Abstract
The control of crystal orientation provides a method to manipulate the properties of polymer. One of efficient methods to control the crystal orientation is through the use of nanoscale template. This thesis is dedicated to studying the crystallization behavior, in particular the preferred crystal orientation, of the crystalline polymer blends within the 2-D confined space templated by anodic alumina oxide (AAO) nanochannels. The crystal orientation and the crystallization behavior of Poly (L-lactic acid) (PLLA) developed in the PLLA/PEO blend confined in the AAO channels have been investigated. PLLA/PEO blends with various compositions were infiltrated into AAO channels by a solution method, which led to the rod morphology due to homogeneous filling of the nanopores. The effect of AAO channel diameter (DAAO) and crystallization condition on the crystal orientation have been revealed by synchrotron wide angle X-ray scattering (WAXS). The crystallization of PLLA was enhanced inside AAO channels compared to that in the bulk state. It was also found the mixing with PEO promoted the crystallization rate of PLLA even in the nanochannels. For the PLLA crystal orientation revealed by the azimuthal scan of the (200)/(110) peak in the 2D WAXS patterns, three modes of orientation, namely, parallel, perpendicular and tilt orientation have been identified. For the as-prepare samples, the smaller channel diameter (DAAO= 23 nm) led to parallel orientation, whereas larger pore diameter (DAAO= 89 nm) resulted in perpendicular orientation. Nonisothermal melt crystallization inside the AAO channels with DAAO= 89 nm gave rise to the existence of the perpendicular orientation and a tilt orientation with the crystallites tilting 30° away from the channel axis. However after blending with PEO, PLLA only displayed the perpendicular crystal orientation under nonisothermal crystallization condition. For the samples going through isothermally crystallization, both perpendicular and tilt orientation were observed when the crystallization temperature was sufficiently high.