Synthesis, Characterization, and Epoxidation of an Aliphatic Polycarbonate from 2,2-(2-Pentene-1,5-diyl)trimethylene Carbonate (cHTC) Ring-Opening Polymerization

Abstract

2,2-(2-Pentene-1,5-diyl)trimethylene carbonate (cHTC) was synthesized from cyclohexene-4,4-dimethanol in high yield (>80%). This new carbonate monomer was successfully ring-open polymerized to form P(cHTC) in bulk at 90 °C using various organometallic catalysts including aluminoxanes (methyl and isobutyl), BunSnCl4-n (n = 1, 2, 3), BunSn(OMe)4-n (n = 2, 3), ZnEt2, and ZnEt2−H2O. Comparison of these systems showed that the Zn- and Al-based catalysts were preferred for the preparation of high molecular weight polymers in yields ≥89% and reaction times of ≤8 h. For the BunSnX4-n catalysts investigated, values of n = 1 when X is Cl and n = 2 when X is OMe resulted in relatively greater polymerization rates and higher polymer molecular weights. The effects of reaction time and monomer/catalyst molar ratio were investigated for the Al and Zn catalysts. An outcome of this study was determining that the ZnEt2−H2O (1/0.5) catalyst for a monomer/catalyst (M/C) molar ratio of 400 and a 2 h reaction time gave a product with Mn = 276 000 in 98% yield. The P(cHTC) products were characterized by FTIR, 1H-NMR, 13C-NMR, DSC, TGA, and GPC. NMR results showed that cHTC decarboxylation did not occur during chain propagation. P(cHTC) has a moderate glass transition temperature (Tg = 30 °C) with high thermal stability. 13C NMR at 62.5 MHz did not resolve chain diad sequences although the polymers are likely atactic. Epoxidation of P(cHTC) vinyl side groups was carried out to various extents by using 3-chloroperoxybenzoic acid at room temperature.