Inverse Miniemulsion Enables the Continuous-Flow Synthesis of Controlled Ultra-High Molecular Weight Polymers

Abstract

We report the controlled synthesis of ultra-high molecular weight (UHMW) polymers (M n ≥ 10 6 g/mol) via continuous flow in a tubular reactor. At high monomer conversion, UHMW polymers in homogeneous batch polymerization exhibit high viscosities that pose challenges for employing continuous flow reactors. However, under heterogeneous inverse miniemulsion (IME) conditions, UHMW polymers can be produced within the dispersed phase, while the viscosity of the heterogeneous mixture remains approximately the same as the viscosity of the continuous phase. Conducting such IME polymerizations in flow results in a faster rate of polymerization compared to batch IME polymerizations while still providing excellent control over molecular weight up to 10 6 g/mol. Crucial emulsion parameters, such as particle size and stability under continuous flow conditions, were examined using dynamic light scattering. A range of poly(N,N-dimethylacrylamide) and poly(4-acryloylmorpholine) polymers with molecular weights of 10 4 −10 6 g/mol (Đ ≤ 1.31) were produced by this method using water-soluble trithiocarbonates as photoiniferters.

Diversification of Acrylamide Polymers via Direct Transamidation of Unactivated Tertiary Amides

“…To date, the PPM of synthetic ultrahigh-molecular-weight (UHMW) polymers, specifically those with molecular weights exceeding 10 6 g·mol –1 , has not been reported, despite growing interest in engineering functional UHMW polymers to better mimic the size of naturally occurring macromolecules such as mucins and lubricins. − We reasoned that recent advances in accessing UHMW acrylamide and (meth)­acrylate polymers through photoiniferter polymerization, , particularly PDMA, , along with the direct transamidation of PDMA, paves the way for new opportunities in the diversification of UHMW polymers. As a proof of concept, we subjected well-defined UHMW PDMA ( M n,SEC = 1220 kg·mol –1 , Đ = 1.14, degree of polymerization ( DP n ) = 12,000) synthesized by photoiniferter polymerization to the optimized transamidation conditions using benzylamine in the presence of LiHMDS (Figure A).…”

Ultrahigh-Molecular-Weight Triblock Copolymers via Inverse Miniemulsion Photoiniferter Polymerization

“…Inverse miniemulsions involve dispersed aqueous phase droplets within an oil-based continuous phase. , Our group recently reported the successful synthesis of UHMW water-soluble homopolymers via photoiniferter polymerization under inverse miniemulsion conditions . The technique was optimized for various monofunctional photoiniferters and was later shown to enable UHMW homopolymers under continuous flow …”

Robust Miniemulsion PhotoATRP Driven by Red and Near-Infrared Light

“…Importantly, the RDRP process can be controlled by external stimuli, such as redox reagents (e.g., tin compounds, ascorbic acid), enzymes, , ultrasound, , electric current, − or light. − Among these, light has emerged as a particularly promising approach due to relatively milder reaction conditions, spatiotemporal control, and convenient setup. − Previous efforts on the photoinduced RDRP (photoRDRP) in dispersed media include (inverse) microemulsion, miniemulsion, − emulsion, − and dispersion (Scheme A). − For instance, photoATRP in emulsion can be initiated through the in situ generation of the ATRP activator [Cu I /L] + (where L is an ATRP ligand). This could be achieved by either UV irradiation (370 nm) or electron transfer from an excited photocatalyst (PC) under blue light (460 nm), reducing [X–Cu II /L] + (where X = Br or Cl).…”