Different commercial applications of unmodified hemicelluloses (in particular xylans) in healthcare, cosmetics, food and other industries already exist. Controlling the depolymerisation of hemicelluloses into oligomers and/or functionalizing them with specific properties could even widen the range of future uses of these biopolymers. One interesting way of exploiting its potential is by coupling these highly hydrophilic materials with hydrophobic fatty acids derivatives to create new totally bio-based amphiphilic conjugates via click chemistry approaches. In tnis work, beech xylans were first fully characterized before their acidic hydrolysis. Mild hydrolysis conditions were optimized in order to obtain well-defined oligomeric xylooligosaccharides (XOS) chains of about six xylose units that have only one methylglucuronic acid unit positioned at the non- reductive chain end. Two "click chemistry" approaches were used to couple XOS and two model fatty acids (methyl ricinoleate - MeRic and methyl oleate - MeOl): azide-alkyne (AA) or thiol-ene (TE) couplings. Either the aldehyde group already present at the reductive chain end of XOS or new aldehyde groups formed by periodate oxidation were used to introduce an azide (XOS-N3) or an allyl (XOS-All) group by reductive amination. Fatty acids were functionalized by transesterification with 3-butyn-1-ol to introduce an alkyne function (Bu-OI or Bu-Ric) or by UV-assisted thiol-ene coupling to introduce a SH function (SH-Ol or SH-Ric). Both AA and TE couplings were then tested. The first one was the coupling between SH-Ol or SH-Ric and XOS-All. Although total conversion could not be reached, this pathway seems very promising as it is easy to be carried out and could be easily optimized. The second coupling between the Bu-Ol and Bu-Ric and XOS-N3 was also achieved. Prelimiinary physico-chemical characterization of the amphiphilic conjugates was performed and demonstrated the potential for numerous applications such as surfactants, active substance delivery applications, wood protection, etc.

Hybrid materials from hemicelluloses oligomers and fatty acids

251st National Meeting (2016)

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