola and O. Ikkala)

09.1999–09.2004 Master of Science and Technology, Tampere University of Technology.

Dissertation: "Nonlinear optical properties of self-assembled polymer systems"

(Tutor Prof. M. Kauranen)

 

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