No abstract

Experimental Section Materials: n-butyl acrylate (nBA, Aldrich, 99%) and N,N-dimethylformamide (DMF; Aldrich, 99+%) were distilled and stored at-15 ºC. Dichloromethane (DCM; IRIS Biotech GmbH, peptide grade) was distilled from CaH 2. N-isopropylacrylamide (NIPAM, Acros 99%) was recrystallized from n-hexane prior to use. Oligo(ethylene glycol) acrylate (OEGA; M n,PEÕ 454, Aldrich), triethylsilane (TES, Aldrich 99%), N,N-diisopropylethylamine (Acros, peptide grade), piperidine (Acros, peptide grade), trifluoroacetic acid (TFA; Acros, peptide grade), dodecanethiol (Alfa Aesar, 98%), methyltrioctylammoniumchloride (Aliquot 336, Fluka, >97%), trifluorethanol (TFE, Fluka, 99%), N,N-diisopropylcarbodiimide (DIC; Fluka, 99%), and N-methyl-2-pyrrolidone (NMP, 99.9% peptide synthesis grade) have been used as received. Fmoc-amino acid derivatives (Fmoc-Arg(Pbf) OH), Fmoc-Asp(tBu) OH, Fmoc-Gly OH, Fmoc-Ser(tBu) OH, 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluoro phosphate (HBTU) and polystyrene-(2-chloro-trityl chloride) resin (loading: 1.56 mmol/g) were used as received from IRIS Biotech. S-1-dodecyl-S'-(R,R'-dimethyl-R''acetic acid) trithiocarbonate (II) was synthesized from dodecanethiol, chloroform, acetone, and carbon disulfide in the presence of Aliquot 336 according to established literature procedures. 1 Instrumentation: The peptide synthesis was performed on a fully automated ABI 433a peptide synthesizer (Applied Biosystems, Germany). Mass spectrometry was performed on a high performance liquid chromatograph electro spray ionization mass spectrometer (LC-ESI-MS) (Shimadzu, qp8000 , Duisburg, Germany) without chromatographic separation. Reverse-phase HPLC-MS was carried out, using a Shimadzu LC-MS-qp8000 system;

The self-assembly of the amphiphilic block copolymer poly(butadiene)-block-poly[2-(dimethylamino)ethyl methacrylate] at the air-water interface and the mineralization of the monolayers with calcium phosphate was investigated at different pH values. As expected for polyelectrolytes, the subphase pH strongly affects the monolayer properties. The focus of the current study, however, is on the effect of an oscillating (instead of a static) polymer monolayer on calcium phosphate mineralization. Monitoring of the surface pressure vs. mineralization time shows that the monolayer is quite stable if the mineralization is performed at pH 8. In contrast, the monolayer at pH 5 shows a measurable decrease of the surface pressure already after ca. 2 h of mineralization. Transmission electron microscopy reveals that mineralization at low pH under constant oscillation leads to small particles, which are arranged in circular features and larger entities with holes of ca. 200 nm. The larger features with the holes disappear as the mineralization is continued in favor of the smaller particles. These grow with time and form necklace-like architectures of spherical particles with a uniform diameter. In contrast, mineralization at pH 8 leads to very uniform particle morphologies already after 2 h. The mineralization products consist of a circular feature with a dark dot in the center. The increasing contrast of the precipitates in the electron micrographs with mineralization time indicates an increasing degree of mineralization vs. reaction time. The study therefore shows that mechanical effects on mineralization at interfaces are quite complex.