Synthesis and Structure Properties of Gradient-Modulus Star Copolymers

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The aim of this project is to study the novel synthesis and structural ordering of gradient-modulus star copolymers. The results obtained are as follows.1. Gradient-modulus star copolymers were prepared by crosslinking poly[isoprene(I)-block-I/styrene(S)-block-S] tapered block monoanions with divinylbenzene(DVB) in benzene. The dilute-solution properties of these stars were characterized by static and dynamic light scattering (SLS and DLS). The ratio of radius of gyration over the Stokes radius (R_G/R_H) in benzene decreased gradually and approached unity as the arm number became large. Even gradient-modulus stars with multiarms behave not as near hard spheres but as soft spheres which were penetrable near the edge in a good solvent. It was found from the results of DLS that gradient-modulus stars formed unimolecular micelles even in selective solvent.2. Structural orderings of stars were investigated through the small-angle X-ray scattering in benzene and through the transmission electron microscopy (TEM) measurements. All of the star samples formed a lattice with a body-centered-cubic (BCC) structure near the overlap threshold (C'). In the star specimens with arm number n<67, this structure changed to the lamellae in the bulk film, in the star specimen with n=289, it showed an interesting tendency for the spherical structure to be maintained with the dimension of the unimolecular micelle even in the bulk film.3. Gradient-modulus stars formed a lattice with BCC structure near the C'. After these stars formed a cubic lattice in methyl methacrylate (MMA) monomer, the polymeric superstructures were constructed by locking permanently ordered lattice in a solid matrix by means of free-radical polymerization of MMA monomer. This technique is one of the best methods fir creating nanoscopic polymeric superstructures.