Surfactant-Emulating Amphiphilic Polycarbonates and Other Functional Polycarbonates through Metal-Free Copolymerization of CO₂ with Ethylene Oxide

Abstract

Three types of ethylene oxide-based and carbonate-containing copolymers were prepared through copolymerization of ethylene oxide (EO) with CO2 under metal-free conditions in the presence of triethylborane (TEB), using onium salts (OS) as initiator. Hydrophobic poly­[(ethylene carbonate) x -co-(ethylene oxide) y ] (PECEO) samples with carbonate contents above 90% (x ≫ y) were first prepared under a CO2 pressure of 10–30 bar with a ratio of [TEB] to [OS] of 1–1.2 equiv in tetrahydrofuran (THF) or in hexane. The above PECEO (carbonate > 91%) then served as a macroinitiator to grow two external poly­(ethylene oxide) (PEO) blocks and generate in one-pot amphiphilic PEO-b-PECEO-b-PEO triblocks. Lastly, the copolymerization of EO under a low pressure of CO2 (1–2 bar) with a ratio of [TEB] to [OS] of 1.2–2.0 equiv afforded hydrophilic poly­[(ethylene oxide) y -co-(ethylene carbonate) x ] (PEOEC) random copolymers with carbonate contents below 10% (y ≫ x); allyl glycidyl ether (AGE) was also terpolymerized with EO and CO2 under the same conditions to introduce functional groups along the backbone of PEO chains. Critical micelle concentrations (CMC) and size of micelles were measured for amphiphilic PEO-b-PECEO-b-PEO samples and compared with the values of other nonionic surfactants. The properties of “PEO-like” hydrophilic PEOECs were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and wettability test; their degradation behavior was further investigated under different conditions.

Anionic Copolymerization of o-Phthalaldehyde with Epoxides: Facile Access to Degradable Polyacetals and Their Copolymers under Ambient Conditions

“…Another benefit of this chemistry is the possibility of synthesizing degradable polyethers. In our previous attempts at deriving degradable polyethers, few degradable ester linkages could be incorporated into the polyether backbone through random copolymerization of epoxides with CO 2 , cyclic esters, or anhydrides. − Copolymerization of ethylene oxide with epichlorohydrin followed by an efficient elimination reaction to generate degradable methylene ethylene oxide (MEO) and also the copolymerization of ethylene oxide with 3,4-epoxy-1-butene (EPB), whose allyl moieties can be isomerized into pH-cleavable propenyl units, were also reported. In this investigation, we focused our effort on the preparation of high molar mass polyether with acid-labile acetal linkages.…”

Tertiary and Quaternary Phosphonium Borane Bifunctional Catalysts for CO2/Epoxide Copolymerization: A Mechanistic Investigation Using In Situ Raman Spectroscopy

“…This strategy can be further extended to highly active bifunctional Co − and Al systems featuring pendant ammonium cations (Chart ). It has been proposed that the ammonium cation can interact with the anionic polymer chain-end, whereas the metal center binds/activates CO 2 and epoxide. , Owing to these advances, novel random/block copolymers of polyalkylene carbonates have been developed with emerging applications. − …”

Orthogonally grown polycarbonate and polyvinyl block copolymers from mechanistically distinct (co)polymerizations

“…Distinct polymerizations using TTC-COOH in a dual role of an initiator and a chain transfer agent For our initial attempt at growing a polycarbonate block, we relied on our previous contributions where the use of carboxylate salts as initiators of the ROCOP of CO 2 /epoxides was described; 9,10,13 we thus used 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl] pentanoic acid (TTC-COOH) playing a dual role as an initiator for the ROCOP of CO 2 /epoxides and a transfer agent for the RAFT polymerization of vinyl monomers (Scheme 1). The tetrabutylammonium carboxylate salt (TTC-COO − , Bu 4 N + ) obtained after the deprotonation of TTC-COOH using tetrabutylammonium hydroxide was characterized by 1 H NMR to check its structure (Fig.…”

“…Based on the success of AB diblock copolymer synthesis, the synthesis of ABC triblock copolymers was also attempted with a focus on the synthesis of copolymer samples of high molar mass. Due to the versatility of the TEB/onium initiating system, 9,38 as shown in Scheme 1, more than one block could be grown by the ROCOP of CO 2 /epoxide or by the ROP of a cyclic monomer. A similar observation can be made about the RAFT trithiocarbonate chain transfer agent which also allows the controlled growth of more than one poly(vinyl) block.…”

“…Over the past decade, several examples of successful syntheses of aliphatic polycarbonates through metal-based catalytic systems, [1][2][3][4][5][6][7][8] and more recently through metal free systems, have been disclosed. [9][10][11][12][13][14][15] These chemistries described efficient ring-opening copolymerizations (ROCOP) of CO 2 with epoxides, leveraging the direct utilization of over-emitted CO 2 as a means to reduce carbon footprint and avoid fossil feedstock. However, applications derived from CO 2 -based polymers are still very limited due to their rather poor mechanical and thermal properties.…”