What Are Graft Copolymers And Explain Something About Organometallic Catalysts?

Graft copolymers also consist of blocks of two different monomers except that the main chain consists of one type of monomer unit and the branches of the other. The second monomer is polymerized onto the trunk of the chain or attached through reactive groups, similar to grafting a branch of one tree onto the trunk of another kid of tree.

An important technical application of graft coplymeriszation is the manufacture of impact-resistant polystyrene and of acrylonitrile-butadiene-stryrene copolymer. In both cases a hard polymer component and a highly tough, elastomeric component are combined by means of graft copolymerization to produce a high-impact polymeric material.

With newer organometallic catalysts, the metallocene catalysts, it is possible to prepare polymers of great molecular homogeneity, i.e. narrow molecular weight distribution, carefully designed arrangement of co-monomers, and selected tacticiy. With increased uniformity of chain length and composition, the characteristic properties of polymer are better defined; the transition ranges become sharper, the resistance to stress cracking increases, and so does resistance to chemical degradation.

On the other hand if the regularity of the polymer is systematically reduced, the crystallinity of the polymer is reduced and thereby the melting temperature can be lowered. This leads to improved optical properties, e.g. number of short and long branched chains, the rheological behavior of the melt can be modified. The benefit of this method of synthesis is the avoidance of solvents and the ability to bypass secondary cleansing operations