Synthesis and Self-Assembly of Silicon-Containing Azobenzene Liquid Crystalline Block Copolymers

Abstract

The synthesis and self-assembly of a high interaction parameter silicon-containing liquid crystalline block copolymer (Si-LCBCP) are reported, containing thermally and photo-responsive azobenzene mesogens in the side chains which undergo molecular structural transitions, influencing phase transitions and orientation in the block copolymer. A series of the azobenzene-containing Si-LCBCPs, poly{dimethylsiloxane-b-11-[4-(4-cyanophenylazo)phenoxy]undecane methacrylate}, were synthesized through atom transfer radical polymerization, and the bulk self-assembly as well as the influence of the liquid-crystalline (LC) phase transition of the LC block on the microphase-separated nanostructure of the BCPs is described. As the volume fraction of the PMAAzo block (f PMAAzo) changes from 41 to 71%, lamellar, double gyroid (GYR), orthorhombic Fddd network, hexagonally packed cylindrical (HEX), and body centered cubic nanostructures were obtained. When f PMAAzo = 55–57%, a thermally reversible HEX-GYR-Fddd phase transition induced by the temperature change and LC phase transition was observed. Bulk morphologies are compared with thin-film self-assembly, and pattern transfer into silica nanostructures is demonstrated.

Photoresponsive block copolymer nanostructures through implementation of arylazopyrazoles

“…23,30,31 Upon irradiation with UV light, AAPs undergo a change in configuration to the bent Z isomer, which has an increased dipole moment and a lower hydrophobicity as compared to the linear E isomer. 32 Many photoresponsive BCPs exhibit a shape transition in the solid state [33][34][35] or their transitions in solution are based on supramolecular interactions, such as host-guest complexes. [36][37][38][39] In comparison, less examples exist on the self-assembly of BCPs with photoresponsive blocks in solution.…”

Si-Containing Reverse-Gradient Block Copolymer for Inorganic Pattern Amplification in EUV Lithography

“…The directed self-assembly (DSA) of block copolymer (BCP) systems has been widely studied as a practical bottom-up technique for creating highly ordered patterns ranging from a few nanometers to hundreds of nanometers in scale. − High-resolution DSA patterns can be achieved by maintaining sufficient segregation strength in BCPs, which requires a high Flory–Huggins interaction parameter (χ). − Several studies have designed BCPs with high χ values, such as poly(styrene)- b -poly(dimethysiloxane) (PS- b -PDMS), poly(2-vinlypyridine)- b -poly(styrene)- b -poly(2-vinylpyridine) (P2VP- b -PS- b -P2VP), poly(styrene)- b -poly(propylene carbonate) (PS- b -PPC), poly(styrene)- b -poly(4-trimethylsilylstyrene) (PS- b -PTMSS), and poly(styrene)- b -poly((4-vinylpyridine)propane-1-sulfonate) (PS- b -PVPS), which can provide high-resolution perpendicular lamellae structures to be combined with EUV patterns. − However, for these BCPs to be utilized effectively in EUVL, the vertical lamellae structure should be formed with achieving not only high resolution, but also a significantly high AR.…”

Photoresponsive Block Copolymer Nanostructures through Implementation of Arylazopyrazoles

“…Many photoresponsive BCPs exhibit a shape transition in the solid state, − or their transitions in solution are based on supramolecular interactions, such as host–guest complexes. − In comparison, fewer examples exist on the self-assembly of BCPs with photoresponsive blocks in solution. In one prominent example, Wang et al studied an alternating azo copolymer that can undergo a photoinduced deformation .…”