Synthesis of high molar masses of poly(n-butyl methacrylate)-b-polystyrene diblock copolymers by ATRP. Formation of lamellar phases in thin films

International audienceDiblock copolymers are known to self-organize in ordered domains. The morphology of this microphase separation depends essentially on the relative amount of each immiscible block in the copolymer (e.g. spherical, cylindrical, gyroidal and lamellar phases). The lamellar nanoscopic structures can serve as templates for the selective incorporation of inorganic nanoparticles , , for instance to get nanopatterned surfaces or for new applications such as wave guides. , In most of the studies concerning diblock copolymer self-assembly in lamellar periodic structures, diblock copolymers were synthesized by anionic polymerization which is a suitable technique to prepare well-defined high molar mass diblock copolymers. , In the present study, our aim is the synthesis of high molar mass poly(n-butyl methacrylate)-b-polystyrene diblock copolymers by Atom Transfer Radical Polymerization (ATRP). Compared to anionic polymerization, controlled radical polymerization (CRP) is a more versatile technique which requires less drastic experimental conditions. Our results highlight the self-assembly of the symmetric poly(n-butyl methacrylate)-b-poly(styrene) diblock copolymer synthesized by ATRP into a lamellar ordered structure after an annealing treatment

Synthesis of block copolymers by ATRP for the combination with magnetic nanoparticles to obtain nano-composite films

Nanocomposite materials which associate inorganic nanoparticles and polymers with a high degree of organization are highly interesting for their applications in visible light optics (reflectors and guides) and hyper-frequencies (antennae and switches). We focus our study on a complex system combining self-organization of a diblock copolymer A-B and orientation properties under magnetic field of inorganic magnetic nanoparticles. We present here an experimental protocol for the synthesis by Atom Transfer Radical Polymerization (ATRP) of the symmetrical poly(n-butylmethacrylate)-b–poly(styrene) diblock copolymer (PBMA-b-PS) with high molar masses (about 100 000 g/mol). After spin-coating on a flat substrate (float glass, silicone or alumina) from a solution in a volatile solvent and annealing above the glass temperature, a thin film of such well-defined symmetrical diblocks are expected to self-organize into a lamellar (smectic type) order. The second component of the system consists in nanoparticles made of either superparamagnetic maghemite oxide Γ-Fe2O3 (soft magnets) or ferrimagnetic cobalt ferrite CoO.Fe2O3 (strong magnets). We are working on the proper dispersion of these nanoparticles within the PS blocks in order to obtain “sandwiches” made of magnetic thin layers alternating with the lamellae of the copolymer matrix. Optical Reflection Interference Contrast Microscopy (RICM) is convenient and fast to measure the thickness of the films (from a number of fringes) directly on their substrate and to detect characteristic defects of the long-range organization of the films (like holes). High resolution microscopies such as AFM and TEM will enable to measure the lamellar period but require to prepare thin films cross-sections