An Improvement of Mechanical Properties of Two Kinds of Silicone Resins Containing Ladder Segments by Chemical Modification with Trimethylborate.

We suggest a new method for postsynthesis modification of silicones containing silanol groups. It was found that trimethylborate is an effective catalyst for dehydrative condensation of silanol groups with the formation of ladder-like blocks. The utility of this approach was demonstrated on postsynthesis modification of poly-( poly(dimethylsiloxane)- ladder-like poly(phenylsiloxane)) and poly-( poly((3,3',3″-trifluoropropyl-methyl)siloxane)- ladder-like poly(phenylsiloxane) with a combination of linear and ladder-like blocks having silanol groups.

Earliness and morphotypes of common wheat cultivars of Western and Eastern Siberia.

The global and local climate changes determine the producing of highly-adaptive common (bread) wheat commercial cultivars of a new generation whose optimal earliness matches the climatic features of the territory where the cultivars are farmed. Principal component analysis involving our own and published data has been applied to investigate 98 commercial common wheat cultivars from Western and Eastern Siberia comparing their morphotypes; cultivar zoning time; length of the vegetation period; 1000-grain weight, and inheritance of spring growth habit. It demonstrated that the dominant Vrn gene polymorphism determining the spring growth habit of the Siberian cultivars was minimally polymorphic.

Influence of Interpenetrating Chains on Rigid Domain Dimensions in Siloxane-Based Block-Copolymers.

H spin-diffusion solid-state NMR was utilized to elucidate the domain size in multiblock-copolymers (BCPs) poly-( poly(dimethylsiloxane)- ladder-like poly(phenylsiloxane)) and poly-( poly((3,3',3″-trifluoropropyl-methyl)siloxane)- ladder-like poly(phenylsiloxane). It was found that these BCPs form worm-like morphology with rigid cylinders dispersed in amorphous matrix. By using the combination of solid-state NMR techniques such as C CP/MAS, C direct-polarization MAS and 2D H EXSY, it was shown that the main factor which governs the diameter value of these rigid domains is the presence of interpenetrating segments of soft blocks.

Linear/Ladder-Like Polysiloxane Block Copolymers with Methyl-, Trifluoropropyl- and Phenyl- Siloxane Units for Surface Modification.

Multiblock copolymers containing linear polydimethylsiloxane or polymethyltrifluoropropylsiloxane and ladder-like polyphenylsiloxane were synthesized in a one-step pathway. The functional homopolymer blocks and final multiblock copolymers were characterized using solution and solid-state multinuclear H, C, F, and Si NMR spectroscopy. It was shown that the ladder-like block contains silanol units, which influence the adhesion properties of multiblock copolymers and morphology of their casted films.

Interplay of Structural Factors in Formation of Microphase-Separated or Microphase-Mixed Structures of Polyurethanes Revealed by Solid-State NMR and Dielectric Spectroscopy.

A set of aromatic-oxyaliphatic polyurethanes (PUs) with different mass fractions of components also containing fluorinated fragments was synthesized and studied using various solid-state NMR techniques and dielectric spectroscopy. In contrast to the common model suggested by Cooper and Tobolsky in 1966, the rigid domains of microphase separated PUs are formed, not only by units containing urethane bonds, but also by oxyethylene fragments that form a common rigid phase. The urethane bonds and oxyethylene fragments are incorporated into both rigid and soft phases.