Synchronous Control of Chain Length/Sequence/Topology for Precision Synthesis of Cyclic Block Copolymers from Monomer Mixtures

Abstract

Precision synthesis of cyclic polymers with predictable molecular weight and low dispersity is a challenging task, particularly concerning cyclic polar vinyl polymers through a rapid chain-growth mechanism and without high dilution. Harder yet is the precision synthesis of cyclic block copolymers (cBCPs), ideally from comonomer mixtures. Here we report that Lewis pair polymerization (LPP) capable of thermodynamically and kinetically compounded sequence control successfully addressed this longstanding challenge. Thus, LPP of acrylate/methacrylate mixtures under ambient temperature and normal concentration conditions rapidly and selectively affords well-defined cBCPs with high molecular weight (M n = 247 kg/mol) and low dispersity (Đ = 1.04) in one step. Such cBCPs have been characterized by multiple techniques, including direct structural observation by imaging.

Mechanism of Spatial and Temporal Control in Precision Cyclic Vinyl Polymer Synthesis by Lewis Pair Polymerization

“…Our latest work seemed to overcome this limitation by providing cyclic di-BCPs of MMA and n BA with M n up to 267 kg mol À 1 and Đ as low as 1.03. [22] It is now quite clear that this exquisite control is the consequence of a temporal control (i.e., when cyclization occurs) that arises from the necessity for LA activation during the proton transfer/cyclization steps. When there is a considerable amount of free monomer present in the system, the monomer will outcompete the sorbate terminus for control over the LA and thus propagation will continue.…”

“…[55,57] Intrigued by this hypothesized mechanism, we most recently adapted Takasu's methodology for our compounded sequence control (CSC) LPP method [58,59] to make cyclic di-BCPs of n-butyl acrylate ( n BA) and MMA in one pot and one step. [22] By utilizing this unique strategy, we successfully synthesized high molecular weight (M n up to 267 kDa) cyclic P n BA-b-PMMA with narrow dispersity (Đ = 1.03) at room temperature (RT) and without highly dilute conditions. By several lines of evidence including hydrodynamic radius (V h ), radius of gyration (R g ), solution viscometry, bulk viscometry, and TEM, we supported the cyclic topology of these di-BCPs.…”

Dual-initiating and living frustrated Lewis pairs: expeditious synthesis of biobased thermoplastic elastomers

“…Owing to their unique, unquenched reactivities, frustrated Lewis pairs (FLPs) not only demonstrated well-established utilities in small molecular chemistry 28 – 36 but also exhibited unique applications in polymer synthesis 37 – 47 . By selecting a suitable organoaluminum Lewis acid (LA) with appropriate steric hindrance and acidity, we achieved the first example of living polymerization of methacrylates by an authentic FLP 48 .…”

A scalable and continuous access to pure cyclic polymers enabled by quarantined heterogeneous catalysts

“…This feature of cyclic polymers is envisioned as a viscosity modifier to prolong the lubricant lifetime. Since our discovery of the ring expansion route to cyclic polymers in 2002 11 , we [12][13][14][15][16] and other groups [17][18][19][20][21][22][23][24][25][26] have done exciting research on more functionalized and purer cyclic polymers.One of the most important needs is the development of a practical synthetic process to produce pure cyclic polymers on a larger scale for testing in many applications. To date, all the reported synthetic protocols were operated on a milligram scale in solution by homogeneous catalysis, which was accompanied by rigorous ex situ processes for polymer purification without actual catalyst recovery (Fig.…”

“…This feature of cyclic polymers is envisioned as a viscosity modifier to prolong the lubricant lifetime. Since our discovery of the ring expansion route to cyclic polymers in 2002 11 , we [12][13][14][15][16] and other groups [17][18][19][20][21][22][23][24][25][26] have done exciting research on more functionalized and purer cyclic polymers.…”