Ti obu 4

Adipic acid (AdA) (purity: >99.5%), poly(phosphoric acid) (PPA) and 1,3-propanediol (1,3-PD) (purity: >99.6%) were purchased from Fluka (Steinheim, Germany). Titanium butoxide (purity: >97.0%), Ti(OBu)₄) and tin(II) 2-ethylhexanoate (Sn(Oct)₂) were used as catalysts, l-Lactide (LA), (3S)-cis-3,6-Dimethyl-1,4-dioxane-2,5-dione (98%) and poly(vinyl alcohol) (PVA), M_w 31,000–50,000 Da (87%–89% hydrolyzed) were purchased from Sigma Aldrich Chemical Co (Steinheim, Germany). Rhizopus oryzae and Pseudomonas cepacia were purchased from BioChemika (Steinheim, Germany). Naltrexone base (99.9%) was kindly donated by Pharmathen S.A. (Athens, Greece). All other reagents and solvents used for the analytical methods were of analytical grade.

Indium tin oxide (ITO, ≤15 Ω/∀) sheet glass, titanium foil (Ti, Sigma-Aldrich, 0.25-mm thickness, 99.7% purity), ammonium fluoride (NH₄F, Sigma-Aldrich, 98 + %), ethylene glycol (Junsei Chemical Co, 99.0%), cadmium chloride (CdCl₂, Kanto Chemical Co, 98.0%), indium choride (InCl₃, Sigma-Aldrich, 99.999%), sodium sulfide nonahydrate (Na₂S, Sigma-Aldrich, 98.0%), cupric chloride (CuCl₂, Junsei Chemical co., Ltd, >97.0 + %), and Ti(OCH₂CH₂CH₂CH₃)₄ (Ti(OBu)₄, Sigma-Aldrich, 97%). All the materials were used directly without further purification.

1,4-dimethylcyclohexanedicarboxylate (DMCE), containing 99% trans isomer (TCI Europe, Zwijndrecht, Belgium), 1,3-propanediol (1,3-PD), neopentyl glycol (NPG), and titanium tetrabutoxide (Ti(OBu)₄) (Sigma Aldrich, Milan, Italy) were used as supplied, without any preliminary purification. Only the catalyst Ti(OBu)₄ was distilled before use.