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<p>The structure of several classes of polyhydroxyalkanoates was studied via micro-Raman spectroscopy, including poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxyoctanoate) (PHO) and poly(3-hydroxy butyrate-co-4-hydroxybutyrate) (PH34B) polyesters. PHB, PHBV and PHO samples were biosynthesized at lab-scale by pure and mixed microbial cultures while the study included also commercially available materials including PH34B. The aim was to correlate the vibrational contribution of the side chains with the 3HV content, as well as to extend the correlation to higher branches or methylene sequences of recently emerging alternative hydroxyalkanoates, such as the medium-chain-length (mcl) 3-hydroxyoctanοate or even 4-hydroxybutyrate. The micro-Raman statistical data for PHBV were correlated with those from the standard GC-FID chromatographic characterization technique with the correlation accounting for an R<sup>2</sup> of over 0.96 for the peak at 840&#xa0;cm<sup>− 1</sup>. A second peak (at 1363&#xa0;cm<sup>− 1</sup>), which has also been taken into account previously, is hindered due to overlap by spectral features of additives found in commercial materials. Regarding the different HAs, it is demonstrated in the present work that the correlation through the 1450&#xa0;cm<sup>− 1</sup> peak (R<sup>2</sup> = 0.98) is capable of quantitatively comparing the degrees of copolymerization in different PHA classes containing short or medium chain length (scl or mcl) HAs. The effect of the extent of the biosynthetic copolymerization was depicted on the thermal properties of these materials by delaying their crystallization kinetics and significantly reducing both their non-equilibrium and equilibrium melting temperatures, predicted by the random copolymer crystallization theories, as shown by DSC, with copolymerization not affecting their decomposition temperatures (TGA). It is thus demonstrated that either intracellular copolymerization with 3HV or switching to mcl HAs, quantitatively observed by Raman spectroscopy, could increase the processing window of these materials, providing a handy insight into the intended heat treatment of scl or mcl types of PHA materials.</p>

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The Estimation of Composition in Biosynthetic PHA Materials via fast Raman spectra giving insights into thermal processability dynamics

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月31日

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  • Panagiotis C. Tsaousis,
  • Elianta Kora,
  • Konstantinos S. Andrikopoulos,
  • Ioanna Ntaikou,
  • Giannis Penloglou,
  • Gerasimos Lyberatos,
  • George A. Voyiatzis

摘要

The structure of several classes of polyhydroxyalkanoates was studied via micro-Raman spectroscopy, including poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxyoctanoate) (PHO) and poly(3-hydroxy butyrate-co-4-hydroxybutyrate) (PH34B) polyesters. PHB, PHBV and PHO samples were biosynthesized at lab-scale by pure and mixed microbial cultures while the study included also commercially available materials including PH34B. The aim was to correlate the vibrational contribution of the side chains with the 3HV content, as well as to extend the correlation to higher branches or methylene sequences of recently emerging alternative hydroxyalkanoates, such as the medium-chain-length (mcl) 3-hydroxyoctanοate or even 4-hydroxybutyrate. The micro-Raman statistical data for PHBV were correlated with those from the standard GC-FID chromatographic characterization technique with the correlation accounting for an R2 of over 0.96 for the peak at 840 cm− 1. A second peak (at 1363 cm− 1), which has also been taken into account previously, is hindered due to overlap by spectral features of additives found in commercial materials. Regarding the different HAs, it is demonstrated in the present work that the correlation through the 1450 cm− 1 peak (R2 = 0.98) is capable of quantitatively comparing the degrees of copolymerization in different PHA classes containing short or medium chain length (scl or mcl) HAs. The effect of the extent of the biosynthetic copolymerization was depicted on the thermal properties of these materials by delaying their crystallization kinetics and significantly reducing both their non-equilibrium and equilibrium melting temperatures, predicted by the random copolymer crystallization theories, as shown by DSC, with copolymerization not affecting their decomposition temperatures (TGA). It is thus demonstrated that either intracellular copolymerization with 3HV or switching to mcl HAs, quantitatively observed by Raman spectroscopy, could increase the processing window of these materials, providing a handy insight into the intended heat treatment of scl or mcl types of PHA materials.