Chiral micelles have been drawing ever-increasing attention because of their potentials in mimicking the unique stereochemical effects of enzymes. This article reports on the first success in preparing chiral micelles through self-assembly of helical polyacetylene bearing cholic acid pendants. The micelles were further used as chiral nanoreactor, in which achiral acetylenic monomer smoothly underwent helix-sense-selective polymerization (HSSP). The HSSPs directly established optically active core/shell nanoparticles whose shell and core both were constructed by helical polymers. The shells (or micelles) provided a protective effect for the preferably induced one-handed helical polymer chains in the cores. The present work provides insights into the self-assembly of chiral helical polymers, and also provides a powerful strategy for constructing novel chiral polymer nanoarchitectures.
Optically active nano- and microparticles have constituted a significant category of advanced functional materials. However, constructing optically active particles derived from synthetic helical polymers still remains as a big challenge. In the present study, it is attempted to induce a racemic helical polymer (containing right- and left-handed helices in equal amount) to prefer one predominant helicity in aqueous media by using emulsifier in the presence of chiral additive (emulsification process). Excitingly, the emulsification process promotes the racemic helical polymer to unify the helicity and directly provides optically active nanoparticles constructed by chirally helical polymer. A possible mechanism is proposed to explain the emulsification-induced homohelicity effect. The present study establishes a novel strategy for preparing chirally helical polymer-derived optically active nanoparticles based on racemic helical polymers.
A green approach has been developed for the synthesis of hydroxypropyl
cellulose-g-polytetrahydrofuran (HPC-g-PTHF) graft copolymer via combining living cationic ring-opening
polymerization and nucleophile substitution reaction. The living PTHF
chains (M
n = 3200 g·mol–1) were synthesized in bulk initiated by allyl bromide/AgClO4 without any other hazardous solvents. Then, the living PTHF chains
reacted with hydroxyl groups on the HPC backbone with grafting efficiency
of ca. 100% to create a series of HPC-g-PTHF graft
copolymers with various average grafting numbers (G
N). The nanosized phase separation micromorphology was
dependent on G
N in HPC-g-PTHF. The water contact angles on graft copolymer film surfaces
increased from 61.7° to 87.7° with increasing G
N from 3 to 10 and after annealing treatment. The silver
nanoparticles (AgNPs) in situ formed from AgClO4 uniformly
dispersed in graft copolymer matrix and Ag contents were close to
the theoretical data based on AgClO4. The HPC-g-PTHF graft copolymer films show good anti-protein adsorption performance
against bull serum albumin. The HPC-g-PTHF/AgNPs
compounds present good antibacterial activity.
Hybrid materials consisting of polymers and graphene are gathering ever-growing interest. This article reports a novel methodology for preparing chirally helical polyacetylene/graphene hybrid microspheres (MPs) via suspension polymerization in which graphene oxide (GO) or alkynylated GO (MGO) serves as a sole stabilizer. Such polymerizations show remarkable advantages in circumventing the difficulties in usual suspension polymerizations and especially in directly providing clean hybrid MPs. Scanning electron microscopy (SEM), Raman spectra, and electron dispersive spectroscopy indicate that graphene sheets cover the MPs through physical interaction (GO) or covalent bonds (MGO). The hybrid MPs are also characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy, and thermogravimetric analysis. Circular dichroism spectra demonstrate that the polymer chains constituting the MPs adopt predominantly one-handed helices, endowing the MPs with intriguing optical activity. The established strategy opens a new approach for preparing hybrid MPs constructed by acetylenic polymers and GO.
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