## 3 Results and Discussion
### Three-Component Analysis  
As we explained in the introduction, one of the keys to the identification of the appropriate fraction of water is its melting temperature. For this purpose, we assigned each component a corresponding temperature in this process. Figure 4 shows an example, where determined raw HPC components were grouped in an order determined by the temperature--from the highest to the lowest: first series--the highest temperature--free water fraction FW, second series, fraction of freezing bound water FBW, and third series--last in order, the lowest temperature--NFW fraction. Such assignment allows observing how water fractions are distributed in the polymer matrix or its mixture with drugs. One can see that the T\({}_{\text{max}}\) temperatures of the FW fraction (blue circles) were mostly positive, while the non-freezing water pool (red empty circles) was characterized by negative temperatures. This is due to the fact that the NFW is defined only by water molecules strongly bound by hydrogen bonds and/or embedded in nanocavities of polymer chains. What are nanocavities? FW, FBW, and NFW coexisting in the polymer system form complexes consisting of polymer chains, ice (frozen water), unfrozen water, and air, represented by empty spaces. Both ice and unfrozen water can be trapped in the cavities and/or pores of the matrix. When the dimensions of such a spatial formation do not exceed several Angstroms, the crystallization process is difficult or even impossible. [PERSON] et al. (2019) called such hollow spaces \"nanocavities\" and proved that they are able to form the NFW fraction of water. In this way, they concluded that hydrogen bonding is not the only one factor influencing water crystallization and suggested that it is just one of the possible physical states of hydrated systems. As the NFW pool increases, the interactions between successive layers of water are still strong enough, but they weaken as the water concentration increases. Thus, the temperature T\({}_{\text{max}}\) of the water fraction is initially negative and then, when the distances between the binding sites decrease, it becomes positive. In this way, the next fraction of water appears in the matrix. The FBW fraction's temperatures are negative at low water concentrations (up to around 1.5 g/g), but positive at higher concentrations (>1.5 g/g). In the next section of this paper, we show the dependence of the surface area of the water fractions, obtained after a deconvolution procedure (grouped using the maximum temperatures T\({}_{\text{max}}\)), on water concentration W\({}_{\text{c}}\). Figure 5 provides a very interesting observation. The FW fraction (blue circles) is below the other fractions, and for low concentrations--around W\({}_{\text{c}}\)\(\leq\) 1.1 g/g--the concentrations of all water fractions are almost the same. Initially it may seem strange, but such a phenomenon was explained using Raman spectroscopy (Kal  
hydroxypropy cellulose type MF. In the conclusions of this work, the authors pointed out that for low water contents equal to 0.69 g/g, all water found in the matrix was considered to be non-freezing. That is why the concentrations of all water fractions were almost the same. Next, it was mentioned that in the polymer samples with a water concentration of 1.41 g/g, a decrease in FWB water content was found, while the concentrations of the other types of water remained at the same level. This phenomenon can be easily seen in Figure 5. Finally, the authors concluded that for a water content W\({}_{\text{c}}\geq\) 2.2 g/g, the increase in the concentrations of all types of water began after 16 days. These features seem to be associated with a transition from an anisotropic to an isotropic structure, caused by the clustering of hydrophobic groups. The above-mentioned process appears in the form of irregular changes in the concentration of each water fraction: an initial increase, then a decrease, and finally a new increase.