The answer depends on the polymer used in the blend.  To maintain dispersion of the titanium dioxide particles in the blend you should try to match the chemistry/surface energy of the silane and polymer.  Surface energy can be approximated/measured by contact angle techniques.  Measure or search the literature to find contact angles of films of your polymer and various silanes.  Choose silanes whose films exhibit surface energies near those of a film of your polymer.  For example, you might select a silane like octadecyltrimethoxysilane or octyltriemthoxysilane to disperse particles in polyethylene or polypropylene, whereas you might select a silane like phenethyltrimethoxysilane to disperse the particles in polystyrene. 

Dear Jabair

Your question is not enough understood. I assume that you want to coat TiO2 surfaces with a poly layer and you want first to anchor the TiO2 with silane ligand.

If so, my answer is: The silane must have the structure (RO)3Si(CH2)n-L.   The (RO)3Si end will be useful to react with TiO2 surface hydroxide groups via a condensation reaction.

The best type of L end is decided by the type of the polymer to be used itself.

Dear Hikmat

thanks for your response. Actually we are looking to blend TiO2 in Polymers and in order to have a good dispersion, we need to graft the TiO2 with silane. So, i was looking for suggestion on the best possible silane to be used in this case.

Hi,

Choice of good silane agent is based on its functionality, chain length etc.

Basic Silane agents which are frequently use to improve  the dispersion of nano particles are Chlorotrimethylsilane (CTMS), Aminopropyltriethoxy or methoxy (APTES/ APTMS) Please see this webpage for different silanes available

http://en.wikipedia.org/wiki/Silanes

The answer depends on the polymer used in the blend.  To maintain dispersion of the titanium dioxide particles in the blend you should try to match the chemistry/surface energy of the silane and polymer.  Surface energy can be approximated/measured by contact angle techniques.  Measure or search the literature to find contact angles of films of your polymer and various silanes.  Choose silanes whose films exhibit surface energies near those of a film of your polymer.  For example, you might select a silane like octadecyltrimethoxysilane or octyltriemthoxysilane to disperse particles in polyethylene or polypropylene, whereas you might select a silane like phenethyltrimethoxysilane to disperse the particles in polystyrene. 

Try titanate coupling agent.

best atricle for your answer:

How to Prepare Reproducible, Homogeneous, and Hydrolytically

Stable Aminosilane-derived Layers on Silica

Langmuir. 2012 January 10; 28(1): 416–423. doi:10.1021/la203638g

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3243110/

 So, If used APTS to graft onto TiO2 nanoparticle surface, the obtained products can soak into oil or not?

Which is water-based or oil based for your polymer?