Hybrid Materials Based on the Embedding of Organically Modified Transition Metal Oxoclusters or Polyoxometalates into Polymers for Functional Applications: A Review

Mauro Carraro,Silvia Gross

doi:10.3390/ma7053956

Abstract

The covalent incorporation of inorganic building blocks into a polymer matrix to obtain stable and robust materials is a widely used concept in the field of organic-inorganic hybrid materials, and encompasses the use of different inorganic systems including (but not limited to) nanoparticles, mono- and polynuclear metal complexes and clusters, polyhedral oligomeric silsesquioxanes (POSS), polyoxometalates (POM), layered inorganic systems, inorganic fibers, and whiskers. In this paper, we will review the use of two particular kinds of structurally well-defined inorganic building blocks, namely transition metals oxoclusters (TMO) and polyoxometalates (POM), to obtain hybrid materials with enhanced functional (e.g., optical, dielectric, magnetic, catalytic) properties.

Highlights

The reason why a sharply growing attention is devoted to the development of organic-inorganic hybrid materials, from the world of production [15,16], is the possibility to tailor the properties of the final materials by a careful modification of the chemical nature, structure and amounts of the starting organic and inorganic building blocks
If we further focus on the first group, i.e., macromolecular networks embedding inorganic components, we enter the manifold world of composite materials, in which the properties of polymers are improved, typically in terms of thermal and mechanical stability, flame retardancy, barrier properties, etc., by the incorporation of tailored inorganic fillers
More importantly, the possibility to chemically tailor the composition, structure and functionalities of the inorganic building block and of the polymer matrix pave the way to the obtainment of multifunctional materials

Summary

Introduction

When dealing with organic-inorganic hybrid materials, two main underlying concepts are “combination” and “synergy”, since the basic idea behind the development of this rapidly expanding class of materials is to combine organic and inorganic building blocks to afford a material endowed with the properties of both components and eventually to overcome the structural limits of conventional materials (polymers, ceramics, metals, etc.) [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. Several parameters can be changed to tailor the features of the final material: beside the nature and number of metal ions, the polyhedral structure and connectivity of the inorganic building block, further diversity can be generated by varying the chemical nature of the surface functionalization This latter is dictated on the chemical nature of the polymer host, since the chemical bond between organic and inorganic domains is formed among the surface moiety of the inorganic unit and the monomer leading to the formation of the macromolecular skeleton. The investigation of the nature of the organic/inorganic interphase is very challenging from an analytical point of view, and typically it is addressed by a combination of different characterization methods, such as FT-IR, Raman, solid-state NMR [142,143,144,145,146], etc

Oxocluster-Based Hybrid Materials

Polyoxometalate-Based Hybrid Materials

Findings

Conclusions