Effects of Intermolecular Hydrogen Bondings on Isothermal Crystallization Behavior of Polymer Blends of Cellulose Acetate Butyrate and Poly(3-hydroxybutyrate)

Abstract

Effects of hydrogen bondings (HBs) on the isothermal crystallization kinetics and mechanisms of poly(3-hydroxybutyrate) (PHB) in neat PHB and its blends with cellulose acetate butyrate (CAB), amorphous melts at the crystallization temperature, were investigated by using time-resolved Fourier transform infrared spectroscopy (FTIR). The FTIR investigation focused on the characteristic bands of PHB in the crystalline phase and in the amorphous phase. The results revealed the following pieces of evidence. (1) The crystallization of PHB in both neat PHB and PHB/CAB blends commonly involves a multistep process: (i) transformation from amorphous melts to an intermediated structure between amorphous and crystals (process (b1) shown above), (ii) from the intermediate structure to crystals without intramolecular HBs (intra) (b2), and (iii) finally to crystals with intra (b3). (2) These transformations sequentially occur with increasing time. More specifically, the transformations (ii) and (iii) dominantly occur respectively in the primary and secondary crystallization process in both neat PHB and the blends. The Avrami analysis revealed that (3) the crystallization in both neat PHB and the blends involves essentially the same nucleation and growth mechanism, as evidenced by almost the same value of the Avrami exponent n; however (4) the crystallization rate constant k A, also determined from the Avrami analysis, is strikingly reduced by blending CAB (see the k A value for the PHB/HCAB blend in the text), which is attributed to physical cross-links formed by intermolecular HBs between PHB and CAB in addition to molecular entanglements.

Mechanical and Morphological Evaluation of the Reinforcement of Polycaprolactone With Different Cellulose Fibers

“…For PCL blends with amorphous cellulose derivatives, Kusumi et al proposed that derivatives such as cellulose alkyl esters and ethyl cellulose were miscible with PCL chains and the resulting diluent effect could lead to decreased crystallization temperature of PCL and reduced crystallization rates. Similar results have also been reported for poly(butylene succinate) and poly(b‐hydroxybutyrate) blends with amorphous cellulose.…”

Multistep Crystallization Process Involving Sequential Formations of Density Fluctuations, “Intermediate Structures”, and Lamellar Crystallites: Poly(3-hydroxybutyrate) As Investigated by Time-Resolved Synchrotron SAXS and WAXD

“…It is interesting to note the followings: each of the 020 and 110 diffraction profiles at 218 s has a peak position slightly larger than those up to 32 s. The multiple diffraction profile at 218 s shows the three distinct diffraction peaks around q = 14.2, 15.1, and 15.9 nm −1 as shown by the arrows together with the corresponding lattice 21 provided the following piece of evidence in favor of model (b) as will be described below.…”

Intermolecular hydrogen bondings in the poly(3-hydroxybutyrate) and chitin blends: Their effects on the crystallization behavior and crystal structure of poly(3-hydroxybutyrate)

“…In the PHB/cellulose acetate butyrate (CAB) blends [27], the weak intermolecular hydrogen bonds between the OH groups in CAB and the C=O groups in the amorphous part of PHB (O-H···O=C) are formed in the blends with the high CAB content. These intermolecular interactions in the PHB/CAB blends highly depend on temperature and affect the crystallization kinetic of PHB in the blends [28]. Accordingly, the presence of these hydrogen bondings in the general polymer blends plays significant effects on the crystallinity, thermal properties, solubility and miscibility of the polymer blends [33,34].…”

“…On the other hand, chitin has hydroxyl and amide functional groups that may promote the formation of intermolecular hydrogen bondings with carbonyl groups of PHB. The intermolecular interaction, such as C=O···H−O and C=O···H−N hydrogen bonds, is an essential factor to reduce the crystallinity of PHB M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT which further will improve the physical properties of PHB [16,17,27,28]. Therefore, the blending of PHB with chitin is expected to fabricate a good biodegradable and biocompatible polymer with more wide-range applications.…”

“…Our group has reported a series of studies on PHB, including its copolymers and blends from the structure, thermal and crystallization behavior points of view by combination of various experimental techniques, such as infrared, near infrared, Raman and terahertz spectroscopy, X-ray diffraction (Wide-angle X-ray diffraction; WAXD and Small-angle scattering; SAXS), two-dimensional correlation spectroscopy and quantum chemical calculations [12,13,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. One of the most important features in our M A N U S C R I P T…”