Polymer Grafting
Thursday, 20 January 2011 20:32
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Graft polymerization typically involves polymer grafting and/or graft polymerization as shown in the Figure to the left. Engineering of ceramic-supported polymer surfaces, consisting of with a terminally anchored polymer layer, requires careful control of the surface density and molecular weight of the polymeric chains.

 

 Our group developed a number of different methods of surface graft polymerization including a patented two-step method that is based on surface activation with organosilanes, a controlled free-surface graft polymerization and a plasma-assisted graft polymerization.

 

 

The degree of polymer graft yield, as well as chain length and density, are sensitive functions of reaction conditions as shown in the Figure to the left.

 


Our group has developed such models for free-radical polymerization (see Figure to the left for the PVP/silica system). These models enable predictions of graft yield and molecular weight distribution of the tethered polymer chains.



 

To date, detailed kinetic models for the graft polymerization of vinylpyrrolidone and vinyl acetate (see Figure to the left) have been developed. The kinetic models account for the simultaneous homopolymerization and graft polymerization reactions and consider the unique initiation mechanisms of those systems. Present work is continuing to allow improved predictions of the molecular weight distribution of the terminally anchored polymer chains. Also, various surface modification procedures and reaction conditions are being investigated in order to provide for improved control over the molecular weight distribution of the surface.

The resulting physicochemical and transport properties of the grafted polymer layer depend on the conformation and topology of the tethered polymer phase. The polymer chain configuration will vary from the extreme brush like configuration for high density coverage to separated chains in the so-called mushroom regime as shown below.

Grafted Polymer Chains

In order to control the structure of the grafted polymer phase (both chain density and chain length) various graft polymerization methods have been proposed as summarized in the Table below.

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Last Updated ( Thursday, 17 February 2011 15:15 )