Polydimethylsiloxane-block-poly(ε-caprolactone)-block-polystyrene ABC-type triblock copolymer (PDMS-b-PCL-b-PS) was synthesized via the sequential ring-opening polymerization and atom transfer radical polymerization. The ABC triblock copolymer was incorporated into epoxy to prepare the nanostructured thermosets. In terms of the difference in miscibility of epoxy with the subchains of the ABC triblock copolymer after and before curing reaction, it is proposed that the formation of the nanostructures follows the combined mechanisms of self-assembly and reaction-induced microphase separation. The self-organized nanophases could be formed before the curing reaction since the PDMS subchains of the triblock polymer is immiscible with the precursors of epoxy before curing reaction. The reaction-induced microphase separation of PS subchains occurred in the presence of the PDMS nanophases whereas the PCL subchains remain miscible with epoxy after and before curing reaction. By means of atomic force microscopy and small-angle X-ray scattering, the morphological structures of the thermosets containing the ABC triblock copolymer were examined, and the formation of the nanostructures was addressed on the basis of the combination of self-assembly and reaction-induced microphase separation mechanisms.

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Polystyrene-block-poly(ε-caprolactone)-block-poly(n-butyl acrylate) (PS-b-PCL-b-PBA) triblock copolymer was synthesized through the combination of atom transfer radical polymerization, copper-catalyzed Huisgen 1,3-dipolar cycloaddition and ring-opening polymerization. The PS-b-PCL-b-PBA ABC triblock copolymer was incorporated into epoxy to access the nanostructures in the thermoset. The microphase-separated morphology was investigated by means of atomic force microscopy (AFM), small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA). It was found that depending on the concentration of the triblock copolymer in the thermosets several kinds of nanodomains were formed and they were arranged in lamellar lattice. The formation of the nanostructures was ascribed to the tandem reaction-induced microphase separation of PBA and PS blocks in the thermosetting blends. The investigation of the model binary thermosetting blends showed that the phase separation of PBA occurred at the conversion much lower than that of PS. It is proposed that the PBA nanophases were formed prior to the PS nanophases in the thermosetting blends and the microdomains of PBA subchains could behave as the template for the demixing of PS blocks. The coupling of the two-stage reactioninduced microphase separation exerted a profound impact on the formation of nanostructures in the epoxy thermosets containing the ABC triblock copolymer. Thermal analysis shows that with the formation of the nanostructures in the thermosets a part of poly(ε-caprolactone) subchains were demixed from epoxy matrix; the fractions of demixed PCL blocks have been estimated according to the T g -composition relation of the model binary blends of epoxy and PCL.

A tetraarmed star‐shaped poly(methyl methacrylate) (s‐PMMA) was synthesized via atom transfer radical polymerization with 2‐bromoisobutyryl pentaerythritol as the initiator. For comparison, a linear PMMA with the identical molecular weight (l‐PMMA) was also prepared. The blends of the two PMMA samples with poly (vinylidene fluoride) (PVDF) were prepared to investigate the effect of macromolecular topological structure on miscibility and crystallization behavior of the binary blends. The behavior of single and composition‐dependent glass transition temperatures was found for the blends of s‐PMMA with PVDF, indicating that the s‐PMMA is miscible with PVDF in the amorphous state just like l‐PMMA. The miscibility was further evidenced by the depression of equilibrium melting points. It is found that the blends of s‐PMMA and PVDF displayed the larger k value of Gordon–Taylor equation than the blends of l‐PMMA and PVDF blends. According to the depression of equilibrium melting points, the intermolecular parameters for the two blends were estimated. It is noted that the s‐PMMA/PVDF blends displayed the lower interaction parameter than l‐PMMA/PVDF blends. The isothermal crystallization kinetics shows that the crystallization of PVDF in the blends containing s‐PMMA is faster than that in the blends containing the linear PMMA. The surface‐folding free energy of PVDF chains in the blends containing s‐PMMA is significantly lower than those in the blends containing l‐PMMA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2580–2593, 2007

Sub-100 nm cocontinuous structures were prepared successfully in poly(vinylidene fluoride)/poly(Llactic acid) (PVDF/PLLA) blend with extremely low volume/viscosity ratio by melting blending. The reactive compatibilizer with poly(methyl methacrylate) (PMMA) side chains and random epoxide groups plays an important role in the formation and the size decrease of these structures. On one hand, PMMA side chains exhibit excellent entanglement with PVDF; on the other hand, the epoxide groups can react with carboxyl group of PLLA. The resultant comb-like compatibilizer exhibits greater capacity to maintain the stress balance on two sides. The repulsion state of the binary brushes enlarges the interface curvature radius, dominating the formation of cocontinuous structures.