Design and Evaluation of Nonfluorous CO₂-Soluble Oligomers and Polymers

Abstract

Ab initio molecular modeling is used to design nonfluorous polymers that are potentially soluble in liquid CO2. We have used calculations to design three nonfluorous compounds meant to model the monomeric repeat units of polymers that exhibit multiple favorable binding sites for CO2. These compounds are methoxy isopropyl acetate, 2-methoxy ethoxy-propane, and 2-methoxy methoxy-propane. We have synthesized oligomers or polymers based on these small compounds and have tested their solubility in CO2. All three of these exhibit appreciable solubility in CO2. At 25 degrees C, oligo(3-acetoxy oxetane)6 is 5 wt % soluble at 25 MPa, the random copolymer (vinyl methoxymethyl ether30-co-vinyl acetate9) is 5 wt % soluble at 70 MPa and random copolymer (vinyl 1-methoxyethyl ether30-co-vinyl acetate9) is 3 wt % soluble at 120 MPa. These oligomers and polymers represent new additions to the very short list of nonfluorous CO2-soluble polymers. However, none of these are more soluble than poly(vinyl acetate), which exhibits the highest CO2 solubility of any known polymer containing only the elements C, H, and O.

Supercritical carbon dioxide: a solvent like no other

“…There are also several factors that have been identified as having a negative impact on polymer solubility, including the presence of amine-functional groups and allyl polymers with a –CH 2 -spacer between the polymer backbone and the side chain or group [85,91]. These have since been used more as a set of guidelines as opposed to a set of hard-and-fast rules; poly(methyl acrylate) (PMA - Table 2, compound 22 ) has a greater degree of acetylation than poly(vinyl acetate) (PVAc - Table 2, compound 23 ) but has a much higher melting point and is insoluble in CO 2 [84]. …”

“…Beckman and Enick et al have a large body of both practical and theoretical work around polymer solubility in carbon dioxide [84]. The first reported use of ab initio modelling to design oxygenated hydrocarbon polymers for use in CO 2 was in 2009, where one oligomer and two polymers were synthesised and found to be soluble in CO 2 after ab initio predictions.…”

“…This is thought to be due to their high molar volume and as well as their lower polarisability volume and solubility parameter, leading fluorocarbons to be more akin to CO 2 (with low dielectric constant) than the respective hydrocarbon counterparts. There has been success in the design and synthesis of non-fluorinated polymers and surfactants, with hydrocarbon based, siloxane based and carbonyl and oxygenated hydrocarbon surfactants and polymers successfully solubilised [11–13 26,83–84 86,91]. …”

Supercritical carbon dioxide as a solvent for deposition of a tailored dye in dye sensitized solar cells

“…Current work is directed at applying these concepts to other dyes and investigating alternative non-fluorinated CO 2 -solublizing groups. 40 …”

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

“…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]. Nevertheless, poly(vinyl acetate) (PVAc) remains the most CO 2 -soluble polymer composed solely of carbon, hydrogen and oxygen that has yet been identified.…”