Controlled synthesis of bottlebrush
polymers with high grafting
density and carrying polymeric side chains on every backbone atom
remains a great challenge. In this work, a series of well-defined
poly(l-lactic acid) (PLLA) and poly(d-lactic acid)
(PDLA) bearing polymerizable phenyl isocyanide on chain ends were
prepared. Polymerization of the terminal phenyl isocyanide of these
macromonomers by an alkyne-palladium(II) catalyst yielded bottlebrush
polymers carrying PLLA or PDLA side chains on every backbone atom.
The grafted side chains were directly packed together without separating
from other atoms. The polymerizations were proceeded in a living/controlled
manner, and the degree of polymerization could be up to 250. The chiral
macromonomers induced an asymmetric polymerization and resulted in
a poly(phenyl isocyanide) backbone with a preferred one-handed helix
and large optical activity. Remarkably, the densely grafted bottlebrush
polymers exhibited intriguing photoluminescence, although the macromonomers
and poly(phenyl isocyanide) backbone were all nonluminescent. Moreover,
the preferred one-handed helix of the backbone induced clear circularly
polarized luminescence (CPL) with defined handedness and a tunable
dissymmetric factor.
Diazoacetate polymerization has attracted considerable research attention because it is an effective approach for fabricating carbon–carbon (C–C) main chain polymers. However, diazoacetate polymerization based on inexpensive catalysts has been a long-standing challenge. Herein, we report a Ni(II) catalyst that can promote the living polymerization of various diazoacetates, yielding well-defined C–C main chain polymers, polycarbenes, with a predictable molecular weight (Mn) and low dispersity (Mw/Mn). Moreover, the Ni(II)-catalyzed sequential living polymerization of thiophene and diazoacetate monomers affords interesting π-conjugated poly(3-hexylthiophene)-block-polycarbene copolymers in high yields with a controlled Mn, variable compositions, and low Mw/Mn, although the structure and polymerization mechanism of the two monomers differ. Using this strategy, amphiphilic block copolymers comprising hydrophobic poly(3-hexylthiophene) and hydrophilic polycarbene blocks are facilely prepared, which were self-assembled into well-defined supramolecular architectures with tunable photoluminescence.
Inspired by highly efficient and enantioselective reactions catalyzed by biomacromolecules, developing artificial helical polymer-based catalysts for enantioselective reactions is an interesting work. In this work, a series of one-handed helical polyisocyanides bearing aryl iodine pendants were readily produced via asymmetric polymerization of achiral isocyanides using chiral Pd(II)-catalysts. Despite the inexistence of any stereogenic centers, these polymers showed large optical activity owing to the one-handed helicity. Remarkably, these polymers could catalyze asymmetric dearomatization spirocyclization of 1-hydroxy-N-aryl-2-naphthamide derivatives and gave chiral spirooxindole products with high enantioselectivity. The enantioselectivity was contributed by the helicity of the polyisocyanide backbone; helical polyisocyanides in opposite helicity produced the enantiomeric antipode products with comparable yields and similar high enantioselectivity. Thanks to the high molecular weight, the helical polymer catalysts could be recycled 10 times with maintained activity and stereoselectivity.
Immobilizing organocatalyst onto helical polymers not only facilitates the catalyst recycling from homogeneous reactions, but also boosts enantioselectivity. In this work, achiral organoiodine-functionalized single left- and right-handed helical polyisocyanides were prepared from the same monomers, which catalyzed three asymmetric oxidations gave the desired products in high yields and excellent enantioselectivity. The enantiomeric excess of the target products was up to 95%. Remarkably, the enantioselectivity can be switched by reversing the helicity of the polymer backbone. The polymer catalysts can be facilely recovered and recycled in different asymmetric oxidations with maintained excellent activity and enantioselectivity.
In this investigation, dodecyl dimethyl (vinylbenzyl) ammonium chloride is synthesized through the reaction between 4-vinylbenzyl chloride and N,N-dimethyl-dodecylamine. This resultant compound is characterized by H-NMR, FTIR, TGA, and antibacterial assays. It is found that this chemical reaction is achievable. Moreover, it is also observed that this compound have good thermal ability, and its decomposition temperature is 207°C. The antibacterial tests prove that it have excellent antibacterial abilities against E.coli and S. aureus. Therefore, these results are demonstrated that it can be applied in bulk modification of polymers for better antibacterial and mechanical properties.
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