i dont know , what kind of material you are going to prepare. My suggestion is you can do a coating with hydrophobic material in the final form of your material......not a functionalization ....jus a coating using spray drying or my sputter form...

I am not familiar with Polysaccharide material, but It seems to me that Polysaccharide is a highly hydrophilic material , to make it hydrophobic you may functionalise it with fluorocarbon CF group, hydrocarbon CH group or silane. In order to make it more hydrophobic after functionalisation, roughness is another factor that magnifies the hydrophobicty of material surfaces. However with high degree of roughness, even hydrophilic material can be turned into highly hydrophobic material. Thanks

Khedir, is there any way to obtain the above mentioned "lotus leaf" effect in a very economical way, like just adding additive to bulk material?

i dont know , what kind of material you are going to prepare. My suggestion is you can do a coating with hydrophobic material in the final form of your material......not a functionalization ....jus a coating using spray drying or my sputter form...

Venkatachalam , that is possible only in case we make simple shapes (no corners or turns) and if we don't do any further transformations with the material ...

Khlestkin, I agree with Natarajan, you may need to spray or drop cast a thin layer of hydrophobic coating to your bulk material. If the bulk material is already hydrophobic you can just use mechanical sanding, using sand papers, to physically modify it surface. Dry/wet etching also can be used to rough the surface, Another easy technique is sonicating the material, before becoming bulk, with a chemical solvent that would introduce fluorocarbons or hydrocarbons to the material using van der Waal forces, without functionalisation. I hope one of these techniques would work. Thanks

try to add small amount of citric acids/or difunction acids to crosslink polysacharride at 80C to 100C.

Spray and dry RainX. You will find the content on the bottle, a mixture of many different hydrophobic silanes that coats on different cloth, plastic, glass etc. Or use it as additive, will not work though if your polysaccharide is extremely hydrophilic. Lotus leaf effect is a combination of nanostructured surface + hydrophobic material, can work economically if you can harvest enough lotus leaf and print those structures using transfer printing on the polysaccharides (along with hydrophobic additives).

Hongjin Qiu : right, we already use the approach, thanks.

Palash Gangopadhyay: I still think lotus leaf effect may be performed in bulk in a technological way. Maybe, even by spray drying... of nano-something (fibers, tubes, etc), for example.

Does it work with citric acids? You can also try to diisocyanate. you may reduce a little water asborbance depending on the amounts but it is cytotoxic. You can add more than 20% in the materials. reaction should be very fast. Hope it is helpful.

sorry, you can NOT add more than 20% of diisocyanate in the materials

to mix your polysacharide with emulsion of mineral oil... Previously fragmentation and partially dessication your polysacharid for introduction of oil drop

Vasilij, thank you, that may help with some modifications. The drawback is decrease of mechanical properties.

I dessicate gel of cellulose by means of etanol, after permeated mineral oil, after washed from oil, and rehydratation gel of cellulose. For kontrol used polarisation microscope or red oil stained.

You don't need to make the material more hydrophobic to reduce the water/moisture uptake. By cross-linking the material, it is possible to reduce swelling of the material and hence reduce the water or water vapor uptake.

Yes, I Think Erik is right. Crosslinking with gutaraldehyde or any linker will make the material stronger and reduce swelling.

Erik, Inimfon, your suggestion is valuable. But the drawback with x-linking is that x-linked material is not thermoplastic any more.

Crosslining can work but be carefull to the choiche of the chemicals to avoid the use of toxic substances, considering your possible final use, and keep in mind that crosslinking can slow down biodegradation..in the past I had interesting results with hexamethoxymethylmelamine with citric acid as catalyst.

Patrizia, thank you so much. Indeed, we should take into account safety cosiderations when choosing additives. As far as I know, melamine derivatives are toxic. How do you treat that risk? It seems to me, you should make sure all x-linker is chemically attached to the matrix polymer and cannot be releazed by hydrolysis...

Citric acid does work, it is a bit tricky though! You have to think about kinetics for two reactions, cross-linking and hydrolysis but there are 3 publications I have written (you can find them on my profile) that you could cite!

Erik, thank you for the suggestion, I will certainly read your papers (and cite in case we use the knowledge)!

By adding oils that also could give some advantages to the system such as antimicrobial properties.

See this article: Article: Functional properties of Sodium and Calcium Caseinate antimicrobial active films

M. P. Arrieta, M.A. Peltzer, J. López, M.C. Garrigós, A.J.M. Valente, A. Jiménez

Dear Vadim apologise my late answering back. When we used exa methoxy methylmelamine it was first for production of wood adhesive then for crosslinking PVA and starch. We expect that the melamine was completely reacted but we did not specific realsing tests, indeed these should be addressed if targeting for example food packaging applications or similar.

I know that cross-linking will result in the material going towards beeing a thermoset, but here there are some important questions one needs to ask.How neccesary is the thermoplastic properties? Or more exactly, when does the material have to behave like a thermoplast? By doing a "smart" cross-linking like polysacharides cross-linked with citric acid (or other polycarboxylic acids), it is actually possible to get a bit of both worlds. Thermoplastic when forming, non-swelling like a thermoset and thermoplastic in the sence of remoldability would be the best combination of course. By getting the cross-linking reaction to occur in solid state after the final material is formed and having "easily broken" cross-links this is possible. Also, the amount of cross-links is important, few cross-links and it is more thermoplastic and more it goes towards more thermoset.