Photo-induced functionalization of spherical and planar surfaces via caged thioaldehyde end-functional polymers

The synthesis and application of a novel reversible addition-fragmentation chain transfer (RAFT) agent carrying a photocaged thioaldehyde moiety is described (λmax = 355 nm). RAFT polymerization of styrene, dimethylacrylamide and a glycomonomer is evidenced (3600 g mol-1 ≤ Mn ≤ 15 000 g mol-1; 1.07 ≤ D{stroke} ≤ 1.20) with excellent end-group fidelity. The photogenerated thioaldehyde on the chain ends can undergo hetero Diels-Alder reactions with dienes as well as reactions with nucleophiles. The terminal photoreactive polymers are photografted to porous diene-reactive polymeric microspheres. The grafted particles are in-depth characterized via scanning electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, and high resolution FT-IR microscopy, leading to a qualitative as well as quantitative image of the core-shell objects. Grafting densities up to 0.10 molecules nm-2 are reached. The versatility of the thioaldehyde ligation is evidenced by spatially resolved grafting of polystyrene onto nucleophilic groups present in poly (dopamine) (PDA)-coated glass slides and silicon wafers via two-photon direct laser writing (DLW) imaged by ToF-SIMS. The combination of thioaldehyde ligation, RAFT polymerization, and DLW allows for the spatially resolved grafting of a vast range of polymers onto various substrates in any desired pattern with sub-micrometer resolution. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim