Functional Poly(ester-alt-sulfide)s Synthesized by Organo-Catalyzed Anionic Ring-Opening Alternating Copolymerization of Oxiranes and γ-Thiobutyrolactones

Abstract

The copolymerization of tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), ethoxyethyl glycidyl ether (EEGE) and 1,2-epoxybutane (BO) with γ-thiobutyrolactone was investigated using benzyl alcohol–phosphazene bases as initiating systems. The prepared copolymers display perfect (poly­(ester-alt-sulfide)) alternating structures for all epoxide monomers as evidenced by 1H, 13C, and 2D NMR and MALDI–TOF mass spectrometry. A marked influence of the reaction temperature on the occurrence of transesterification side reactions has been evidenced. In particular, at elevated temperature, transesterification reactions led to the formation of alternating macrocycles. The choice of the phosphazene base (tBuP4, tBuP2, or tBuP1) has a strong impact on the system reactivity and on the control of the polymerization. The use of tBuP1 led to very slow polymerization rates. The polymerization is much faster in the presence of tBuP2 even at low temperature. The use of tBuP4 shows an intermediate polymerization rate and enabled a good polymerization control at moderate temperatures. Finally, the synthesis of well-defined polyether-block-poly­(ester-alt-sulfide) and the polymerization of a challenging substituted γ-thiolactone were proven to be feasible.

Bio-based poly(ester-alt-thioether)s synthesized by organo-catalyzed ring-opening copolymerizations of eugenol-based epoxides and N-acetyl homocysteine thiolactone

“…This phenomenon has been previously found for the alternating ring-opening copolymerization of thiolactone with epoxides and was explained by undesired chain transfer reactions to water molecules and by transesterification reaction between the propagating alcoholate species and the ester groups of the main chain. 34,35 In order to reduce the occurrence of side reactions, one solution is to add solvent and to decrease the reaction temperature. Thus, a NHTL-DEGE copolymerization with an identical reactant ratio was performed in THF at 55°C (Table 1, run 6).…”

Alternating copolymerization of bio-based N-acetylhomocysteine thiolactone and epoxides

“…Considering that no homopolymerization of both monomers occurred using the same initiating system at 90°C and by analogy with the recently reported alternating AROP of γ-thiolactone with epoxides, perfectly alternating structures are postulated (Scheme 1). [29] Three experiments were performed at 90, 60 and 30°C (Table 1, runs 3, 7-8). An increase of the viscosity followed by a phase separation took place.…”

“…A similar behavior was previously described for the alternating copolymerization of γ-butyrothiolactone with epoxides. [29] A higher amount of BEMP (2 eq., Table 1, run 5) resulted in even more reduced M n and higher Ð (Table 1, run 5). It was previously demonstrated that higher amount of phosphazene base favor the occurrence of side-reaction due to an increase the propagating center reactivities.…”

“…A better control of the alternating ring-opening copolymerization and an extension of the epoxyde monomer scope was recently achieved using alcohol-phosphazene bases as initiating systems. [29] The generated poly(thioether-alt-ester)s are attractive functional materials due to the presence of both biodegradable ester groups and oxydable (reactive oxygen speciessensitive) thioether groups in each repeating unit of the main backbone. The use of two distinct monomer sets could advantageously enabled the facile tuning of the properties of the resultant copolymers.…”

“…b Decomposition temperature at maximum degradation rate (derivative thermogravimetry). c Prepared according to Puchelle et al[29]…”