Molecular Rotors with Aggregation-Induced Emission (AIE) as Fluorescent Probes for the Control of Polyurethane Synthesis

In this work, the use of fluorescent molecular rotors such as 9-(2,2-dicyanovinyl)julolidine (DCVJ) and 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl) phenyl)amino)phenyl)fumaronitrile (TPETPAFN) was proposed for the real-time monitoring of polyurethane (PU) formation in a solution of dimethylacetamide starting with 4,4′-methylenediphenyl diisocyanate (MDI) and different polyethylene glycols (PEG400 and PEG600) as diols. Notably, relative viscosity variations were compared with fluorescence changes, recorded as a function of the polymerization progress. The agreement between these two parameters suggested the innovative use of a low-cost fluorescence detection system based on a LED/photodiode assembly directly mountable on the reaction apparatus. The general validity of the proposed experiments enabled the monitoring of polyurethane polymerization and suggested its effective applications to a variety of industrial polymers, showing viscosity enhancement during polymerization.

Effect of chemical structure on properties of polyurethanes: Temperature responsiveness and biocompatibility

Polyurethanes are known as one of the most biocompatible and inherently blood-compatible materials and have a wide range of applications in the medical field due to their controllable structure and properties. Durability, elasticity, elastomeric structure, fatigue resistance, versatility, and easy acceptance by the biological media after the application makes these polymers preferable in medical area. In this study, polyurethane films were prepared using poly(propylene-ethylene glycol) and either toluene-2,4-diisocyanate or 4,4′-methylenediphenyl diisocyanate without adding any other ingredients such as solvent, catalyst, or chain extender to prevent negative effects of leachable molecules. Mechanical tests were performed at room temperature while swelling tests were conducted in water and phosphate-buffered saline at 4°C, 25°C, and 37°C. Temperature responsiveness was observed for the samples synthesized using toluene-2,4-diisocyanate and poly(propylene-ethylene glycol). These samples had more than 100% swelling at 4°C and about 4% swelling at 25°C and 37°C. Cytocompatibility tests were performed by culturing the samples and their extracts with mouse fibroblast cells (L929). Viability of human umbilical vein endothelial cells was studied to examine the compatibility of the films for blood contacting devices. Both toluene-2,4-diisocyanate and 4,4-methylenediphenyl diisocyanate–based polyurethane films showed no cytotoxic effect and good biocompatibility. Oxygen plasma treatment enhanced hydrophilicity of the films. After plasma treatment, human umbilical vein endothelial cell attachment on toluene-2,4-diisocyanate–based polyurethane films improved and 4,4-methylenediphenyl diisocyanate–based polyurethane films maintained their high cell affinity. Polyurethanes presenting temperature responsiveness, high biocompatibility, and high affinity for human umbilical vein endothelial cells were synthesized in medical purity and in a reaction media involving only diisocyanate and diol components without addition of any solvent, chain extender, or catalyst. Polyurethanes with these properties and as produced in this study are reported for the first time in the literature.

Ionic liquid-mediated solvothermal synthesis of 4,4′-methylenediphenyl diisocyanate (MDI): an efficient and environment-friendly process

Mechanism for MDI synthesis via decomposition of MDC catalyzed by Zn(OAc)2–[EAmim]BF4.

The Effect of Molecular Complexes of Lactam-Containing and Proton-Donor Substances on the Adhesion Properties of Adhesive Composites

The results of investigating the effect of a molecular complex (MC) based on a lactam-containing product and a hydroxyl-containing compound on the adhesion properties of elastomeric adhesives are set out. The MCs comprise binary melts based on triatomic alcohol (TA) and ε-caprolactam. An MC was introduced into an adhesive based on chloroprene rubber in different ratios together with the isocyanate 4,4’-methylenediphenyl diisocyanate (MDI). The adhesion activity of the MC was assessed from the bond strength between the elements in rubber–cord composites (a rubber compound based on BNKS-40AMN nitrile butadiene rubber + cord coated with a rubber mix based on general-purpose rubbers according to GOST 6768-75). Comparison of the IR spectra (FSM 1201 IR Fourier spectrometer) of the MC and its individual constituents makes it possible to suggest the presence of hydrogen bonds in the MC. Analysis of NMR spectra (Bruker Avance-400 NMR spectrometer) of the MC showed the absence of new chemical bonds between its components. Theoretically, a binary MC introduced into an adhesive composite together with isocyanate should promote an increase in the bond strength between the substrates through the formation of urethane groups. The results of testing the MC in the composition of adhesives showed that a higher bond strength is possessed by rubber–cord specimens with a ratio of TA and ε-caprolactam of 2:1. The introduction of an MC together with MDI leads to a 25% increase in adhesion strength in the adhesive joint.