Facile Synthesis of Hybrid Silica Nanoparticles Grafted with Helical Poly(phenyl isocyanide)s and Their Enantioselective Crystallization Ability

Abstract

In this contribution, we report on the facile synthesis of hybrid silica nanoparticles grafted with helical poly(phenyl isocyanide)s via both "grafting from" and "grafting to" strategies. First, triethoxysilanyl functionalized alkyne− Pd(II) initiator was anchored onto the surface of bare silica nanoparticles through silanization coupling reaction. Polymerization of phenyl isocyanide using the Pd(II)−anchored silica nanoparticles lead to the formation of hybrid nanoparticles grafted with helical poly(phenyl isocyanide)s. The surfaceinitiated polymerization was revealed to proceed in a living/controlled chain-growth manner, afforded the hybrid nanoparticles with controlled thickness. 31 P NMR analysis indicated the initiation efficiency of the surface-anchored Pd(II) initiators is very high, and almost quantitative. The grafting density was determined to be ∼0.89 nm 2 /chain based on the thermal gravity analysis (TGA). Polymerization of optically active phenyl isocyanide bearing an L-alanine with a long decyl chain using the Pd(II)anchored silica nanoparticles formed chiral hybrid nanoparticles grafted with helical poly(phenyl isocyanide) arms in preferred handedness. Second, the hybrid silica nanoparticles were prepared via "grafting to" strategy. Well-defined triethoxysilanyl terminated poly(phenyl isocyanide) was prepared in controlled manners. The polymer was grafted to the surface of bare silica nanoparticles via the silanization coupling reaction, afforded hybrid silica nanoparticles grafted with helical poly(phenyl isocyanide). TGA indicates the grafting density is ∼0.76 nm 2 /chain. Taking advantage of this synthetic method, left-handed helical poly(phenyl isocyanide) was grafted to the surface of silica nanoparticles, generated chiral hybrid silica nanoparticles with high optical activity. Such chiral nanoparticle exhibited good performance in enantioselective crystallization of racemic Bocalanine. The enantiomeric excess (ee) of the induced crystal is up to 95%.

Dispersion Polymerization of Substituted Acetylenes in the Presence of Chiral Source for Preparing Monodispersed Chiral Nanoparticles

“…Optically active helical polymer nanoparticles have attracted great attention due to the well‐known chiral amplification effects . They stimulate ever‐growing interest and hold remarkable potential applications in chiral‐related areas . In general, chiral helical polymer nanoparticles can be directly prepared by chiral monomers.…”

Facile Synthesis of Optically Active and Magnetic Nanoparticles Carrying Helical Poly(phenyl isocyanide) Arms and Their Application in Enantioselective Crystallization

“…After another 96 h, the crystals were filtrated from the residual solution. Comparing to other optically active nanoparticles reported in our previous work, this kind of nanoparticles is not only optical activity but also magnetism. Thus it can be easily separated from the induced crystals after the enantioselective crystallization.…”

“…As shown in Scheme , oleic acid (OA) coated Fe 3 O 4 magnetic nanoparticle with an average diameter of ≈46 nm was prepared followed the reported procedures . A triethoxysilanyl functionalized alkyne‐Pd(II) (TEOS‐Pd(II)) was synthesized and anchored onto the surface of OA‐coated Fe 3 O 4 through exchange reaction (see the Supporting Information for details) . The afforded Pd(II)‐anchored Fe 3 O 4 nanoparticle (Fe 3 O 4 ‐Pd(II)) was then used as a macroinitiator to promote the polymerization of phenyl isocyanide.…”

“…The PPI‐grafted magnetic nanoparticle was then attempted to be prepared via “grafting onto” strategy. As shown in Scheme , a TEOS‐terminated left handed helical PPI, poly‐ l ‐ 1 100 ‐TEOS was prepared according to reported literature . Grafted poly‐ l ‐ 1 100 ‐TEOS onto the surface of Fe 3 O 4 nanoparticle was realized through the exchange reaction (see the Supporting Information for details).…”

Facile Synthesis of Helical Rod–Coil Block Polymers by the Combination of ATRP and Pd(II)‐Initiated Isocyanides Polymerizations

“…The rigid rod helical conformation allows the polyisocyanide to be widely applied in chiral recognition, enantiomeric separation, and liquid crystallization . Helical polyisocyanides have been fabricated into block copolymers, grafted polymer brushes, and star polymers . Recently, our group reported a family of alkyne‐Pd(II) complexes which can initiate the living polymerization of isocyanide monomers and lead to the formation of stereoregular helical polyisocyanides with controlled molar masses ( M n s) and narrow molar mass distributions ( M w / M n s).…”