## 3 Results and Discussion  
### Structural Investigation of Star-Shaped PLA Polymers  
Star polymers present lower \(\mathrm{T_{m}}\) as well as \(\mathrm{T_{g}}\), and crystallization temperatures (\(\mathrm{T_{c}}\)) than their linear equivalents. Furthermore, star-shaped PLA copolymersers exhibit coiling, and have lower hydrodynamic volumes and higher viscosity than linear PLA. Numerous studies on PLA star polymers have investigated their potential use in drug delivery and self-assembled micelles [49; 50; 51; 52]. Researchers have examined their morphology, solution behavior, and loading capacity. Small molecules and model drugs have been successfully encapsulated, with release profiles typically showing reduced burst effects and shorter initiation times compared to similar linear systems. Star-shaped architectures provide enhanced control over degradation rates, presenting significant potential for fine-tuning these systems for controlled release in biomedical applications [50].  
The structural characteristics of the synthesized copolymers were investigated using \({}^{1}\)H NMR spectroscopy. The spectrum, shown in Figure 2, displays all the expected resonance signals corresponding to PLA. Specifically, a doublet at 1.58 ppm is attributed to the methyl group (-CH\({}_{3}\)), while a quartet at 5.16 ppm corresponds to the methine group (-CH). Additionally, a peak at 5.02 ppm indicates the presence of residual unreacted lattice. For the PLA-polyol samples, a resonance signal at 4.36 ppm is observed, which arises from the hydroxyl groups (-OH) adjacent to the terminal chain-end, CHOH. These findings are in alignment with those previously reported, confirming the successful ring-openingpolymerization (ROP) of lactic into PLA [53]. The presence of the characteristic signals for both the main polymer backbone and residual lactic underscores the efficient polymerization process. For copolymers incorporating polyols such as glycerol, sorbitol, and pentaerythntol, the proton signals from the polyols are not prominently visible in the corresponding spectra. This is likely due to the low concentration of polyols used during polymerization (0.5% _w/v_).  
In combination with \({}^{1}\)H NMR, ATR-FTIR spectroscopy was also utilized to further confirm the structure of the synthesized polymers (Figure 3). In the PLA spectrum, several characteristic peaks were identified: a double peak at the region of 2900 cm\({}^{-1}\), corresponding to the stretching vibrations of the C-H bond (assymetric, symmetric); a strong peak at 1753 cm\({}^{-1}\), attributed to the carbonyl group (C=O); a peak at 1452 cm\({}^{-1}\), associated with the methyl hydrogens (-CH\({}_{3}\)); the peaks at 1180 cm\({}^{-1}\) and 1082 cm\({}^{-1}\), arising from the stretching vibrations of the C-O-C bond. Similarly, the spectra of the PLA copolymers exhibited the same characteristic peaks, indicating that the core structural features of PLA were retained in all samples. Again, the very low concentrations of the polyols incorporated into the copolymers (e.g., glycerol, sorbitol, and pentaerythntol) did not significantly alter the spectral features. Their presence led to a slight broadening of the aforementioned peaks, without introducing new or shifting existing peaks.  
Figure 2: \({}^{1}\)H NMR spectra of the synthesized PLA-based polyesters in CDCl\({}_{3}\).