SummaryThe (salen)Co(III) complex 1 tethering four quaternary ammonium salts, which is a highly active catalyst in CO2/epoxide copolymerizations, shows high activity for propylene oxide/phthalic anhydride (PO/PA) copolymerizations and PO/CO2/PA terpolymerizations. In the PO/PA copolymerizations, full conversion of PA was achieved within 5 h, and strictly alternating copolymers of poly(1,2-propylene phthalate)s were afforded without any formation of ether linkages. In the PO/CO2/PA terpolymerizations, full conversion of PA was also achieved within 4 h. The resulting polymers were gradient poly(1,2-propylene carbonate-co-phthalate)s because of the drift in the PA concentration during the terpolymerization. Both polymerizations showed immortal polymerization character; therefore, the molecular weights were determined by the activity (g/mol-1) and the number of chain-growing sites per 1 [anions in 1 (5) + water (present as impurity) + ethanol (deliberately fed)], and the molecular weight distributions were narrow (M
w/M
n, 1.05–1.5). Because of the extremely high activity of 1, high-molecular-weight polymers were generated (M
n up to 170,000 and 350,000 for the PO/PA copolymerization and PO/CO2/PA terpolymerization, respectively). The terpolymers bearing a substantial number of PA units (f
PA, 0.23) showed a higher glass-transition temperature (48 °C) than the CO2/PO alternating copolymer (40 °C).
The conventional Phillips ethylene trimerization catalyst prepared by reacting Cr(EH)3 (EH = 2-ethylhexanoate), 2,5-dimethylpyrrole (Me2C4H2NH), Et3Al, and Et2AlCl in an aromatic hydrocarbon solvent was improved to obtain a congener composed of a new chromium precursor (EH)2CrOH, (Me2C4H2N)AlEt2, and Et3Al·ClAlEt2. Reaction of CrCl3 with 3 equiv. Na(EH) in water did not generate Cr(EH)3, but unexpectedly produced (EH)2CrOH. In comparison with the erratic catalytic performance of the original Phillips system, due to the ill-defined nature of the Cr(EH)3 source (16 or 6.8 × 10(6) g per mol-Cr h depending on the source), the improved system exhibited consistently high activity (54 × 10(6) g per mol-Cr h). Reaction of (EH)2CrOH with (Me2C4H2N)AlMe2·OEt2 afforded the dimeric Cr(II)-complex (6) coordinated by (η(5)-Me2C4H2N)AlMe2(NC4H2Me2) and μ2-κ(1):η(2)-Me2C4H2N ligands. 6 provided highly active species when activated with Et3Al·ClAlEt2.
High-molecular-weight poly(1,4-butylene carbonate) (PBC) (M n : 40,000290,000) was prepared through the condensation polymerization of dimethyl carbonate (DMC) and 1,4butanediol (BD) in the presence of 0.05 mol % sodium alkoxide catalyst. The subsequent feeding of 15 mol % HOAOH, such as 1,6-hexanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, or 1,4-benzenedimethanol and stirring at 190-150 C converted the extremely thick high-molecular-weight polymer to lowmolecular-weight macrodiols with GPC-measured M n $2000. The analysis of the 1 H NMR spectra indicated that the -A-units and 1,4-butylene units were randomly distributed in the resulting oligomers. The chopping of the high-molecular-weight PBC using either triols or tetraols such as glycerol propoxylate, 1,1,1-tris(hydroxymethyl)ethane, or pentaerythritol also afforded macropolyols containing branched chains with GPCmeasured M n $2000. When the chopped polymers were genuine PBCs, the resulting macrodiols or polyols were in a waxy state at room temperature. However, permanently oily compounds were obtained when the chopped polymers were prepared using 0.90 mole fraction of BD admixed with various other diols. The macrodiols and polyols synthesized in this study may have potential applications in the polyurethane industry.
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