We report on tuning swelling pH transitions of hydrogel hollow capsules that were derived from hydrogen-bonded multilayers via chemical cross-linking. The capsules were either of a single component -a weak poly(carboxylic acid), such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(ethacrylic acid) (PEAA) -or contained two hydrogen-bonding polymers, such as in poly(carboxylic acid)/poly(N-vinylpyrrolidone-co-NH 2 ) (PVPON-co-NH 2 ) or in poly(carboxylic acid)/ poly(N-vinylcaprolactam-co-NH 2 ) (PVCL-co-NH 2 ) systems. By varying the acidity of weak polyelectrolytes, the capsule swelling can be tuned over a wide pH range from 5 to 10. We show that differently from one-component capsules, the swelling amplitude of two-component capsules is limited by the number of cross-links provided by amino-containing units of a PVCL-co-NH 2 copolymer. For two-component capsules with the same degree of cross-linking, permeability at the minimum swelling pH was decreased for PMAA-neutral copolymer capsules as compared to those of PAA-neutral copolymer. We also demonstrate that swelling pH of one-component capsules in the acidic region can be modulated via reversible association with a polycation. The fine control over the swelling pH transitions and permeability of hydrogel capsules enables their use in biomedical applications.

Graphical abstractHighlights  Pyrenedihydrodioxins(PDHDs) are very effective DNA binding agents.  Pyrenequinone is released photochemicallyfrom PDHDs.  Pyrenequinone cleaves DNA ribose backbones and damages bases in a localized fashion  Pyrenequinone initiates its photochemical release from PDHD autocatalytically.  Electron capture by the coordinated action of two pyridinium rings is described. ABSTRACTPyrenedihydrodioxins (PDHD) comprise effective DNA intercalation agents that are masked ortho-quinones, which can be released by near ultraviolet or visible irradiation. We have studied the binding and photoreactions of chiral dipyridiniumPDHDs with herring sperm DNA and an 11-mer duplex DNA containing all 10 basepair steps. Binding affinities to herring sperm DNA were determined for purified enantiomers (K b = 1.6 ±0.15 ×10 5 and 2.3 ± 0.2 ×10 5 M -1 ). UVmelting experiments using the 11-mer DNA revealed significant stabilization of duplex DNA, 2 (T m = 11.5° and T m = 15.3° C). Both enantiomers linearized (double-strand cleavage) supercoiled X174 plasmid DNA with high efficiency. PDHDs have specificity to cleave and/or damage DNA duplexes at Gs and have preferable binding to GG DNA sites.A full range of transient spectroscopy from the ultrafast femtosecond to the microsecond domains has been applied in the study of this system. These studies have revealed a novel mechanism for quinone release via the pyrene radical cation and the entrapment of the released electron by the coordinated action of the two pyridinium rings. These same studies have shown that the released pyrenequinone can photochemically initiate the further release of pyrenequinone. Thus, this reaction is autocatalytic and can be initiated with visible light.

Methods for syntheses of new polyfluorinated compounds, viz., silanes containing substitu ents CF 3 CF 2 CF 2 C(CF 3 ) 2 (CH 2 ) 3 (R F ) at the silicon atom and 1,3,5 tris(R F ) 1,3,5 tri methylcyclotrisiloxane that can be used for the synthesis of fluorocontaining oligo and polysiloxanes of different structure, were developed. The polymerization of cyclotrisiloxane in the presence of 1,3 divinyltetramethyldisiloxane gave linear oligomers, whose chain contain -(R F )Si(Me)O-units.

A new method for the synthesis of polyfluorinated compounds, viz., chlorosilanes with 2 perfluoroalkoxy 2,3,3 trifluorocyclobutane substituents containing different numbers of tetrafluoro(ethylene oxide) (CF 2 CF 2 O) n units (n = 3-6), was developed. The structures of siloxanes formed by the hydrolysis of these chlorosilanes were studied: the hydrolysis of monochlorosilanes affords disiloxanes and that of dichlorosilanes produces cyclotrisiloxanes, cyclotetrasiloxanes, and cyclic (the number of siloxane units >4) and linear polysiloxanes.

Organo-silicon compounds S 0060Synthesis and Some Properties of Silanes and Siloxanes with 5,5,6,6,7,7,7-Heptafluoro-4,4-bis(trifluoromethyl)heptyl Substituents. -Methods for the synthesis of new polyfluorinated silanes and siloxanes are presented. Polymerization of (VI) in the presence of 1,3-divinyltetramethyldisiloxane affords the corresponding oligomers.-(SHAMAEV, A. E.; IGNATENKO, A. V.; KRUKOVSKY*, S. P.; Russ. Chem.