Synthesis of Thermo‐, Oxidation‐, pH‐, and CO₂‐Responsive Polymers via the Combination of Aza‐Michael and Thiol‐Michael Reactions in One Pot

Abstract

additional base since amines can act as both nucleophiles and bases, which means that the adducts can be accessed via easily mixing amines with activated olefins. Derived from the step-growth aza-Michael addition polymerization, the amine-containing polymers are generally pH-responsive and CO 2 -responsive, and they can usually be protonated and electropositive so as to interact electrostatically with negatively charged materials. [2,3,[10][11][12][13][14][15][16][17][18] In the case of thiol-Michael reactions, the thiols are the Michael donors. However, bases or nucleophiles as the catalyst are usually indispensable to make the addition smoothly occur. Thiol-Michael reaction has been used to form polymers from simple, ideal step-growth reactions of dithiol and divinyl monomers. The resulting thioether linkages in the backbone endow the polymers with unique characters such as a high degree of flexibility, oxidation-responsiveness, and a relatively high refractive index. [8,9,[19][20][21][22] Owing to the dual role of the amine in which it can directly add to activated olefins (nucleophile) and meanwhile catalyze the thiol-Michael reaction (base), the aza-and thiol-Michael reactions are anticipated to be carried out in a one-pot fashion and no additional catalyst is needed. This may be an effective polymer synthesis strategy because of the distinct advantages as mentioned above. Furthermore, due to the availability of appropriate amine and thiol derivatives, diverse functionalities from the monomers can be facilely incorporated into the polymer backbones, allowing the production of sophisticated macromolecular systems and offering the flexibility to tune their properties, which can largely enrich the functions and diversities of the polymers. Therefore, this strategy can serve as a powerful tool for the design and synthesis of multifunctional polymers. Surprisingly, to the best of our knowledge, even though tremendous efforts have been devoted to apply single type of Michael reaction for polymer synthesis, no example has been focused on the combination of them for synthesis of multifunctional polymers.Herein, we report for the first time the robust synthesis of multifunctional polymers via the combination of efficient azaand thiol-Michael reaction using the commercial diamine, dithiol, and diacrylate in one pot. Specifically, as shown in Scheme 1, the secondary amine undergoes an aza-Michael addition to poly(ethylene glycol) diacrylate (PEGDA) from Multifunctional PolymersThe combination of efficient and harmonious aza-Michael and thiol-Michael reactions in one pot is first reported for the convenient synthesis of thermo-, oxidation-, pH-, and CO 2 -responsive polymers. The simultaneous two-type Michael reactions are proved to proceed smoothly without additional catalyst. The dithiol and diamine are involved in the copolymerization competitively and thus in a random distribution. A wide range of commercially available starting materials are utilized for the simultaneous two-type Michael reactions in one pot to obt...

Aggregation-Induced Emission-Active Fluorescent Polymer: Multi-Targeted Sensor and ROS Scavenger

“…The oxidation of the thioether to sulfoxide or sulfone was further verified by FT-IR (Figure S11). Moreover, the diameter of nano-assemblies distinctively decreasing from 40 to 18 nm after oxidation (Figure S8A) also indicates the polymer to be ROS-responsive.…”

“…The overproduction of ROSs causes oxidative stress, which often destructs the structure of DNA, lipids, and proteins. 40 The thioether functionalities in the backbone can be oxidized to hydrophilic sulfoxide or sulfone groups, 46,47 and thus, PEGDA−ODT−SADA is considered to be ROSresponsive. The ROS response of the polymer was confirmed by 1 H NMR.…”

Preparation and characterization of temperature/pH/CO2-triple-responsive homopolymers and their substituent determined response

“…This strategy is simple and applicable to a wide range of monomers, and many temperature/pH/CO 2 -responsive copolymers have been reported. [30][31][32][33][34] However, the purification of copolymers is usually complex, the responsive interval is generally wide, and more importantly, due to the incompatibility of each block, it is difficult to systematically explore the relationship between the polymeric structures and their responsiveness. Another method has been developed by combining temperature and pH/CO 2 responsive groups in a single monomer, and temperature/pH/CO 2 -responsive homopolymers can be obtained by the polymerization of monomers which can overcome the above shortcomings.…”

Novel Temperature/pH/CO2/Redox-Quadruple-Responsive Ferrocene-Containing Homopolymers and Their Self-Assembly Behavior

“…There are mainly two types of multistimuli-responsive polymers: multistimuli-responsive copolymers and multistimuli-responsive homopolymers. Between them, copolymers have been studied and applied more because of their simple design principle and wide application scope. − Their types are very rich, for example, temperature/pH, − temperature/pH/redox, , O 2 /CO 2 , temperature/pH/light, , temperature/pH/oxidation/light, , and temperature/pH/CO 2 /oxidation. , However, this kind of copolymers usually has some shortcomings: (1) the synthesis or purification steps of copolymers are usually complicated, and the molecular controllability is poor; (2) the response range of a copolymer is generally broad, and the sensitivity is relatively low; (3) due to the incompatibility of each block, it is difficult to systematically study the relationship between different responsiveness and its structure. However, multistimuli-responsive homopolymers, prepared by precisely setting the spatial arrangement of different responsive groups in the monomer first and then polymerization, can greatly alleviate the abovementioned shortcomings. − …”