To explore the effects
of end groups on the confined crystallization
of an alkyl chain, 3-pentadecylphenol (PDP) was infiltrated into the
anodic aluminum oxide template (AAO) to investigate the melting and
crystallization behaviors of PDP in a nanoconfined environment. Wide-angle
X-ray diffraction (WAXD) found that the solid–solid phase transition
of PDP occurred under confined conditions, and the absence of the
(00L) reflections indicated that the stacking of the end groups of
the alkyl chain layered structure was seriously disturbed. Thermal
analysis (TG) showed that the thermal stability of the confined samples
decreased due to the confinement effect, and the introduction of end
groups made the confinement effect more obvious. Differential scanning
calorimeter (DSC) results well reflected the space–time equivalence
in the PDP crystallization processes, i.e., the solid–solid
phase transition can be achieved by reducing the cooling rate or confining
PDP in the nanometer space. Compared with C15, the introduction
of the end groups with a phenol ring led to the disappearance of the
solid–solid phase transition of an alkyl chain at high cooling
rates. In the confined environment, the introduction of the end groups
with a phenol ring caused the melting double peaks of the alkyl chain
to become a single melting peak, and it also caused the disappearance
of the surface freezing monolayer for alkyl chains. Through the analysis
of crystallinity, it was found that AAO-PDP was more sensitive to
AAO pore size changes than AAO-C15, the X
c of AAO-PDP had a good linear relationship with the pore
size d, but the X
c of
the AAO-C15 had a nonlinear relationship with the pore
size d. Attenuated total reflection (ATR)-IR proved
that in the confined environment, the order of the alkyl chain decreased
and the degree of chain distortion increased.
Due to the brittle performance of polyamide 6,12 (PA6,12) in high impact environment, we report a facile, efficient, and scalable method to toughen PA6,12 by establishing intermolecular hydrogen bonding (H‐bonding) interaction with 3‐pentadecylphenol (PDP). Interestingly, the intermolecular H‐bonding interaction obviously hindered PA crystallization, which was evidenced by decrease of crystalline temperature from 186.8 to 175.8°C and prolong of crystallization half‐time from 0.27 to 0.37 min, when the amount of PDP was increased to 30 wt%. Consequently, the toughness of the PA6,12/PDP composites containing 30 wt% PDP was improved and their notched impact strength reached to 17.5 kJ m−2, about three times higher than that of the neat PA6,12. It was deduced that both plasticizing effect and intermolecular H‐bonding interaction played critical roles in PA6,12 resultant composites toughness, which opens a new perspective of PA6,12 toughening for a wide range of applications.
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