i think  nearly find an article about this but i can remember detail about this. if find more, i will be share it for you.

your opinion is about growing cellulose in nano scale?

No. My question is understanding auxetics at the nano level. Keep me posted.

http://www.cellworkshop.se/index_files/Page402.htm

Speaker no 12.

I am looking for intermolecular and molecular causes of auxetics in cellulose. Can all topic followers help here?

I see that you are working on nano-scale auxeticity in cellulose. Just wanted to suggest you to also read my work on macro-scale auxetic behavior of cellulose networks. I highly doubt that the mechanism operating on both scales would be the same, but there can be some relation.

I am also interested in reading about what you are/will be doing. Keep up the good work!

Article Deconstructing the auxetic behavior of paper

Verma,

Your poster and paper was one of the very first work I reviewed for my research. My work was aimed at understanding auxetics and how it may translate from the nanoscale to the macrocscale. As has been suggested in several other publications, network systems formed by fibres as in paper or cellulose microfibrils as in all cellulose composites is thought to be the source of auxetics. However, my work shows that the intrinsic chirality of glucose (from glucose chiral centres) as is evident in cellulose molecule/chain (wherein primary C-O-C bonds forms a continuum with chiral centres) makes cellulose auxetic in and out of plane, and not necessarily the network system that fibres or microfibrils form with secondary intermolecular hydrogen bonding as in all other viscoelastic materials modulating the auxesis. That is, the more intermolecular hydrogen bonds there are as in crystalline cellulose, the lower the auxesis; and the less intermolecular hydrogen bonds there are as in amorphous cellulose the higher the auxesis. The only role that network system evidently seen plays is in strain to failure: the higher the network system, the higher the strain to failure. If anything, network system rather limits auxetics.  

A keener reading of my paper 'what makes cellulose auxetic?' sheds more detailed light on the how comes.    

My second paper 'what auxetics and conformational isomerism typify cellulose?' (on which a poster is published) points unambiguously to the fact that variations in cellulose materials processing influence or alter auxetic behaviour, and the influence may be reversible or irreversible within clearly defined limits.

Are you done with your PhD? I am available to discuss more with you over skype. Cheers!

Hello Akwasi,

I will go ahead and read more on your research through the papers you recommend. Your work is very intriguing. It will help better understand the relationships between nanoscale and macroscale structure-property relationships in many auxetic systems of the present and the future, not just cellulose. I wish you luck!

I am done with my PhD (this past December) and am actively looking for a post-doctoral position in the US. I will contact you for a Skype! But once I have read through your papers. Thanks!

Yes, my papers says a lot more than is apparent to the passive reader. In the US, I would recommend Dr. Roderic Lakes and Dr. Ray H. Baughman, but in the UK I would recommend Dr. Ken Evans and Dr. Andrew Alderson. They come across as very thorough and practical. My contacts are:

Website: http://akwasi-asamoah.branded.me

Website: http://www.researchgate.net/profile/Akwasi_Asamoah/publications

Email: [email protected], [email protected]

TeL: 00447800539105, 00447946860712

Skype: kokotekokote 

This is a very interesting question!  Could the various forms of twisting of cellulose (both twisting of individual microfibrils and twisting of bundles of microfibrils) play a role? I have attached a long-ago paper of mine in which the twisting is described and discussed. We were not aware of the auxesis of cellulose at the time this paper was written.

Another ancient paper that could be relevant is attached here.  I think the fact that polymerization and crystallization of cellulose are linked and occur in an unusual environment creates the special properties of cellulose. Without cellulose, tall plants with intricate forms cannot exist.

Dear Dr. Willison,

I must confess your papers are decades old, but full of good inferences and intuition. Of particular interest to me in your papers, which I think my work adequately addresses, are the questions of 'whether cellulose from all other sources twists?'; 'what are the possible causes of twisting in cellulose? and 'whether cellulose twisting happens at the same time as cellulose laying?     

Yes, I would say cellulose from all sources twist at the molecular level from inherent chirality (4 chiral centres around which glucose twists) and intramolecular hydrogen bonding which most likely come to be at the same time as glucose units are joined (packed on) on each other in the periplasma zone. Thus, cellulose from all other sources would twist as much as possibly reentrant intermolecular hydrogen bonds, impeding lignin and pectin matrix allow, especially when there is all indication that pitch is uniform in cellulose from all native sources.          

The excitement here is that there is possibility of engineering chemically for higher auxesis.         

Dear Dr. Asamoah,

Thanks for your valuable answer.  In the case of the specimens I examined, no lignin was present to impede the behaviour of the cellulose microfibrils, but hemicelluloses and pectins would have been present and would act in much the same way (less rigid, but cross-bonded enough to impede).  The main exception is bacterial cellulose, which is surrounded by water (+ the culture medium).  But it is also a much bigger cellulose bundle, and so interaction with adjacent cellulose microfibrils would also reduce the capacity for chirality to be expressed. Regarding the auxetic behaviour of cellulosic materials, I am intrigued by this but I doubt I can add any knowledge.  I see you are not alone in trying to figure this out:

http://rbi1.gatech.edu/news/research-auxetic-behavior-fiber-cellulose-networks-shows-promise-new-paper-applications

Paper, as a material, contains a very crude cellulosic matrix, so I'm not sure it's good for experimental work.  But bacterial cellulose can be thorougly cleaned up and made into mats for experimental use.  Also, there are some unicellular algae that make extremely orderly cell walls.  These cells could be grown up and empty single-cell micro-mats extracted for experimental use ... though at the moment I cannot imagine how to use them!

While writing this, I also remembered cellulosic helicoidal arrays, in which there is an angular shift between the long axes of layers of micribrils.  The shift is always by about the same angle from one layer to the next.  We worked on quince seed slime, but considered that the angular shift was due to the matrix polysaccharide, not the cellulose itself. The "slime" is easy to obtain in October if you have access to some trees of the right species, which grow readily in England though few people grow them these days.

Sorry I can't be of more help!  I worked on this decades ago, as you have noted, and I assume that significant advances have been made since I stopped working on cellulose and turned to other interests.

If any of my papers that are not available on the Researchgate website are of interest to you I can scan them and send to you.

Best regards,

Martin

Martin,

You are very right. Though amorphous states exhibit relatively higher auxesis, hemicellulose with its numerous branchings or side chains would limited auxesis just as orthogonally lying lignin, and brittle calcareous pectin would. Yes, bacterial cellulose is pure -the reason it is often used as a control sample. Its bigger bundles and intertwinings only enhance their strain-to-failure but not their auxesis-in fact it limits auxesis as you rightly said. This is because tensile properties prove very much independent of auxesis its and associated properties. Yes, I am not alone in this quest. Dr. Verma is an acquaintance of mine whose work on paper auxetics was one of the first I had to review for my work, and with whom I look forward to collaborating in the nearest future.

Orderly and disorderly would be very important not only in further understanding auxesis but crystal structure and its dynamisms in material behaviour. As previously pointed out cellulose by itself is chiral, and yes, its surrounding matrices have every potential to shape their orientation as must be the case in quince seed slime.

You are very much on point for someone who switched interests many years ago. I guess when you got it you got it for good. Thank you very much for engaging with me on this topic. I will do well to be in touch if and when the need arises. 

Shalom,

Akwasi 

Thanks Akwasi!  I took a strong interest in cellulose at one time (long ago) and am pleased to hear about your work.  It's always good to know that the work one did in the past was not wasted.  I had never heard about the auxetic behaviour of cellulose until you posted your question here, and learning is always good for keeping an old mind from siezing up!

Best wishes,

Martin

Simply because of its internal structure shape. In fact, the mechanism of the auxetic response stems from the rich hydroxyl surface of the non-woven network structure of cellulose fibers. During compressive stages of papermaking, hydrogen bonding between fibers locks them into a crumpled microstructure that expands when stretched.