期刊
ACS APPLIED POLYMER MATERIALS
卷 3, 期 8, 页码 4109-4117出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsapm.1c00590
关键词
polyhydroxyalkanoates; stress-induced crystallization; beta-form; tie chain; poly((R)-3-hydroxybutyrate-co-4-hydroxybutyrate); synchrotron radiation X-ray scattering
资金
- National Natural Science Foundation of China [51973207, 51903230]
- Natural Science Foundation of Anhui Province [2008085ME137, 202004a05020075]
The study investigated the stress-induced crystallization and transformation mechanism of the beta-form of P(3HB-co-4HB) during stress loading and unloading processes. It was found that specific conditions are required for the formation of the beta-form, which can enhance the overall performance of PHAs.
The stress-induced crystallization of the metastable beta-form of poly((R)-3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) during the stress loading and unloading process was systematically investigated by in situ synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) measurement. During deformation, the major content of the beta-form is found to be transformed from the fully extended tie chain, while a minor part from the deformed alpha-form. During retraction, the beta-form finally transforms into a highly oriented alpha-form. The stress-induced crystallization rate of the beta-form is not affected by temperature, implying the constant nucleation barrier of the beta-form at different temperatures. The critical stress of beta-form formation and melting is determined to be about 7.8 and 1.5 MPa, respectively. The necessary conditions for the formation of the beta-form are summarized as follows: (1) the tie chains between lamellae need to be fully extended, and (2) the applied stress needs to exceed the critical stress of formation of the beta-form. The unveiled beta-form formation mechanism can directly contribute to our understanding of the origin of enhanced macroscopic performances of biodegradable polyhydroxyalkanoates (PHAs) through incorporating comonomer.
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