Fundamentals and Calibration of the DSC Technique for Hydrogel Thermoporometry

Abstract

Hydrogels are cross-linked polymeric networks. They can be used in many biomedical applications such as drug delivery, tissue engineering and bio-separations. Characterization of the hydrogel pore structure is very important in order to select the appropriate gel type for a particular application. Thermoporometry is a powerful technique that is may be used to study the structure of hydrogels. Both pore-size and pore-size distribution may be measured by using an instrument called the differential scanning calorimetry(DSC). This technique relies on the melting or freezing temperature depression of the water confined in a pore. Thermoporometry by DSC is a unique method for characterizing gel networks. Since there is no general procedure for measuring pore-size, further investigation is required to establish guidelines for the analysis of specific materials. Although some formulas have been developed, choosing the right equation for calculating pore size is still challenging. Many of the parameters incorporated in these equations are specific to the gel type (e.g. the natural of the porous material, the range of the pore size tested, and the probe liquid used). For this reason, it is important to develop an equation for the specific pore size of the hydrogel of interest.
In this work, the DSC has been well-calibrated with high purity mercury. Two gel types will be characterized: regular hydrogel and nanotemplated hydrogels with a modified pore structure. The results will then be analyzed in order to study the effects of the size, geometry and shape of the templating agent on hydrogel performance.