Preparation And Properties Of The Polyacrylate-base Shape Memory Polymers And Nanocomposites

Shape memory polymers?SMPs?are a class of smart materials capable of fixing one or many temporary shapes and recovering their permanent shape upon exposure to external stimulus.The development of shape memory polymers have drawn much attentions due to their excellent structure versatility,low manufacturing cost,easy in processing,and high elastic deformation.These unique properties of shape memory polymers let them to be used in various fields,including smart clothing manufacturing,deployable space structures,morphing aircraft,medical treatment,and many other applications.Generally,shape memory polymers consist of both switch units and net-points,where the switch units can responsive to a specific or predetermined external stimulus for controlling the shape fixity and shape recovery,and the net-points,either physical or chemical cross-links,determine the permanent shape.Based on the switch type,shape memory polymers can be subdivided into three types of T_g-type SMPs with an amorphous phase,T_m-type SMPs with a crystalline phase and Ti-type SMPs with a liquid crystalline phase.Among them,T_g-type SMPs have become increasing attractive due to their widespread applications in biomedical areas and diverse triggered ways.Here,a novel shape memory polymers have been readily prepared by free-radical copolymerization of methoxyethyl acrylate?MEA?and N,N-dimethylacrylamide?DMAA?.Similarly,the corresponding shape memory nanocomposites are synthesized by in situ polymerization of MEA and DMAA in the presence of nanoparticles.Besides,the multiple shape memory MH copolymers for self-depolyable device were successfully prepared using MEA and N-Methylol acrylamide?HAM?as comonomers;the PVA/Al₂O₃ nanocomposites have been facilely prepared and demonstrate the thermal-and water-responsive shape memory effect with high mechanical performance.The main research contents and conclusions of this thesis are as follows:?1?The superior self-healing elastomers were readily prepared by free-radical copolymerization of 2-Methoxyethyl acrylate?MEA?and N,N-dimethylacrylamide?DMAA?.The synergistic interaction between shape memory effect and the reversible unconventional hydrogen bonds lead to the excellent self-healing properties and high mechanical strength of the elastomers.By taking advantage of the two outstanding performances,we demonstrated that various novel one-dimensional,two-dimensional?2D?,and three-dimensional?3D?shape memory devices can be designed delicately on the basis of self-healing mediated assembly of the elastomers as building blocks.Similarly,a novel multiple shape memory polymers?MSMPs?are successfully prepared using a facile,inexpensive,and effective approach of multistage polymerization procedures.The resultant samples comprising of three copolymers with well-separated glass transition temperatures can change their shapes in a pre-defined way over a broad range temperature with almost full recovery of all temporary shapes.?2?Combining with the nanoparticles,such as clay,Fe₃O₄ nanoparticles,and TiO₂nanoparticles,the shape memory polymer composites with superior shape memory effect and enhanced mechanical strength were successfully prepared.With the incorporation of clays,the mechanical strength,thermal-stability,the force of shape recovery and shape memory efficiency of materials were significantly improved,and enabled that the materials could show the dual responsive performance of water-and thermal-sensitive.The application of Fe₃O₄ nanoparticles in MD polymers ensured that the material can be actuated by an externally magnetic field and improved the mechanical strength and self-healing abilities of the materials.Thus,these magnetic polymers are capable of remote controlling in shape memory process and actuating behaviors.With the addition of TiO₂nanoparticles,the physical cross-linking net-work formed within MD-T nanocomposites improved the stability of structures.The mechanical strength,glass transition temperatures,and the self-healing performance were adjustable with the changing of TiO₂ contents,and the results demonstrated the effective recovery of complicated shape and self-construction behaviors in 37°C water of materials indicated that the nanocomposites could be used in wide biomedical areas.?3?A novel PVA/Al₂O₃ nanocomposites?PVA-A?based on polyvinyl alcohol?PVA?was prepared by introducing Al₂O₃ nanoparticles as cross-linking netpoints.The results indicated that the PVA-A show superior water-and thermal-induced double responsive shape memory effect.