Studies on Chemical IR Images of Poly(hydroxybutyrate–co–hydroxyhexanoate)/Poly(ethylene glycol) Blends and Two-Dimensional Correlation Spectroscopy

Abstract

Biodegradable poly-[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoates] (PHBHx) have been widely studied for their applications in potentially replacing petroleum-based thermoplastics. In this study, the effect of the high molecular weight (Mn = 3400) poly(ethylene glycol) (PEG) blended in the films of PHBHx with different ratios of PEG was investigated using chemical FTIR imaging. Chemical IR images and FTIR spectra measured with increasing temperature revealed that PEG plays an important role in changing the kinetics of PHBHx crystallization. In addition, two-dimensional correlation spectra clearly showed that thermal properties of PHBHx/PEG blend film changed when the blending ratio of PHBHx/PEG were 60/40 and 50/50. Consequently, PEG leads to changes in the thermal behavior of PHBHx copolymers.

Accelerated Weathering Effects on Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV/TiO2 Nanocomposites

“…The chemical structure changes of the PHBV and the PHBV/TiO 2 samples before and after the weathering test were investigated by FTIR. It can be seen in Figure 6 , the PHBV presents the characteristic bands of the neat polymer identified in previous works [ 25 , 31 , 32 , 34 , 72 , 73 , 93 ], i.e., the observed region of 3000–2800 cm −1 is assigned to the asymmetric and symmetric deformations in the methylene chains (–CH 2 –), and the bands at 1472, 1448, 1425, 1338, 1335 and 1313 cm −1 are due to the CH 2 and CH 3 asymmetric and symmetric deformations, and the C–O stretching characteristic bands are seen at 1255–1245 cm −1 for the crystalline domains, while the amorphous phase is indicated by the 1180 cm −1 peak. The strong absorbance peaks at 1713 and 1720 cm −1 are attributed to the stretching vibrations of the crystalline C=O carbonyl groups, while the absorption bands at 1730 and 1740 cm −1 are assigned to the amorphous C=O stretching.…”

“…To further confirm the extent of the degradation of each phase, the carbonyl index (ratio of the intensity heights of C=O/CH 3 ) was quantified before and after accelerated weathering. The absorbance ratios of 1720/1388 and 1713/1388 cm −1 were used to quantify the crystalline C=O of the PHBV and its nanocomposites, whereas 1730/1388 and 1740/1388 cm −1 were used to measure the amorphous carbonyl content [ 31 , 32 , 72 , 73 ]. The quantitative analysis of the carbonyl index and the ratio of crystalline/amorphous phases are presented in Table 1 .…”

“…In addition, a quantitative analysis of the ratio of the crystalline/amorphous phases was conducted. The absorbance ratios of the 1720/1388 and 1713/1388 cm −1 were used to quantify the crystalline carbonyl (C=O) content, while 1730/1388 and 1740/1388 cm −1 were used to calculate the amorphous C=O content of PHBV and its composites [ 31 , 32 , 72 , 73 ].…”

Understanding Thermal Behavior of Poly(ethylene glycol)-block-poly(N-isopropylacrylamide) Hydrogel Using Two-Dimensional Correlation Infrared Spectroscopy

“…Two-dimensional correlation spectroscopy (2D-COS) 20 is a very powerful analytical method to deeply understand the complicated IR spectra of the polymers. [21][22][23][24][25][26][27] In our previous study, we have successfully elucidated the phase transition mechanisms of PNiPAAm homopolymer hydrogel 26 and poly(N-isopropylacrylamide-co-acrylic acid) [P(NiPAAm-co-AAc)] copolymer hydrogel 22 using the 2D-COS.…”