Preparation And Properties Of Shape Memory Poly (ε-caprolactone)Polyurethane Nanocomposites

Shape memory polymer (SMP), as a family of Intelligent material, has broad application prospects in textile, biomedical and spaceflight field. Poly (s-caprolactone)-polyurethane (CLPU) is a type of SMP which has good biocompatibility. CLPU has a high degree of micro-phase separation so that it has good shape memory properties while being induced by direct heating. However, it is not suitable enough to realize the shape memory effect (SME) by direct heating in some conditions such as human body. Thus, inductive heating will be a solution. Magnetic field triggering and voltage triggering SME are two convenient ways. The SME may be realized by heating from inside particles of SMP nanocomposites under specific conditions. Base on the above backgrounds, some research works have been done as follows:1. Synthesis and properties of iron(Ⅱ,Ⅲ) oxide/CLPU nanocompositesA series of iron(Ⅱ, Ⅲ)oxide (Fe3O4)/CLPU nanocomposites were prepared by in situ polymerization method. The thermal properties, mechanical properties, magnetic properties and shape memory properties were systematically investigated. The results showed that with the increase content of Fe3O4nanoparticles, the melting temperature (Tm) and crystallinity (Xm) increased, the melting enthalpy(△Hm) decreased, mechanical properties decreased, and magnetic properties increased. For the presence of Fe3O4nanoparticles, the temperature that Fe3O4/CLPU nanocomposites started to recover their original shape was raised to40℃which indicated that these nanocomposites might be used as biomedical implant materials. The shape recovery temperature of Fe3O4/CLPU nanocomposites was45℃. Fe3O4/CLPU nanocomposites showed good shape memory properties in both45℃hot water and alternating magnetic fields. The shape recovery rate of nanocomposites was above90%and the highest reached97%(f=45kHz, H=35.7kA·m-1), and the shape recovery time was less in60s and the shortest was18s (45℃).2. Synthesis and properties of Fe3O4/multi-walled carbon nanotube-crosslinked CLPU nanocompositesA series of Fe3O4/multi-walled carbon nanotube-crosslinked (MWCNT)-crosslinked CLPU nanocomposites were synthesized by in situ polymerization method. MWCNTs were used as crosslinking agents The thermal properties, mechanical properties and shape memory properties were systematically investigated. Because the MWCNTs were treated by nitric acid, there were chemical bonds between MWCNTs and polymer matrix, and a network structure was formed. With the increase content of MWCNTs, Tm,△Hm and Xm decreased, and the mechnical properties increased first and then decreased. The shape recovery temperature was45℃. The shape recovery properties of Fe3O4/MWCNT-crosslinked CLPU nanocomposites showed good shape memory properties in both45℃hot water and an alternating magnetic field. The shape recovery rate of nanocomposites was above92%and the highest reached97%(f=45kHz, H=29.7kA·m-1), and the shape recovery time of nanocomposites was less in38s and the shortest was13s (45℃).3. Synthesis and properties of iron powder/MWCNT-crosslinked CLPU functionally gradient nanocompositesA series of iron (Fe) powder/MWCNT-crosslinked CLPU functionally gradient nanocomposites were synthesized by in situ polymerization method. Fe powders were deposited on one side of nanocomposites during the sample formation resulting in a gradient distubtion in the nanocomposites. The thermal properties, mechanical properties, magnetic properties and shape memory properties were systematically investigated. Nanocomposites showed good mechanical properties. Due to the good magnetic properties and high electrical conductivities, such a kind of nanocomposties could gain the original shape while being induced by temperature heating, Joule heating and magnetic field heating. The shape memory properties were affected by the location of the layer of Fe powders in folded samples. Folded samples which the layer of Fe powders located inside of them showed better shape memory properties. The shape recovery temperature was45℃. The shape recovery rate was above87%and the highest reached97%(f=45kHz, H=46.5kA·m-1, the layer of Fe powders inside), and the shape recovery time of nanocomposites was less in2min and the shortest was8s (45℃, the layer of Fe powders inside).