Star Synthesis Using Macroinitiators via Electrochemically Mediated Atom Transfer Radical Polymerization

Abstract

Electrochemically mediated atom transfer radical polymerization (eATRP) was investigated for synthesis of star polymers using macroinitiators (MIs), achieving high star yield with low Cu catalyst loading (∼100 ppm, w/w). The arm first method, using MIs, is one of the most robust procedures for star polymer synthesis. During the polymerization, MIs can react with cross-linkers (divinyl or multivinyl compounds) for initial chain extension followed by the cross-linking reaction. The MIs can be transformed to arms of the star, and the cross-linker can form the star core. In this study, poly(ethylene oxide) (PEO, M n = 2000) based MIs (PEO MIs) were prepared, and the chain-end functionalities were confirmed by 1H NMR analysis. The ATRP functionalized PEO MIs were then used for the star synthesis by reacting with ethylene glycol diacrylate cross-linkers. Various experimental conditions were conducted for optimizing star formation, including MI concentration, MI to cross-linker molar ratio, and applied potential (E app).

Synthesis of cationic star polymers by simplified electrochemically mediated ATRP

“…The structure of the ligand, monomer, dormant species as well as reaction conditions (solvent, temperature and pressure) can strongly influence the values of the rate constants (k a , k da and K ATRP (= k a /k da )) [5,19]. In most cases electrochemically mediated ATRP reactions were carried out in DMF [14,15,19,23,24] and acetonitrile (MeCN) [20] as solvents. The polymerization in DMF was faster in comparison to the reactions conducted in MeCN, this is because more polar system could enhance ATRP equilibrium constants (K ATRP = k a /k da ) [59].…”

“…Consequently, the radical species propagate to form polymeric chains by reacting with monomers (M), or are deactivated back to the dormant species (P n -X) ( Figure 1) [14,15,17,18]. This method has been applied to hydrophobic (meth) acrylates [14,15,[19][20][21][22][23][24][25][26], and hydrophilic (meth)acrylates and (meth)acrylamides [14, 16-18, 25, 27-31] for the synthesis of well-defined polymeric architec-tures. Star-shaped cationic polymers, consisting of multiple arms linked to a central β-cyclodextrin (β-CD) core, have recently attracted much attention, because of their dense branched architecture with moderate flexibility, tunable properties like solubility, chemically crosslinked structure, temperature or pH sensitivity, which could be manipulated by the parameters such as the block composition, MW, and arm number [32][33][34][35][36][37][38][39][40][41][42][43][44].…”

Star Polymers

“…Bisht et al explored the synthesis of nonoptically active star polymers with spatially directional PCL arms via a core-first approach. 97,98 The conformation constraints imposed on this synthesized star originate from the rigid, bowl-shaped resorcin [4]arene core initiator (I2.10, Figure 22). …”

Synthesis and self-assembly in bulk of star-shaped block copolymers based on helical polypeptides

“…The "arm-first approach" is viewed to be an efficient way to synthesize star-shaped polymer because it allows for a high degree of control at every stage of the synthetic process, and the arms can be characterized easily prior to star formation [31,32]. On the other hand, Cu(I)-catalyzed Huisgen's 1,3-dipolar cycloaddition reaction between azide and alkyne, that is, click reaction, as designated by Sharpless and coworkers [33], has recently been applied to synthesize various kinds of star block copolymers due to its rapid proceeding and high yield [34,35].…”