Multiple Hydrogen Bonding for Reversible Polymer Surface Adhesion

Specific and reversible adhesion of a terminal thymine-functionalized polystyrene (PS−thymine) was demonstrated for a silicon surface with complementary adenine recognition sites. A novel adenine-containing triethoxysilane (ADPTES), which was suitable for covalent attachment to silanol containing surfaces, was synthesized in one step from adenine and 3-isocyanatopropyl triethoxysilane (IPTES). 1H and 13C NMR spectroscopy and fast atom bombardment mass spectroscopy confirmed the chemical structure, and 29Si NMR spectroscopy indicated the absence of any premature hydrolysis of the alkoxysilane derivative. X-ray photoelectron spectroscopy (XPS) and water contact angle measurements indicated the attachment of PS−thymine to silicon surfaces that were modified with a mixture of ADPTES and 3-mercaptopropyl triethoxysilane (MPTES). PS−thymine attachment to surfaces that were modified with only MPTES was not observed. The exclusive attachment of PS−thymine to an ADPTES/MPTES-modified surface confirmed hydrogen bonding-mediated adenine−thymine association to silicon surfaces containing a sufficiently low concentration of adenine recognition sites. Although PS−thymine attachment to the ADPTES/MPTES-modified surfaces was insensitive to THF rinsing, the PS−thymine was completely removed from the surface upon DMSO rinsing because of the disruption of adenine−thymine hydrogen bonding with a more polar aprotic solvent. PS−thymine was successfully reattached to the ADPTES/MPTES-modified surface following the DMSO rinse, demonstrating the solvato-reversible nature of the adenine−thymine association.