MORPHOLOGY OF POLY(L-LACTIDE) SOLUTION-GROWN CRYSTALS

Solution-grown crystals (SGC) of poly(L-lactide) (PLLA) were prepared from 0.01% (w/w) or 0.08% (w/w) acetonitrile solution by an isothermal crystallization method. Their morphology and structural features were examined by transmission electron microscope with the diffraction mod e, wide-angle X-ray diffractometry and atomic force microscope. The mo lecular chains are packed in the manner perpendicular to the basal pla ne of the well-defined, lozenged, thin SGC with developed spiral dislo cation growths; highly-ordered electron diffraction patterns produced by the crystal provided the orthorhombic unit cell parameters: a = 1.0 78 nm, b = 0.604 nm, c (fibre axis) = 2.87 nm. This unit cell of the P LLA SGC contains 20 monomeric units in terms of density measurements. On the basis of the crystal characteristics of SGC, we propose that th e two molecular chains locate at the centre and also at each corner of the unit cell. The annealing effects of SGC were studied in parallel to indicate the existence of surface roughening and lamella thickening , depending on the annealing conditions. (C) 1997 Elsevier Science Ltd .