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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.

The crystal melting behaviors of poly(3-hydroxybutyrate) (PHB) and cellulose acetate butyrate (CAB) blends were studied using infrared (IR) and near-infrared (NIR) imaging, which provided information about spherulite growth in dynamic blend systems. By analyzing the changes in the IR and NIR imaging spectra in the regions of the first and second overtones of the CO stretching vibrations of PHB and CAB, the evolution of heterogeneous spherulite during the time-resolved isothermal crystallization process was explored. Time-resolved IR and NIR imaging and polarized microscopic studies detected the PHB domains are able to separate from the PHB/CAB blends early in the process. Principal component analysis (PCA) was used to classify the distribution of the different morphologies of spherulite. The first principal component suggests that the discrimination of the imaging spectra relies largely upon the crystallinity, while the second principal component indicates the variations in the amorphous portion of PHB, the CAB contents, and the intermolecular hydrogen bonding of PHB and CAB. The PC1–PC2 scores of different parts of the spherulite suggest that the areas of low crystallinity in the blend spherulite contain both PHB and CAB.

Self-assembly of poly­(3-hydroxybutyrate) (PHB) and cellulose acetate butyrate (CAB) blends prepared by solvent casting was investigated by simultaneous synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction as a function of temperature in a heating process of the blends. The results revealed different elemental processes occurring in three characteristic temperature regions: (1) low-T region, where cold crystallization (CC) of PHB into one-dimensional (1D) assemblies of PHB lamellar crystals occurs in the temperature (T) range T cc,PHB ≤ T ≤ T cc,CAB, where T cc,PHB and T cc,CAB are the onset temperature for CC in PHB and CAB, respectively; (2) crossover-T region, where partial melting/recrystallization of PHB occurs concurrently with CC of CAB in the interstitial amorphous matrix among the 1D PHB lamellar assemblies at T cc,CAB < T ≤ T*, where T* is a characteristic temperature close to the T at the higher melting endothermic peak of differential scanning calorimetry (DSC), T m,DSC; and (3) high-T region, where PHB crystals melt and CAB partially melts/recrystallizes at T > T*. The study also elucidated for the first time in this blend systems, to our best knowledge, the following points: (a) the existence of two glass transition temperatures (T g’s) in the amorphous matrix, with a lower T g (T g,l) determined by DSC and a higher T g (T g,h) determined from the SAXS intensity at low q (magnitude of the scattering vector) values as a function of T; (b) the evolution of the large length-scale composition fluctuations in the amorphous matrix of the blend at T g,h ≤ T ≤ T cc,CAB; (c) crystallization of CAB at T > T cc,CAB and a melting temperature for CAB crystals higher than 183 °C. The roles of intermolecular hydrogen bondings (HBs) between PHB and CAB, intramolecular HBs within PHB, and those within CAB as well as roles of the exchanges of those HBs on the self-assembling process, the composition fluctuations, and the miscibility of the blends in the amorphous phase were also clarified in the text.

In this research, near-infrared (NIR) spectroscopy in combination with moving window partial least squares-discrimination analysis (MWPLS-DA) was utilized to discriminate the variety of turmeric based on DNA markers, which correlated to the quantity of curcuminoid. Curcuminoid was used as a marker compound in variety identification due to the most pharmacological properties of turmeric possessed from it. MWPLS-DA optimized informative NIR spectral regions for the fitting and prediction to {-1/1}-coded turmeric varieties, indicating variables in the development of latent variables in discrimination analysis. Consequently, MWPLS-DA benefited in the selection of combined informative NIR spectral regions of 1100 -1260, 1300 -1500 and 1880 -2500 nm for classification modeling of turmeric variety with 148 calibration samples, and yielded the results better than that obtained from a partial least squares-discrimination analysis (PLS-DA) model built by using the whole NIR spectral region. An effective and rapid strategy of using NIR in combination with MWPLS-DA provided the best variety identification results of 100% in both specificity and total accuracy for 48 test samples.