An Environmentally-Friendly Approach To Synthesize Vinyl-Based Oligocelluloses

Cellulose is the most common biopolymer, and we use it each day for many products such as paper, composite, and even building materials. Scientifically, it is considered to be a linear polymer, consisting of hundreds to thousands of glucosyl units which are linked via the glycosidic bond.

There are cellulose oligomers commonly referred to as oligocelluloses with fewer glucosyl units which are synthesized in an environmentally-friendly way. They have been of much interest in the past decade considering they have properties such as those of natural cellulose. Also, they have the potential to be used for non-digestible dietary fiber products.

Usually, two methods have been used in the synthesis of oligocelluloses. One of them has been the degradation of the natural cellulose. This method is quicker and easier since only cheap acidic reagents are required. The disadvantage of this method is that it has less control when it comes to the chemical and crystalline structure of the oligocellulose formed. The second one is through a synthetic pathway with the help of enzymatic reaction. This method has good control of the structures of the products obtained in the one-step polymerization. Besides, the enzymes are not toxic compounds and can be easily isolated from sustainable resources; thus, the method is environmentally-friendly.

The overall reaction of this method can be considered an environmentally-friendly way to manufacture vinyl-based oligocelluloses. This is a result of the starting materials, the catalysts and the solvents used in the reaction, which are environmentally-friendly. The starting materials are derived from renewable feedstocks where enzymes are used as a biocatalyst. The solvent used is a water-based buffer solution. Moreover, vinyl groups which are available in the reduction end of the oligocelluloses provide a higher reactivity and versatility as far as polymerization with different, smaller results to polymers with novel physical and chemical properties.

Different methods are used in the environmentally-friendly pathway of detecting the quality of the vinyl-based oligocellulose synthesized. The first one is Thin Layer Chromatography (TLC), which is carried out on an aluminum sheet of silica gel with the help of an eluent. There is a synthesis of five types of vinyl-based oligocelluloses from the given vinyl glucosides. Besides, there is also the synthesis of the native oligocellulose with the help of the natural substrate with the aim of comparing the characteristics of the synthesized vinyl-based oligocellulose with the natural ones. The synthesis of the vinyl-based oligocelluloses via the environmental pathways is followed by the TLC using eluent mixtures of the n-butanol/isopropanol/water. Optimal reaction condition has been achieved when the concentration of the glucosyl donor is twenty times the concentration of the glycosyl acceptor.

It should, therefore, be obvious that the environmental vinyl-based oligocellulose follows the cellulose II polymorph structure and is thermodynamically stable. The vinyl-based oligocelluloses are as a result of strong intermolecular hydrogen bonds through the enzymatic synthesis. Though as a way of safeguarding the environment, the solution of the oligocellulose in solution could be improved with the help of ionic liquids.

These findings are described in the article entitled Environmentally friendly pathways towards the synthesis of vinyl-based oligocelluloses, recently published in the journal Carbohydrate Polymers. This work was conducted by Azis Adharis, Dejan M. Petrović, Ibrahim Özdamar, Albert J.J. Woortman, and Katja Loos from the University of Groningen.