ACS Macro Lett 2020 Nov 14;9(11):1521-1526. Epub 2020 Oct 14.
Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China.
Elastic moduli, , of free-standing polystyrene (PS) single-layers and polystyrene-polydimethylsiloxane (PS-PDMS) bilayers are measured by uniaxial tensile testing at room temperature under different strain rates, γ̇, and for PS thicknesses, , from 8 to 130 nm. As γ̇ increases, increases initially, then approaches the bulk value, , when γ̇ exceeds a characteristic value (≡ τ) that decreases with increasing . The noted variation of with γ̇ shows that stress relaxation occurs in the films during measurement when γ̇τ ≪ 1, while the noted variation of τ with shows that thinner films relax faster. Read More