Photothermal and magnetocaloric-stimulated shape memory and self-healing via magnetic polymeric composite with dynamic crosslinking

Magnetic Nanoparticles Improve Flow Rate and Enable Self-Healing in Covalent Adaptable Networks

Covalent adaptable networks (CANs) combine the mechanical and chemical stability of thermosets with the reprocessability of thermoplastics through the incorporation of stimuli-responsive dynamic crosslinks. To allow for processing through induction heating, we have created associative CANs that include fillers in the polymer matrix for efficient heat transfer. While the inclusion of inorganic fillers often decreases flow rate in CANs and complicates reprocessing of the material, the presence of Fe₃O₄ nanoparticles had no detrimental effect on flow behavior in a vinylogous urethane vitrimer, an observation we attribute to the catalytic nature of nanoparticles on the dynamic exchange chemistry. We employed two methods of nanoparticle incorporation: blending bare nanoparticles and crosslinking chemically modified nanoparticles. The vitrimers with covalently crosslinked nanoparticles exhibited a decreased relaxation time compared to those with blended nanoparticles. The magnetic character of the Fe₃O₄ nanoparticles enabled self-healing of the vitrimer composite materials upon exposure to an alternating electromagnetic field during induction heating.

Sustainable Engineered Design and Scalable Manufacturing of Upcycled Graphene Reinforced Polylactic Acid/Polyurethane Blend Composites Having Shape Memory Behavior

Material design in shape memory polymers (SMPs) carries significant importance in attaining high performance and adjusting the interface between additive and host polymer matrix to increase the degree of recovery. Herein, the main challenge is to enhance the interfacial interactions to provide reversibility during deformation. The present work describes a newly designed composite structure by manufacturing a high-degree biobased and thermally induced shape memory polylactic acid (PLA)/thermoplastic polyurethane (TPU) blend incorporated with graphene nanoplatelets obtained from waste tires. In this design, blending with TPU enhances flexibility, and adding GNP provides functionality in terms of mechanical and thermal properties by enhancing circularity and sustainability approaches. The present work provides a scalable compounding approach for industrial applications of GNP at high shear rates during the melt mixing of single/blend polymer matrices. By evaluating the mechanical performance of the PLA and TPU blend composite composition at a 9:1 weight percentage, the optimum GNP amount was defined as 0.5 wt%. The flexural strength of the developed composite structure was enhanced by 24% and the thermal conductivity by 15%. In addition, a 99.8% shape fixity ratio and a 99.58% recovery ratio were attained within 4 min, resulting in the spectacular enhancement of GNP attainment. This study provides an opportunity to understand the acting mechanism of upcycled GNP in improving composite formulations and to develop a new perspective on the sustainability of PLA/TPU blend composites with an increased biobased degree and shape memory behavior.