Polar Thermoplastics with Tunable Physical Properties Enabled by the Stereoselective Copolymerization of Vinyl Ethers

Abstract

A series of isotactic, semicrystalline vinyl ether copolymers (up to 94% meso diads) were synthesized using a chiral BINOL-based phosphoric acid in combination with a titanium Lewis acid. This stereoselective cationic polymerization enabled the systematic tuning of both glass transition (T g ) and melting temperature (T m ) in copolymers derived from alkyl vinyl ethers (i.e., ethyl, butyl, isobutyl). Additionally, a vinyl ether comonomer bearing an acylprotected alcohol was utilized as a platform for postfunctionalization.Copolymers containing the masked alcohols were shown to undergo deprotection and subsequent coupling with a desired acid chloride. Collectively, these results highlight the diverse material properties and expanded chemical space accessible through stereoselective cationic polymerization mediated by a chiral anion.

An Ion‐Pairing Approach to Stereoselective Metal‐Free Ring‐Opening Metathesis Polymerization

“…Within the context of the MF‐ROMP mechanistic hypothesis, we predicted that understanding the environment near the active chain end would reveal methods for controlling alkene stereoselectivity. Toward this end (Scheme 1, bottom), we investigated: (1) counteranions, which were influential in previously reported examples with poly(vinyl ethers) and asymmetric small molecule syntheses; [27–32] (2) reaction conditions, with emphasis on solvent and temperature; and (3) steric parameters of enol ether initiators. Typical conditions for MF‐ROMP of norbornene use ethyl propenyl ether ( 2 b ) as initiator, 2,4,6‐tris(4‐methoxyphenyl)pyrylium tetrafluoroborate ( 3 a ) as photocatalyst, dichloromethane as solvent, and an LED light source with an emission centered at 450 nm, all at room temperature.…”

An Ion‐Pairing Approach to Stereoselective Metal‐Free Ring‐Opening Metathesis Polymerization

“…Within the context of the MF-ROMP mechanistic hypothesis,we predicted that understanding the environment near the active chain end would reveal methods for controlling alkene stereoselectivity.T oward this end (Scheme 1, bottom), we investigated:( 1) counteranions, which were influential in previously reported examples with poly(vinyl ethers) and asymmetric small molecule syntheses; [27][28][29][30][31][32] (2) reaction conditions,with emphasis on solvent and temperature;a nd (3) steric parameters of enol ether initiators.T ypical conditions for MF-ROMP of norbornene use ethyl propenyl ether (2b)a si nitiator, 2,4,6-tris(4-methoxyphenyl)pyrylium tetrafluoroborate (3a)a sp hotocatalyst, dichloromethane as solvent, and an LED light source with an emission centered at 450 nm, all at room temperature.…”

Hydrogen Bond Donor Catalyzed Cationic Polymerization of Vinyl Ethers

“…However, developing polymerization methods with living characteristics is challenging and often requires specialized reagents and reaction conditions. Specifically, living cationic processes often require rigorously dried solvents, cold temperatures, and additives to avoid deleterious termination and chain transfer events [2–16] . Therefore, designing a robust controlled cationic polymerization under mild conditions that can produce high‐molecular‐weight polymers remains a challenge.…”

“…Specifically, living cationic processes often require rigorously dried solvents, cold temperatures, and additives to avoid deleterious termination and chain transfer events. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Therefore, designing a robust controlled cationic polymerization under mild conditions that can produce high-molecular-weight polymers remains a challenge.…”