Multiple vapor deposited polymer compositions been demonstrated for biomedical applications including the surface modification of implants, biosensing, and tissue culture. Homopolymer and copolymer surfaces can be designed directly from the library of functional groups processed by the vapor phase monomers.  Post-deposition modification of the functional groups of the monomeric units in the polymer films with bioactive molecules further enhances the precise chemical signaling at the surface. For interactions with living cells and tissues, surface modification layers must be free of impurities and stable under the conditions of use. A vapor deposition approach eliminates the possibility of contamination by residual solvent. Additionally, purifying monomers, which are small molecules, is much easier than purifying macromolecular polymer chains. The method of initiated Chemical Vapor Deposition (iCVD) has produced uniform coverage over neural probes and lead wires. These implants have microscale geometric features which must be conformally encapsulated by high-purity, pinhole-free, electrically insulating polymer layers. These biopassivation layers must be thin in order to minimize the disruption caused by implantation into the cortex. Since film growth proceeds upwards from the substrate, iCVD offers the opportunity for interfacial engineering prior to beginning iCVD synthesis. Grafting is essential for tethering swellable hydrophilic surface modification layers. Indeed the durability of iCVD hydrogels and zwitterionic layers is greatly enhanced by grafting for the prevention of delamination.