Development of efficient methods for CO 2 recovery from industrial waste gases etc. is extremely important in relation to both reutilization of CO 2 as carbon resources 1 and environmental issue concerned with the greenhouse effect. 2 One of the most commonly used processes for CO 2 recovery is chemically reversible CO 2 fixation by primary or secondary amines based on CO 2 fixation by amines at room temperature to give ammonium carbamates, and CO 2 release from ammonium carbamates upon heating. 3 Application of CO 2 fixation in functional polymers has been also examined, 4 for instance, copolymers of styrene bearing pendant amino groups fixed CO 2 under ambient conditions. 4b A more attractive process may be CO 2 fixation by tertiary amines giving zwitterion adducts that may provide a more easily handled fixation-release treatment, since these zwitterions could release CO 2 at reduced temperatures owing to their lability (primary-(secondary) amines; at >100°C). Furthermore, this process can provide zwitterions having a unique reactivity. However, detailed studies concerning CO 2 fixation by tertiary amines and its application to functional polymers have not been carried out. Here we report a new type of reversible CO 2 fixation by amidine derivatives and by polymers bearing an amidine moiety both in solution and solid state.In the course of the study of CO 2 fixation by tertiary amines, there has been one example of CO 2 fixation by 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) to afford the zwitterion adduct. 5 Assuming the reasons why DBU can react with CO 2 are its high nucleophilicity and stabilization of the cation species by delocalization in the amidine moiety, we constructed the idea that amidine derivatives with higher nucleophilicity may provide a success of CO 2 fixation. N-Methyltetrahydropyrimidine (MTHP) containing an amidine structure was synthesized, 6 since it would have higher nucleophilicity due to decrease in the steric hindrance around the nitrogen atom of imine moiety. CO 2 fixation using MTHP was performed in N,N-dimethylformamide (DMF) at 25°C under atmospheric pressure. 7 Fixing efficiency (%, mmol of CO 2 /mmol of MTHP) was estimated from the weight increase in the reaction mixture. When CO 2 was bubbled into a DMF solution of MTHP, a white precipitate was formed immediately, and the weight increase in the reaction mixture ceased after 1 h to afford the corresponding zwitterion adduct (MTHP)CO 2 ) in quantitative fixing efficiency. On the other hand, DBU needed 100 h to fix CO 2 in 89% fixing efficiency, 8 thus, MTHP proved to be an excellent agent for CO 2 fixation. The IR spectrum of MTHP)CO 2 showed two absorption bands assignable to the CO 2 moiety at 1689 and 1389 cm -1 . The 1 H NMR spectrum of MTHP)CO 2 showed that the signal of the imine proton was shifted to lower field (0.57 ppm) compared with MTHP and the 13 C NMR spectrum showed a signal attributable to the carbonyl group at 161.3 ppm.Reversibility of CO 2 fixation by MTHP was examined ( Figure 1): The obtained zwitterion addu...

We have successfully synthesized a series of polyoxymethylene (POM) random copolymers between the deuterated (D) and hydrogeneous (H) monomeric units by a cationic polymerization reaction. The randomness of D and H units in the copolymers was characterized by the quantitative analysis of 13 C NMR and Fourier transform infrared spectral data. The equilibrium melting point T°m was estimated on the basis of Gibbs−Thomson equation using the experimental data of DSC melting points plotted against the crystallite thickness evaluated from the smallangle X-ray scattering data. The T°m of pure D-POM (208.5 °C) is higher than that of pure H-POM (homopolymer, 190.0 °C). The T°m changes systematically with the D content in the copolymer. The blend samples between D-POM and H-POM (homopolymer) show the similar D content dependence, but the T°m is as a whole higher than that of the copolymer. Another type of blend samples consisting of D-POM and H-POM containing small amount of ethylene oxide (Duracon) shows the similar but slightly different D content dependence of T°m, compared with homopolymer case, since Duracon's melting point is about 5 °C lower than the latter. The kinetics of melt−isothermal crystallization behavior of these copolymers have been investigated using the time-dependent DSC data collected at the various isothermal crystallization temperatures, from which the crystallization rate constant (k) and growth dimension (n) were estimated on the basis of Avrami's plot, where the induction time of nucleation was corrected. In parallel, the tangential line of Avrami's curve at the crystallinity 0.5 was analyzed, from which the crystallization rate was estimated. These two methods of analysis were found to give almost the same results. By comparing the thus-obtained parameters among all the samples, several important results were obtained: (i) the POM-D shows the lowest crystallization rate compared with the POM-H samples; (ii) the crystallization rate decreased gradually with the increment of the D content in both the cases of D/H random copolymers and D/H blends when compared at the same ΔT c or the degree of supercooling; (iii) the existence of regimes I and II has been detected, the boundary temperature of which was found to change systematically depending on the D content. The crystallization rates were compared also between the two types of D/H blend samples, which showed remarkably different behaviors as a whole. In this way the isotopic effect on the thermal and crystallization behavior of D/H POM copolymers and blends has been revealed for the first time.