Aliphatic polycarbonate-based polyurethane elastomers and nanocomposites. I. The influence of hard-segment content and macrodiol-constitution on bottom-up self-assembly

Analysis of the microphase structure and performance of self-healing polyurethanes containing dynamic disulfide bonds

Self-healable polyurethanes can be used in various fields for extended service life and reduced maintenance costs. It is generally believed that the shape memory effect is helpful for achieving a high healing efficiency. The morphological features were focused on in this study as microphase separation is one of the main factors affecting various performances of polyurethanes, including their shape memory behavior and mechanical properties. Microphase separation can be regulated by changing the content and types of the hard segments. With this in mind, polyurethanes from polycaprolactone diol, hexamethylene diisocyanate, and different chain extenders were synthesized, characterized, and designed as promising self-healing polymers. All the polyurethane specimens were equipped with a similar content of hard segments but diverse types, such as aliphatic, aromatic, and disulfide-bonded. Differential scanning calorimetry, thermogravimetric analysis, X-ray diffractometry, infrared spectroscopy, and atomic force microscopy were used to describe the microstructures of the polyurethanes, including the crystalline regions. The relationship between the microphase separation structures and material properties was focused on in this examination. Various properties, including the thermal stability, mechanical behavior, hydrophobicity, and self-healing efficiency showed significant differences due to the change in the hard segments' structure and multiphase distribution. The aliphatic disulfide stimulated the conformation of a proper microphase separation structure (the large heterogeneous structure at physical length scales as well as a more sufficient combination of soft and hard phases), which helped to improve the healing effect as much as possible by effective wound closure and the exchange reactions of disulfide bonds.

Thermal and Mechanical Behavior of New Transparent Thermoplastic Polyurethane Elastomers Derived from Cycloaliphatic Diisocyanate

New transparent thermoplastic polyurethane elastomers (TPURs) with the hard-segment content of ≈50 mass % were synthesized by one-step melt polyaddition of 1,1'-methanediylbis(4-isocyanatocyclohexane), 2,2'-methylenebis[(4,1-phenylene)-methylenesulfanediyl]diethanol (diol E), 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoic acid (DMPA), a poly(oxytetramethylene) diol of M ¯ n = 1000 g/mol (PTMO), or a poly(hexametylene carbonate) diol of M ¯ n = 860 g/mol (PHCD). Herein, I prepared TPURs in which 20, 40, and 60 mol % of diol E was replaced with DMPA, an ionic chain extender. The structure of polymers was examined by ATR-FTIR. Their thermal and mechanical behaviors were determined by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile tests, and Shore A/D hardness. Their optical properties are described. Generally, the addition of carboxyl groups to the polymer resulted in decreases in their thermal stability, transparency, and refractive indexes. Furthermore, the use of different soft segments revealed significant differences in both mechanical and thermal properties of the polymers obtained.

The Influence of Calcium Glycerophosphate (GPCa) Modifier on Physicochemical, Mechanical, and Biological Performance of Polyurethanes Applicable as Biomaterials for Bone Tissue Scaffolds Fabrication

In this paper we describe the synthesis of poly(ester ether urethane)s (PEEURs) by using selected raw materials to reach a biocompatible polyurethane (PU) for biomedical applications. PEEURs were synthesized by using aliphatic 1,6-hexamethylene diisocyanate (HDI), poly(ethylene glycol) (PEG), α,ω-dihydroxy(ethylene-butylene adipate) (Polios), 1,4-butanediol (BDO) as a chain extender and calcium glycerolphosphate salt (GPCa) as a modifier used to stimulate bone tissue regeneration. The obtained unmodified (PURs) and modified with GPCa (PURs-M) PEEURs were studied by various techniques. It was confirmed that urethane prepolymer reacts with GPCa modifier. Further analysis of the obtained PURs and PURs-M by Fourier transform infrared (FTIR) and Raman spectroscopy revealed the chemical composition typical for PUs by the confirmed presence of urethane bonds. Moreover, the FTIR and Raman spectra indicated that GPCa was incorporated into the main PU chain at least at one-side. The scanning electron microscopy (SEM) analysis of the PURs-M surface was in good agreement with the FTIR and Raman analysis due to the fact that inclusions were observed only at 20% of its surface, which were related to the non-reacted GPCa enclosed in the PUR matrix as filler. Further studies of hydrophilicity, mechanical properties, biocompatibility, short term-interactions, and calcification study lead to the final conclusion that the obtained PURs-M may by suitable candidate material for further scaffold fabrication. Scaffolds were prepared by the solvent casting/particulate leaching technique (SC/PL) combined with thermally-induced phase separation (TIPS). Such porous scaffolds had satisfactory pore sizes (36–100 μm) and porosity (77–82%) so as to be considered as suitable templates for bone tissue regeneration.

New thermoplastic poly(carbonate-urethane)s based on chain extenders with sulfur atoms

New thermoplastic segmented polyurethanes were obtained by a one-step melt polyaddition using 40, 50 and 60 mol% poly(hexane-1,6-diyl carbonate) diol of [Formula: see text] g mol-1, 1,1'-methanediylbis(4-isocyanatobenzene) and 2,2'-[sulfanediylbis(benzene-1,4-diyloxy)]diethanol, 2,2'-[oxybis(benzene-1,4-diylsulfanediyl)]diethanol or 2,2'-[sulfanediylbis(benzene-1,4-diylsulfanediyl)]diethanol as a chain extender. FTIR, atomic force microscopy, differential scanning calorimetry and thermogravimetry were used to examine the polyurethanes' structure and thermal properties. Moreover, their Shore A/D hardness, tensile, adhesive and optical attributes were determined. They were transparent high-molar-mass materials showing good tensile strength (up to 51.9 MPa). The polyurethanes exhibited improved adhesion to copper taking into consideration that of conventional ones, and middle or high refractive index values (1.57-1.60), and both these parameters increased with an increase of the content of sulfur atoms in the polyurethane chain. The newly obtained polyurethanes can be considered as materials for numerous medical and optical appliances.

The self-assembly of copolymers with one hydrophobic and one polyelectrolyte block in aqueous media: a dissipative particle dynamics study

The reversible self-assembly of copolymers with one hydrophobic and one polyelectrolyte block.

Poly(urethane-dimethylsiloxane) copolymers displaying a range of soft segment contents, noncytotoxic chemistry, and nonadherent properties toward endothelial cells

Polyurethane copolymers based on α,ω-dihydroxypropyl poly(dimethylsiloxane) (PDMS) with a range of soft segment contents were prepared by two-stage polymerization, and their microstructures, thermal, thermomechanical, and surface properties, as well as in vitro hemo- and cytocompatibility were evaluated. All utilized characterization methods confirmed the existence of moderately microphase separated structures with the appearance of some microphase mixing between segments as the PDMS (i.e., soft segment) content increased. Copolymers showed higher crystallinity, storage moduli, surface roughness, and surface free energy, but less hydrophobicity with decreasing PDMS content. Biocompatibility of copolymers was evaluated using an endothelial EA.hy926 cell line by direct contact, an extraction method and after pretreatment of copolymers with multicomponent protein mixture, as well as by a competitive protein adsorption assay. Copolymers showed no toxic effect to endothelial cells and all copolymers, except that with the lowest PDMS content, exhibited resistance to endothelial cell adhesion, suggesting their unsuitability for long-term biomedical devices which particularly require re-endothelialization. All copolymers exhibited excellent resistance to fibrinogen adsorption and adsorbed more albumin than fibrinogen in the competitive adsorption assay, suggesting their good hemocompatibility. The noncytotoxic chemistry of these synthesized materials, combined with their nonadherent properties which are inhospitable to cell attachment and growth, underlie the need for further investigations to clarify their potential for use in short-term biomedical devices.