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Atomic-force-microscopy-based single-molecule force spectroscopy (AFM-SMFS) was used to study the bond strength of self-complementary hydrogen-bonded complexes based on the 2-ureido-4[1H]-pyrimidinone (UPy) quadruple H-bond motif in hexadecane (HD). The unbinding force corresponding to single UPy-UPy dimers was investigated at a fixed piezo retraction rate in the nonequilibrium loading rate regime. The rupture force of bridging supramolecular polymer chains formed between UPy-functionalized substrates and AFM tips in the presence of a bis-UPy derivative was found to decrease with increasing rupture length. The rupture length was identified as the chain length of single, associating polymers, which allowed us to determine the number of supramolecular bonds (N) at rupture. The rupture force observed as a function of N was in quantitative agreement with the theory on uncooperative bond rupture for supramolecular linkages switched in a series. Hence, the value of the dimer equilibrium constant Keq=(1.3+/-0.5) x 10(9) M(-1), which is in good agreement with previously estimated values, was obtained by SMFS of supramolecular polymers at a single loading rate.

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Highly localized, selective deprotection chemistry and efficient grafting reactions in microcontacts between elastomeric stamps and reactive polystyrene‐block‐poly(tert‐butyl acrylate) (PS690‐b‐PtBA1210) diblock copolymer films are developed. The procedure yields well‐defined protein–poly(ethylene glycol) (PEG) nanopatterns (see figure), which may find applications in, for example, cancer‐cell–surface interaction studies.

The recognition of self-complementary quadruple urea-aminotriazine (UAT)-based hydrogen-bonded arrays was investigated in solution and at surfaces. For this purpose, an UAT-based donor-acceptor-donor-acceptor (DADA) array and complementary receptors were synthesized. Two-dimensional proton nuclear magnetic resonance ((1)H NMR) measurements in CDCl(3) pointed at an intramolecular hydrogen-bond stabilization of the UAT, which promotes a planar molecular geometry and, thereby, results in a significant stabilization of the dimeric complex. The bond strength of the UAT dimers at surfaces was determined by atomic force microscopy-based single molecule force spectroscopy (AFM-SMFS) in hexadecane. The UAT receptor was immobilized on gold surfaces using an ultrathin layer of ethylene glycol terminated lipoic acid and isocyanate chemistry. The layers obtained and the reversible self-complementary recognition were thoroughly characterized with contact angle measurements, grazing angle Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and AFM. Loading rate-dependent SMFS measurements yielded a barrier width x(β) and a bond lifetime at zero force t(off)(0) of 0.29 ± 0.02 nm and 100 ± 80 ms, respectively. The value of the corresponding off-rate constant k(off) suggests a substantially larger value of the dimerization constant compared to theoretical predictions, which is fully in line with the additional intramolecular hydrogen-bond stabilization detected in solution by (1)H NMR spectroscopy.