Amphiphilic core-cross-linked micelles functionalized with bis(4-methoxyphenyl)phenylphosphine as catalytic nanoreactors for biphasic hydroformylation

Abstract

a b s t r a c tCore-cross-linked micelles (CCM) functionalized at the core with covalently linked bis(p-methoxyphenyl) phenylphosphine (BMOPPP) ligands have been synthesized by a three-step one-pot radical polymerization in emulsion, using the polymerization-induced self-assembly (PISA) strategy and reversible addition-fragmentation chain transfer (RAFT) as the controlling method. The CCM are obtained by chain extending in water poly(methacrylic acid-co-poly(ethylene oxide) methyl ether methacrylate) (P(MAAco-PEOMA), degree of polymerization of 30, MAA/PEOMA units molar ratio of 50:50) synthesized in a first step by RAFT with a 95:5 M mixture of styrene and 4-[bis(p-methoxyphenyl)phosphino]styrene (BMOPPS) units. The resulting micelles exhibiting a core composed of P(S-co-BMOPPS) segments with a degree of polymerization of 300 are then crosslinked in a third step with a mixture of di(ethylene glycol) dimethacrylate (DEGDMA) and styrene. The resulting BMOPPP@CCM exhibit a narrow size distribution (PDI ¼ 0.16) with an average diameter of 81 nm in water and swell in THF or by addition of toluene to the latex. The addition of [Rh(acac) (CO) 2 ] to the toluene-swollen latex results in metal coordination to the phosphine ligands. 31 P{ 1 H} NMR spectroscopy shows that the Rh centers undergo rapid intraparticle phosphine ligand exchange. Application of these nanoreactors to the aqueous biphasic hydroformylation of 1-octene shows excellent activity and moderate catalyst leaching.

Coordination Chemistry inside Polymeric Nanoreactors: Metal Migration and Cross-Exchange in Amphiphilic Core-Shell Polymer Latexes

“…After 1 h 30, a 0.5-mL sample was withdrawn for analysis, and the polymerization was quenched by immersion of the flask in iced water. The overall conversion of S and DEGDMA (98%) was determined by 1 H NMR in THF-d 8 and that of BMOPPS (100%) was measured by 31 …”

“…The outer shell backbone protons (MAA CH 3 , CH 2 and CH protons and PEOMA CH 2 and CH protons) are also invisible, because the shell backbone is not solvated and remains solidary with the hydrophobic core. All protons become visible, however, in THF-D 8 , showing that the low cross-linking density (one cross-linker for 40 monomers in the hydrophobic core) confers sufficient mobility to the full macromolecule, like for the corresponding more flexible CCM. The core phosphine functions become visible in the 31 P{ 1 H} NMR spectrum with a single resonance at δ´11.5.…”

“…The structure of the CCM polymers, made by a convergent one-pot three-step procedure using reversible addition-fragmentation chain transfer (RAFT) polymerization [28][29][30][31][32][33] through the "polymerization-induced self-assembly" (PISA) approach in aqueous dispersed media [34,35], is shown in Figure 1. We have recently applied catalytic nanoreactors and, more specifically, phosphine ligand-functionalized core-cross-linked micelles (CCM) made in our laboratory, for the first time, to aqueous biphasic catalysis based on the micellar catalysis principle, namely with the catalytic act taking place within the hydrophobic core of the water-phase-confined polymer and with the catalytic phase being recovered by decantation [7][8][9]. This operating protocol differs from those previously applied in nanoreactor catalysis, which used either homogeneous conditions with catalyst recovery by precipitation/filtration or by ultrafiltration or aqueous biphasic conditions with separation/recovery by decantation, but with the catalytic act occurring either in the organic phase at high temperature by the thermomorphic approach [21,22] or at the water/organic interface [23][24][25][26][27].…”

“…The structure of the CCM polymers, made by a convergent one-pot three-step procedure using reversible addition-fragmentation chain transfer (RAFT) polymerization [28][29][30][31][32][33] through the "polymerization-induced self-assembly" (PISA) approach in aqueous dispersed media [34,35], is shown in Figure 1. Catalytic nanoreactors previously made in our laboratory [7][8][9][10].…”

“…The cross-linker and the functionalized monomer were added simultaneously in Step 3, after a short chain extension with styrene in Step 2. Catalytic nanoreactors previously made in our laboratory [7][8][9][10].…”