PhD Theses

Ring-opening polymerization of non-ionic eutectic mixtures for the synthesis of macroporous polyesters by emulsion templating

(2023) Martin Castillo Santillan

This work encompasses the study of the sequential ring-opening polymerization (ROP) of deep eutectic system monomers (DESm) composed of L-lactide (LLA) and ε-caprolactone (CL) at low temperatures and in solventless conditions.

The tunable average molecular weight, crystallinity, polymer architectures, and controlled degradation profiles of these polyesters depended on the organocatalysts employed, including 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), a new catalyst for the LLA-CL DESm ROP. Thus, fine-tuning the synthetic parameters led to the synthesis of polymer blends and a block copolymer. The toolbox of DESm capable of undergoing low-temperature and solventless ROP was further extended to LLA and various lactones, including δ-valerolactone and δ-hexalactone. The ROP of these DESm was also catalyzed by guanidine- and sulfonic acid-based organocatalysts for LLA and lactones, respectively. Finally, polycaprolactone triol (PCLT) and OH-terminated polyethylene glycol (PEG) were investigated as multifunctional macroinitiators in the solventless ROP of LLA-CL DESm catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and methanesulfonic acid. Branched or linear PLLA copolymers with PCLT or PEG, respectively, were blended with PCL after the sequential ROP of LLA-CL DESm. The insights gained into the DESm ROP in bulk were advantageously used to design polymerizable high internal phase emulsions (HIPEs) oil-in-DESm. These emulsions sustained the efficient organocatalyzed ROP of the continuous phase. The resulting polymer replicas of the HIPEs, characterized by macroporous and interconnected structures, were capable of sorbing crude oil.

The mild polymerization temperatures and solventless conditions stand as green features of the ROP developed in this work to prepare resorbable biomaterials with programmable degradation profiles.