End-grafted low-molecular-weight PNIPAM does not collapse above the LCST

Improvement of metal and tissue adhesion on surface-modified parylene C

A general method for chemical surface functionalization of parylene C [PC, (para-CH2-C6H3Cl-CH2-)n] films is reported. Friedel-Crafts acylation is used to activate the surface of the PC film, and the resulting carbonyl groups are then used to form a range of different organic functional groups to the surface of the parylene film, including alcohol, imine, thiol, phthalimide, amine, and maleimide. The presence of these functional groups on the parylene surface was confirmed by Fourier transform infrared spectroscopy. Static water drop contact angle measurements were also used to demonstrate the changes in hydrophilicity of the PC film surface, consistent with each of the surface modifications. Enhanced metal (gold) adhesion was achieved by anchoring a thiol group onto the acylated surface of PC film. Acylation of parylene with 2-chloropropionyl chloride gave a surface bound chloropropionyl group. Grafting of poly-N-isopropylacrylamide (pNIPAM) onto the chloropropionyl substituted PC film via atom transfer radical polymerization (ATRP) was carried out. The grafted pNIPAM on the parylene surface leads to temperature-dependent cellular tissue adhesion on the PC film.