Method for synthesizing brush-like polymers based on poly(n-heterocyclic carbene) structure self-catalyzed self-initiated ring-opening and the prepared brush-like polymers

Abstract

The invention discloses a method based on autocatalysis self-initiation ring opening of a poly(N-heterocylic carbene) structure to synthesize a brush polymer. The method includes: under inert gas shielding, adding annular monomer capable of being in ring opening polymerization under catalytic action of N-heterocylic carbene into an organic solution containing poly(N-heterocylic carbene), wherein a molar ratio of poly(N-heterocylic carbene) repetitive unit to at least one annular monomer is 1:1-1000, reaction temperature is minus 80 DEG C-120 DEG C, and reaction time is 10s-48h. The invention further discloses the brush polymer of a poly(N-heterocylic carbene) carbon dioxide adduct structure obtained by adding carbon dioxide to terminate reaction in the method. More brush polymers various in structure can be obtained by repeating the method. The method is simple in step, an initiator is not needed, a catalyst is metal-free, and the obtained polymer is narrow in molecular weight distribution, controllable in structure, high in grafting density and wide in application range.

Description

technical field [0001] The invention belongs to the technical field of polymer preparation, and in particular relates to a preparation method based on a poly(N-heterocyclic carbene) structure capable of synthesizing a brush-like polymer through self-catalysis and self-initiation ring-opening, and a poly(N- Hybrid carbene) carbon dioxide adduct structure brush polymer. Background technique [0002] Brush polymers are a class of polymers in which polymer side chains are grafted onto a linear backbone. When the grafting density is high, the main chain is greatly stretched due to the steric hindrance effect between the side chains, thus forming a stable worm-like molecular morphology. This unique molecular structure makes it play an important role in many application fields, such as photonic crystals, photolithography, ultrasoft elastomers, drug release, and molecular templates for preparing nanomaterials (Chem. Soc. Rev., 2015 , 44, 2405-2420). [0003] At present, there are...

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Problems solved by technology

"Grafting through" is a method to obtain brush-like polymers by polymerizing active macromonomers, but this method is difficult to obtain a main chain with a high degree of polymerization, and the conversion rate of macromonomers is lower than 80%, so that the remaining macromonomers are also difficult to remove; "grafting onto" is a method of coupling the main chain and side chains synthesized separately to obtain a brush-like polymer, due to the space between the polymer chains The steric hindrance effect and the low activity of the coupling reaction group lead to the grafting density obtained by this method is generally lower than 60%; "grafting from" is to further polymerize the side chain on the pre-synthesized main chain to obtain the brush polymer-like method, this method can obtain a high degree of polymerization of the main chain, but the degree of polymerization of the side chains is limited

[0004] In order to solve the problem of difficult synthesis and low controllability of brush-like polymers with high graft density, Y.Xia et al. Further improved the controllability of the "graftingthrough" method to synthesize brush-like polymers, but this method introduces heavy metal ruthenium, which is neither environmentally friendly nor conducive to the use of subsequent products

A. Khan et al. (Macromolecules, 2014, 47, 35–40) used a thiol-epoxy coupling reaction to synthesize a brush-like polymer, which increased the grafting density of the brush-like polymer synthesized by the "grafting onto" method to 88 %, but due to the cumbersome synthesis steps and the difficulty in controlling the structure of this method, it cannot be applied in a wide range

Although "grafting from" is more commonly used to synthesize brush polymers than the other two methods, there is still no significant difference in terms of side chain grafting rate, controllability of molecular structure, reaction efficiency, and cumbersome synthesis steps. breakthrough

[0005] At present, N-heterocyclic carbene is used to catalyze the preparation of aliphatic polyesters, because of its high catalytic activity, mild reaction conditions, short polymerization time, and the obtained polymers do not contain metals, and the polymer molecular weight distribution is narrow. Extensive research, but these technologies all use small molecule N-heterocyclic carbene as a catalyst, and need to add an initiator to complete the polymer preparation, while the in-situ self-catalyzed self-initiation preparation based on the poly(N-heterocyclic carbene) structure The method of brush polymers and the brush polymers prepared therefrom have not appeared in the prior art

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