Effect of Lignin without Surface Treatment inIn SituMethylMethacrylate Miniemulsion Polymerization br

Lignin has been analyzed as reinforcement inpolymers due to its properties as a nontoxic, biorenewable, andinexpensive natural raw material. Nevertheless, the use of lignin inpolymers has proved to be very restricted since technical lignin ishighly hydrophilic and polymers are usually hydrophobic. Usually,the lignin surface is modified to enable its dispersion; however, thisprocedure is costly and time-consuming.In situpolymerizationgenerally achieves more efficient dispersion; however, the radicalscavenger capacity of lignin poses a major challenge for thistechnique. In this study, poly(methyl methacrylate) (PMMA)/lignin composites were prepared byin situminiemulsionpolymerization without changing the surface of lignin. Two kindsof technical lignins were used: Kraft lignin and lignosulfonate.Lignin was fed in the reactor in two different ways: before and after the beginning of the polymerization. Synthesis withlignosulfonate presented higher conversions, probably due to its lower radical scavenger capacity. Synthesis carried out feedinglignosulfonate after the beginning of the polymerization presented higher conversions, demonstrating excellent potential to producePMMA/lignosulfonate composites byin situpolymerization with nonmodified lignosulfonate. Lignosulfonate acted as anantioxidant, improving the polymer thermo-oxidative properties. Cryogenic electron microscopy (Cryo-EM) images showedequidistant, nonagglomerated, and spherical nanoparticles in the latices, revealing good stability