Synthesis and Biodegradability of Tartaric Acid-Based Poly(ester-thioether)s via Thiol-Ene Click Polymerization.

Using scandium triflate [Sc(OTf)3] as a catalyst, chemoselective esterification of tartaric acids by 3-butene-1-ol was performed, and we produced three dialkene monomers: l-di(3-butenyl) tartrate (BTA), d-BTA, and meso-BTA. Thiol-ene polyaddition of these dialkenyl tartrates and dithiols including 1,2-ethanedithiol (ED), ethylene bis(thioglycolate) (EBTG), and d,l-dithiothreitol (DTT) proceeded in toluene at 70 °C under nitrogen to give tartrate-containing poly(ester-thioether)s (Mn, (4.2-9.0) × 103; molecular weight distribution (Mw/Mn), 1.6-2.5). In differential scanning calorimetry, the poly(ester-thioether)s showed single Tgs between -25 and -8 °C. In biochemical oxygen demand (BOD) tests using activated sludge, poly(l-BTA-alt-EBTG) and poly(l-BTA-alt-ED) showed 32 and 8% biodegradability, which is comparable to that of similar l-malate-containing poly(ester-thioether)s (23 and 13% biodegradation, respectively). Notably, we observed enantio and diastereo effects on biodegradation because poly(l-BTA-alt-EBTG), poly(d-BTA-alt-EBTG), and poly(meso-BTA-alt- EBTG) showed different degradation behaviors during the biodegradation test (BOD/theoretical oxygen demand (TOD) values after 28 days, 32, 70, and 43%, respectively). Our findings provide insights into the design of biomass-based biodegradable polymers containing chiral centers.

Catenane formation of a cyclic poly(alkyl sorbate) via chain-growth polymerization induced by an N-heterocyclic carbene and ring-closing without extreme dilution.

1,3-Di-tert-butylimidazol-2-ylidene (NHCtBu), a typical N-heterocyclic carbene (NHC), was previously found to induce the anionic chain-growth polymerization of ethyl sorbate (ES) in the presence of an aluminum Lewis acid, i.e., methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD), in which the neighboring of α-terminal dienolate with a propagating anion induced cyclization without highly diluted conditions, after monomer depletion, to give the cyclic poly(ES). In this paper, we report that catenane formation occurs by two-step polymerization of ethyl sorbate (ES), in which, after complete monomer (ES) consumption ([ES]0/[NHCtBu]0 = 100/1) in toluene followed by purification by reprecipitation, a second addition of ES monomer ([ES]0/[ NHCtBu]0 = 20/1) in another pot (in toluene or tetrahydrofuran (THF)) resulted in catenane formation, namely a polycatenane. TEM images of a sample from the second step polymerization in THF revealed particles of polycatenane structure consisting of cyclic poly(ES) with sizes ranging from 200 to 1000 nm, showing that this NHCtBu triggered chain polymerization and successive cyclization without highly diluted conditions enabled us to fabricate the intended polycatenane in the successive two-step polymerization.