(234c) Bio-Composite of PLA-b-Pdmaema Copolymer and Carboxymethyl Cellulose (CMC) With Tunable Properties

Abstract: CMC-based nanocomposites have been mainly limited by its hydrophilicity, leading to incompatible with hydrophobic polymers, such as PLA (poly lactic acid).  In this project, the quaternized and hydrophilic PDMAEMA (poly 2-dimethyl-amino ethyl methacrylate) is proposed to be a compatibilizer between hydrophilic CMC and hydrophobic PLA. Meanwhile, the introduction of soft domain (PDMAEMA micelle structure) can play a role as lubricant between stiff micro-fibrils and PLA for energy dissipation. The properties of obtained composites can be tuned by changing CMC mass ratio, copolymer mass ratio and adjusting molecular weight of PLA or PDMAEMA. Various molecular weight of PLA-b-PDMAEMA copolymers were prepared through ring opening polymerization and following ATRP (atom transfer radical polymerization) reaction. The successful synthesis of PLA-b-PDMAEMA with different molecular weight was confirmed by ¹H-NMR (nuclear magnetic resonance) and size exclusion chromatograph (SEC). Then, quaternization was conducted on PDMAEMA to obtain the cationic PLA-b-PDMAEMA copolymer, which can be dispersed into water forming micelle structure. Its hydrodynamic radius was determined by dynamic light scattering (DLS). After that, different mass ratio of cationic PLA-b-PDMAEMA and anionic CMC were mixed together through ionic interaction to form biomimetic nanocomposite.  The effects of mass ratio of CMC, the molecular weight of PDMAEMA and PLA on the physical properties and thermal properties were investigated by Instron tensile machine and thermogravimetric analysis (TGA). The morphologies of the composites were characterized by SEM (Scanning Electronic Microscopy). The properties of final composites can be tuned by the molecular weight or mass of different components and PDMAEMA is acted as good lubricant between stiff CMC and PLA.