Atomic force microscopy (AFM) is used to study the phase separation process occurring in block copolymers in the solid state. The simultaneous measurement of the amplitude and the phase of the oscillating cantilever in the tapping mode operation provides the surface topography along with the cartography of the microdomains of different mechanical properties. This technique thus allows to characterize the size and shape of those microdomains and their organization at the surface (e.g. cubic lattice spheres, hexagonal lattice of cylinders, or lamellae). In this study, a series of symmetric triblock copolymers made of a inner elastomeric sequence (poly(butadiene) or poly(alkylacrylate)) and two outer thermoplastic sequences (poly(methylmethacrylate)) is analyzed by AFM in the tapping mode. The microphase separation and their morphology are essential factors for the potential of these materials as a new class of thermoplastic elastomers. Special attention is paid to the control of the surface morphology, as observed by AFM, by the molecular structure of the copolymers (volume ratio of the sequences, molecular weight, length of the alkyl side group) and the experimental conditions used for the sample preparation. The molecular structure of the chains is completely controlled by the synthesis, which relies on the sequential living anionic polymerization of the comonomers. The copolymers are analyzed as solvent-cast films, whose characteristics depend on the solvent used and the annealing conditions. The surface arrangement of the phase-separated elastomeric and thermoplastic microdomains observed on the AFM phase images is discussed on the basis of quantitative information provided by the statistical analysis by Fourier transform and grain size distribution calculations.

The phase morphology and rheological properties of a series of poly(methyl methacrylate)‐block‐poly(isooctyl acrylate)‐block‐poly(methyl methacrylate) triblock copolymers (MIM) have been studied. These copolymers have well‐defined molecular structures, with a molecular weight (MW) of poly(methyl methacrylate) (PMMA) in the range of 3 500–50 000 and MW of poly(isooctyl acrylate) (PIOA) ranging from 100 000 to 140 000. Atomic force microscopy with phase detection imaging has shown a two‐phase morphology for all the MIM copolymers. The typical spherical, cylindrical, and lamellar phase morphologies have been observed depending on the copolymer composition. MIM consisting of very short PMMA end blocks (MW 3 500–5 000) behave as thermoplastic elastomers (TPEs), with however an upper‐service temperature higher than the traditional polystyrene‐block‐polyisoprene‐block‐polystyrene TPEs (Kraton D1107). A higher processing temperature is also noted, consistent with the higher viscosity of PMMA compared to PS.

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