TY - JOUR
T1 - Influence of precursor solvent and confined environment on the polymorphic transition in electrospun Poly(L-lactide) fibers
AU - Lee, Kuan Hsuan
AU - Huang, Hsiu Feng
AU - Lo, Chieh Tsung
N1 - Funding Information:
This work was financially supported by the Ministry of Science and Technology of Taiwan under Grant No. 108-2221-E-006-053-MY3. The authors express their gratitude to National Cheng Kung University (NCKU) for allowing the use of the small-angle X-ray scattering device belonging to the Instrument Center of NCKU. The authors also thank the National Synchrotron Radiation Research Center of Taiwan for granting beamtime at TLS BL17A1.
Funding Information:
This work was financially supported by the Ministry of Science and Technology of Taiwan under Grant No. 108-2221-E-006-053-MY3 . The authors express their gratitude to National Cheng Kung University (NCKU) for allowing the use of the small-angle X-ray scattering device belonging to the Instrument Center of NCKU. The authors also thank the National Synchrotron Radiation Research Center of Taiwan for granting beamtime at TLS BL17A1.
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/12/10
Y1 - 2021/12/10
N2 - The present study examined the thermal and crystallization properties of poly(L-lactide) (PLLA) chains confined in electrospun fibers. The heat of fusion and crystallite sizes decreased with a decrease in fiber diameter because of the confinement effect. The crystal structure of PLLA fibers exhibited α′ and α forms, which comprised loosely and closely packed chains, respectively. As-electrospun PLLA fibers exhibited an unstable α′ phase because of the rapid solidification of polymer chains during electrospinning. Subsequent thermal annealing at a temperature higher than 140 °C induced a polymorphic transition from the α′ phase to the stable α phase. This finding differed from that observed in bulk PLLA, which exhibited α crystals regardless of annealing temperature. Furthermore, the polymorphic transition of α′ crystals to α crystals in fibers fabricated with 95:5 chloroform/trifluoroethanol solvent occurred with lower annealing temperatures or shorter annealing times relative to those fabricated with 60:40 chloroform/trifluoroethanol solvent. This behavior was attributed to the low entanglement content in the PLLA chains in fibers fabricated with 95:5 chloroform/trifluoroethanol solvent; the low entanglement content increased chain mobility, thereby accelerating polymorphic transition.
AB - The present study examined the thermal and crystallization properties of poly(L-lactide) (PLLA) chains confined in electrospun fibers. The heat of fusion and crystallite sizes decreased with a decrease in fiber diameter because of the confinement effect. The crystal structure of PLLA fibers exhibited α′ and α forms, which comprised loosely and closely packed chains, respectively. As-electrospun PLLA fibers exhibited an unstable α′ phase because of the rapid solidification of polymer chains during electrospinning. Subsequent thermal annealing at a temperature higher than 140 °C induced a polymorphic transition from the α′ phase to the stable α phase. This finding differed from that observed in bulk PLLA, which exhibited α crystals regardless of annealing temperature. Furthermore, the polymorphic transition of α′ crystals to α crystals in fibers fabricated with 95:5 chloroform/trifluoroethanol solvent occurred with lower annealing temperatures or shorter annealing times relative to those fabricated with 60:40 chloroform/trifluoroethanol solvent. This behavior was attributed to the low entanglement content in the PLLA chains in fibers fabricated with 95:5 chloroform/trifluoroethanol solvent; the low entanglement content increased chain mobility, thereby accelerating polymorphic transition.
UR - http://www.scopus.com/inward/record.url?scp=85118890217&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85118890217&partnerID=8YFLogxK
U2 - 10.1016/j.polymer.2021.124339
DO - 10.1016/j.polymer.2021.124339
M3 - Article
AN - SCOPUS:85118890217
SN - 0032-3861
VL - 237
JO - Polymer
JF - Polymer
M1 - 124339
ER -