Solid-State Microstructure of Poly(l-lactide) and l-Lactide/meso-Lactide Random Copolymers by Atomic Force Microscopy (AFM)

Abstract

Tapping mode atomic force microscopy was used to investigate the lamellar morphology of poly(L-lactide) and two poly(L-lactide-co-meso-lactide) random copolymers containing 3% and 6% meso-lactide. Samples were isothermally crystallized at selected temperatures, and qualitative and quantitative analyses of lamellar structure were performed using height and phase images. This is the first study of the morphology of polylactide stereocopolymers using a real-space probe, and the important effects of scanning parameters on the acquired images are described. More open spherulites with an abundance of screw dislocations between edge-on lamellar stacks were observed in samples crystallized at higher temperatures. Mean lamellar thicknesses are lower for the random copolymers compared to PLLA, particularly at lower ∆T, in agreement with the results of our previous small-angle X-ray scattering (SAXS) experiments. Mean lamellar thicknesses derived from the current real-space examination are in good agreement with those determined previously from SAXS. Internal surfaces-from microtomed specimens-were also studied to investigate the bulk crystal morphology. Although quantitative analysis was not feasible (for reasons discussed in the text), lamellar organization similar to that seen in the surface experiments is observed at high magnifications.

An Overview of Polylactides as Packaging Materials

“…The polymer degradation rate is mainly determined by polymer reactivity with water and catalysts. Any factor which affects the reactivity and the accessibility, such as particle size and shape, temperature, moisture, crystallinity, % isomer, residual lactic acid concentration, molecular weight, molecular weight distribution, water diffusion and metal impurities from the catalyst, will affect the polymer degradation rate 1,3,15,21,23,39,95,119–121,123,137,141,166–216. In general, high temperatures and humidity (50 to 60 °C) will cause PLA to degrade rapidly.…”

Time resolved study of oriented crystallisation of poly(lactic acid) during rapid tensile deformation

“…More recently Korturk et al [6] have studied tensile deformation of films between 60 and 80 8C at draw rates up to w0.05 s K1 and found their samples crystallised in the b form. Several morphology studies of isotropic melt crystallised homopolymers and D-lactide and meso-lactid copolymers have shown lamellae crystals whose thickness decreases with increasing comonomer as a result of exclusion of comonomers from the lamellae [7][8][9][10]. Cicero et al [11,12] studied melt spun fibres and found the morphology to be essentially microfibrillar.…”

Stereocomplexation of PLL/PDL–PEG–PDL blends: Effects of blend morphology on film toughness

“…Its blown out picture in Fig. 5(b) shows that the neat PLL spherulite was composed of the long-stripes and planar lamellae aligned in the disorder arrangement [2,15]. Fig.…”

“…Polylactide (PL), one of the well-known aliphatic polyesters, has received much interest due to its enzymatic-/hydroly tic-degradability as well as biocompatibility [1][2][3]. PL finds its use in a wide variety of applications ranging from medical devices to engineering plastics [4][5][6][7].…”