Effect of the Acyl Chain Length of Organomodified Cellulose Nanocrystals on Properties of Biobased Polyurethane Nanocomposites Foams

Abstract

This study details the development of biobased rigid polyurethane (PU) nanocomposite foams synthesized from castor oil and reinforced with cellulose nanocrystals (CN) and functionalized CN via the acylation with acetic anhydride or palmitoyl chloride, yielding acetylated (ACN) and palmitoylated (PCN) hydrophobic nanoparticles with varying chain length. FTIR spectroscopy revealed that the specific surface chemistry of the nanofiller influenced the formation of urethane and urea linkages. While foaming behavior and thermal stability remained largely unaffected, morphological analysis by SEM indicated that PCN-based foams maintained a morphology similar to that of the unloaded sample, whereas CN and ACN prompted increased cell size along the growth direction. Mechanical testing demonstrated that pristine CN optimally enhanced both specific modulus and tensile strength. Furthermore, biological assessments using MC3T3-E1 preosteblasts showed that incorporating CN and ACN significantly boosted the proliferation compared to the base material, while those with PCN exhibited intermediate cytocompatibility. These findings underscore that the architecture and performance of biobased PU foams are highly contingent upon the nanofiller's surface functionalities and carbon chain length, offering a tunable pathway for designing advanced bionanocomposites.