Talk:Liquid crystal/Archive 1

Archive 1

GA Re-Review and In-line citations

Members of the Wikipedia:WikiProject Good articles are in the process of doing a re-review of current Good Article listings to ensure compliance with the standards of the Good Article Criteria. (Discussion of the changes and re-review can be found here). A significant change to the GA criteria is the mandatory use of some sort of in-line citation (In accordance to WP:CITE) to be used in order for an article to pass the verification and reference criteria. Currently this article does not include in-line citations. It is recommended that the article's editors take a look at the inclusion of in-line citations as well as how the article stacks up against the rest of the Good Article criteria. GA reviewers will give you at least a week's time from the date of this notice to work on the in-line citations before doing a full re-review and deciding if the article still merits being considered a Good Article or would need to be de-listed. If you have any questions, please don't hesitate to contact us on the Good Article project talk page or you may contact me personally. On behalf of the Good Articles Project, I want to thank you for all the time and effort that you have put into working on this article and improving the overall quality of the Wikipedia project. Agne 00:16, 26 September 2006 (UTC)

As part of GA quality control, I'm going to have to delist this fro m GA. Though it does have some references, it's not sufficient for the updated good article criteria. I'll pass it on to the unreferenced good article task force. --jwanders^Talk 00:35, 15 February 2008 (UTC)

older entries

I thought that the liquid crystal in an LCD turned into a half-wave plate in an electric field, and the LCD has a polarizer in it. -phma

Any info on what materials go into liquid crystals?

139.222.112.200 (talk) 11:08, 13 April 2008 (UTC)The name liquid crystals implies that we deal with a liquid state which has various degrees of order (or freedom), namely, three rotational and three translational. Isotropic liquids have none of these restrictions, and crystals have all of them, i. e. they have no freedom to rotate around any axis and to migrate in any direction. So, glasses must be a part of liquid crystals due to their ability eventualy to crystalise (to find the energy minimum as time passes), of cause, if they possess only identical molecules with the rigid core. Polymers are not liquid crystals cause one molecule do not possess any rigid part wich could have only these 6 degrees of freedom, instead it possess much more of them. However if such group is present then we can treat them as liquid crystals. And it doesn't matter whether we have only one phase (mesogen in vacuume) or more than one (lyotropic liquid crystals), however, in this case, only one of them is treated as liquid crystals mesogen139.222.112.200 (talk) 11:08, 13 April 2008 (UTC)

seperate nematic section from article?

I think the section on the nematic phase of liquid crystal should be made it's own article. I'm not sure about the rules here, is a consensus needed? Or should a special box be put on top? If a more knowledgeable Wikipedian could help, much appreciated. --72.51.84.91 (talk) 20:13, 10 May 2008 (UTC)

Bogosity

"In 1888, Austrian botanical physiologist Friedrich Reinitzer (1858–1927), working at the Charles University of Prague, was extracting cholesterol from carrots to establish its chemical formula." Freddy would have had a tough time, because carrots, like most vegetables, don't contain cholesterol. Plant sterols (phytosterols) yes, but not cholesterol. Funnily, a web search revealed 100's of other web sites that seem to have copied this fact verbatim from this source, adding credence to the motto "Trust, but verify". Sasata (talk) 04:08, 26 April 2009 (UTC)

Thanks ! I knew about this web phenomenon, but overlooked it in this article.NIMSoffice (talk) 05:52, 26 April 2009 (UTC)

Lasing effect of chirality

I removed the new section below from the article, and put it here for discussion. The editor who added it appears to have a conflict of interest, and I'm not sure this material is sufficiently relevant to be included in this article. If it is sufficiently relevant, someone else should put the text back in the article, after editing it as necessary.--Srleffler (talk) 22:15, 18 June 2009 (UTC)

In 1997, Azriel Genack and Victor Kopp, now of Chiral Photonics, discovered that lasing in cholesteric liquid crystal (CLC) films is a result of their unique self-assembling helical (chiral) microstructure.. Drs. Genack and Kopp decided to pursue the possibility that CLCs, with their natural chiral structure, could provide a platform for a versatile new class of photonic devices. Chiral Photonics has abstracted the self-assembled structure of the organic CLCs to produce analogous optical devices using tiny lengths of inorganic, twisted fiber. Designing novel microforming towers, the company is now able to fabricate devices based on fibers that can be twisted through more than 25,000 revolutions over a one-inch length.

After checking the provided reference and its impact, I found the mentioned achievement worth including into the article (as I did). That said, the text after the reference does appear as commercial advertisement, so as other edits by User:Igfmnbo. I shall look into that and encourage others to do so. Materialscientist (talk) 01:18, 19 June 2009 (UTC)

Toxicity of liquid crystal materials

Does someone have the knowledge to add a section to the main page regarding the toxicity of various liquid crystal materials? It's not my area of expertise, but I know that extensive literature exists on the subject. DFH 10:55, 17 August 2006 (UTC)

Personally I'm not sure this is relevant as it is a bit of PC distraction- should we put various disclaimers here too? If the membership into the topic class somehow is nearly synonymuous with some physiological result that may be interesting but otherwise probably not real relevant. Luckily, a good external link may be this,

[ http://www.ncbi.nlm.nih.gov/sites/entrez?db=pccompound&term=liquid+crystal PubMed Compound to LC ]

which gives as much raw toxicology data as you could want but also includes physical properties and it is quickly updated.

Nerdseeksblonde (talk) 12:54, 1 July 2009 (UTC)

Definition of order parameter

the article now states that:

$S=\langle P_{2}(\cos \theta )\rangle =\left\langle {\frac {3\cos ^{2}\theta -1}{2}}\right\rangle$

where $\theta$ is the angle between the LC molecular axis and the local director (which is the 'preferred direction' in a volume element of a liquid crystal sample, also representing its local optical axis). This definition is convenient, since for a completely random and isotropic sample, S=0

i am not quite familiar with the implied average and dont see how this results in S=0 for an isotropic sample maybe this resolves as a missunderstanding, but anyways it would improve this article if this gets cleared up

as far as i get it average implies something like this: $S=\left\langle {\frac {3\cos ^{2}\theta -1}{2}}\right\rangle ={\frac {\int _{-\pi /2}^{\pi /2}n(\theta ){\frac {3\cos ^{2}\theta -1}{2}}\operatorname {d} \theta }{\int _{-\pi /2}^{\pi /2}n(\theta )\operatorname {d} \theta }}$ where $\theta$ ranges from $-\pi /2$ to $\pi /2$ since the prefered direction with which the angle is compared has no polarity

and the most isotropic arangement of crystals should correspond to n(theta)= constant where every possible angle has the same occupation number but pluging n =const in yields: $S={\frac {n}{n\pi }}\int _{-\pi /2}^{\pi /2}{\frac {3\cos ^{2}\theta -1}{2}}\operatorname {d} \theta \neq 0$

can somebody resolve this, or at least state in the article which averageing function is used thx--77.22.250.139 (talk) 23:39, 20 August 2009 (UTC)

OK, let me try to resolve this issue. For this think of the nematic director as a unit vector whose tail is at the origin and head on a unit sphere. Then in the case of an isotropic sample, the head of the nematic director is isotropically distributed on the sphere. If you want to find the average, integration should be taken over surface of the sphere which brings in $dV=\sin \theta d\theta d\phi$ instead of just $dV=d\theta$. If you try with this, it will indeed be zero for an isotropic sample. Cheers, Zitterbewegung ^Talk 04:42, 21 August 2009 (UTC)

To clarify, you need to average over solid angle $d\Omega =\sin \theta d\theta d\phi$, not just θ. Integrals over $d\phi$ give 2π. Others are
$S\sim {\frac {\int _{0}^{\pi /2}(3\cos ^{2}\theta -1)sin\theta \operatorname {d} \theta }{\int _{0}^{\pi /2}sin\theta \operatorname {d} \theta }}\sim \int _{0}^{1}(3x^{2}-1)\operatorname {d} x=0$ Materialscientist (talk) 05:05, 21 August 2009 (UTC)

ofcourse.. *looking stupid*, thx --77.22.250.139 (talk) 10:21, 23 August 2009 (UTC)

Removed New Section

I recently added a new section to the liquid crystal wiki on topological defects and it was recently removed by Materialscientist with an explanation in the edit summary that didn't make much sense to me. I was hoping that Materialscientist could provide a better explanation for why it shouldn't be included below and for others to talk about whether it should be included or not. Below is a copy of the section proposed to be added.

==Topological Defects==

===Wedge Disclination===

Disclinations that are confined to a plane are commonly referred to as wedge disclinations. Under this arrangement the Frank free energy density using the one-constant approximation simplifies to:

$F_{d}={\frac {1}{2}}K(\nabla \theta )^{2}$

Here $\mathbf {\hat {n}}$ is the director and it makes an angle $\theta (x,y)$ with respect to the x-axis in the xy plane. Minimizing the Frank free energy leads to the following equilibrium condition:

$\nabla ^{2}\theta =0$

At the noyau solutions are commonly found in which $\theta (\phi )$, where $\phi$ is the azimuthal angle. For this condition the solution to Laplace's equation becomes:

$\theta =s\phi +{\text{const.}}=s\arctan \left({\frac {y}{x}}\right)+{\text{const.}}$

The constant $s$ is called the strength of the disclination and describes the molecular arrangement of the liquid crystal molecules around the defect. If a rotation of $2\pi$ is made around a disclination then the director's angle will change by $\vartriangle \theta =2\pi s$. Since the director must return to the same position $\vartriangle \theta =n\pi$, where n is the set of integers, and therefor the strength s is restricted to the set of integers and half integers. Although this condition allows for an infinite number of strengths, in practice only four different types of noyaux are commonly observed including $s=-1,-{\frac {1}{2}},{\frac {1}{2}},1$. Higher strength defects are sometimes found in lyotropic liquid crystals.

I was in the middle of editing it when it was removed and so the references haven't been added yet. I was also planning on adding some more on how strengths are measured, how the brushes seen in disclinations are predicted, some of the other techniques used for imaging defects, some of the electrostatic similarities found in liquid crystals, and some of the recent research. I think it should be added since the topic of topological defects in liquid crystals is of pivotal importance and currently the subject of active research. A lot of the current research focuses on colloidal suspensions in liquid crystals and the imaging and interaction manifested by the topological defects they create. In fact the topic of topological defects in liquid crystals makes up several whole chapters in any decent liquid crystal text. Even the famous text by DeGennes gives three whole chapters to the subject and the book only has ten chapters. In addition the nature of topological defects created by colloids is of critical importance in the subject of nematodynamics. Its rather hard to grasp the more complicated subject of nematodynamics without first understanding the very basic introductory material explained in the proposed section on the nature of defects in liquid crystals. For these reasons I believe the section should be included. If its the main focus of an intro liquid crystal text it should be discussed in any decent encyclopedia article. This was why I was confused when Materialscientist stated in the edit summary that its "absolutely unspecific to LC".Chhe (talk) 02:20, 2 October 2009 (UTC)

You are more than welcome to contribute, and I would be glad to help whenever necessary. However, consider this: I hope you admit that the section above is much more general than liquid crystals. It is also rather technical, contains much unexplained jargon (simply put, most WP readers will not understand it) and incomplete. IMO, it disbalanced this good article, which was the reason for my removal. My advice is to edit this content in User:Chhe/Sandbox and then move it to the wikipedia mainspace, either in a separate article or, preferably, merging it with Distortion free energy density. Regards. Materialscientist (talk) 03:29, 2 October 2009 (UTC)

Are you serious. Technical? The proposed section is not even remotely technical. I'm extremely surprised to even hear you say that. Its basic stuff that would be covered in an introductory liquid crystal text. As far as the proposed section being too general, I don't understand what your trying to suggest by this. Obviously topological defects come up in many fields of research, but the above section specifically discusses there properties in liquid crystals, not any other materials. As an example, one wouldn't exclude from the article Water information about its crystallization properties because other solvents freeze too. Granted you wouldn't want to talk about the crystallization properties of Acetone in an article about Water, but you would want to talk specifically about Water's characteristics. The same goes for liquid crystals. Just because superfluids and superconductors manifest topological defects doesn't give any reason to exclude its discussion in liquid crystals too. You would just want to restrict the discussion about topological defects specific to those properties found in liquid crystals. I don't see how the proposed section violates that. As far as your suggestion to put it into a new article of its own, that suggestion doesn't make sense. When a person searches for liquid crystals in the wiki search box they expect an article that talks about all of the properties of the subject in question. Not a separate article for each of the literally hundreds of different properties on the given material. That is what sections are for. Your other suggestion to put it in Frank free energy density is silly too since its not in keeping with wikipedia convention. The free energy describes tons and tons and tons of different properties intrinsic to liquid crystals. Topological defects just happen to be one of them. You don't see the article on Maxwell's equations talking about how these set of equations can explain how hall sensors work. It note doubt could, but Maxwell's equations explain literally thousands of different things and singling out one from the many is pointless. Obviously you explain electromagnetism behind Hall effect sensors at the Hall effect sensor page and you stick to talking specifically about the properties of Maxwell's equations at that corresponding page. The same should go for the distortion free energy. I don't understand why you think the one topic of topological defects should be singled out there. Obviously the liquid crystal article is a more obvious place for it to be housed at.Chhe (talk) 20:23, 25 November 2009 (UTC)

Consider this: (i) you boil in this topic and consider any equation self evident. Be sure most WP readers do not. This is not to say science should be oversimplified, but it should be made accessible to as many people as possible. (ii) Length of WP articles is limited. Thus explanation should get to the point ASAP. I don't see yet how you can do that from the above equations. Adding text which says "listen up. The process which you observed in the picture above is codified in MathPhys as this and that" :-D doesn't always help. Sure one can expand and demonstrate the consequences of those equations, but IMO it would be easier to do in a separate article oriented at a prepared reader. Regards. Materialscientist (talk) 00:54, 26 November 2009 (UTC)

I'm sorry to say, but your response is nonsensical. You seem to want everything to be explainable to the layman. This is simply not possible. The subject of liquid crystals is an extremely complicated subject matter. It can't be explained in a dumbed down way any more than quantum field theory can. If a reader should come upon a section they don't understand they can simply skip the section or learn more about the equations quoted by following the links. Thats the whole point of having sections. As far as your assertion that the proposed section considers "any equation self evident" this is just factually wrong. The only equation used is the frank free energy which is mentioned (insufficiently I might add) in the article. Everything else follows from this equation using basic mathematics and is clearly explained. Your second contention that wikipedia article's length is restricted is again just factually incorrect. The lengths of the articles can be virtually unlimited due to the multitiered server environment. Thats what makes wikipedia so great. Everything is organized in the sections table of contents and a reader can quickly skip to a particular section if they have no desire to learn about the other material. I have to say I think your wish not to have a section that talks about topological defects is very much akin to not having a discussion of the Meissner effect in a superconducting article or not talking about the band structure in a semiconductor article. Its rather nutty. And so I'm adding an RFC to this section of the discussion page. Its my opinion that having a section on topological defects is just as integral for a wiki article on liquid crystals.Chhe (talk) 02:55, 26 November 2009 (UTC)

Please consult WP:LENGTH and consider the general practice that articles exceeding 100-150k are routinely split up into several articles (I believe this is what you call "multitiered server environment" - there is no alternative for a mainframe WP article). This is an abstract argument yet, as this article is only 50k long. I have nothing against a subsection on topological defects in LCs, and I more than appreciate your will to improve WP and this article. I only want the text and its tone be in harmony with the existing material. In essence, we spend too much time on discussion rather than actual writing - the removed text is incomplete. Materialscientist (talk) 03:16, 26 November 2009 (UTC)

I was actually writing it when you removed it, which was why I stopped to discuss it with you.Chhe (talk) 03:19, 26 November 2009 (UTC)

Good point. When planing a major editing of WP:GA or WP:FA articles, it is a good practice to finalize the part to be inserted at a talk page or a personal sandbox first. Materialscientist (talk) 03:30, 26 November 2009 (UTC)

Playstation - yes, but no Schlieren texture

The pattern shown in the image right below the Schlieren texture is not a Schlieren texture, since the size of the features of that texture are in the sub-mm range. The photo of the Playstation-display shows stress-induced (photoelasticity) birefringence of the cover of the display. The photo should be removed since the explanation of the text is wrong.

See e.g.: Matthias Lehmann, Jens Seltmann: Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules, Figure 5a.

panjasan (talk) 19:57, 6 February 2011 (UTC)panjasan

Agree and removed. (well, it showed not necessarily photoelasticity, but at least not Schlieren and not clear what) Materialscientist (talk) 23:52, 6 February 2011 (UTC)

RFC Topological Defects

I'm creating an RFC to debate whether a new section involving topological defects should be included in the article. In the section above titled "Removed New Section" I proposed an addition that is shown above, but wasn't able to come to an agreement. Should it be included or shouldn't it? Should a section on topological defects be included or shouldn't it?Chhe (talk) 04:27, 26 November 2009 (UTC)

Sure, in principle, but that one needs work. I think this might get better input as a post to WikiProject Physics. - 2/0 (cont.) 05:31, 15 December 2009 (UTC)

Not as is: it is too technical for the average Wikipedia reader. A separate well written article could be linked to. Gerardw (talk) 21:29, 20 December 2009 (UTC) what is the liquid crystal devices? xD — Preceding unsigned comment added by 188.54.225.84 (talk) 18:35, 8 October 2012 (UTC)

Is it Fréedericksz transition or Fredericks transition?

I changed the spelling to Fréedericksz, but I'm not 100% sure if this is correct so I changed it back until someone weighs in. Most books I encountered use Fréedericksz, but some use Fredericks such as de Gennes. The original publication spells the authors name as Fréedericksz. Which is correct?Chhe (talk) 01:48, 11 September 2013 (UTC)

LC->Liquid-crystal

Please replace most uses of LC with liquid-crystal, if someone copies-paste or lands in a random sentence of the article they won't be able to understand what LC is. Cogiati (talk) 20:22, 23 October 2013 (UTC)

Liquid Crystal Water

I'm currently drafting up an article for liquid crystal water, does anyone have a good place to integrate a reference such a page aside from the "see also" section? I feel like it would be very pertinent. HailTheWarpCore (talk) 23:46, 9 April 2015 (UTC)

I'm concerned that "liquid crystal water" (at least as you've described it in your draft) isn't really a thing that exists or is recognized by scientists, save for a very, very tiny minority out on the very distant fringe. It (and related theories) have drawn a modest amount of attention in recent years largely because a small subset of alternative "medicine" promoters (i.e. cranks and charlatans) have seized upon this and other concepts as opportunities to create or bolster "scientific" support for their miracle cure-alls.

I'm not persuaded that the topic is sufficiently noteworthy to warrant a Wikipedia article at all, let alone to be linked from this article. TenOfAllTrades(talk) 01:11, 10 April 2015 (UTC)

I understand your trepidation, but the fringe nature of it is precisely why I think it merits an article. Everything that I've written in the article is sourced to peer-reviewed journals, or books by well established scientists. I want only to make a source for proper factual information regarding the topic as the phenomenon certainly exists, but there is presently no wiki page for it. I've not cited any "cranks" or "charlatans", have made no claims of my own, have not mentioned medical or biological application, and even plan to add a "controversy" section to address the magical claims specifically.HailTheWarpCore (talk) 23:54, 19 April 2015 (UTC)

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Brynmor Jones?

How does this get to be a "good article" without once mentioning Brynmor Jones? Andy Dingley (talk) 10:33, 31 August 2017 (UTC)

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The existence of a true nematic phase in the case of the smectite clays family

The article states:

The existence of a true nematic phase in the case of the smectite clays family was raised by Langmuir in 1938,[42] but remained open for a very long time and was only solved recently.

(1) This is ambiguous. The phrase "only solved recently" fails to answer the question: Is there a true nematic phase in the case of the smectite clays family, or not?

(2) "Recently" should be changed to an approximate calendar date.

The statement should say something like "was only proved in 2015" (or "disproved", if that's the case).

Karl gregory jones (talk) 12:34, 29 January 2019 (UTC)