MULTIFUNCTIONAL CHIRAL POLYMERIC MATERIALS CONTAINING SIDE-CHAIN AZOCARBAZOLE CHROMOPHORES L. Angiolini, L. Giorgini, F. Mauriello Dipartimento di Chimica Industriale e dei Materiali, University of Bologna R. Bozio, T. Dainese, D. Pedron Dipartimento di Scienze Chimiche, University of Padova A. Golemme, R. Termine Dipartimento di Chimica, University of Calabria Synthesis of materials and characterization Photomodulation optical properties Photoconductive and photorefractive properties

Features of the multifunctional polymer studied POLYMERIC BACKBONE Mn = 13400 Mw /Mn = 1.8 Tg = 147°C Td = 363°C CHIRAL FUNCTIONALITY PHOTOCONDUCTIVE & PHOTOREFRACTIVE FUNCTIONALITY High Tg and decomposition temperatures PHOTOCHROMIC FUNCTIONALITY

Pump at 488 nm Probe at 633 nm Carbazole Aromatic of azo-dyes Cis Trans Aromatic of azo-dyes 200 300 400 500 600 0,0 0,5 1,0 1,5 2,0 2,5 Absorbance Wavelength (nm) 488 nm 633 nm Pump at 488 nm Probe at 633 nm Absorption in the visible: azo-dyes n *, * and CT el. trans.

Chiral conformation of one prevailing helical handedness Amplified Chirality + CD spectra - Excitonic splitting CHIRAL GROUP PHOTOREFRACTIVE GROUP AZO-AROMATIC CHROMOPHORE UV-vis spectra Potential use as chiroptical switches

Photoconductive and photorefractive materials Security from Forgery Holographic Interferometry Medical Application •Phase Conjugation •Optical Device •Pattern Recognition Optical Amplification Holographic Data Storage 3-D Holovideo Holographic Data Storage Capacity in bytes Holographic Memories Small Mag.Disks Large Mag. Disks CD ROM Magnetic Tape Floppy disks 104 103 102 101 100 10-1 10-2 Access time in milliseconds 106 107 108 109 1010 1011 1012 Nanolithography Electroluminescents Diodes Integrals circuits

Multifunctional Polymers MULTIFUNCTIONAL POLYMERS FOR PHOTONICS AND OPTOELECTRONICS Carbazole Chiral group Azobenzene Synthetic approach Multifunctional Polymers Chiral group Chiral monomer with carbazole Carbazole MULTIFUNCTIONAL COPOLYMERS MULTIFUNCTIONAL OMOPOLYMERS + Chiral monomer with azobenzene Azobenzene Multifunctional monomer Chiral group

Multifunctional copolymers synthetized Multifunctional homopolymers synthetized

Amorphous thin films obtained by spin-coating Applications as Amorphous thin films obtained by spin-coating Thickness 100-400 nm <900 nm

Photoinduced trans  cis  trans isomerization cycles Ē  rotational diffusion h STOP trans cis

Reversible photoinduced orientation of azobenzene groups LP CP R. Hagen, T. Bieringer Adv. Mater 13, 1805 (2001)

Typical experiment of photoinduced birefringence cycles 1 Write and erase of optical information for OPTICAL STORAGE L. Angiolini, R. Bozio, L. Giorgini, D. Pedron, G. Turco, A. Daurù, Chem. Eur. J., 8, 4241 (2002) L. Angiolini, T. Benelli, R. Bozio, A. Daurù, L. Giorgini, D. Pedron, E. Salatelli, Macromolecules, 39, 489-497 (2006) L. Angiolini, T. Benelli, R. Bozio, A. Daurù, L. Giorgini, D. Pedron, E. Salatelli, Eur. Polym. J, in press (2007)

Photomodulation of birefringence on Poly[(S)-MLECA] Reversible write and erase of optical information for OPTICAL STORAGE Temporal stability of photoinduced signals Pump at 488 nm Ipump  100 mW/cm2 Probe at 633 nm Iprobe < 1 mW/cm2

CHIROPTICAL SWITCHES Reversible inversion of the CD signal by irradiation with CP-L and/or CP-R light poly[(S)-MAP-N] Tg = 208 C thin films 100  300 nm I  160 mW/cm2 x 60 s L. Angiolini, R. Bozio, L. Giorgini, D. Pedron, G. Turco, A. Daurù, Chem. Eur. J., 8, 4241 (2002) L. Angiolini, R. Bozio, L. Giorgini, D. Pedron, Synth. Met., 138, 375-379 (2003) L. Angiolini, T. Benelli, R. Bozio, A. Daurù, L. Giorgini, D. Pedron, Synthetic Metals 139, 743 (2003)

Reversal of the coils or of the domains by irradiating with CP light !?? CHIROPTICAL SWITCHES CP-L CP-R CP-L CP-R Dipolar interactions Side-chain Chiral groups Azo-aromatic groups L. Angiolini, T. Benelli, L. Giorgini, A. Painelli, F. Terenziani, Chem. Eur. J. (2005) L. Angiolini, T. Benelli, L. Giorgini, E. Salatelli, Polymer, 46, 2424 (2005) L. Angiolini, T. Benelli, L. Giorgini, E. Salatelli, Polymer, 47, 1875–1885 (2006)

Photomodulation of the chiroptical properties of Poly[(S)-MLECA] SWITCHES

Surface relief gratings (SRGs) photoinduced on Poly[(S)-MLECA] Irradiation of azo polymer films with an interference pattern for a period of time longer than that required for photoinduced orientation produces a modification of the film surface.

Crossed Surface Relief Gratings SRGs, with 2 mm period, in the x-direction and 1 mm period, in the y-direction, SRGs with 1mm periods, in the x and y directions

Laser Induced Supramolecular Helix (LISH) inscribed on Poly[(S)-MLECA] Unusual superhelix-like (LISH) patterns can be directly photofabricated on the surface of azo polymer films by a interference pattern obtained by EP-L (ellipticity = 0.4) and EP-R (ellipticity < 0.4) light. Combination of the photoinduced chiral orientation and the photoinduced SRG formation. 5 mm Helicoidal structures (LISH) superimposed to a SRG with a period of about 1mm

Photoconductivity properties of Poly[(S)-MLECA] 2.3x10-13 ScmW-1 at 60V/mm

ACKNOWLEDGEMENTS: Prof. Luigi Angiolini Dr. Tiziana Benelli Dr. Francesco Mauriello Dott. Elisabetta Salatelli Dott. Libero Damen Dott. Gianluca Perfetti University of Bologna Prof. Renato Bozio Prof. Danilo Pedron Dott. Tiziano Dainese Dott. Alessandro Daurù Photomodulation of birefringence, chiroptical switches and SRGs University of Padova Prof. Mauro Ghedini Prof. Attilio Golemme Dr. Roberto Termine Photoconductivity and Photorefractive properties University of Calabria Financial support by MIUR (FIRB 2001) and Consorzio INSTM is gratefully acknowledged

Professor Carlo Carlini The author dedicates this work to the memory of Professor Carlo Carlini

OPTICAL STORAGE OPTICAL STORAGE AND CHIROPTICAL SWITCHES PHOTORESPONSIVE PROPERTIES CONVENTIONAL MATERIALS CHIRAL PHOTOCHROMIC POLYMERS Photomodulation of linear birefringence and dichroism OPTICAL STORAGE AND CHIROPTICAL SWITCHES OPTICAL STORAGE Photomodulation of chiroptical properties CHIROPTICAL SWITCHES

Campo elettrico (V/mm) Polimero s/I (S cm W-1) Campo elettrico (V/mm) Poli[MECSI] 100% 1.2 e-14 60 Poli[MECP] 80% DPP 20% 8.0 e-11 40 Poli[MLECA] 100% 3.0 e-14 Poli[MECPS] 85% DPP 15% 2.0e-12

Dr. Elisabetta Salatelli Dr. Delio Alfino Dr. Saverio Cazzoli ACKNOWLEDGEMENTS: Dr. Tiziana Benelli Dr. Daniele Caretti Dr. Elisabetta Salatelli Dr. Delio Alfino Dr. Saverio Cazzoli Dr. Ada delle Donne Mr. Marco Toto Dr. Alessandro Daurù Dr. Giovanni Turco Mr. Andrea Barbiero University of Bologna University of Padova Financial support by MIUR (PRIN 2001) and Consorzio INSTM is gratefully acknowledged

poly[(S)-MAP-C] (Tg = 192 C), heated at 200 C

The application of heat seems to amplify the overall chirality of the system -60 40 -40 -20 20 1 2 250 550 450 350 Absorbance Ellipticity (mdeg) Wavelength (nm) Heat CP-L 190 C 230 C CP-R poly[(S)-MAP-C] Tg = 192 C L. Angiolini et al., Synth. Met., 138, 375-379 (2003)

Chirality increases with the increase of the tot. fluence poly[(S)-MAP-C] 184 nm I  200 mW/cm2 x 180 s 1th - 6th I  100 mW/cm2 x 180 s 7th - 8th I  50 mW/cm2 x 180 s 9th - 10th L. Angiolini et al., Synth. Met., (2003) in press

poly[(S)-MAP-C] 184 nm poly[(R)-MAP-C] 210 nm I  200 mW/cm2 x 180 s 1th - 6th I  100 mW/cm2 x 180 s 7th - 8th I  50 mW/cm2 x 180 s 9th - 10th poly[(R)-MAP-C] 210 nm I  100 mW/cm2 x 400 s 1th - 10th

Synthesis of multifunctional monomers Biphasic medium H2O/CH2Cl2

Photoinduced aggregation? Modification in shape and intensity of the CD and abs. spectra CP-L CP-R

Temporal and thermal stability of photoinduced CD signals poly[(S)-MAP-C] 170 nm I  400 mW/cm2 x 180 s CP-L CP-R Temporal and thermal stability L. Angiolini et al., Synth. Met., in press (2003)

CHIROPTICAL SWITCHES poly[(S)-MAP-N-co-DR1M] 50/50 Film thin 290 nm I  50 mW/cm2 x 180 s 1th - 3th I  100 mW/cm2 x 180 s 4h - 7th I  200 mW/cm2 x 180 s 8th - 10th

After ordering with LP light LC smectic-A phase M. Ivanov, et al., J. Mod. Opt. 2000, 47, 861. After ordering with LP light G. Iftime, et al., J. Am. Chem. Soc. 2000, 122, 12646. LC smectic-A phase

The properties of the materials change by using different co-monomers

Materiali fotorifrattivi Effetto fotorifrattivo I processi fisici legati al meccanismo fotorifrattivo sono: Assorbimento della radiazione luminosa con generazione di cariche Trasporto delle cariche Intrappolamento delle cariche Generazione di un campo elettrico interno Riorientazione molecolare interna con variazione dell’indice di rifrazione DEFINIZIONE: L’effetto fotorifrattivo (PRe) si riferisce alla modulazione spaziale dell’indice di rifrazione generato da un meccanismo specifico: la ridistribuzione fotoindotta di carica in un materiale nel quale l’indice di rifrazione dipende dal campo elettrico applicato.

Materiali fotorifrattivi Effetto fotorifrattivo Molecole organiche coinvolte nel processo Photorefractive material = Photoconducting material +NLO chromophore

Scelta gruppo fotoconduttore Carbazolo Il gruppo carbazolico forma relativamente cationi radicalici stabili (holes) Il carbazolo è un intermedio relativamente economico. Differenti sostituenti possono essere facilmente introdotti nell’anello carbazoico. Materiali contenenti i gruppi carbazolici sono caratterizzati da una elevata stabilità termica e fotochimica Il gruppo carbazolico permette una maggiore coniugazione lungo la catena laterale

Omopolimero poli[(S)-MLECA] 4 5,2 g h 8,1,6 * a c e,f b d Spettroscopia 1H-NMR Omopolimero poli[(S)-MLECA] (S)-MLECA poli[(S)-MLECA] Scomparsa del segnale dei protoni del CH2 metacrilico

Misure di dicroismo circolare stato solido SOLUZIONE STATO SOLIDO + Conservazione ordinamento cromofori - couplet eccitonico Potenziali swithes chiroottici

Misure di fotoconduzione Risultati Preliminari Poly [(S)-MECPS] Poly [(S)-(+)-MECP] PROPRIETA’ FOTOCONDUTTIVE 2 ordini di grandezza maggiore