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Influence of Poly(vinylphenol) Sublayer on the Crystallization Behavior of Poly(3-hydroxybutyrate) Thin Films
journal contribution
posted on 2013-02-26, 00:00 authored by Xiaoli Sun, Zhen Chen, Feng Wang, Shouke Yan, Isao TakahashiThe crystallization behavior of poly(3-hydroxybutyrate)
(PHB) thin
films on poly(vinylphenol) (PVPh) substrate was investigated by surface-sensitive
grazing incident X-ray scattering and infrared reflection–absorption
spectroscopy techniques. Compared with the crystallization of PHB
on a Si wafer, the PVPh sublayer did not significantly affect the
crystallization behavior of PHB in solution-cast samples, while significantly
inhibited the melt crystallization of PHB. For films thinner than
175 nm, amorphous PHB was always fabricated irrespective of melt crystallization
temperature. Only when the film thickness increased to 185 nm, the
PHB started to crystallize at temperatures above 53 °C. The PHB
crystals preferred to orient with the b-axes perpendicular
to substrate. The inhibition of PHB melt crystallization was attributed
to the thickness confinement and interdiffusion of PVPh and PHB, which
caused a concentration gradient of PVPh in the PHB layer. From the
thickness dependence of crystallization behavior, the PHB film can
be divided into two layers: the inactive layer with high fraction
of inter CO and stable amorphous state; the
interactive layer in which crystallization of PHB is sensitive to
temperature. The existence of inactive layer accounts for the formation
of crystals oriented with b-axes perpendicular to
substrate.