Silanizing agents attack compounds that contain hydroxyl groups by displacing the alkoxy groups on the silanizing agent and forming a covalent -Si-O-Si- bond.
It seems to me reacting a silanizing agent with Polyvinyl Alcohol will just add the silane to the alcohol groups - it will add mass to the PVOH chain, but not crosslink anything.
Also, to those reading that don't have experience with silanizing agents, they are kind of nasty compounds. You need to take real care when handling them. They are toxic through contact with skin and corrosive - that is they react with your skin as well.