ABA-type Amphiphilic Triblock Copolymer Synthesis And Application In Catalysis

Amphiphilic block copolymer consists of at least two blocks with different chemical natures in selective solvent, constituting an amphiphilic character. Because of having both hydrophilic and hydrophobic blocks, it has been found that these types of polymers of different structures can self-organize into aggregates of diverse morphologies under certain conditions. Compared to general polymers, amphiphilic block copolymers exhibit unique characters. Because of their potential applications in many fields, such as biomedicine, biomaterials, photoelectric materials and catalysts, amphiphilic block copolymers have attracted considerable attention, in both academia and industry.In this study, a novel ABA-type of amphiphilic triblock copolymer, poly(4-vinylpyridine)-block-poly(ethylene glycol)-block-poly(4-vinylpyridine)(P4VP-PEG-P4VP), was designed and synthesized via anionic polymerization. The copolymers formed into reverse micelles in1-hexanol/water mixed solution by self-assembly. The reverse micelles consisted of a hydrophobic shell of P4VP and a hydrophilic core of PEG, partly with a water pool in the core. Demonstrated by dynamic light scattering, transmission electron microscope and ζ potential, the structure and morphologies of the reverse micelles changed along with solvent composition and the pH of surroundings. To stabilize the structure, bis(2-iodoethoxy) ethane (BIEE) was used to cross-link the shell by quarternizing the nitrogen atoms on the pyridine groups, achieving the shell cross-linked reverse micelles (SCRMs). The SCRMs were reinforced through covalent bonds between P4VP chains, to maintain the structure whenever the environmental conditions changed.After coordinating with copper ions, the Cu-(P4VP-PEG-P4VP) SCRMs complex was obtained as a catalyst for the oxidation of2,3,6-trimethylphenol (TMP). In addition to the advantages as general catalyst carriers, Cu-(P4VP-PEG-P4VP) can take advantage of its mesoscale stereoscopic structure. With the distribution of metal catalytic active centers in the structure, the co-catalysis effect of the immobilized water droplets and the stability provided by shell cross-linking, it demonstrated an efficient catalytic activity and recoverability. It is indicated that the designed polymeric catalyst carrier in mesoscale level has the potential to provide a more reactive and recoverable catalytic system for catalytic oxidation.