Novel, semicrystalline polyamides and co(polyamides) were synthesized from biobased sebacic acid (SA), 2,5-diamino-2,5-dideoxy-1,4;3,6-dianhydroiditol (diaminoisoidide, DAII) as well as from 1,4-diaminobutane (DAB), also known as putrescine in nature. Low molecular weight polyamides were obtained by melt polycondensation of the salts based on these monomers or by interfacial polycondensation. In order to increase their molecular weights the polyamide prepolymers were submitted to a solid state polymerization (SSP) process. The chemical structure of the polymers was confirmed by 2D NMR correlation spectra (COSY), heteronuclear multiple-bond correlation spectra (HMBC) and by FT-IR spectroscopy. In the present work, FT-IR and X-ray techniques were used as a tool for the investigation of the crystal structure of the polymers after SSP. The X-ray diffractograms of the polyamides point to crystals containing both 4.10- and DAII.10-based repeat units. Because of the presence of diaminoisoidide residues the synthesized fully renewable products exhibit tunable polarities and melting points. Since most commercial polyamides have a much higher melting point than their end application requires, especially for fiber applications, this simple adaption can result in a significant reduction of energy consumption during processing.

A study of the mechanical properties and of the crystallization behavior of samples of isotactic polybutene (iPB) of different stereoregularity prepared with metallocene catalysts is presented. Stereoregular samples with concentration of rr defects lower than 2 mol % crystallize from the melt by compression-molding and fast cooling to room temperature in form II, whereas more stereoirregular samples crystallize surprisingly mainly in form III. The stereodefective iPB samples show interesting mechanical properties of high ductility and flexibility that increase with increasing concentration of rr stereodefects, with values of deformation at break higher than 1000% for the most stereoirregular sample containing about 5 mol % of stereodefects. The aging at room temperature produces transformation of form II into form I in more stereoregular samples, whereas no phase transformation occurs in more stereoirregular samples crystallized mainly in form III. A strong increase of Young’s modulus and of stress at yield is observed after transformation of form II into form I. For more stereoirregular samples with concentration of rr defects higher than 2 mol % crystallized in form III, the mechanical properties do not change significantly upon aging at room temperature because no phase transformations occur during aging. Also for the aged samples, a remarkable increase of ductility and flexibility with increasing concentration of rr stereodefects is observed. The mechanical deformation is associated with stress induced transformations of form II and form III into form I. These results indicate that mechanical properties of iPB can be modified by the controlled incorporation of stereodefects and improvement of ductility is easily obtained while maintaining high crystallinity by inclusion of small amounts of rr stereodefects.

The importance of using a large basis set including the electronic correlation correction for conformational energy calculation by ab initio methods has been reported frequently. [1][2][3] The reason is that, the energy difference between flexible conformers calculated at the level of DFT often do not agree with the experimental energy difference. On the other hand, calculated conformational energies at the MP2 level employing a reasonably large basis set (6-311G**) have a high accuracy and agree quite well with the experimentally determined values. Furthermore, as pointed out by Ke et al., 4 DFT is in many cases unable to locate all stationary points predicted by MP2. Therefore, both levels of theory (DFT and MP2) were applied in parallel to test the effects of different treatments of electron correlation and the effect of the basis set. Admittedly, the frequency analysis and the Gibbs free energy calculations become quite expensive and for this reason we decided to constrain the vibrational and thermal analyses to the MP2/6-31G* and B97-1/6-311G** levels of theory. Vibrational frequencies were calculated to ensure that all described geometries are local minima (not saddle points). Conformational AnalysisSince the methylene part of the homopolymer PA2 and copolymer coPA4 is of minor importance for the interpretation of the experimental 1 H and 13 C chemical shifts for the isohexide fragment, the NMR calculations were carried out for a simplified model with terminal propyl groups attached to both sides of the isohexide unit. In addition, we have replaced the propyl groups by methyl groups in the conformational search.The conformations of the isohexide moiety itself are quite similar to the chair/boat conformations of cyclohexane. We have defined UU and DD as the dominant conformations of a boat when both CH 2 groups are pointing either up or down, respectively, while both β N,DAII protons are pointing down.Consequently, UD and DU conformations are the mirrored chair-conformations. Fixing the possible conformations of the isohexide unit to one of the conformations UU, DU, UD, and DD, by varying

The challenge to manufacture medical devices with specific antibacterial functions, and the growing demand for systems able to limit bacterial resistance growth, necessitates the development of new technologies which can be easily produced at an industrial level. The object of this work was the study and the development of silver, titanium dioxide, and chitosan composites for the realization and/or implementation of biomedical devices. Thermoplastic elastomeric polyurethane was selected and used as matrix for the various antibacterial functions introduced during the processing phase (melt compounding). This strategy was employed to directly incorporate antimicrobial agents into the main constituent material of the devices themselves. With the exception of the composite filled with titanium dioxide, all of the other tested composites were shown to possess satisfactory mechanical properties. The best antibacterial effects were obtained with all the composites against Staphylococcus aureus: viability was efficiently inhibited by the prepared materials in four different bacterial culture concentrations.

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