2328 Full Paper Macromol. Chem. Phys. 2011, 212, 2328−2338 © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com Macromolecular Chemistry and Physics DOI: 10.1002/macp.201100471 Hydrogen-Bonding-Induced One-Handed Helical Polynorbornenes Appended With Chiral Alanine Ming-Jui Kao, Chih-Hsien Chen, Po-Yu Tsai, Tsong-Shin Lim, Kin-Chuan Lin, Tien-Yau Luh* Polynorbornenes appended with anthracene and chiral alanine linkers are synthesized. Hydrogen bonding between the adjacent bisamidic linkers brings adjacent anthracene chromophores in a more suitable orientation for exciton coupling and renders one-handed helical structures for these polymers. Excimer formation is observed from their emission spectra. Monoamidic linkers provide only one hydrogen bond, which would be less robust and result in much lower circular dichroic response. M.-J. Kao, C.-H. Chen, P.-Y. Tsai, Prof. K.-C. Lin, Prof. T.-Y. Luh Department of Chemistry, National Taiwan University, Taipei 106, Taiwan E-mail: tyluh@ntu.edu.tw Prof. T.-S. Lim Department of Physics, Tunghai University, Taichung 407, Taiwan PNBs has sporadically been explored. [14–16] We recently reported that ROMPs of norbornenes having 5,6-endo- fused N-arylpyrrolidine by the first generation Grubbs cat- alyst 1a give isotactic PNBs with all double bonds in trans configuration and all pendants aligned coherently toward the similar direction (Equation (1)). [16–18] It is believed that π– π interactions between these pending aryl groups might be responsible for the stereoselectivity. This pro- tocol has successfully been used for the synthesis of rela- tively rigid double stranded ladderphanes, [15,19] and for the replication of a single stranded polynorbornene into the corresponding complimentary polynorbornene [20] or diphenylene-butadyinlyenes. [21] Helical double stranded polybisnorbornenes are obtained when asymmetric centers are amalgamated in the linker. [15] The porphyrin- appended PNBs are known to exhibit exciton coupling in the Soret band of the absorption spectra. [16,18a,19c] Incor- poration of alanine linkers between the porphyrin pen- dants and the PNB backbone (e.g., 2) results in significant enhancement of circular dichroic (CD) intensities in the Soret band of the porphyrin moiety and hence, the poly- mers would be helical. [16] The photophysical behavior of anthracene derivatives is rich. [22] These chromophores have extensively been incorporated into chiral molecules for detailed analysis of 1. Introduction Hydrogen bonding provides powerful arsenal to trans- form an intrinsically flexible architecture into a more robust motif. [1] In particular, the amidic linkage has exten- sively been employed to furnish a range of new classes of supramolecular foldamers with well-organized secondary structures. [1] Incorporation of amino acid or peptide resi- dues onto polyisocyanides [2] and poly(phenylacetylene) s [3] are known to induce one-handed helicity of polymers. Polynorbornenes (PNBs) obtained by metal-catalyzed ring opening metathesis polymerization (ROMP) of the corresponding norbornene derivatives [4] are useful for catalysis, [5] light harvesting and photoinduced electron transfer, [6] ion conductivity, [7] and optoelectronic applica- tions. [8–12] Although chiral catalysts have been used for the synthesis of PNBs, [13] incorporation of chiral auxiliary into Dedicated to Prof. Christian Bruneau on the occasion of his 60th birthday.