CO2-solubility of oligomers and polymers that contain the carbonyl group

Influence of tert-amine groups on the solubility of polymers in CO2

“…Our group employed ab initio calculations to reveal that the carbon of CO 2 can interact to a comparable degree with the etherlike ester oxygen in the acetate group [6,14], confirming earlier reports that interactions of CO 2 with this oxygen could occur [28,29]. The occurrence of multiple binding sites in an amorphous polymer with a low glass transition temperature is thought to be responsible for poly(vinyl acetate) displaying a greater degree of solubility in CO 2 than any other high molecular weight oxygenated hydrocarbon [26]. We recently designed novel oligomers that dissolved in CO 2 , including polyvinyl methoxymethylether and poly(3-acetoxyoxetane) [30] and also demonstrated that poly(1-O-(vinyloxy)ethyl-2,3,4,6-tetra-O-acetyl-b-D-glucopyranoside) (a polymer with pendant sugar acetate groups) and amorphous polylactic acid are CO 2 -soluble over a wide range of molecular weight [31].…”

“…Firstly, an ethylene group separates the acrylate group from the backbone and we know that insertion of a methylene group between the backbone and the acetate group of poly(vinyl acetate), resulting in poly(allyl acetate), has a remarkable deleterious effect on miscibility of poly(allyl acetate) in CO 2 [14]. Secondly, the acrylate group is known to be much less effective than an acetate group at imparting CO 2 -solubility from the comparison of poly(vinyl acetate) versus poly(methyl acrylate) [26]. For PEOX the lack of an oxygen atom between the backbone and the carbonyl group diminishes side chain rotational motion, and hence the free volume of the polymer, leading to less favorable interactions between CO 2 and the polymer side chain [6].…”

“…Enhanced solubility of these polymers in CO 2 was attributed to a specific interaction between the carbon atom of CO 2 and the lone pairs on the oxygen of a carbonyl group, in which CO 2 acts as a Lewis acid and the carbonyl group as a Lewis base [17]. This, in turn, led to studies [18][19][20] aimed at the inclusion of a carbonyl or acetate group in polymers to promote solubility in CO 2 [21][22][23][24][25][26]. Subsequently, Raveendran and Wallen's ab initio calculations indicated that a second interaction, a cooperative interaction between oxygen atoms of CO 2 and hydrogen atoms attached directly to the carbonyl carbon or the a-carbon atom [27], was responsible for the superior CO 2 -philicity of carbonyl-based groups.…”

“…Nevertheless, poly(vinyl acetate) (PVAc) remains the most CO 2 -soluble polymer composed solely of carbon, hydrogen and oxygen that has yet been identified. Unfortunately, the pressure required to dissolve w5 wt% of PVAc in CO 2 at 298 K is on the order of 50-70 MPa [26], which is substantially higher than the pressure required to dissolve perfluoroacrylates or poly(dimethylsiloxane) (PDMS).…”

Controlled/living heterogeneous radical polymerization in supercritical carbon dioxide

“…Lewis acid and base interactions are said to be more possible with the more accessible carbonyl groups of poly(vinylacetate) (PVAc). PVAc is more soluble than other hydrocarbon polymers, 54 although it is still appreciably less soluble than fluorinated or silicone-based polymers. ScCO 2 exhibits the temperature-dependent characteristics of a polar solvent, despite being only weakly polar, and cannot dissolve strongly hydrogen-bonded polymers such as poly(acrylic acid) (PAA) even at 300 C. 46 When using scCO 2 as polymerization medium, the system is initially a homogeneous mixture of CO 2 and the monomer.…”