In our previous work[1], we demonstrated the fabrication of copolymer thin films based on chemical vapor deposition (CVD) copolymerization to yield multifunctional surfaces. Amine and ketone derivatives of [2,2]paracyclophane (PCP) undergo pyrolysis and free radical polymerization to produce poly(p-xylylene) copolymers. Each copolymer is capable of presenting two different functional groups in specified ratios. Not only can one tailor the surface properties, but the copolymers can immobilize two biomolecules in specific ratios.

Using CVD co-polymerization we have now extended these principles to a library of 7 different paracyclophane monomers. Five ketone-functionalized PCPs and two amino-functionalized PCPs were paired into different combinations, and each combination was copolymerized into 5 different chemical ratios. The result is a collection of polymer coatings that can be screened simultaneously. FTIR spectroscopy verifies the bulk ratio of functional groups, and XPS quantified the copolymer ratios at the surface. Furthermore, the library was screened for human umbilical vein endothelial cell (HUVEC) growth and adhesion. Among the homopolymers, the greatest differences in HUVEC behavior were found between 4-aminomethyl-[2,2]paracyclophane and 4-pentafluoropropionyl-[2,2]paracyclophane. Copolymers of these two derivatives induced varying morphologies and different amounts of vinculin. A copolymer library such as this can quickly screen biological interfaces for their responses. The surface properties of each copolymer are decoupled from the bulk polymer, allowing the user to correlate function to structure. Although our work investigates amine and ketone functionalities, the PCP monomers can be modified with many other functional groups[2], and then copolymerized with another derivative. An added advantage is that surface geometry is not a limiting factor for CVD.

[1] Y. Elkasabi, H.Y. Chen, J. Lahann. Adv. Mater. 2006 18(12) 1521-1526 [2] J. Lahann, R. Langer. Macromol. 2002 35(11) 4380-4386.