DSC Differential Spectrum Applied in the Study of Hydrogen Bonding Interaction in Aqueous Solution

Abstract

In this work, thermal signals of the interaction between urea (UR) and partly hydrolyzed polyacrylamide (HPAM) in aqueous solution were first investigated by differential scanning calorimetry (DSC) differential spectrum and 2-dimensional (2-D) differential spectrum analysis. A remarkable interaction between urea and HPAM was found when the temperature was about 40°C. Near this temperature, the hydrogen bonding between the carbonyl group of HPAM and water would dissociate partly, and another hydrogen bonding between carbonyl and amino would form simultaneously. Not only the DSC differential spectrum, but also a rheological experiment and two-dimensional correlation infrared spectrum (2-D-IR) were used to prove this result.

Influence of molecular interplay on the HPAM/UR rheological properties in an aqueous solution

“…However, for various temperature series, the viscosity of the blend solution increases in the order: 65 C < 25 C < 55 C < 35 C < 45 C. It was considered that the addition of UR causes an increase in the viscosity, and this may involve hydrogen bond damage and restructuring, conformation variation, and thermal effect. 41 This behavior has been discussed further in the following section. As discussed above, intrinsic viscosity can directly reect interplay in a dilute solution.…”

“…Temperature has signicant effects on the intermolecular interaction and migration. In our previous study, 41 hydrogen bonding interaction in an aqueous solution explored by DSC differential spectrum was reported, and it was found that in the low shear rate region, the maximum apparent viscosity value occurred near 40 C in the temperature-rise period. Fig.…”

“…7 shows the apparent viscosity versus the shear rate curves for the HPAM solutions involving blends formed from two different compositions: 2000 mg L À1 HPAM and UR. 41 In the low shear rate area, Fig. 4 Schematic for the short-range and long-range interactions.…”

“…On the basis of abovementioned discussion, DSC differential spectrum was employed to explore the abovementioned interplay in an aqueous solution. [41][42][43] The difference of heat ow (DHF) between HPAM/UR and HPAM solutions and the corresponding DSC curves are shown in Fig. 12.…”

Diazepam Loaded Solid Lipid Nanoparticles: In Vitro and in Vivo Evaluations

“…Previous studies confirmed probability of hydrogen bong forming by lipid carriers for some drugs including curcumin and cholesterol as well as amikacin and ampicillin with the same lipid which can cause sustaining release profile of the drug. 28,29 In-vivo studies: According to the findings which were obtained from HPLC and presented in fig. 5, it seems that for free drug, the blood concentrations were higher in each sampling time in comparison with SLNs.…”