Effect of Nanoconfinement on the Isodimorphic Crystallizationof Poly(butylene succinate- ran -caprolactone) RandomCopolymers
2020
In
this paper, we study for the first time the effect of hard confinement
on the isodimorphic crystallization of random copolyesters. A series
of poly(butylene succinate-ran-caprolactone) samples
encompassing the entire composition range were successfully infiltrated
into nanoporous alumina templates (anodic aluminum oxide (AAO)) with
a fixed diameter of 100 nm. The samples were characterized using scanning
electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared
spectroscopy (FTIR), differential scanning calorimetry (DSC), and
grazing-incidence wide-angle X-ray scattering (GIWAXS). FTIR proved
that poly(butylene succinate) (PBS)-rich nanofibers showed interactions
between the copolyester chains and the walls of the AAO templates;
however, the poly(e-caprolactone) (PCL)-rich nanofibers did
not show any interaction with the AAO walls. All infiltrated samples
experienced a very large decrease in crystallization temperature,
as expected, since the level of confinement is large enough to suppress
heterogeneous nucleation. In spite of this, all copolymers were able
to crystallize, regardless of composition. Additionally, when Tc or Tm is plotted
versus copolymer composition, a clear pseudoeutectic point is observed.
These results indicate that the isodimorphic behavior of the copolyesters
is maintained under hard confinement. Infiltrated PCL undergoes homogeneous
nucleation (inside the nanopore volume) as expected by the lack of
interaction with the AAO walls. On the other hand, PBS exhibited a
surface nucleation mechanism triggered by the interactions with the
AAO walls. In the case of random copolymers, all PCL-rich copolymers
nucleated homogeneously. However, in the case of PBS-rich copolymers,
the nucleation gradually changed from surface-induced nucleation for
neat PBS to homogeneous nucleation as the PCL concentration in the
copolymers increased and the interactions of PBS chains with the AAO
walls are diluted. The confinement under 100 nm nanopores did not
change the orientation of the PBS or PCL phase crystals, which kept
their chain direction perpendicular to the pore axis, as demonstrated
by GIWAXS.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
60
References
7
Citations
NaN
KQI