A pair of ATR IR spectra obtained during the crystallization of bioplastic copolymer poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] or PHBHx from the melt by spontaneous cooling were examined using the two-trace two-dimensional correlation spectroscopy (2T2D-COS) analysis. Unlike conventional difference spectra, 2T2D spectra showed unexpected details for the patterns of spectral intensity changes, clearly revealing the existence of two distinct populations of crystalline contributions, attributed to the well-ordered primary crystals and the less ordered secondary crystals, in addition to the amorphous component. The 2T2D spectrum sorts out highly overlapped bands associated with different constituents of the system, based on the fundamental properties and constraint imposed on a pair of spectra. Hetero-mode asynchronous 2T2D correlation analysis between the congested CH-stretching region and better resolved carbonyl-stretching region further indicates that the increase in the intensities of certain methyl and methylene bands during the crystallization process is mostly associated with the growth of the well-ordered primary crystals of PHBHx instead of the formation of the secondary crystals in the confined inter-lamellar space.

在生物塑料共聚物聚[(R)-3-羟基丁酸酯-co-(R)-3-羟基己酸酯]或PHBHx从熔体通过自发冷却结晶过程中获得的一对ATR IR光谱使用两迹二-维相关光谱 (2T2D-COS) 分析。与传统的差分光谱不同，2T2D 光谱显示了光谱强度变化模式的意外细节，清楚地揭示了两种不同的结晶贡献群体的存在，这归因于有序的初级晶体和不太有序的次级晶体，以及非晶态成分。2T2D 光谱基于对光谱施加的基本属性和约束，筛选出与系统不同组成部分相关的高度重叠的波段。