Copolymers bearing DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.3.0]non-5-ene) moieties fixed carbon dioxide under atmospheric pressure. The copolymers bearing DBN moieties fixed carbon dioxide faster than those bearing DBU moieties owing to the lower steric hindrance around the imine structure. These copolymers held trapped CO 2 under a N 2 flow at 25 °C, whereas the corresponding lowmolecular weight amidines release trapped CO 2 under the same conditions. The trapped CO 2 in the copolymers was quantitatively released by a N 2 flow at 120 °C. The CO 2 trapping efficiency of a copolymer bearing DBN moieties is competitive with that of an amidine-containing polymer, whereas the preparative method for the copolymer bearing DBN is easier. The higher CO 2 trapping abilities of the DBN derivatives were supported by computational calculation.

Cationic ring‐opening copolymerization behavior of trioxane (TOX) and a seven‐membered cyclic carbonate, 1,3‐dioxepan‐2‐one (7CC) is described. When TOX and 7CC were cationically copolymerized under various feed ratios using trifluoromethane sulfonic acid (TfOH) as an initiator in nitrobenzene at 30 °C, 7CC was consumed faster than TOX and the decarboxylation was accompanied to afford the corresponding polyacetal–polycarbonate type copolymers containing poly(oxytetramethylene) units. The copolymer composition could be controlled by the feed ratio of 7CC, whose increase resulted in the high copolymer composition of the 7CC unit. The solubility of the copolymers increased as the increase of the 7CC content. Thermogravimetric, size‐exclusion chromatographic, and X‐ray analyses of the copolymers suggest that the sequences of the copolymer chains consist of the segments containing the units originated from 7CC and those with TOX unit‐rich compositions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 733–739, 2008