| Polymer composites with co-continuous morphology on sub-micrometer scale have very wide applications in various areas because of the special structure and performance. In the past decades, the preparation of such composites is attracting wider and wider research interests. Now, there are several ways to prepare the co-continuous polymer composites on sub-micrometer scale. Among them, melt processing of two immiscible polymers is the simpliest one. In this method, one needs to add copolymers as compatibilizers to reduce the domain size down to sub-micrometer scale. However, the addition of the copolymers will increase the onset compositon of the minor phase to form the co-continuous structure and narrow the co-continuous interval.In this thesis, we proposed a new way to overcome the above paradox under the inspirations from comparing with the small molecular water-oil-emulsifier systems. To introduce asymmetric into the chain structure of the copolymers used as compatibilizers could reduce the size of the minor phase domains, lower the onset of the co-continuous structure, and broaden the co-continuous interval simultaneously. The easy, effective, economic, and reliable method to prepare the polymer composites with co-continuous morphology on sub-micrometer scale could give great convenience for the developments of advanced materials.The following aspects were studied:(1) PS (polystyrene)/PMMA (poly(methyl methacrylate)) were chosen as the model blend system. A series of PS-PMMA block copolymers with various asymmetries were synthesized via RAFT polymerization. The influence of the asymmetry of the block copolymers on the morpgology tuning effects in the blends was systematically studied. Unusual phenomenon was observed that as long as the larger block of the aysmmetic copolymer was located in the minor phase side of the interface. the addition of the asymmetric block copolymer could tune the polymer blends from droplet-in-matix structure to co-continuous structure. Because of the balance between the bending energy of the copolymer layer and the interfacial energy of the two homopolymers on the interface, the breakup of the minor phase fibers would be supressed during melt mixing. As a result of the packing of the minor phase fibers, co-continuous structure was formed. Accordingly, three aspects were required in preparing co-continous structured blends through this method:firstly, the compatibilizer should be asymmetric; secondly, the spontaneous curvature of the compatibilizer should curve towards the major phase; finally, the density of compatibilizer on the interface should be high enough.(2) The influence of the asymmetry of the block copolymers used as compatibilizers on the co-continuous interval of the blends was investigated. The asymmetric compatibilizers could not only broaden the co-continuous interval of the blends, but also lower the onset of the interval. The co-continuous interval of the PS/PMMA system in the current thesis was PS/PMMA=45/55-50/50. The addition of the symmetric block copolymer (PMMA110-b-PS110) narrowed the co-continuous interval of the blend. The addition of the asymmetric block copolymer (PMMA110-b-PS433) broadened the co-continuous interval to PS/PMMA=20/80～30/70. The addition of the more asymmetric block copolymer (P(S-r-MMA)22o-b-PS32o) broaden the co-continuous interval to PS/PMMA=10/90-30/70.(3) The influence of the mixing conditions on the morphology of the blends was investigated. The mixing time, shear rate, and mixing protocol had no effect on the phase structure of the blends, but had effect on the characteristic size of the blends.(4) The influence of the asymmetry of the compatibilizer on its interfacial activity was investigated via analyzing the coarsening rate during annealing of the co-continuous structured blends. With the same molecular weights and monomer compositions, the AB diblock copolymer (PMMA110-b-PS433) had higher interfacial activity than the AG diblock copolymer (P(S-g-MMA)2o2-b-PS344). while the AC diblock copolymer (P(S-r-MMA)22o-b-PS320) had the lowest interfacial activity. On the other hand, the characteristic size of the co-continuous structured blends could be easily tuned from 0.1μm to about 5μm via quiescent annealing.(5) The influence of the asymmetry of the compatibilizer on its interfacial strengthening ability was investigated via analyzing the tensile strength of the co-continuous structured blends. With the same molecular weights and monomer compositions, the AG diblock copolymer (P(S-g-MMA)202-b-PS344) had higher interfacial strengthening effect than AC diblock copolymer (P(S-r-MMA)22o-b-PS32o), while the AB diblock copolymer (PMMA110-b-PS433) had the weakest interfacial strengthening effect.
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