Nano-structured polystyrene – polydimethylsiloxane diblock copolymers and nano-composites based on these copolymers and metallic nano-particles: Structure and dynamics

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PDMS behaviour under confinement in strongly segregated mesophases of PS-PDMS diblock copolymers

A dynamic and thermal investigation by means of broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry on the PDMS behaviour in several highly segregated diblock copolymers with varying PDMS molecular weight and volume fraction is presented. The mesophase morphology of these diblock copolymers has been characterized by means of transmission electron microscopy and small angle X-ray scattering. It is found that whereas the lamellar morphology (1D confinement) does not affect significantly the PDMS properties, in the case of the cylindrical (2D confinement) and spherical (3D confinement) segregations of the PDMS component in the PS matrix noticeable effects are evident, such as a strong reduction of the PDMS glass-transition temperature and a strong decrease (even suppression) of PDMS crystallinity ratio

PDMS behaviour under confinement in strongly segregated mesophases of PS-PDMS diblock copolymers

5 páginas, 2 figuras, 2 tablas.A dynamic and thermal investigation by means of broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry on the PDMS behaviour in several highly segregated diblock copolymers with varying PDMS molecular weight and volume fraction is presented. The mesophase morphology of these diblock copolymers has been characterized by means of transmission electron microscopy and small angle X-ray scattering. It is found that whereas the lamellar morphology (1D confinement) does not affect significantly the PDMS properties, in the case of the cylindrical (2D confinement) and spherical (3D confinement) segregations of the PDMS component in the PS matrix noticeable effects are evident, such as a strong reduction of the PDMS glass-transition temperature and a strong decrease (even suppression) of PDMS crystallinity ratio.The authors acknowledge the University of the Basque Country, the Basque Government (A9/ UPV 00206.215-13568/2001), and the Spanish Ministry of Education (MAT 2007- 63681) for support. L. del Valle-Carrandi acknowledges the grant of the Basque Government. The support of the European Community within the SoftComp Network of Excellence (NoE) program (Project No. NMP3-CT-2004-502235) is also acknowledged.Peer reviewe

Unexpected PDMS behavior in segregated cylindrical and spherical nanophases of PS-PDMS asymmetric diblock copolymers

The structure and dynamics of the poly(dimethylsiloxane) (PDMS) segregated nanophase in block copolymers with polystyrene (PS) has been analyzed in detail by combining wide- and small-angle X-ray diffraction, infrared absorption, differential scanning calorimetry, and dielectric relaxation spectroscopy. In particular, we have investigated PS-rich PS-PDMS diblocks where the minority PDMS phase is segregated into cylindrical and spherical regions with diameter in the range 10-20 nm and compared the results with those previously reported on symmetric diblocks with lamellar phases of similar size. It is found that in these highly segregated cylindrical and spherical regions in the copolymers PDMS presents a rather unexpected behavior as probed by X-ray diffraction, infrared absorption, differential scanning calorimetry, and dielectric relaxation spectroscopy. Structural techniques indicate poor packing of the PDMS segments, whereas calorimetric experiments evidence both strong suppression of PDMS crystallization and significant reduction of the glass transition temperature range. Connected with that, the dielectric relaxation probing the PDMS segmental dynamics is much more heterogeneous and markedly faster not only than that observed for PDMS in lamellar nanophases but more strikingly than that of PDMS melt. 2011 American Chemical Society.The authors acknowledge the University of the Basque Country and Basque Country Government (Ref. No. IT-436-07, Depto. Educación, Universidades e Investigación) and the Spanish Ministry of Science and Innovation (Grant No. MAT 2007-63681) for their support.Peer Reviewe