Rtespa 300 30

AFM analyses of the COPET-PLLA blends were performed on trimmed surfaces with a Dimension Icon system (Bruker Corp., Billerica, MA, USA) in PeakForce Tapping mode with Quantitative Nanomechanical Mapping (PFT-QNM). A factory-calibrated probe, RTESPA-300–30 (Bruker Corp., Billerica, MA, USA), with a spring constant of 48.87 N m⁻¹ and a tip apex radius of 34 nm was used. AFM images (256 × 256 pixels) with dimensions ranging between 3 × 3 and 30 × 30 µm² were acquired. The PeakForce frequency and amplitude were 2 kHz and 30 nm, respectively. The PeakForce set point was set to 75 nN, corresponding to an indentation depth between 2 and 3 nm. Under these conditions, the contact radius remained smaller than 10 nm [25 (link)].

The force measurements were conducted using a commercial AFM (MultiMode 8, Bruker Corporation) in tapping mode with a silicon cantilever with a triangular pyramid tip (RTESPA-300-30, Bruker Corporation). In order to ensure the accuracy of the downforce effect, the normal spring constant of the cantilever was calibrated and two kinds of tips with different spring constants (k = 9 N m⁻¹ and 40 N m⁻¹) were used for the monochiral system with smaller Young’s modulus and the racemic system with larger Young’s modulus. All AFM experiments were carried out at room temperature. In a typical experiment, the AFM tip is moved normally toward and eventually penetrates into the prepared DOPA-coated mica substrate surface (coating thickness of ~60 μm) then the tip is retracted away from the surface. The adhesive interactions are manifested as negative force values. NanoScope Analysis software (1.90, Bruker Corporation) and AtomicJ software (version 1.7.3)^{70 (link)} were used to analyze the force curves and adhesive forces.