Intermolecular Hydrogen Bonding between Poly[(R)-3-hydroxybutyrate] (PHB) and Pseudoboehmite and Its Effect on Crystallization of PHB

Abstract

In the present study, we focused on the intermolecular H-bonding interactions of poly­[(R)-3-hydroxybutyrate] (PHB) with an inorganic material, pseudoboehmite (PB), and their effect on PHB crystallization. Noncrystallizable atactic PHB and crystallizable isotactic PHB (a-PHB and i-PHB) ultrathin films were spin-coated on a PB substrate, as well as an aluminum oxide (AO) and a gold substrate for comparison. Infrared reflection–absorption spectroscopy (IRRAS) data show an absorption peak in the carbonyl region located at 1724 cm–1 for a 2.8 nm a-PHB film deposited on PB. A peak at this frequency, often observed for thick bulk crystalline i-PHB films, was not observed for a 1.4 nm a-PHB film deposited on a gold or AO substrate, indicating that the 1724 cm–1 peak observed for a-PHB on PB is not due to a geometric confinement effect or crystallization but due to the existence of intermolecular H-bonding (H-bondinter) between −CO of a-PHB and −OH from PB. Supercooled, amorphous i-PHB was also found to exhibit the same H-bondinter with PB. It was found that a PB surface significantly modified the crystal orientation and morphologies of the films. Grazing incident wide-angle X-ray diffraction (GIWAXD) data show that the crystallites in i-PHB on PB are randomly oriented, whereas those on AO are predominantly edge-on oriented. Polarized optical microscopy (POM) images show spherulites for i-PHB on AO, whereas no spherulites were observed for i-PHB on PB. This study demonstrates a novel method of using PB to modulate the crystallization behavior of PHB thin films.

Effect of Graphene Oxide on the Properties of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate)

“…All these facts are indicative of the strong PHBHHx-GO interactions. Similar behaviour of peak shift due to H-bond formation has been previously reported for PHB reinforced with other fillers such as ZnO [9], silica [30], pseudoboehmite [31], cellulose [32], etc.…”

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Bionanocomposites with Crystalline Nanocellulose and Graphene Oxide: Experimental Results and Support Vector Machine Modeling

“…The shift is stronger for the nanocomposite with 1 wt% CNC and 1.5 wt% GO, suggesting the formation of additional hydrogen bonds between the remaining OH moieties of the nanofillers that acted as proton donors and the CO moieties of the ester groups of the polymer that acted as proton acceptors [ 14 ]. An analogous phenomenon of a shift in the peak position due to the formation of hydrogen bonds, albeit with smaller changes in wavenumber, has been previously reported for other polyhydroxyalcanoates reinforced with different nanofillers such as ZnO [ 7 ], silica [ 28 ], or pseudoboehmite [ 29 ].…”

Multifunctional montmorillonite/polyhydroxy butyrate composites using surfactant structure modulation strategy for packaging applications

“…The ordered hydrogen-bonded C=O structure is associated with the absorption peaks in the bands ranging from 1600 to 1680 cm À1 , whereas the disordered non-hydrogen-bonded bound structure is mostly associated with the bands ranging from 1680 to 1800 cm À1 . 36 The samples' 1600$1800 cm À1 bands contained six subpeaks in total, with M7@PHB having a lower relative hydrogen-bonded C=O concentration (6.03%) in these bands. The relative content of hydrogenbonded C=O exhibits a considerable increase followed by a decline to the degree of modification; sample C16M7@PHB has the greatest relative content of hydrogen-bonded C=O, at 9.03%.…”

“…The strength and bandwidth of the hydrogen-bonded C=O absorption peaks can vary depending on the changes in the contact force between the groups caused by hydrogen bonding. 35,36 The choice was made to adapt the operation to the hydrogen bonding of the composite films to obtain insight into the impact of various structurally active agents on that bond. A comparison can be done based on the shift degree of characteristic peaks because hydrogen bonding enables a decrease in the density of the electron cloud distribution of the groups, which causes a red shift of the characteristic peaks.…”