Crystal structure of diaquatris(1-ethyl-1H-imidazole- jN3)(sulfato-jO)nickel(II)

In the title complex, [Ni(SO4)(C5H8N2)3(H2O)2], the NiII ion is coordinated by three facial 1-ethyl-1H-imidazole ligands, one monodentate sulfate ligand and two water molecules in a slightly distorted octahedral coordination environment. In the crystal, two pairs of O—H...O hydrogen bonds link complex molecules, forming inversion dimers incorporating R24(8), R22(8) and R22(12) rings. The dimeric unit also contains two symmetry-unique intramolecular O—H...O hydrogen bonds. In addition, weak C—H...O hydrogen bonds, weak C—H...π interactions and π–π interactions with a centroid–centroid distance of 3.560 (2) Å combine to form a three-dimensional network. One of the ethyl groups is disordered over two sets of sites with occupancies in the ratio 0.586 (7):0.414 (7)

Hidrogélek kölcsönhatása biológiai szempontból jelentős vegyületekkel = Interaction of hydrogels with biologically relevant species in aqueous phase

Az orvosbiológiai és elválasztástechnikai célokra is elterjedten használt reszponzív polimer alapú rendszerekben az anyagfelvételt és -leadást irányító kölcsönhatásokat még mindig nem ismerjük pontosan. Térhálós poli-N-izopropil-akrilamid (PNIPA) hidrogélek fázisátalakulási tulajdonságait különböző biológiailag releváns ionok, aromás molekulák, aminosavak és protein jelenlétében vizsgálva megállapítottuk, hogy hatásuk nemcsak az oldószer ’jóságának’ módosítására vezethető vissza, hanem anyagi minőségüktől függően speciális kölcsönhatás(oka)t alakíthatnak ki a PNIPA oldalláncával. A kölcsönhatásokat befolyásoló tényezők feltérképezésére komplex megközelítést alkalmaztunk (mikrokalorimetria, NMR, szórási módszerek, duzzadási vizsgálatok, mechanikai tulajdonságok, porozitás, stb.). Az irodalomban elsőként publikáltuk a kölcsönható egységek lehetséges konformációit és az atomi távolságokat. Hidrofób módosításokkal kísérletet tettünk a PNIPA gél több tulajdonságának (mechanikai, szorpciós) javítására. A hőmérsékletérzékeny NIPA származékok mellett pH- és redox-érzékeny poli(aszparaginsav) (PASP) géleket is vizsgáltunk. Kettős reszponzív tulajdonságuk, magas víztartalmuk és mechanikai stabilitásuk orvosbiológiai alkalmazásokban előnyös lehet. Kriogén körülmények között NIPA és PASP alapú szupermikropórusos géleket állítottunk elő. Ezek gyors kinetikájuknak köszönhetően igen ígéretesek a célzott és programozott hatóanyagleadásban. | The majority of thermosensitive gels used in biotechnological applications are either homopolymers or co-polymers of N-isopropylacrylamide (NIPA). These applications are based on the ability of PNIPA hydrogels to adsorb, retain and separate different target molecules. The still poorly understood nature of the interactions with small molecules is a vital indicator in understanding a wide variety of systems of biomedical interest. Our observations based on high-resolution DSC, SANS and solid-state NMR converge to show that small aromatic molecules (SAMs) interact with PNIPA hydrogels not only by altering the average solvent quality of the diluent, but also by specific association with the side-chain groups in the NIPA subunits. The effect is strongly influenced by the substituent(s) of the aromatic ring. The most probable conformations and the interactions on atomic level were specified the first time. The potential improvement of the sorption and mechanic properties of PNIPA by hydrophobic modifications was studied. pH and redox responsive poli(aspartic acid) (PASP) gels were also investigated. Their stimuli sensitive properties along with their high water content and good mechanical stability make disulfide cross-linked PASP hydrogels good candidates for human biological applications. NIPA and PASP based supermacroporous polymers were synthesized also in cryogenic conditions. Due to the fast kinetics they are promising vectors for targeted and time controlled drug delivery

A versatile characterization of poly(N-isopropylacrylamideco- N,N'-methylene-bis-acrylamide) hydrogels for composition, mechanical strength, and rheology

Poly(N-isopropylacrylamide-co-N,N"-methylene-bisacrylamide) (P(NIPAAm-co-MBA)) hydrogels were prepared in water using redox initiator. The copolymer composition at high conversion (> 95%) was determined indirectly by HPLC (high performance liquid chromatography) analysis of the leaching water and directly by solid state 13C CP MAS NMR (cross polarization magic angle spinning nuclear magnetic resonance) spectroscopy of the dried gels, and was found to be close to that of the feed. The effect of cross-linker (MBA) content in the copolymer was investigated in the concentration range of 1.1–9.1 mol% (R:90–10; R = mol NIPAAm/mol MBA) on the rheological behaviour and mechanical strength of the hydrogels. Both storage and loss modulus decreased with decreasing cross-linker content as revealed by dynamic rheometry. Gels R70 and R90 with very low cross-linker content (1.2–1.5 mol% MBA) have a very loose network structure, which is significantly different from those with higher cross-linker content manifesting in higher difference in storage modulus. The temperature dependence of the damping factor served the most accurate determination of the volume phase transition temperature, which was not affected by the cross-link density in the investigated range of MBA concentration. Gel R10 with highest cross-linker content (9.1 mol% MBA) behaves anomalously due to heterogeneity and the hindered conformation of the side chains of PNIPAAm

Coupling of poly(lactic acid) with a polyurethane elastomer by reactive processing

A segmented polyurethane elastomer (PU) was synthesized in poly(lactic acid) (PLA) melt by reactive processing. The isocyanate component was anticipated to react with the end-groups of PLA resulting in the formation of block-copolymers. The stoichiometry of the functional groups was optimized in the preliminary experiments. Two different processing methods were compared in the further experiments: conventional mixing of PU with PLA (PLA/PU), and reactive blending (PLA-b-PU). The comparison of the structure and properties of compatibilized reactive blends and conventional physical blends clearly shows the benefits of reactive processing. Coupling resulted in a finer dispersion of the particles in the matrix leading to better mechanical properties in the reactive blend. The successful synthesis of PLA-b-PU block copolymers was confirmed by NMR spectroscopy. The isocyanate component was found to react only with the hydroxyl end-groups of PLA, while the formation of amide and acylurea groups was not detected on the carboxyl end