Formation of Poly(3-hydroxybutyrate) (PHB) Inclusion Compound with Urea and Unusual Crystallization Behavior of Coalesced PHB

Abstract

PHB-U-IC has been prepared for the first time by the cocrystallization method. The structure and conformation of poly­(3-hydroxybutyrate) (PHB) chains encapsulated in urea (U) channels formed in the PHB-U inclusion complex (PHB-U-IC) were studied by DSC, FTIR, and solid-state NMR spectroscopy. The XRD pattern and FTIR spectroscopy demonstrated that PHB-U-IC takes a different crystal structure than the well-reported hexagonal and trigonal crystal structures of polymer urea inclusion compounds. PHB-U-IC takes an expanded tetragonal crystal structure. The conformation of PHB in the confined environment has been characterized by solid-state NMR spectroscopy and shown that PHB adopts a conformation similar to bulk PHB. The crystallization and thermal properties of as-received PHB and PHB coalesced from its U-IC were compared and demonstrated that the coalesced PHB crystallizes much slower than as-received PHB. Crystallinity of nonisothermally melt crystallized as-received PHB was found to be significantly higher than the crystallinity of nonisothermally melt crystallized coalesced PHB, indicating that coalesced PHB is not easily converted into semicrystalline PHB.

Confinement Effects on the Crystallization of Poly(3-hydroxybutyrate)

“…PHB is also an ideal model system to investigate crystallization under confinement. ,,, First, there is abundant data on the crystallization of PHB in the bulk and thin films, providing an excellent base for comparison to understand the influence of interfacial interactions and curvature of the interface. − Second, the segmental dynamics of PHB molecular chains (α-process) can be easily investigated by BDS either in the molten or crystalline state, enabling a facile route to study crystallization. , From the frequency dependence and strength of the α-process, interfacial, , spatial confinement effect, and crystallization behavior,,, can be directly accessed.…”

Construction of Stretchable and Large Deformation Green Triboelectric Nanogenerator and Its Application in Technical Action Monitoring of Racket Sports

“…As the results show, pure PLCL presented a relatively obvious absorption peak at 2942 cm –1 , which corresponds to the −CH 2 – stretching group in the molecular skeleton of PLCL. − In addition, with the increase of PLCL contents, the absorption peak of the −CH 2 – stretching group gradually widened. Due to the stretching vibration of the −CO– bond of the carbonyl group, the PHB membranes, the PHB/PLCL composite membranes, and the PLCL membranes had strong characteristic absorption peaks of −CO– in the region between 1700 and 1793 cm –1 . ,, The vibration absorption peak of −C–H– appeared at 1454 cm –1 , and that of −C–O– appeared at 1084 cm –1 . The absorption peak became significantly larger with the increase of PLCL contents.…”

Enhancing Stereocomplexation Ability of Polylactide by Coalescing from Its Inclusion Complex with Urea

“…The new melting point, which was consistent with previous reports on other polymer/urea complexes, indicated the successful preparation of the PLLA/urea inclusion complex [ 42 ]. More interestingly, inclusion complexes between poly( r -3-hydroxybutyrate) (PHB) and urea, and between polypropylene and urea, showed almost the same melting point (136.8 and 138.0 °C) as PLLA/urea complex [ 44 , 45 ], so the melting point at around 137 °C might be a common phenomenon for the polymer/urea inclusion complexes when polymer chains contain pendant methyl groups. Figure 1 B shows the FTIR spectra of in the regions from 3500 to 3300 cm −1 and 1820 to 1400 cm −1 obtained for urea, the PLLA/urea complex, and PLLA.…”