A new type of photolabile, surface-initiated, atom-transfer radical polymerization (SI-ATRP) initiator 3-(2bromo-2-methylpropanamido)-3-(2-nitrophenyl)propanoic acid was synthesized, and immobilized via an aminosilane linker onto a flat silicon surface. Poly(lauryl methacrylate) and polystyrene brushes were grown from the surface via SI-ATRP, and the surface-tethered polymer chains cleaved off under UV irradiation. The kinetics of the cleavage process were investigated, and an apparent effect of osmotic forces within the polymer brush could be observed. The molecular weight of the cleaved polymers could be readily determined by means of size-exclusion chromatography.

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Chain-density gradients of poly(l-lysine)-graft-dextran (PLL-g-dex), a synthetic comblike copolymer with a poly(l-lysine) backbone grafted with dextran side chains, were fabricated on an oxidized silicon substrate. The influence of the changing dextran chain density along the gradient on the local coefficient of friction was investigated via colloidal-probe lateral force microscopy. Both in composition and structure, PLL-g-dex shares many similarities with bottlebrush biomolecules present in natural lubricating systems, while having the advantage of being well-characterized in terms of both architecture and adsorption behavior on negatively charged oxide surfaces. The results indicate that the transition of the dextran chain density from the mushroom into the brush regime coincides with a sharp reduction in friction at low loads. Above a critical load, the friction increases by more than an order of magnitude, likely signaling a pressure-induced change in the brush conformation at the contact area and a corresponding change in the mechanism of sliding. The onset of this higher-friction regime is moved to higher loads as the chain density of the film is increased. While in the low-load (and low-friction) regime, increased chain density leads to lower friction, in the high-load (high-friction) regime, increased chain density was found to lead to higher friction.

Thin films of fullerene C60 and molybdenum oxide (MoO3) are ubiquitously used as the electron acceptor material and hole extraction interfacial layer for the fabrication of organic photovoltaic (OPV) cells. It is well known that light exposure induces color changes in MoO3 (photochromism) and the formation of intermolecular bonds between C60 molecules (photopolymerization). The influence of these photoinduced reactions on the long‐term stability of OPV cells, however, has not previously been studied in detail. Here, a study and discussion of the early (<5 days) aging mechanisms occurring in illuminated ITO/MoO3/organic cyanine dye/C60/Alq3/Ag bilayer solar cells under nitrogen atmosphere is presented. A degradation process at the organic heterojunction is identified and the formation of Mo5+ species during illumination is found to adversely affect cell behavior. For these widely used materials, the results suggest that light processing is a first necessary step before OPV characteristics can be meaningfully rated.