In bone surgery and orthopedics, bioresorbable materials can be helpful in bone repair and countering post-op infections. Explicit antibacterial activity, osteoinductive and osteoconductive effects are essential to achieving this objective. Nonwoven electrospun (ES) fibers are receiving the close attention of physicians as promising materials for wound dressing and tissue engineering; potentially, in high contrast with dense materials, ES mats hamper regeneration of the bone extracellular matrix to a lesser extent. The use of the compositions of inherently biodegradable polyesters (poly(ε-caprolactone) PCL, poly(lactoglycolide), etc.), calcium phosphates and antibiotics is highly prospective, but the task of forming ES fibers from such compositions is complicated by the incompatibility of the main organic and inorganic ingredients, polyesters and calcium phosphates. In the present research we report the synthesis of hydroxyapatite (HAp) nanoparticles with uniform morphology, and demonstrate high efficiency of the block copolymer of PCL and poly(ethylene phosphoric acid) (PEPA) as an efficient compatibilizer for PCL/HAp mixtures that are able to form ES fibers with improved mechanical characteristics. The materials obtained in the presence of vancomycin exhibited incremental drug release against Staphylococcus aureus (St. aureus).

Composites of synthetic bone mineral substitutes (BMS) and biodegradable polyesters are of particular interest for bone surgery and orthopedics. Manufacturing of composite scaffolds commonly uses mixing of the BMS with polymer melts. Melt processing requires a high homogeneity of the mixing, and is complicated by BMS-promoted thermal degradation of polymers. In our work, poly(L-lactide) (PLLA) and poly(ε-caprolactone) (PCL) composites reinforced by commercial β-tricalcium phosphate (βTCP) or synthesized carbonated hydroxyapatite with hexagonal and plate-like crystallite shapes (hCAp and pCAp, respectively) were fabricated using injection molding. pCAp-based composites showed advanced mechanical and thermal characteristics, and the best set of mechanical characteristics was observed for the PLLA-based composite containing 25 wt% of pCAp. To achieve compatibility of polyesters and pCAp, reactive block copolymers of PLLA or PCL with poly(tert-butyl ethylene phosphate) (C1 and C2, respectively) were introduced to the composite. The formation of a polyester-b-poly(ethylene phosphoric acid) (PEPA) compatibilizer during composite preparation, followed by chemical binding of PEPA with pCAp, have been proved experimentally. The presence of 5 wt% of the compatibilizer provided deeper homogenization of the composite, resulting in a marked increase in strength and moduli as well as a more pronounced nucleation effect during isothermal crystallization. The use of C1 increased the thermal stability of the PLLA-based composite, containing 25 wt% of pCAp. In view of positive impacts of polyester-b-PEPA on composite homogeneity, mechanical characteristics, and thermal stability, polyester-b-PEPA will find application in the further development of composite materials for bone surgery and orthopedics.

As is known, the polymerization of 1,3 butadiene in the presence of Ziegler type titanium containing catalytic systems based on tetravalent titanium mostly yields cis 1,4 polybutadiene.The catalytic systems of tri and divalent titanium (α , γ , or δ ), TiCl 3 /R 3 Al possess the trans regulat ing ability in the polymerization of butadiene [2]. The polymerization of butadiene catalyzed by the system TiX 4 /organomagnesium compound/Al(i C 4 H 9 ) 3 (X = Cl, I) gives rise to polybutadiene containing 90-95% trans 1,4 units [3].For polymerization of conjugated dienes [4][5][6][7][8][9], the stereoregulation and activity of catalytic systems and the molecular mass distribution and microstructure of polydienes are substantially affected by such parame ters as the nature and valence state of a transition metal (titanium, vanadium), the catalyst concentra tion, the nature of an organoaluminum compound, the type of modifying additives, the polymerization temperature, the nature of the support (MgCl 2 , SiO 2 ) , and the homogenization or heterogenization of the catalytic system [4][5][6][7][8][9].On the basis of the published data, the authors of review [6] arrived at the conclusion that titanium con taining Ziegler systems cannot be regarded as promis ing for the trans polymerization of butadiene and 1 This work was supported by the Russian Foundation for BasicResearch, project no. 09 03 00231 a. † Deceased. other dienes in terms of their stereospecificity and activity. In summary, they mentioned that the situa tion changes when titanium containing catalysts sup ported on the surface of solid supports (MgCl 2 , SiO 2 ) are used.A series of studies was devoted to the polymeriza tion of 1,3 dienes and characterization of the resulting polymers [10][11][12][13][14][15]. It was shown that the polymeriza tion of both butadiene and isoprene occurs in the pres ence of silica gel supported titanium-magnesium catalysts (TMCs) combined with Al(i C 4 H 9 ) 3 and TMCs modified with organometallic compounds of Ni or Zr to produce polydienes containing 80-98% trans 1,4 units.The advancement of studies in the field of design ing stereospecific and highly active TMCs enabled the authors of [16-20] to develop a new family of TMCs, titanium-magnesium nanocatalysts (TMNCs), which are suitable for the trans polymerization of con jugated dienes (butadiene, isoprene) [21][22][23][24], ethyl ene polymerization that yield ultrahigh molecular weight PE, and the polymerization of α olefins (pro pylene, 3 methyl 1 butene) [25][26][27].The aim of this study is to investigate the polymer ization of 1,3 butadiene in the presence of TMNCs and to characterize the trans 1,4 polybutadiene (TPB) being synthesized.Abstract-The suspension polymerization of butadiene in the presence of titanium-magnesium nanocata lysts combined with triisobutylaluminum is studied. The resulting polybutadiene is shown to contain up to 99% trans 1,4 units. The dependences of polymer microstructure on temperature and the Al to Ti ratio are investigated. The kinetic parameters of...

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