Molecular Organization of Polylactides Immobilized on a Flat Surface: Observation of Single Crystal Arrays of Homochiral and Stereocomplexed Polylactides

Formation of single crystal arrays of polylactides (PLA) was found on a flat surface immobilized with poly­(d-lactide) (PDLA) having different chain lengths. Monoalkoxydimethylsilyl-terminated PDLAs were synthesized by hydrosilylation of (allyloxy)­ethyl-terminated PDLAs and covalently immobilized onto silicon surfaces by a silicone coupling reaction in which the immobilization took place homogeneously through a single Si–O–Si bond. Atomic force microscopy (AMF) of the immobilized surfaces revealed that PDLA chains having M_n = 2400–7000 formed many projections (dots) on the surface of the polymer layers, each having a diameter of 30 nm and a height less than 1.0 nm with a narrow size distribution. When these surfaces were treated with free PDLAs and enantiomeric poly­(l-lactide)­s (PLLA) having similar chain lengths, nano-ordered arrangement of single crystallites arrays of homochiral (hc) and stereocomplexed (sc) PLAs were formed with ordering by the deposition of PDLA and PLLA chains on the surface-immobilized PDLA chains, respectively.