## 3 Results and Discussion
### Solubility Studies
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Solvent 1**} & **PET Cyclic** & **PET Cyclic** & **PET Cyclic** & **PET Cyclic** & **PET Cyclic** & **PET Cyclic** & **PET** (Polymer)** \\ \cline{3-8}  & **Dimer** & **Trimer** & **Tetramer** & **Pentamer** & **Hexamer** & **Heptamer** & **Insoluble** \\ \hline \multirow{2}{*}{**Methanol**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**Ethanol**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**2-propanol**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**Acetonitrile**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**DMF**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Slightly soluble} \\ \hline \multirow{2}{*}{**DMA**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**DMSO**} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**HFIP**} & Freely Soluble & Freely Soluble & Freely Soluble & Freely Soluble & Freely soluble & Freely soluble & Soluble \\ \hline \multirow{2}{*}{**THF**} & Freely Soluble & Freely Soluble &soluble & Soluble & & & & \\  & Soluble & Soluble & & & & & & \\ \hline \multirow{2}{*}{**TFE**} & Freely Soluble & Freely Soluble & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Very slightly soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Very slightly soluble} \\ \cline{2-2} \cline{5-5}  & Soluble & Soluble & & & & & & \\ \hline \multirow{2}{*}{**CH\({}_{2}\)Cl\({}_{2}\)**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**CHCl\({}_{3}\)**} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Soluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} & \multirow{2}{*}{Insoluble} \\ \hline \multirow{2}{*}{**TFA/CHCl\({}_{3}\) * 8:1 v/v**} & Freely Soluble & Freely Soluble & Freely Soluble & Freely Soluble & Freely soluble & Freely soluble & Freely soluble \\ \hline \hline \end{tabular} Note: solubility test procedures and solubility ranges adapted from WHO/FAO protocol [21]. 1\({}^{\text{ 1}}\) Solvent abbreviations: DMF: N,N-dimethylformamide; DMA: N,N-dimethylacetamide; DMSO: dimethyl sulfoxide; HFIP: 1,1,1,3,3-3; hexafluoro-2 propanol; THF: tetrahydrofuran; TFE: trifluoroethanol; TFA: trifluoroacetic acid. * In case of CHCl\({}_{3}\), the deuterated form (CDCl\({}_{3}\)) has also been tested.  
\end{table} 
Table 1: Solubility studies’ results for PBT cyclic oligomers (dimer to pentamer), using the method described in WHO/FAO [21]. aforementioned work for PBT oligomers: strong organic solvents, such as HFIP (considered as a strong Lewis acid) [23], must be used in order to solubilize both oligomer types [18].