Synthesis of Solution-processable Block and Random Copolymers of Poly(polyoxometalate norbornene) and Poly(hexanoic acid norbornene) and Study on their Catalytic Activity

Cheng, Q (Cheng, Qia)^[ 1 ] ; Miao, WK (Miao, Wen-ke)^[ 1 ] ; Yan, YK (Yan, Yu-kun)^[ 1 ] ; Wang, W (Wang, Wei)^[ 1,2 ]

ACTA POLYMERICA SINICA, 2017, 7; 1159-1168

DOI: 10.11777/j.issn1000-3304.2017.17029

  WOS:000408552400015

Abstract

Polyoxometalates (abbreviated as POM), are a class of anionic metal-oxygen clusters, which consist of early transition metals in their highest oxidation states. Thus they show excellent catalytic function. In the past years we have concentrated on synthesizing POM-containing polymers, so-called poly(polyoxometalate)s, to obtain a class of novel organic-inorganic hybrid materails with good processabililty and mechnical properties of organic polymers and catalytic function of inorganic POM clusters. We connected an organic-functionalized Wells-Dawson POM with norbornene to prepare a POM-containing norbornene monomer. Then, using the ring-opening metathesis polymerization (ROMP) approach, hybrid block and random copolymers of poly(POM norbornene) and poly(hexanoic acid norbornene) (denoted as Poly(POM)(m)-b-Poly(COOH)(n)) and Poly(POM)(m)-Poly(COOH)(n)) were synthesized in the presence of Grubbs 3rd catalyst. These copolymers thus prepared included block copolymers with m = 5 and n = 50, 100, 200 and 300, as well as a random copolymer with m = 5 and n = 100, i.e., Poly(POM)(5)-r-Poly(COOH)(100). The chemical structures of these hybrid copolymers were characterized by H-1-NMR, P-31-NMR and FTIR. The characterization results indicated that all the copolymers were successfully synthesized. Their absolut molecular weights and polydispersity indexes were determined by size exclusion chromatography (SEC) equipped with light scattering and infrared detectors. The results indicated that the molecular weights of the obtained hybrid copolymers were well-controlled with narrow molecular weight distribution coefficient. These hybrid copolymers were solution-processable. Their solid samples, prepared from their solution, were flexible. These hybrid copolymers also demonstrtated the catalytic activity of the parent POM cluster. The study on their capacity in catalytic oxidation of tetrahydrothiophene (THT) into cyclobutylsulfoxide (THTO) showed that their catalytic efficiencies were lower than that the hybrid homopolymer, poly(polyoxometalate) and decreased with increasing length of Poly(COOH) blocks. The findings obtained in this study offer a competitive strategy for developing novel hybrid materials with both functions of inorgnaic compnents and mechanical properties and pocessebility of the organic polymers.