## 3 Results and Discussion
### Characterization of the Rods and Rod with ARP
#### 3.3.2 Thermal Study  
Analysis of the DSC curves representing the first heating runs for the Td,L 21 rod, Tl 59 rod, and Tl 77 rod also did not reveal clear endotherms (Figure 6 and Table 3), which indicated the unchanged crystallographic state of the terpolymers in the blank rods after HME. However, for the Td,L 21 rod-ARP, Tl 59 rod-ARP, and Tl 77 rod-ARP, clear endotherms in the first heating run at 128.7 \({}^{\circ}\)C, 133.4 \({}^{\circ}\)C, and 133.6 \({}^{\circ}\)C (respectively) were revealed, which shows the presence of ARP. The peaks observed for the rods with ARP possessed lower values compared to raw ARP (140 \({}^{\circ}\)C) (Figure 2 and Table 2). Moreover, these were less intense and less sharp (Figure 6). Considering the data obtained from the XRD (Figure 1 and Table 1), DSC (Figure 2 and Table 2), HSM (Figure 3), and SEM  
Figure 7: The \({}^{1}\)H NMR spectra of blank rods (Td,L 21 rod, Tl 59 rod, and Tl 77 rod) and rods with ARP (Td,L 21 rod-ARP, Tl 59 rod-ARP, and Tl 77 rod-ARP) (600 MHz, DMSO-d6, 80 \({}^{\circ}\)C). \({}^{1}\)H NMR spectra: the proton region of the lactidyl units (1), the methylene proton region of the glycolidyl (2), and carbonate units (3). (Figure 4) studies on the structural characterization of ARP after HME, the difference between the \(T_{m}\) value of the identified form III of ARP (Figure 2 and Table 2) and the \(T_{m}\) of the rod-ARP (Figure 6 and Table 3) results from a relatively small amount of drug substance in the polymer carrier. It is an orderly and stable arrangement of two phases, _i.e._, crystalline APR suspended in the amorphous terpolymer. It should be pointed out that in the second heating run for the T_d_,\(l\) 21 rod-ARP and T_l_ 77 rod-ARP, endotherms at 130.3 \({}^{\circ}\)C (1.728 J/g) and 132.4 \({}^{\circ}\)C (0.705 J/g), respectively, were also observed (Figure 6). This may evidence the restoration of the orderly arrangement after amorphization of the samples during quenching. However, for the T_l_ 59 rod-ARP, the endothermic peak was absent, which may suggest the ARP was in an amorphous state or in a disordered crystalline phase of molecular dispersion in the polymer matrix. A similar conclusion was indicated by [PERSON] and coworkers for praziquantel-loaded poly(d,l-lactide-_co_-glycolide) (d,l-PLGA) nanoparticles in which one interpretation of the lack of an endotherm in the first heating run was that the drug was in an amorphous state or in a disordered crystalline phase of molecular dispersion in the PLGA polymeric matrix [28]. Analysis of the second heating runs revealed that the \(T_{g}\) of terpolymers is below the \(T_{m}\) of ARP. In addition, the terpolymers also have a flow temperature below the \(T_{m}\) of ARP. This makes it possible to formulate rods based on the synthesized thermoplastic terpolymers by HME at 105 \({}^{\circ}\)C without changing the crystallographic properties of form III of ARP. Moreover, analysis of the second heating runs revealed the well-known thermal phenomena for formulated rods showing that the formulation of blank rods did not reveal important changes for the stability of the formulation. The decrease in the \(T_{g}\) was revealed in the range of 1.2-2.6 \({}^{\circ}\)C comparing raw terpolymers and blank rods (Figure 6 and Table 3). The literature data point to the fact that the \(T_{g}\) decrease as a result of HME at a temperature above 100 \({}^{\circ}\)C is related to short-term hydrolytic degradation caused by the presence of moisture [29]. However, it should be noted that during the first heating run in this study, water evaporation as a flat endotherm was not revealed (Figure 6). The presence of oxygen in thermal degradation during HME is also not insignificant. It should be pointed out that the total elimination of moisture and oxygen is practically impossible [12; 29]. Furthermore, the plasticization effect for the T_d_,\(l\) 21 rod-ARP and T_l_ 59 rod-ARP was noted because of the decrease in the \(T_{g}\) (1.4 \({}^{\circ}\)C and 2.3 \({}^{\circ}\)C, respectively) (Figure 6 and Table 3).