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Rheological behavior in melt of aliphatic hyperbranched polyesters (AHBP), synthesized using pseudo-one-step and one-step procedure, was investigated in this work. Three commercially available AHBP were also examined. Because of the presence of relatively strong hydrogen bonds between numerous end hydroxyl groups, AHBP of lower generation number, as well as the sample of tenth pseudo generation, show non-Newtonian behavior in the entire investigated frequency and temperature region. However, for other examined AHBP, the slope of the frequency dependence of complex viscosity (g* ¼ f(x)) becomes smaller with the temperature increase. Therefore, samples of fourth, fifth, and sixth pseudo generations show Newtonian behavior at temperatures higher than 70 C. Value of glass transition temperature, melt flow activation energy, fractional free volume, and thermal expansion coefficient were determined for the investigated AHBP. The influence of the type of end groups on rheological properties of AHBP was also examined.

The rheological investigation of concentrated solutions of aliphatic hyperbranched polyesters (AHBP) in N‐methyl‐2‐pyrrolidinon (NMP) is presented. Two series of hydroxy‐functional AHBP were synthesized using pseudo‐one‐step and one‐step procedure. Three commercial (Boltorn®) AHBP were also investigated. In the examined temperature region (10–50 °C), AHBP solutions (c ≤ 45 wt.‐%) exhibited Newtonian behavior. The same was observed for 50 and 55 wt.‐% solutions at T ≥ 40 °C. However, at T < 50 °C, solutions of AHBP of higher concentrations (50 and 55 wt.‐%) showed shear thinning behavior. Values of the flow activation energies were calculated for all examined AHBP. The influence of the procedure for the synthesis, concentration and temperature on rheological behavior of AHBP solutions in NMP is discussed.magnified image

Kappa-, iota-, and lambda-carrageenan (food grade) were analyzed by static light scattering (MALS in batch mode) in 0.1M NaNO 3 at 25 and 60 C, earlier heated up to 90 C or not. At 25 C, there was a strong tendency for a concentration-dependent aggregation in the order lambda < kappa < iota. At 60 C, all samples were molecularly dispersed. The strongly temperature-dependent refractive index increments (equilibrium dialysis) differ. Data interpretation in terms of the wormlike chain model using the Skolnik-Odijk-Fixman approach led to an intrinsic persistence length around 3 to 4 nm and expansion factors as high as 1.5 and above in a thermodynamically good solvent for all three types. and a nearly identical molar mass dependence of the radius of gyration. HPSEC at 25 C on kappa-carrageenan confirmed formation of soluble aggregates. Special emphasis was put on analytical and methodological aspects. The reliability of the experimental data was demonstrated by analogous measurements on dextran calibration standards.

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In this work, MALDI-TOF mass spectrometry was used for the characterization of aliphatic hyperbranched polyesters (AHBP), synthesized from 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and di-trimethylolpropane. From the obtained results it was concluded that it was not possible to take complete advantages of MALDI-TOF MS in this particular case, since the AHBP used in this work were polydisperse. The intensity of the signals from the high mass tail of these samples (pseudo generation higher than four) was underestimated and insufficient to distinguish it from the baseline and to use it for the analysis of the spectra. As a consequence of that, lower values of the Mn were obtained. At the same time, Mw were also underestimated, which led to very low values of the polydispersity index. On the other hand, it was possible to obtain molar masses of individual molecules from the MALDI-TOF mass spectra of AHBP and to qualitatively determine the extent of cyclization (side reactions) at each degree of polymerization. Using the adequate set of equations and results obtained from MALDI-TOF mass spectra of AHBP, every signal from the spectra was identified. The obtained results show that formation of poly(bis-MPA), intramolecular esterification and intramolecular etherification occurred as side reactions during the synthesis of these polyesters. The relative amount of the cycles increases with the number of pseudo generation (from the second up to the fifth pseudo generation). It was also observed that the relative proportion of the signals which represent cyclic structures increases with the increasing degree of polymerization. In this work the basic principles of MALDI-TOF MS are also presented, as well as, a review of adequate published articles

Hydrogel scaffolding biomaterials are one of the most attractive polymeric biomaterials for regenerative engineering and can be engineered into tissue mimetic scaffolds to support cell growth due to their similarity to the native extracellular matrix. The novel, versatile hydrogel scaffolds based on alginate, gelatin, 2-hydroxyethyl methacrylate, and inorganic agent hydroxyapatite were prepared by modified cryogelation. The chemical composition, morphology, porosity, mechanical properties, effects on cell viability, in vitro degradation, in vitro and in vivo biocompatibility were tested to correlate the material’s composition with the corresponding properties. Scaffolds showed an interconnected porous microstructure, satisfactory mechanical strength, favorable hydrophilicity, degradation, and suitable in vitro and in vivo biocompatible behavior. Materials showed good biocompatibility with healthy human fibroblast in cell culture, as well as in vivo with zebrafish assay, suggesting newly synthesized hydrogel scaffolds as a potential new generation of hydrogel scaffolding biomaterials with tunable properties for versatile biomedical applications and tissue regeneration.