Structure Evolution in Amylopectin/Ethylene Glycol Mixtures by H-bond Formation and Phase Separation Studied with Dielectric Relaxation Spectroscopy

Abstract

The interaction between amylopectin, a starch polysaccharide, and ethylene glycol (EG) was investigated using broad-band dielectric relaxation spectroscopy. Water-free amylopectin (AP) was mixed with 21 wt % ethylene glycol. This resulted in a continuous ethylene glycol phase, as well as a molecularly mixed AP/EG fraction. After storage at room temperature or annealing, the mixture shows dynamic properties typical of a polymer with weak intermolecular interactions, suggesting that EG binds preferentially to AP and forms intrachain H-bridges leading to increased chain stiffness and thus an increased glass transition temperature. This structure evolution is accompanied by a sharp reduction in the size of the ethylene glycol droplets to a few nanometers, as revealed by pronounced confinement effects in the R-relaxation of the dispersed EG.

Diffusion mechanism for physical aging of polycarbonate far below the glass transition temperature studied by means of dielectric spectroscopy

“…To give experimental evidence to the existence of such regions, a number of PC samples subjected to the same cooling rates used for aging experiments were exposed to ethylene-glycol (EG) for a fixed time of 3 days. EG was chosen for its high tendency to aggregate in low density regions, as recently demonstrated by Smits et al [22] for a starch polysaccharide. After this treatment, the PC samples were weighed in order to evaluate the amount of absorbed EG.…”

Multiple glass transitions in the plastic crystal phase of triphenylene derivatives

“…4 and 5, which show the dielectric loss e 00 deriv ðf ; T Þ for both materials as a function of the frequency and temperature. Like in previous studies [17,19,20], we have used the Ôconduction-freeÕ dielectric loss (e 00 deriv ), computated from the real part of the dielectric spectrum e 0 (f) [17], in order to eliminate excessive contributions from (Ohmic) conduction in the loss spectra. The resulting loss spectra reveal various relaxation processes as well as marked discontinuities indicating the first-order phase transitions.…”

Effect of corn starch content in thermoplastic starch/low‐density polyethylene blends on their mechanical and flow properties

“…Also, utilizing a plasticizer to improve dispersion of starch in PE matrix and promoting interfacial adhesion between PE and starch has been investigated 13, 14. Some materials, such as glycerol, sorbitol, glycol, urea, ethanolamine, ethylenebisformamide, and water are usually used to plasticize starch 15–20. Starch granules swell after absorbing plasticizers, like glycerol, through hydrogen bonding with their free hydroxyl groups, but they still retain their order and crystallinity 21.…”