A 677 OULU 2016 A 677 UNIVERSITY OF OULU P.O. Box 8000 FI-90014 UNIVERSITY OF OULU FINLAND ACTA UNIVERSITATISUNIVERSITATIS OULUENSISOULUENSIS ACTA UNIVERSITATIS OULUENSIS ACTAACTA SCIENTIAESCIENTIAEA A RERUMRERUM Elina Pulkkinen NATURALIUMNATURALIUM Elina Pulkkinen Professor Esa Hohtola CHEMICAL MODIFICATION University Lecturer Santeri Palviainen OF SINGLE-WALLED CARBON Postdoctoral research fellow Sanna Taskila NANOTUBES VIA ALKALI METAL REDUCTION Professor Olli Vuolteenaho University Lecturer Veli-Matti Ulvinen Director Sinikka Eskelinen Professor Jari Juga University Lecturer Anu Soikkeli Professor Olli Vuolteenaho UNIVERSITY OF OULU GRADUATE SCHOOL; UNIVERSITY OF OULU, FACULTY OF SCIENCE Publications Editor Kirsti Nurkkala ISBN 978-952-62-1243-2 (Paperback) ISBN 978-952-62-1244-9 (PDF) ISSN 0355-3191 (Print) ISSN 1796-220X (Online) ACTA UNIVERSITATIS OULUENSIS A Scientiae Rerum Naturalium 677 ELINA PULKKINEN CHEMICAL MODIFICATION OF SINGLE-WALLED CARBON NANOTUBES VIA ALKALI METAL REDUCTION Academic dissertation to be presented with the assent of the Doctoral Training Committee of Technology and Natural Sciences of the University of Oulu for public defence in the Arina auditorium (TA105), Linnanmaa, on 15 June 2016, at 12 noon UNIVERSITY OF OULU, OULU 2016 Copyright © 2016 Acta Univ. Oul. A 677, 2016 Supervised by Professor Marja Lajunen Doctor Janne Asikkala Reviewed by Professor Markku Leskelä Professor Mika Pettersson Opponent Professor Tuula Pakkanen ISBN 978-952-62-1243-2 (Paperback) ISBN 978-952-62-1244-9 (PDF) ISSN 0355-3191 (Printed) ISSN 1796-220X (Online) Cover Design Raimo Ahonen JUVENES PRINT TAMPERE 2016 Pulkkinen, Elina, Chemical modification of single-walled carbon nanotubes via alkali metal reduction. University of Oulu Graduate School; University of Oulu, Faculty of Science Acta Univ. Oul. A 677, 2016 University of Oulu, P.O. Box 8000, FI-90014 University of Oulu, Finland Abstract Carbon nanotubes are a promising material for various applications due to their unique collection of properties. However, carbon nanotube material as such is inert and insoluble, which hampers the true realization of its potential. In order to enhance the applicability of carbon nanotubes, their surface must be modified. This work concerned the chemical modification of single-walled carbon nanotubes (SWNT) by the Birch reduction, which is based on the reduction of the SWNT surface with the valence electron of alkali metal solvated in liquid ammonia. The reduction generates a SWNT anion, which reacts with electrophiles resulting in the covalent attachment of functional groups to the tube surface. In this work, aryl halides or alcohols were used as electrophiles to yield arylated or hydrogenated SWNTs, respectively. At first, the goal was to modify SWNTs as a filler material for polystyrene. The use of five halogenated ethenylphenyl derivatives as electrophiles revealed that the structure of electrophile affected the success of functionalization and the solubility of SWNTs in polystyrene-toluene solution. The most successful functionalization and solubilization of SWNTs were achieved with 1-chloro-4-ethenylbenzene. In the second part, liquid ammonia was replaced with a new solvent, 1-methoxy-2-(2- methoxyethoxy)ethane (diglyme) in order to avoid the restrictions, hazards and inconvenience of its handling. The work concentrated on the study of alkali metal reduction of SWNTs in diglyme by the use of arylation with 4-iodobenzoic acid or 4-chlorobenzoic acid and hydrogenation as model reactions. Li, Na or K was used as an alkali metal while naphthalene or 1-tert-butyl-4-(4- tert-butylphenyl)benzene was used in order to enhance the solvation of electrons. As a result, functionalization was simplified and enhanced. Electrophile affected the functionalization in such a way that arylation was significantly more successful than hydrogenation. The effect of alkali metal and electron carrier varied with electrophile. The most successful hydrogenation was achieved with the complex of Li and 1-tert-butyl-4-(4-tert-butylphenyl)benzene while arylation was the most successful with the complex of K and naphthalene. The solubility of SWNTs in water, ethanol, methanol and dimethylformamide was clearly improved by arylation whereas hydrogenation led to moderate improvement. Keywords: alkali metal, arylation, Birch reduction, carbon nanotube, functionalization, hydrogenation, solubilization Pulkkinen, Elina, Yksiseinäisten hiilinanoputkien kemiallinen modifiointi alkalimetallipelkistyksellä. Oulun yliopiston tutkijakoulu; Oulun yliopisto, Luonnontieteellinen tiedekunta Acta Univ. Oul. A 677, 2016 Oulun yliopisto, PL 8000, 90014 Oulun yliopisto Tiivistelmä Hiilinanoputket ovat ainutlaatuisten ominaisuuksiensa vuoksi lupaava materiaali moniin sovel- luksiin, mutta liukenemattomuus ja epäreaktiivisuus haittaavat niiden tehokasta hyödyntämistä. Käytettävyyttä voidaan parantaa kemiallisella modifioinnilla. Tässä työssä yksiseinäisiä hiili- nanoputkia modifioitiin Birch-pelkistyksellä, joka perustuu putken pinnan pelkistykseen neste- mäiseen ammoniakkiin solvatoituneella alkalimetallin valenssielektronilla. Pelkistyksessä hiili- nanoputkesta muodostuu anioni, joka reagoi elektrofiilin kanssa johtaen funktionaalisten ryhmi- en kovalenttiseen sitoutumiseen putken pintaan. Tässä työssä hiilinanoputkia aryloitiin käyttä- mällä aryylihalideja elektrofiilinä tai vedytettiin käyttämällä alkoholia. Aluksi tavoitteena oli hiilinanoputkien modifiointi sellaiseen muotoon, että niitä voitaisiin käyttää polystyreenin täyteaineena. Viittä aryylihalidia käyttämällä havaittiin, että elektrofiilin rakenne vaikutti funktionalisoinnin määrään ja putkien liukoisuuteen polystyreeni-tolueeni-liu- okseen. 1-Kloori-4-etenyylibentseenillä saavutettiin onnistunein arylointi ja paras liukoisuus. Työn toisessa osassa luovuttiin ammoniakin käytöstä siihen liittyvien rajoitteiden ja haittojen vuoksi. Keskityttiin hiilinanoputkien alkalimetallipelkistyksen tutkimiseen uudessa liuottimes- sa, 1-metoksi-2-(2-metoksietoksi)etaanissa (diglyymi). Mallireaktioina käytettiin arylointia 4- jodibentsoehapolla tai 4-klooribentsoehapolla ja vedytystä alkoholilla. Ammoniakin korvaami- nen diglyymillä yksinkertaisti ja tehosti funktionalisointia. Reaktiot suoritettiin eri alkalimetal- leilla (Li, Na tai K). Naftaleenia tai 1-tert-butyyli-4-(4-tert-butyylifenyyli)bentseeniä käytettiin elektronien solvatoinnin parantamiseksi. Elektrofiilin rakenne vaikutti funktionalisointiin siten, että aryylihalidi johti huomattavasti onnistuneempaan funktionalisointiin kuin alkoholi. Alkali- metallin ja elektroninkantajamolekyylin vaikutus vaihteli elektrofiilin mukaan. Litiumin käyttö 1-tert-butyyli-4-(4-tert-butyylifenyyli)bentseenin kanssa johti onnistuneimpaan vedytykseen. Kaliumin käyttö naftaleenin kanssa johti onnistuneimpaan arylointiin. Hiilinanoputkien liukoi- suus vaihteli elektrofiilin mukaan. Arylointi paransi selkeästi hiilinanoputkien liukoisuutta veteen, etanoliin, metanoliin ja dimetyyliformamidiin. Vedytyksen vaikutus liukoisuuteen oli vähäisempi. Asiasanat: alkalimetalli, arylointi, Birch-pelkistys, funktionalisointi, hiilinanoputki, liukoisuuden parantaminen, vedytys To Laura, Timo and Arttu. 8 Acknowledgements The present work was carried out in the research unit of Sustainable Chemistry (former Department of Chemistry) at the University of Oulu between August 2008–May 2013 and April 2014–February 2015. This thesis would not have seen the day of light without the crucial help and contribution of several wonderful and helpful persons which is why I would like to take this opportunity to show my appreciation to all the kind people around me, to only some of whom it is possible to give particular mention here. I express my deepest gratitude to my supervisor Professor Marja Lajunen for her guidance, immense support and patience throughout the research. Thank you for introducing me to the wonderful world of carbon nanotubes. I sincerely thank Dr. Janne Asikkala for mentoring this work and for his endless encouragement, advice and support during all these years. Marja and Janne, this thesis exists because of you. Thank you for believing in me. I greatly thank Tuula Selkälä and Annu Rusanen for their diligent and hard work in the laboratory and for their contribution to my research. I thank the reviewers, Professor Markku Leskelä and Professor Mika Pettersson, for reading and giving valuable comments of the manuscript of this thesis. I also thank Dr. Mark Jackson for language revision. I would like to thank Professor Ghassan Jabbour for his supervision and support during my visiting period at the Flexible Display Center at Arizona State University between August 2009 and August 2010. I also thank my colleagues and personnel at the Arizona State University. The financial support from the Fulbright-Technology Industries of Finland Grant Program, Jenny & Antti Wihuri Foundation, Tauno Tönning Foundation, Finnish Cultural Foundation and its North-Ostrobothnia and Kainuu Regional Funds and the University of Oulu Graduate School are gratefully acknowledged. I also thank the Advance Materials Doctoral Programme at the University of Oulu and The National Doctoral Programme in Nanoscience. I greatly appreciate my colleagues and personnel at the Department of Chemistry, and at the Center of Microscopy and Nanotechnology at the University of Oulu. I thank you all for the help, friendliness and smiles during these years. A special recognition is directed to Johanna Kärkkäinen and Katja Lappalainen for their