Complex Architecture Silicon Containing Copolymers as Potential Candidates for Nanopatterning Applications(Parallel Session II)

Utilizing anionic polymerization in combination with chlorosilane chemistry, novel monodispersed silicon containing miktoarm star and star block copolymers with varying volume fractions of the PS(PDMS)_m, PDMS(PS)_m and (PS-b-PDMS)_n (where m =2, 3 and n=1, 2, 3, 4, 6) sequences were synthesized respectively.

All manipulations took place according to the high standards of anionic polymerization leading to well-defined polymers, exhibiting molecular and compositional homogeneity, verified by several molecular characterization techniques such as size exclusion chromatography, vapor pressure/membrane osmometry and proton nuclear magnetic resonance spectroscopy techniques, among others.

The structural behavior of all miktoarm star and star block copolymers in bulk was studied through transmission electron microscopy and small angle X-ray scattering experiments to determine the potential impact on the structure/properties relationship due to the additional arms as well as the different architectures [PS(PDMS)_m vs. PDMS(PS)_m, where (where m=2, 3)] and for the different (PS-b-PDMS)_n (where n=1, 2, 3, 4, 6) sequences respectively.

Higher flexibility of the PDMS chains, attributed to the increased bond angle in the inorganic backbone chain when compared to the stiffer amorphous PS components and the topological constraints imposed by the complex architecture, holds a key role in the final adopted morphology in all miktoarm star cases. Apart from the χΝ product, the obtained nanostructures are affected by the curvature due to the overcrowding effect, considering the flexibility of the multiple PDMS arms in the PS-core related copolymers and the stiffness of the PS chains for the PDMS-core miktoarm stars as well as the PS volume fraction.

For the star block copolymer sequences [(PS-b-PDMS)_n (where n=1, 2, 3, 4, 6)], these can be exploited as an innovative tool for the induction of perpendicular to the substrate nanodomains and even smaller dimensions. Conformational asymmetry and overcrowding effect due to the existence of multiple chains lead to entropic penalties. As a result, a highly improved ordering degree can be achieved while the defects and dislocations are limited. The repulsive energy between the identical segments leads to chain stretching parallel to the interface, further facilitating long-range order and minimization of nanofeatures.

Speakers

Apostolos Avgeropoulos

KAUST

KAUST Research Centers

KCC Research Groups