Properties of the Cluster-Based Hybrid Polymers

Investigation of the materials properties of the cluster-based hybrid polymers is in its infancy, and the properties of the new hybrid polymers are far from being exploited. We have seen two clear trends in the materials properties of inorganic-organic hybrid polymers prepared by polymerization of metal oxo clusters with organic comonomers. They depend on the portion of incorporated cluster and, surprisingly, also on the kind of incorporated cluster.  

We do not yet understand how the employed cluster can possibly influence the materials properties. Several hypotheses have to be tested  

The properties of the hybrid polymers observed so far are typical of highly crosshnked polymers. Small amounts of the cluster (typically 0.5-2 mol%) are sufficient to achieve drastic property changes compared with the parent polymers. 

Different polymer morphologies can be obtained when the solvent is changed. When MMA was copolymerized with 1 mol% Zr6(0H)404(0Mc)i2 or Tig04(0Et)8 (OMc)g in the absence of a solvent or in benzene solution, hard transparent glasses were obtained. However, the polymer structure of the two glasses must be somewhat different because the polymer prepared without solvent swells less and takes up only half the amoimt of ethyl acetate compared to the polymer prepared in benzene solution. Polymerization in a heptane/benzene mixture (1 1) resulted in a colorless powder with a specific smface area of 3.2m /g.  

The specific smface areas of the insoluble powders obtained by copolymerization of the (meth)acrylate-substituted clusters with MA also depend on the cluster proportion. For example, the BET surface area of PMA crosslinked by the Ti604 (OEt)g(OMc)8 increased from 12m /g to 200m /g when the cluster proportion was increased from 0.3 to 2mol%. 

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