Aging in diblock copolymers under soft and hard confinement

Self-assembly of block copolymer formats hierarchical architectures that could be utilized as templates or scaffolds in nanotechnologies. Naturally, polymers under T_g are non-equilibrium materials，aging may dramatically impact properties of a polymeric material in its service life. On the other hand, the microphase separation in block copolymers creates mass of interfaces between macromolecular blocks in nanometer length scale, and thus, the physical properties of blocks in copolymers should deviate from the corresponding homopolymers, owing to the confinement effect. Here we show the aging behavior of copolymer blocks, with emphasis on effect of hard and soft confinements. This is achieved by investigating aging of PS blocks in PS-b-PMMA and PS-b-PBMA at the same temperature and time scale. All blocks in the two model materials have the same molecular mass. Due to the T_g difference of PMMA (120 °C) and PBMA ( 26 °C), the PS blocks at aging temperature not far below its T_g (105 °C) in these materials are considered under hard ( confined by PMMA glass) and soft (confined by PBMA liquid) confinements, respectively. Our results show the aging behaivor and associated phase evolution, and compare the effect of hard and soft confinement on physical aging of copolymers.