Liquid Crystal Dimers

246 Pages·2017·21.629 MB·English

by  Sandeep Kumar, Santanu Kumar Pal

Liquid Crystal Dimers
Liquid crystal (LC) dimers are formed by connecting two mesogenic cores through flexible spacers.
They are soft materials that exhibit unique functionality of combining both order and mobility at a
molecular, supramolecular and macroscopic level. Although a lot of research is happening in this area,
no exclusive book describing the basic design principles, transitional properties, device fabrication
and applications of dimeric LCs is available. At best a chapter on LC dimers can be seen in some
books. This book comprehensively covers the design principles, synthesis and thermal behaviour of
all types of LC dimers. Besides fundamental concepts, it also discusses recent advances in the field
of calamitic, discotic and bent-core dimeric mesogens.
Beginning with a chapter on the introduction of LC dimers, odd-even behaviour, basic classification
and most common mesophases in dimers, this book focuses on the usage of LC dimers in developing
new materials to study a range of interesting phenomena such as formation of biaxial nematic phase
containing rod-like and disc-like mesogenic units. It covers transitional properties, molecular field
theories of dimers, the dielectric, conductivity studies, modelling and simulation, fabrication and
testing of display and electro-optic devices of several LC dimers in detail. It also presents technological
relevance of LC dimers including dopants in LC display mixtures exhibiting faster relaxation time
and strong flexoelectric coupling.
Santanu Kumar Pal is an Associate Professor in the Department of Chemical Sciences, Indian
Institute of Science Education and Research Mohali (IISERM), India. His research interests include
design, synthesis and characterization of soft materials, LC based biosensors and nanoparticles in LCs.
Sandeep Kumar works as a Professor in Soft Condensed Matter Group at Raman Research Institute,
Bangalore, India. His areas of research include design, synthesis and applications of various liquid
crystalline materials.
13:50:01, subject to the Cambridge Core terms of use, available at
13:50:01, subject to the Cambridge Core terms of use, available at
Liquid Crystal Dimers
Santanu Kumar Pal
Sandeep Kumar
13:50:01, subject to the Cambridge Core terms of use, available at
University Printing House, Cambridge CB2 8BS, United Kingdom
One Liberty Plaza, 20th Floor, New York, NY 10006, USA
477 Williamstown Road, Port Melbourne, vic 3207, Australia
4843/24, 2nd Floor, Ansari Road, Daryaganj, Delhi – 110002, India
79 Anson Road, #06–04/06, Singapore 079906
Cambridge University Press is part of the University of Cambridge.
It furthers the University’s mission by disseminating knowledge in the pursuit of
education, learning and research at the highest international levels of excellence.
www.cambridge.org
Information on this title: www.cambridge.org/9781107157590
© Santanu Kumar Pal and Sandeep Kumar 2017
This publication is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without the written
permission of Cambridge University Press.
First published 2017
Printed in India
A catalogue record for this publication is available from the British Library
Library of Congress Cataloging-in-Publication Data
Names: Pal, Santanu Kumar, 1981- author. | Kumar, Sandeep, 1959- author.
Title: Liquid crystal dimers / Santanu Kumar Pal, Sandeep Kumar.
Description: Daryaganj, Delhi, India : Cambridge University Press, 2017. |
Includes bibliographical references and index.
Identifiers: LCCN 2016054803| ISBN 9781107157590 (hardback ; alk. paper) |
ISBN 1107157595 (hardback ; alk. paper)
Subjects: LCSH: Liquid crystals. | Dimers. | Polymer liquid crystals.
Classification: LCC QD923 .P35 2017 | DDC 621.3815/422--dc23 LC record available at
https://lccn.loc.gov/2016054803
ISBN 978-1-107-15759-0 Hardback
Additional resources for this publication at www.cambridge.org/9781107157590
Cambridge University Press has no responsibility for the persistence or accuracy
of URLs for external or third-party internet websites referred to in this publication,
and does not guarantee that any content on such websites is, or will remain,
accurate or appropriate.
13:50:01, subject to the Cambridge Core terms of use, available at
To
Dipika Pal, my wife
Arghya Pal, my son
My father, family members and the memory of my mother
Santanu Kumar Pal
To
My family members and friends
Sandeep Kumar
13:50:16, subject to the Cambridge Core terms of use, available at
13:50:16, subject to the Cambridge Core terms of use, available at
Contents
Preface ix
Acknowledgements xi
1. Introduction 1
1.1 Liquid Crystals 1
1.2 LC Dimers 2
1.3 Classification of LC Dimers 2
1.4 Calamitic Dimers 2
1.5 Discotic Dimers 5
1.6 Bent-Core Dimers 7
2. Calamitic–Calamitic LC Dimers 10
2.1 Introduction 10
2.2 Linear LC dimers 11
2.3 H-Shaped LC Dimers 26
2.4 T-Shaped LC Dimers 37
2.5 T-Shaped Chiral Dimers 46
2.6 U-Shaped LC Dimers 46
2.7 O-Shaped LC Dimers 51
3. Calamitic–Cholesteric LC Dimers 59
3.1 Introduction 59
3.2 Structure–Property Relationship of Cholesteric Dimers 60
4. Discotic LC Dimers 118
4.1 Discotic–Discotic LC Dimers 118
4.2 Discotic–Calamitic LC Dimers 169
13:49:59, subject to the Cambridge Core terms of use, available at
viii Contents
5. Bent-Core LC Dimers 185
5.1 Symmetrical Bent-Core LC Dimers 185
5.2 Nonsymmetrical Bent-Core LC Dimers 201
5.3 Unconventional Bent-Core LC Dimers 219
6. Perspectives 225
6.1 P hotoresponsive Cholesteric Dimers for Rewritable Recording Materials 225
6.2 Discotic Dimers as Dopants for LC Display (LCD) Mixtures 227
6.3 Discotic Dimers as Organic Light-Emitting Diodes (OLEDs) 228
6.4 Bent-Core Dimers for Display Devices 229
6.5 Bent-Core Dimers for Conducting Molecular Wires 229
6.6 Bent-Core Dimers for Photo-responsive Functional Systems 229
Index 233
13:49:59, subject to the Cambridge Core terms of use, available at
Acknowledgements
It would not be possible to write this book without the help and support of numerous people
around me including my teachers, family, friends and colleagues. At the end, it is a pleasant task
to express my gratitude to all those who contributed in many ways to make this book possible and
made it memorable for me.
I would like to express my sincere gratitude to Professor N. Sathyamurthy, Director at IISER
Mohali, for his support and constant encouragement during the course of this work. I would like
to thank various publishers and authors for their permission to reproduce figures from previous
publications. These figures, taken in part or adapted from other sources, are duly acknowledged
wherever they appear in the book.
I would like to thank my research scholars and post-doctoral fellows who contributed in drafting
different chapters of this book. Shilpa Setia, a research scholar at IISER Mohali, has contributed in
drafting Introduction, Cholesteric–calamitic Liquid Crystal (LC) dimers, Discotic LC dimers and the
Perspectives section of this book. Harpreet Singh, a research scholar at IISER Mohali, participated
in drafting Calamitic–calamitic LC dimers. Joydip De, a research scholar at IISER Mohali, has
contributed in drafting Calamitic LC dimers. Golam Mohiuddin, a post-doctoral fellow at IISER
Mohali, has contributed in drafting Bent-Core LC dimers. I would like to express my sincere
gratitude to my students Monika Gupta, Indu Bala, Indu Verma, Sumyra Sidiq, Supreet Kaur, Vidhika
Punjani, Gurdeep Singh and Manmohan from IISER Mohali for their interest and help throughout
the preparation of this book.
This book could not have been written without the support of my family members. I thank my
father Lakshman Chandra Pal for his constant support. I would also like to thank my wife Dipika
Pal and son Arghya Pal for their patience, encouragement, cooperation and moral support during the
course of this work.
Santanu Kumar Pal
I would like to express my sincere gratitude to my students and friends for their constant support in
my research career. This book could not have been written without the blessings of my mother and
other elder family members. I would like to thank Navita, Navdeep, Shivani, Sudeep, Swati and my
beloved granddaughter Shubhangi for their love and cooperation during the course of this work.
Sandeep Kumar
13:36:21, subject to the Cambridge Core terms of use, available at
13:36:21, subject to the Cambridge Core terms of use, available at