Modification of polysaccharides for a new generation of renewable plastics

Polysaccharides natural polymers are very abundant in nature and available in most part of heart and seas. Among polysaccharides starch is capturing attention because of its large availability in nature. Starch is an example of renewable resource suitable as raw material for plastic consumer market. Compared to plastics derived by fossil resources it has the advantages of biodegradability, biocompatibility and possible conversion to energy source such as biogas. Nowadays modified starch has not yet mechanical robustness and chemical inertness to be competitive with plastics present on the market, however the research is intense and with interesting sparks. Some research activities concern the modification of starch with natural molecules. Cinnamic acid, in particular, is characterized by anti-inflammatory properties. The studies are devoted to the synthesis of an augmented polymer by merging the biocompatibility with the therapeutic properties of the functional group. Present work study different strategies for the modification of starch (Scheme 1) in order to introduce the cinnamyl group. Moreover this group allows the photoinduced cross-linking of starch improving mechanical properties. Modification of starch is accomplished by different chemistries in order to optimize the degree of substitution (DS), defined as the average number of functional groups introduced in the anhydro glucose unit (AGU). DS is the key parameter to quantify the modification of the polymer and 1H-NMR is the chosen for this determination, preferred to titration that suffers from lack of accuracy and reproducibility.1 In the 1H-NMR analysis the dissolution of the sample and the presence of hydroxyl groups make hard the accurate DS determination.