Critical Review on Sustainable Homogeneous Cellulose Modification: Why Renewability Is Not Enough

As we passed the 20th anniversary of the publication of the 12 principles of green chemistry, the sustainable modification of cellulose, being the most abundant biobased polymer, is certainly worth considering. Many researchers work on an efficient valorization of this renewable resource due to its manifold and promising application possibilities, but very often the use of non-sustainable approaches (i.e., solvents, reactants and modification approaches) only addresses the renewability aspect of cellulose, while neglecting most or all of the other principles of green chemistry. In this review, we have employed the use of E-factors together with basic toxicity information to compare between various approaches for homogeneous cellulose modification. This approach, though simple and certainly not overarching, can provide a quick and useful first sustainability assessment. Therefore, in order to achieve a truly sustainable modification of cellulose, its renewability combined with mild and efficient reaction protocols is crucial in order to obtain sustainable materials that are capable of reducing the overall negative impact of today's fossil-based polymeric materials.