Anatomy of a Discovery: The Twist–Bend Nematic Phase

Round 1

Reviewer 1 Report

The manuscript provides the historical flow and scientific trace of the discovery of the twist-bent nematic phase. I found the manuscript is extremely pleasant to read for knowing the development of the discovery. The manuscript provides important information on the discovery of the twist-bent nematic phase. These information shall pave the way to track for those who are interested in joining the exploration of this new discovery. The manuscript is strongly recommended to be published in Crystals.

Some suggestions are provided herein for considerations:

It is true that the recent review titled “The twist-bend phases: structure–property relationships, chirality and hydrogen-bonding” by R. Walker included details of the special phase, however, I believe that those who, especially graduate students not following closely this special phase will pick up more easily the content of the current manuscript with visual aids, i.e. figures.

The potential applications of the new discovery is only briefly mentioned in page 10. Readers will benefit significantly if more thoughts of potential applications are elaborated.

Page 8: ‘8.3nm’ to be ‘8.3 nm’

Reference format is to be unified and doubly checked.

Author Response

I note that the reviewer strongly recommends publication of the manuscript.

I have carefully considered the helpful suggestions of the referees.

Additionnal figures. - This paper is concerned with the development of the science rather than the science itself. It would be difficult to include all the relevant figures so the author has decided to rely on the original references.

Potential applications - Again these are only briefly referred to as full coverage would require a very long review. Some essential references are included, but the purpose of the article is to give a record of the research rather than the research itself.

Editorial corrections - these will be made

Reviewer 2 Report

See attached Report

Comments for author File: Comments.pdf

Author Response

The author thanks the referee for the kind remarks and the recommendation for publication.

In reply to the points made for consideration.

1. I have carefully reviewed the papers cited by B Mettout, and I believe that the paper I cite ref. 20 is the most comprehensive and deals with the group theoretical approach to the identification of new nematic phases. I agree that with the reviewer that the paper of Mettout does not specifically exclude a heliconical phase, and I have changed the text accordingly.
2. I thank the reviewer for drawing my attention to these points, and I have changed the text to emphasise the importance of the cited reference 54.

Reviewer 3 Report

This manuscript is an excellent review of experimental and theoretical work on the novel twist-bend nematic phases. It has been a pleasure to read this very well written and documented text by one of the experts on this problem. I suggest publication as it is.

Author Response

I thank the reviewer for recommending publication as is.

Reviewer 4 Report

This nicely written short review covers very peculiar recent developments in the liquid crystal science related to the discovery, identification and understanding of the new types of nematic phases. The paper is very timely: the topic attracts increasing attention, and such an account of events by one of the main contributors will not only be of historical value, but can readily guide the newcomers. I am sincerely glad that the paper presents an exemplary impartial point of view and details the achievements of several groups worldwide.

I propose to publish after the following minor technical issues are considered:

1. How appropriate is the citation of 4 papers in the abstract? Note that these references will lead nowhere in the abstract indexed by the databases, etc.
2. I was unable to comprehend the discussion of local and macroscopic biaxiality of cholesterics in lines 81-83. We are all used to the “optical” definition of biaxiality mentioned in lines 71-73. Introducing other types of biaxiality might cause confusion.
   
   
3. I am unaware of a proof that rod-like molecules “with transverse dipoles have a tendency for a net parallel alignment of molecular dipoles”, as mentioned in lines 115-116. If the author refers to ferroelectric smectics, the polarization there arises due to a more complex mechanism involving biaxiality induced by layers and tilt and critically depending on the chirality. This mechanism is not simply “magnified in smectic phases” (line 119), but is available exclusively in them.
   
   
4. The graph on page 8 shows “numbers of papers with “twist-bend nematic” in the title”, which presumably describes the result of a search performed within a certain database at a certain moment of time. The origin of the data should be specified. Also the numbers for 2020 and 2021 must be already available.

Author Response

The author thanks the reviewer for a careful consideration of the manuscript. In answer to the points raised.

1. Agreed - the reference citations will be removed from the abstract
2. I have removed the offending text. I agree that it is confusing.
3. This is an important point on which the author has researched and published extensively. The excluded volume of pairwise interacting rods and discs necessarily means that dipoles located on the rods or discs have the preferential alignments mentioned in the manuscript. The mean field theory of this is given in Dunmur and Palffy-Muhoray Mol.Phys. 76, 1015 (1992) and a review of theory and experiment is given in Dunmur, Proceedings of SPIE Vol. 4759, 196-208 (2002). These references will be added to the manuscript.
4. The reviewer is correct. But databases take time to accumulate the necessary citations, and the graph is only intended to be indicative of a sudden dramatic change in the literature. It is not quantitative since as pointed out in the text the numbers depend on the precise wording of the title.