Akademik Veri Yönetim Sistemi
CHEMISTRYSELECT, cilt.10, sa.22, 2025 (SCI-Expanded)
D-Lactide (D-LA) monomer was polymerized at 20 degrees C by ring-opening polymerization (ROP) in the presence of twelve different trans- and cis-diaminocyclohexane (DACH) bifunctional squaramide organocatalysts. Almost all poly(D-lactide) (PDLA) polymers were synthesized in very high conversions (>99%) and very narrow PDI values between 1.07 and 1.13 according to spectroscopic (NMR) and chromatographic (GPC) analyses. Among all trans/cis-DACH-based squaramide catalysts tested, the PDLA with the highest M-n was obtained in the presence of trans-3 catalyst containing 3,5-bis(trifluoromethyl)phenyl)amine on one side of squaramide and a piperidine ring attached to DACH on the other side. Moreover, while the molarity of the benzyl alcohol (BnOH) initiator was kept constant in the presence of trans-3, the M-n values of PDLA increased in accordance with the theoretical values as a result of the increased D-LA feed ratio. Cis-9, the isomer of trans-3, catalyst was the most effective among cis catalysts in D-LA of ROP. The catalytic performance of both trans-3 and cis-9 catalysts in the ROP of D-LA is likely attributable to their pronounced acidity. When the methyl protons of PDLA-3 and 9 were irradiated in the double resonance H-1 NMR, the neighboring methine proton peak was transformed from a quartet to a single peak, which ensures selective PDLA polymerization and no racemization or epimerization. Trans-3 and cis-9 catalysts resulted in a polymer with semi-crystalline character with close T-g (similar to 50 degrees C) and T-cc (similar to 89 degrees C) values in DSC analyses, but PDLA-9 obtained with cis-9 has higher Delta H-m and Delta H-cc values, indicating that this polymer has higher crystallinity, and two different T-m values for PDLA-3 show that it has two different crystal morphologies.