Using atomic force microscopy (AFM) coupled with a hot stage, we studied the morphological evolution of superheated poly(ethylene oxide) (PEO) crystal monolayer on the mica surface. The PEO possesses a number average molecular weight (M-n) of 4250 g/mol and a polydispersity of 1.03. The superheated monolayer was obtained when the entire periphery of a triply-folded chain crystal [IF(3)] was thickened to be a twice-folded chain crystal [IF(2)] 'dam'. The IF(3) crystal was laterally confined by the IF(2) 'dam' and remained unchanged at its unconfined melting temperature (T.). In superheated conditions, the interior IF(3) crystal unfolded, resulting in domains with a thickness in between the fold lengths of the IF(3) and the IF(2) crystals accompanied by hole formation. After its nucleation, the hole enlarged its area quickly and migrated long distances within the area bounded by the IF(2) crystal 'dam'. (c) 2006 Elsevier Ltd. All rights reserved.