Casein functionalization with levulinic acid for self-crosslinkable materials

CENCHA, LUISA G.; ALLASIA, MARIANA; CÓRDOBA, CARLOS A.; NIERES, PABLO D.; VAILLARD, SANTIAGO E.; VAILLARD, VICTORIA A.; GUGLIOTTA, LUIS M.; MINARI, ROQUE J.

Ciudad Autonoma de Buenos Aires

Congreso; WCCE11 - 11th WORLD CONGRESS OF CHEMICAL ENGINEERING; 2023

Asociación Argentina de Ingenieros Químicos

Including proteins into polymeric formulations gives materials of increased biodegradability and reduced environmental hazards. However, due to proteins hydrophilicity, hybrid materials have poorer water/mechanical resistance. In this sense, proteins crosslinking is an effective way of improvement. One of the most explored crosslinking reactions in the coating field is the keto-hydrazide reaction, which involves a ketone group (KG) and a hydrazide by forming an imine [1] . This reaction occur at room temperature [2] , and it is favored in absence of water. Typically, diacetone acrylamide is used for providing KG in acrylic latexes—though is a big threat for environment and health—, and adipic acid dihydrazide (ADH) is one of the most used crosslinkers in this system.We have studied the addition of KG to casein by its reaction with N-hydroxysuccinimide (NHS) ester of biobased levulinic acid (LA), avoiding acrylamide compounds. First, LA-NHS ester was synthesized by the reaction of LA and NHS. Then, the reaction between native casein (N-Cas) and LA-NHS ester was done varying the molar ratio N-Cas: LA-NHS ester; 1:5, 1:15, and 1:30 for modified caseins (M-Cas) A, B, and C, respectively.IR spectra of M-Cas (Fig. 1a,b) shows a shoulder due to the KG added to N-Cas, and NMR spectra (Fig. 1c,d) shows chemical shifts typical of the LA. Also, elemental analysis allowed to know that 1.2, 6.1, and 8.3 mol of KG/mol of M- Cas were attached to the protein, for M-Cas A, B, and C, respectively. Finally, the ability of the M-Cas to crosslink via ADH was tested by quantifying the insoluble fraction of M-Cas films after its immersion in water. It was found that crosslinking is maximized when 0.5 mol ADH/mol KG were used (stoichiometric ratio) and that M-Cas samples allow higher crosslinking degree than N-Cas.These are promising results since they indicate that M-Cas through its reaction with the bio-based LA product represents an environmentally friendly alternative for obtaining hybrid latexes which have the potential to replace purely synthetic derivatives in many applications. The development of room-temperature self-crosslinkable hybrid acrylic/protein waterborne latexes is the next step of this research.