are cut into squares and placed onto the plastic frame. One side of
the film is fixed to the frame with tape (3M Scotch Crystal Tape,
United Kingdom), and the sample is then prestretched in the opposite
direction of the tape by 10, 20, or 100%, respectively. Subsequently,
the stretched side of the film is fixed to the plastic frame with
tape. A detailed scheme for how the sample is prestretched uniaxially
is presented in more detail in Supporting Information