Instability, glass transition temperature (Tg), and thermal expansion of polystyrene (PS) films are evaluated with respect to the thickness of a silicon oxide (SiOx) interlayer that mediates favorable long-range interaction from the non-oxide Si substrate. Taking into account that a SiOx interlayer is less favorable with an overlying PS film, we designed a systematic set of H-passivated (H-Si), native SiOx (N-Si), and non-native SiOx interlayer (P-Si) substrates. Here, P-Si denotes a substrate prepared by a plasma surface activation with oxygen to create an effective minimum SiOx thickness (∼9 nm) that is sufficient for the instability of PS films. The wetting-dewetting behavior differs in 100 and 43 kg/mol PS films supported on the three different substrates. Reflected in Tg and thermal expansion coefficient at the rubbery state for the overlying PS films, P-Si is found to be enough to promote the nontrivial instability of the films, leading to a marked decrease in Tg and increase in αr with decreasing film thickness (more than those on N-Si). Our results demonstrate the ability to use P-Si to effectively modulate favorable long-range interaction from the Si substrate better than a typical N-Si does.
Bibliographical noteFunding Information:
This research was supported by the NRF grants (2017R1A2A2A05001048, 2017R1A4A1014569) funded by the Ministry of Science, ICT & Future Planning (MSIP) and funding (20163030013960) from the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE), Korea. NR experiments at the Materials and Life Science Experimental Facility of the J-PARC were performed under a user program (Proposal No. 2018A0216).
© 2019 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry