To test the mechanical properties of APCNs swollen in an organic solvent, the samples were immersed in n-hexane overnight and then subjected to stress-strain experiments. With increasing CNC content, the stress-at-break increased from 3.5 ± 0.5 MPa for samples without CNCs to 5.5 ± 1.3 MPa for samples with 22 wt% HCNCs. APCNs with 6 wt% CNCs showed the highest strainat-break (245 ± 10 %), which dropped to 31 ± 11 % for the highest CNC concentration tested, and therefore below the strain-at-break of the APCN without CNCs. Young´s modulus increased continuously from 3.4 ± 0.4 at 0 wt% CNCs to 19 ± 11 MPa for 22 wt% CNCs. The highest toughness of 5.6 ± 0.4 MJ m -3 was measured for samples with 6 wt% CNCs, and the lowest toughness was recorded for APCNs with 22 wt% CNCs. In summary, the CNCs also increased the mechanical properties of the APCNs swollen in n-hexane. The addition of HCNCs up to 6 wt% increased maximum stress, maximum strain, and toughness. However, higher CNC concentrations caused a reduction in mechanical performance, except for the Young´s modulus, which increased continuously with CNC concentration, i.e., the APCNs became stiffer with increasing CNC content.