Preparation And Properties Of Thermoresponsive Shape Memory Fibers And Gels

In recent years, the study and application of shape memory polymers have been paid much attention. Especially the thermoresponsive shape memory polymers, for the wide application, the flexible control of responsive condition and the good capability of their shape reversion, have been a hot subject in the intelligent materials' fields. The technices of preparation of thermoresponsive shape memory fibers and gels are specially researched in this paper, and the shape memory fibers and gels are successfully prepared, with the different testing measures to study the fibers and gels' structures, properties of energetics and dynamics and their shape memory character.The thermoresponsive shape memory polymers can form the function of shape memory with the crystal state and the amorphous state. By crosslinking, the polymers with two states can produce the rigid segment (the amorphous state) to maintain a certain shape and the soft segment (the crystal state) to adversely solidify and intenerate, with which the polymer materials remember their own primitive shapes. It's known that the copolymers of the stearyl acrylate (SA) and the acrylic acid (AA) have a structure of crystal and amorphism, which can been spinned easily with PVA, and the shape memory fibers are produced by crosslink of the dope thread in the condensation bath. During the experiment, the monomer SA is firstly prepared , then to synthesize the copolymer P (SA-co-AA) with the refined AA. Furthermore , the well-proportioned dope are compounded with P (SA-co-AA) and PVA, and the shape memory filament are prepared immediately. With the table L₉(3)⁴, the better spinning schemes are determined. By the testing of viscosity, the important factors to the stability of dope are found. In virtue of the plot of DSC and x-Radiation, the melting temperature and structure of crystal are understood. With the analysis of DMA, to know that the highest Young's modulus of fibers is 10¹⁰Pa, which make us be sure that the fibers are provided with the property of shape memory, according to the theory of modulus to measure the character of shape memory materials. Finally, by the testing of shape memory ratio and speed, it is proved that the fibers are able to remember and revert to the original shapes.The gels equipped with the function of shape memory also need the structure of crystal and amorphism. SA has the long side chains in which easily forms a kind offilm crystal, and an innoxious n-Undecylenic Acid (HA) has the amorphous state. With a crosslinking agent N, N'-methlyenebis(acrylamide) (MBAA), a gel P(SA-co-HA) is obtained in presence of SA and HA. Though the formed gels of P(SA-co-HA) have high modulus, it is a pity that can not present the feature of shape memory for the long side chains and their strong brittleness. And then the third monomer acrylamide (AM) with short side chain is added in the gel systems to decrease brittleness and increase elasticity. The result of experiment is shown that the third monomer can well improve the gel's property, and the three-unite gels exhibit the better character of shape memory.