Modified hydroxypropylmethylcellulose (HPMC) belongs to an important family of compounds in pharmaceutical applications. Basically, this polymer (and other simmilar materials) is used for controled release of active pharmaceutical ingredients (so the drug is released at a more or less constant pace in the body). As normally happens in chemistry, the chemical characteristics of these materials have a decisive impact on its physical properties (solubility, cloud point, release decay curve, etc.). Characterization of these materials is not trivial beacuse of several reasons. One of the main hurdles is that these materials are polydisperse in many domains (they can have different size, different degrees of substitution, different tacticity, etc.). In this project we were using two-dimensional chromatography to characterise the substance. To our surprise, not only the separation conditions in first- and second-dimension separation were critical, but also the temperature at which the analysis is performed, due to the phenomenon of thermal gelation. We could correlate the temperature at which half of the polymer is gelated with the cloud-point temperature by using (non-linear) sigmoid regression [33a].
This project was developed at different institutions. Several people were involved. Look into presentations co-authorship for more information.