Crystallization kinetics of poly (S-2-hydroxybutanoic acid) [P(S-2HB)] and P(S-2HB)/P (R-2HB) stereocomplexes were investigated by in situ atomic force microscopy, polarized optical microscopy, and differential scanning calorimetry. For the homopolymer, an equilibrium melting temperature T-m(degrees) of 130.3 degrees C is obtained according to the Hoffman-Weeks method. In the case of thin films of 50 nm in thickness, a large number of edge-on lamellae form rapidly on the edge of the scratch line induced by the AFM tip. The edge-on lamellae change their orientation to flat-on lamellae at crystallization temperatures equal or higher than 75 degrees C. The lamellar and radial growth rates exhibit a bell-shaped temperature dependence with a maximum around 400 +/- 50 nm/min at a crystallization temperature of 77 +/- 2 degrees C, in contrast to the stereocomplexes whose growth rates peak at 19.6 mu m/min. Analysis of the growth rates using the Lauritzen-Hoffman model shows that crystallization of homopolymers and stereocomplexes occurs in Regime II, with an end surface free energy sigma(e) of 6.2 x 10(-2) J/m(2) in the first case and 7.6 -8.5 x 10(-2) J/m(2) in the second, and work of chain folding q between 18 and 24 kJ/mol for the homopolymer and 26-30 kJ/mol for the stereocomplexes, which is in the range of moderately stiff chains without bulky side-groups. (C) 2017 Elsevier Ltd. All rights reserved.