The H2 uptake from s-PS samples exhibiting different crystalline phases and different
morphologies has been studied by gravimetric measurements at 77 K in the hydrogen pressure range from
0 up to 1.7 MPa and compared with molecular simulations relative to s-PS crystals. Gravimetric experiments
show that the molecular hydrogen sorption is strongly dependent on the sample morphology and is maximum
for low-density polymer aerogels. However, independently of the morphology, theH2 uptake is minimum for
the dense \u3b2 and \u3b3 crystalline phases, intermediate for the channel-shaped nanoporous \u3b5 phase, and maximum
for the cavity-shaped nanoporous \u3b4 phase. In particular, although the two nanoporous crystalline phases
present essentially the same density (0.98 g/cm3), the hydrogen uptake from the \u3b4 phase is roughly double with
respect to the uptake from the \u3b5 phase, both for powders and for aerogels. Infrared measurements and
molecular simulations well agree with these quantitative sorption data and clearly indicate that, for both low
and high pressure, the hydrogen molecules are preferentially adsorbed into the nanoporous crystalline
phases. In particular, molecular simulations indicate that the maximum average hydrogen uptake is of nearly
3 molecules per cavity of the \u3b4 phase and of nearly 3.5 molecules per unit height of the channels of the \u3b5 phase
