Alfano Sara, Pagnanelli Francesca, Martinelli Andrea
Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
Polymers (Basel). 2023 Oct 18;15(20):4127. doi: 10.3390/polym15204127.
A great research effort is involved in polyhydroxyalkanoates (PHAs) production and characterization since they are an attractive degradable polyester family that potentially could substitute oil-based polymers. This is due to two main key factors: their production is sustainable, being that they are produced by microorganisms possibly fed by organic waste-derived products, and they are degradable. Moreover, PHAs' thermal and mechanical properties could be tuned by varying their monomeric composition through the proper selection of microorganism feedstock and bioreactor operative conditions. Hence, a rapid and facile determination of the PHA chemical structure by widely available instrumentation is useful. As an alternative to the standard gas-chromatographic method, a new procedure for the composition determination of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HBV), the most common PHA copolymer, by attenuated total reflection FTIR (ATR-FTIR) is presented. It is based on the linear dependence of selected and normalized absorption band intensity with the molar fraction of repeating units. To break free from the crystallinity variability, which affects the result reproducibility and data scattering, the polymer sample was rapidly quenched from the melt directly on the surface of the ATR internal reflection element and analyzed. The data obtained from 14 samples with a molar fraction of 3-hydroxybutyrate repeating units () ranging from 0.15 to 1 were analyzed. According to preliminary analyses, the normalized intensity of two absorption bands was selected to develop a calibration method able to predict of unknown samples and to evaluate the related uncertainty through prediction intervals of inverse regression. The proposed method proves to be useful for an easy and rapid estimation of P3HBV composition.
聚羟基脂肪酸酯（PHA）的生产和表征涉及大量的研究工作，因为它们是一类有吸引力的可降解聚酯家族，有可能替代石油基聚合物。这主要归因于两个关键因素：它们的生产是可持续的，因为它们是由可能以有机废物衍生产品为食的微生物生产的，并且它们是可降解的。此外，通过适当选择微生物原料和生物反应器操作条件来改变PHA的单体组成，可以调节其热性能和机械性能。因此，利用广泛可用的仪器快速简便地测定PHA的化学结构是很有用的。作为标准气相色谱法的替代方法，本文提出了一种通过衰减全反射傅里叶变换红外光谱（ATR-FTIR）测定聚（3-羟基丁酸酯-co-3-羟基戊酸酯）（P3HBV）（最常见的PHA共聚物）组成的新方法。它基于选定的归一化吸收带强度与重复单元摩尔分数的线性关系。为了摆脱影响结果重现性和数据分散性的结晶度变化，将聚合物样品从熔体中直接快速淬灭到ATR内反射元件表面并进行分析。分析了14个样品的数据，这些样品中3-羟基丁酸酯重复单元（）的摩尔分数范围为0.15至1。根据初步分析，选择两个吸收带的归一化强度来建立一种校准方法，该方法能够预测未知样品的，并通过反向回归的预测区间评估相关不确定性。所提出的方法被证明对于轻松快速地估计P3HBV组成是有用的。
