TY - JOUR
T1 - Lamellae assembly in dendritic Spherulites of Poly(L-lactic Acid) crystallized with poly(p-Vinyl Phenol)
AU - Nurkhamidah, Siti
AU - Woo, Eamor M.
AU - Yeh, Yu Ting
AU - Luo, Faliang
AU - Katiyar, Vimal
N1 - Funding Information:
Funding: This work was funded by the Ministry of Science and Technology of Taiwan by grant number MOST-105-2221-E-006-246-MY3.
Funding Information:
Acknowledgments: This work has been financially supported by a basic research grant (MOST 105-2221-E-006-246-MY3) for three consecutive years from the Ministry of Science and Technology (MOST), to which the authors express their gratitude. Collaborative work and exchanged discussions in the past couple of years among researchers of different labs led to further refinement of the contents.
Funding Information:
This work has been financially supported by a basic research grant (MOST 105-2221-E-006-246-MY3) for three consecutive years from the Ministry of Science and Technology (MOST), to which the authors express their gratitude. Collaborative work and exchanged discussions in the past couple of years among researchers of different labs led to further refinement of the contents This work was funded by the Ministry of Science and Technology of Taiwan by grant number MOST-105-2221-E-006-246-MY3.
Publisher Copyright:
© 2018 by the authors.
PY - 2018/5/18
Y1 - 2018/5/18
N2 - Lamellar assembly with fractal-patterned growth into dendritic and ringed spherulites of crystallized poly(L-lactic acid) (PLLA), of two molecular weight (MW) grades and crystallized at (temperature of crystallization) Tc = 120 and 130 °C, respectively, are evaluated using optical and atomic-force microscopies. The results of surface-relief patterns in correlation with interior microscopy analyses in this work strongly indicate that the observed birefringence changes in PLLA polymer dendritic or ringed spherulites (from blue to orange, or to optical extinction) need not be definitely associated with the continuous helix twisting of lamellae; they can be caused by sudden and discontinuous lamellae branching at intersected angles with respect to the original main lamellae, as proven in the case of dendritic and zig-zag rough-ringed spherulites. Intersection angles between the main stalks and branches tend to be governed by polymer crystal lattices; for PLLA, the orthorhombic lattice (α-form) usually gives a 60° angle of branching and hexagonal growth. The branching lamellae then further bend to convex or concave shapes and finally make a 60-90° angle with respect to the main stalks. Such mechanisms are proven to exist in the straight dendritic/striped high-molecular weight (HMW)-PLLA spherulites (Tc = 120 °C); similar mechanisms also work in circularly ringed (Tc = 130 °C) HMW-PLLA spherulites.
AB - Lamellar assembly with fractal-patterned growth into dendritic and ringed spherulites of crystallized poly(L-lactic acid) (PLLA), of two molecular weight (MW) grades and crystallized at (temperature of crystallization) Tc = 120 and 130 °C, respectively, are evaluated using optical and atomic-force microscopies. The results of surface-relief patterns in correlation with interior microscopy analyses in this work strongly indicate that the observed birefringence changes in PLLA polymer dendritic or ringed spherulites (from blue to orange, or to optical extinction) need not be definitely associated with the continuous helix twisting of lamellae; they can be caused by sudden and discontinuous lamellae branching at intersected angles with respect to the original main lamellae, as proven in the case of dendritic and zig-zag rough-ringed spherulites. Intersection angles between the main stalks and branches tend to be governed by polymer crystal lattices; for PLLA, the orthorhombic lattice (α-form) usually gives a 60° angle of branching and hexagonal growth. The branching lamellae then further bend to convex or concave shapes and finally make a 60-90° angle with respect to the main stalks. Such mechanisms are proven to exist in the straight dendritic/striped high-molecular weight (HMW)-PLLA spherulites (Tc = 120 °C); similar mechanisms also work in circularly ringed (Tc = 130 °C) HMW-PLLA spherulites.
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U2 - 10.3390/polym10050545
DO - 10.3390/polym10050545
M3 - Article
AN - SCOPUS:85047239935
SN - 2073-4360
VL - 10
JO - Polymers
JF - Polymers
IS - 5
M1 - 545
ER -