Preparation And Properties Of Fe₃O₄/Polylactide-based Polyurethanes Shape Memory Nanocomposites

Shape memory polymers, as a family of smart materials, have been gaining in interest and have broad application prospects in avigation, spaceflight, casing and especially in biomedical and engineering field. So far, most shape memory polymers that have been investigated are thermo-responsive shape memory polymers, which are can be mainly achieved by using heated liquid or gas as an internal stimulus. But in some special accasions such as human body which can't be heated directly, the non-contact induction heating should be used to heat polymers to their shape transition temperatures.Polylactide-based shape memory polyurethane (PLAU) is a kind of biocompatible and biodegradable shape memory polymers, which have good shape memory properties by directly heating. Fe₃O₄ nanoparticles have special surface effect so they are often modified withsurface active agents and used to fill polymers to improve their properties. In this paper, some research works on the Fe3O4/ Polylactide-based polyurethanes shape memory nanocomposites have been done.1. Preparation and properties of Fe₃O-4/PLAU121 shape memory nanocompositesFe₃O₄/PLAU121 shape memory nanocomposites with hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) as hard segments, polylactide (PLA) as soft segments, and Fe3_O4 as nanoparticles were synthesized with in-situ polymerization method. And we investigated the affect of different content Fe₃O-4 nanoparticles to the thermal property, mechanical property and shape memory property both in hot water and in an alternating magnetic field. The result shows that with the increase of Fe₃O₄ nanoparticles contents,the glass transition temperatures were constant, mechanical properties were reduced, the shape memory properties were first rased and then reduced. The composites have good shape memory property both both in hot water and in an alternating magnetic field. Their shape recovery temperature between 40℃and 55℃. Their shape fixation rates reach over 97%.Their shape recovery rates reach over 80%, and the best recovery rates reach 99.4%.The lowest shape memory temperature could be adjusted by adjusting the Fe₃O₄ nanoparticles contents.2. Preparation and properties of Fe₃O₄/PLAU shape memory nanocomposites with different ratio of soft segments and hard segments.By changing the ratio of soft segments and hard segments, we synthesized a series of Fe₃O₄/PLAU shape memory nanocomposites with different contents of Fe₃O₄ nanoparticles by in-situ polymerization method, and compared their thermal,mechanical and shape memory properties. The result shows that wih theincrease of hard segments contents, the crystallization propertities were better, the glass transition temperatures, the elongation and the shape memory time were reduced, while their tensile strength and shape memory ratio were increased. Both nanocomposites have good shape memory property both in hot water and in an alternating magnetic field. Their shape recovery temperature between 35℃and 55℃. Their shape fixation rates reach over 97%.Their shape recovery rates reach over 85%, and the best recovery rates reach96.4%.3. Preparation and properties of Fe₃O₄/MPU shape memory nanocompositesBy changing HDI to MDI, we synthesized a series of Fe₃O₄/MPU shape memory nanocomposites with different contents of Fe₃O₄ nanoparticles by in-situ polymerization method, and compared their thermal,mechanical and shape memory properties with Fe₃O₄/PLAU shape memory nanocomposites with HDI as hard segments. The result shows that the composites with MDI as hard segments has worse elongation, but higher glass transition temperatures and better shape memory properties. The nanocomposites have good shape memory property both both in hot water and in an alternating magnetic field. Their shape recovery temperature between 40℃and 55℃.Their shape fixation rates reach over 97%.Their shape recovery rates reach over 85%, and the best recovery rates reach 96.4%.