The progress of the interfacial reaction of polystyrene chains end-capped by a primary amine (PS-NH2) and PMMA chains end-capped by an anhydride (PMMA-anh) has been monitored by SEC-UV, by using anthracene-labeled polystyrene chains (anth-PS-NH 2) as a probe. Assemblies of an anth-PS-NH2 layer and a PMMA-anh layer were annealed at 200 °C for various periods of time. The interfacial reaction rate depends on the molecular weight (MW) of the reactive precursors in relation to the χN value of the chains. For chains of low χN (χN ) 6), the reaction is faster because the interface becomes more diffuse with time, as observed by TEM and AFM, consistent with compatibilization of the weakly immiscible polymers by the copolymer formed in-situ. For chains of higher molecular weight and χN (10, instead of 6), the interface is much sharper and the residence time at the interface of the symmetric diblock copolymer of higher molecular weight is also increased, which dramatically restricts the progress of the interfacial reaction under the annealing conditions used in this work.

Radical polymerization of styrene and copolymerization of styrene and acrylonitrile (60/ 40) are controlled when conducted in the presence of N-tert-butyl-R-isopropylnitrone, which is easily synthesized from cheap reagents. However, for the control to be effective, the nitrone has to be prereacted with the radical initiator. Nitroxides are then formed "in situ", such that this nitrone system is an attractive alternative for the classical nitroxide-mediated polymerization (NMP), which may require a multistep synthesis of nitroxides or alkoxyamines. The choice of the radical initiator is important because it dictates the structure of the nitroxide and thus its capacity to control the radical polymerization. Well-defined poly(styrene)-b-poly(styrene-co-acrylonitrile), poly(styrene)-b-poly(n-butyl acrylate), and poly(styrene)-bpoly(isoprene) copolymers have been successfully synthesized by this process.

ω-Isocyanate PMMA, R-anhydride PMMA, and PS-co-PSNH2 have been prepared by atom transfer radical polymerization (ATRP) with controlled molecular weights (10 4 and 3.5 × 10 4 ) and low polydispersity (1.2). They have been used as precursors of PS-g-PMMA copolymers and let to react in the melt (170 °C, for 10 min) under moderate shear rate. The well-controlled molecular characteristics of these precursors are a substantial advantage to study the effect of the kinetics of the interfacial reaction on the phase morphology. When the grafting reaction is fast (NH2/anhydride pair) and low molecular weight chains are used, the interfacial reaction is quasi-complete and a nanophase morphology is observed, whereas limited reaction and formation of microphases are observed in all the other cases. A high reaction yield requires not only that the functional groups are highly mutually reactive but also that the interface is anytime made available to the functional polymers for the reaction to progress. Then, a nanophase morphology may be observed, which is that of the copolymer formed by the interfacial reaction. A low reaction yield is dictated by either a slow interfacial reaction or a slow diffusion of the copolymer away from the interface. In the latter case, the phases formed by the unreacted precursors are stabilized by the copolymer which resides at the interface.

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PMMA was nanostructured by ∼100 nm liposome-like vesicular objects by melt blending with 20 wt % of a symmetric poly(styrene)-b-poly(isoprene)-b-poly(methyl methacrylate) (PS-b-PIP-b-PMMA) triblock copolymer in the dry-brush regime. Whenever the blend was prepared by casting toluene solution, thus under zero-shear conditions, a continuous network of lamellar copolymer sheets was formed in PMMA, which however underwent a transition to the aforementioned vesicles upon application of large amplitude oscillatory shear.

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Reactive blending of phthalic anhydride end-capped polystyrene-b-polyisoprene diblock (PSb-PIP-anh) with 80 wt % of polyamide 12 (PA12) results in the very rapid formation of a PS-b-PIP-b-PA triblock copolymer, which self-assembles with formation of characteristic nanoobjects, within the polyamide matrix. For instance, a vesicular nanostructure is formed in the particular case of a symmetric, lamellarforming diblock copolymer. This morphology actually complies with the lower curvature possible for ABC lamellae diluted in a continuous C phase under shear. In contrast, when the diblock composition is typically asymmetric (at constant molecular weight), vesicles disappear in favor of a core-shell morphology with a cucumber-like suborganization. This spontaneous nanostructuration of the PA12 matrix is quite general. Indeed substitution of an amorphous primary amine end-capped styrene/acrylonitrile random copolymer (SAN-NH 2) for PA12 results in exactly the same phase morphology upon reactive blending with PS-b-PIP-anh.

The interface of a two-layer assembly of polystyrene (PS) and poly(methyl methacrylate) (PMMA) was modified by an intermediate layer of either a premade poly(styrene-g-methyl methacrylate) copolymer (P(S-g-MMA)) or a preblend of mutually reactive PS and PMMA synthesized by atom transfer radical polymerization (ATRP). No significant difference was found in the interfacial fracture toughness measured by the double cantilever beam test, although the morphology of the interfacial region was not the same when observed by transmission electron microscopy. The premade copolymer formed a distinct interphase, in contrast to the sharp interface that was observed in the case of the reactive system. The analysis of the fracture surfaces by Raman confocal microscopy showed that the fracture occurred alternatively in the PS phase and either at the PS/copolymer interface for the non reactive system or at the PS/PMMA interface for the reactive one.