A CO₂-switchable amidine monomer: synthesis and characterization

Figures & data

Figure 1. The hydrophobic to hydrophilic transformation of 4-vinylbenzyl amidine upon stimulation of CO₂. The solvent is n-hexane and water (v/v = 1:1).

Figure 2. Conductivity variation of 4-vinylbenzyl amidine in wet DMF solution (~1 v% water) when CO₂ and N₂ is alternatively bubbling.

Figure 3. ¹H NMR spectra of 4-vinylbenzyl amidine before and after reaction with CO₂ and the reaction equation of amidine and CO₂. The solvent is wet DMSO-d6.

Figure 4. Snapshots of the RAFT polymerization product of 4-vinylbenzyl amidine. (a) product after reaction; (b) product in watch-glass; (c) product after drying.

Figure 5. Illustration of possible radical structures of 4-vinylbenzyl amidine in radical polymerization (structure 3 and 4) and reported amandine monomers by the groups of Yuan (compound 5, Ref. [11]) and Yung (compound 6, Ref. [14]).

Scheme 1. Synthesis route of 4-vinylbenzyl amidine.

Scheme 2. RAFT polymerization of 4-vinylbenzyl amidine.

Table 1. Reaction conditions of RAFT polymerization of 4-vinylbenzyl amidine.

No.	De-oxygenization	Solvent	Initiator/CTA^c	Product
1	Freezing-thaw	HAc/DMF=1:1^a	0.2:1	None
2	Freezing-thaw	HAc^b	0.2:1	None
3	Freezing-thaw	HAc	1:1	None
4	Bubbling N2 30 min	HAc	0.2:1	None
5	Bubbling N2 30 min	HAc	1:1	Cross-linked gel

^a Volume ratio.

^b Glacial acetic acid.

^c Molar ratio.

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