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The risk of clot formation in blood-contacting devices is a significant concern. Therefore, development of biomaterials with improved hemocompatibility is a clinical need. Altering surface properti...

Smart coatings have aroused a growing interest because of the performance of predefined surface functions upon reacting to external stimuli. Among them, responsive polymer coatings to water, which often benefit from the presence of a mobile hydrophilic material, are of great interest. Polyurethanes (PUs) are versatile materials with respect to the structure-property relationship. Therefore, the incorporation of hydrophilic segments in PUs is a rational way to produce water-sensitive smart coatings; however, having a considerable amount of hydrophilic material deteriorates the physical properties because of a large amount of water uptake. In this study, we have analyzed previously synthesized smart PUs, based on hydrophobic polycarbonate (PC) and hydrophilic polyethylene glycol (PEG) soft segments, in which only a limited amount of PEG is used. These coatings maintain, more or less, zero water contact angle, whereas the water uptake remains below 15 wt %. The combination of experimental analysis and coarse-grained molecular dynamics (CG MD) simulations reveals that PEG segments migrate to the coating/water interface and partially cover the surface, whereas the hydrophobic nature of the PC keeps the bulk of the coating intact when the coating is covered with water. Moreover, our CG MD simulations and experimental analysis suggest a reversible phase arrangement under wet/dry cycles on molecular and macroscopic scales.

PEG-modification is a proven method to enhance the hydrophilicity, protein resistance, and anti-biofouling properties of polymer coatings. It is considered as the gold standard interfacial modification technique such that the higher PEG content, the higher hydrophilicity, and lower protein adsorption, i.e., the initial stage of the biofouling process. Nevertheless, increasing the PEG content causes a higher water uptake, which declines the polymer mechanical strength and increases its hydrolytic degradation rate. Thus, an effective strategy to produce a limited-water-absorbing PEG-modified polymer is to force the majority of PEG molecules to migrate towards the interfacial region while the modification takes place. In the current paper, we report the synthesis and characterization of crosslinked polycarbonate-based polyurethanes (PU) containing methoxy polyethylene glycol (mPEG) dangling chains. We show that the simultaneous incorporation of a limited amount of a low-surface-energy dangling chain, i.e., 1-octadecanol (oDEC), along with mPEG, results in a considerably higher mPEG surface concentration, according to X-ray photoelectron spectroscopy (XPS), and a significantly lower water contact angle (WCA), up to 45° lower. We also put forward a reasonable mechanism for our outstanding observation and verified it through extensive experiments, e.g., dynamic WCA, Atomic force microscopy (AFM), and XPS. Moreover, we outline a delicate dynamic WCA experimental protocol, by which the smart and responsive behavior of our coatings is illustrated. Eventually, we examined the mixed hydrophobic/hydrophilic dangling chains strategy for low-protein adsorption applications, in which a great potential has been discovered.

Incorporation of hydrophilic and hydrophobic agents into a polymer backbone is an effective approach to control its interfacial characteristics. Segmented polyurethanes (PUs) are easy-fabricating and cost-effective candidates in this respect. In this work, we have synthesized polycarbonate (PC)-based PUs containing hydrophilic Polyethylene glycol (PEG) and hydrophobic Polyhedral Oligomeric Silsesquioxane (POSS) in the lab as well as in molecular dynamics simulations. We employed several experimental techniques and a coarse-grained (CG) molecular dynamics (MD) method to evaluate the morphology and microphase arrangement of PUs. We successfully synthesized superior hydrophilic and hydrophobic coatings by replacing some parts of the soft segment (PC) with PEG and the chain extender (1,4-butandiol) with POSS, respectively. Our CG MD simulations showed that POSS is dispersed in PC uniformly, while PEG is completely phase separated from PC and formed a lamellar structure. This was also confirmed by experimental thermal analysis. Eventually, water contact angle (WCA) measurements proved development of very hydrophilic (PU-PEG), slightly hydrophilic (PU), and very hydrophobic (PU-POSS) coatings. The surface free energy analysis indicated that POSS decreases polar and apolar components of surface free energy, while PU-PEG exhibits omniphilic behavior. The presence of PEG and POSS on the surface was also confirmed by contact angle and AFM measurements. According to MTT and LDH assays, PEG and POSS incorporation significantly enhanced the biocompatibility of PU such that PU-PEG and PU-POSS coatings become prospective candidates for biomedical applications.

Designing surfaces with patterns of varying wettability is of significant importance for many applications. This fascinating feature is inspired by nature where it is vital for the survival of some living creatures. This research shows that an inherent incompatibility between different soft segments of segmented polyurethanes can play a pivotal role in designing such surfaces. We employed experimental techniques as well as coarse-grained molecular dynamics (CG MD) simulations to illustrate the microphase separation between soft segments with significantly different wettability. We started with poly(hexamethylene carbonate) polyurethane and partially replaced the polycarbonate diol (PC), the hydrophobic soft segment, with poly (ethylene glycol) (PEG), the superhydrophilic soft segment. Experimental analyses indicated a phase separation between PEG and PC, as soft segments, and our simulations merely confirmed it. This led to a core-shell morphology in which the hard segments are squeezed between two incompatible soft segments. Our combined simulation and experimental analyses proved a concurrent phase mixing of hard/soft segments with phase separation between soft segments. Moreover, the CG MD simulations elucidated the evolution of microphase organization as the polymerization proceeds and our further analysis shed light on the microarchitecture of the individual PU chains.

The steel samples were pre-treated by cerium conversion layer. Then, zinc phosphate conversion coating was used as sealing agent for the cerium conversion layer to enhance its corrosion resistance. The corrosion performance and surface characteristics of the samples were characterized by electrochemical impedance spectroscopy, scanning electron microscope and X-ray photoelectron spectroscopy. Results revealed that the post-treatment of the cerium conversion coating by phosphate coating significantly increased its corrosion resistance. A denser conversion layer with less cracks were precipitated on the steel surface after post-treatment by zinc phosphate. The surface free energy was significantly increased after post-treatment by zinc phosphate.