A reactive hydrophobically modified ethoxylated urethane (HEUR) associative polymer bearing benzophenone terminal groups: Synthesis, thickening and photo-initiating reactivity

Hydrophobically Modified Polyacrylamide Incorporating Both Hydrophilic and Hydrophobic Units: Enhanced Printability and Stability in Aqueous Ink

For this research, three hydrophobically modified polyacrylamides, HPAAB, HPAAF, and HPAAS, with multiple hydrophobic monomers were designed, synthesized, and used as thickeners in aqueous ink for digital ink-jet printing. The structures were characterized by Fourier transform infrared (FTIR) analysis and nuclear magnetic resonance (NMR) spectroscopy. The viscosity-average molecular weight was determined by intrinsic viscosity determination and was adjusted according to hydrophobic content. The critical association concentration (CAC) of polymers was measured simultaneously using the apparent viscosity method and the fluorescence spectrum. The formation of a network structure and the mechanism of hydrophobic association are visualized dynamically with a scanning electron microscope (SEM) at different concentrations. Under the same conditions, HPAAB exhibited excellent thickening ability across different pH levels, temperatures, and shear rates, which is caused by the longer hydrophobic side chain and the stronger hydrophobic effect of the behenyl polyoxyethylene ether methacrylate (BEM) group. Furthermore, an aqueous ink using HPAAB as a thickener displays significant printability and stability, functioning much better than a corresponding aqueous ink that uses a commercial thickener. This is the first example of a hydrophobic associating polyacrylamide, incorporating both hydrophilic and hydrophobic units within a single hydrophobic chain, thereby serving as an efficient thickener for aqueous ink.

Reactive Extrusion Synthesis of Biobased Isocyanate-Free Hydrophobically Modified Ethoxylated Urethanes with Pendant Hydrophobic Groups

Development of hydrophobically modified ethoxylated urethane (HEUR) rheology modifiers enabled the widespread application of waterborne paints and coatings, replacing their environmentally burdening solvent-based predecessors. However, the diisocyanates, required for the conventional synthesis of HEURs, pose severe eco-sustainability threats. In this paper, we demonstrate an innovative approach to avoiding toxic components in the preparation of rheology modifiers by obtaining a new class of water-soluble isocyanate-free hydrophobically modified ethoxylated poly(hydroxy-urethane)s (IFHEURs). The first step in the synthetic pathway was the preparation of CO₂-based five-membered poly(ethylene glycol) bis(cyclic carbonate) and its subsequent aminolysis using 4,7,10-trioxa-1,13-tridecanediamine, yielding poly(hydroxy-urethane) (PHU) prepolymers terminated with cyclic carbonate groups. The PHU prepolymers were further extended in a reactive extrusion (REX) synthesis using biobased hydrophobic diamine PRIAMINE 1075. The REX technique made it possible to overcome the typical limitations of the aminolysis reaction and to reach the desired conversion within a moderate reaction time. IFHEURs have been structurally elucidated using FT-IR and NMR spectroscopy techniques, MALDI-ToF mass spectrometry, and SEC analysis and applied as rheology modifiers. The study of their associative behavior in aqueous solutions confirmed that the architectural flexibility of the obtained IFHEURs, containing terminal and pendant hydrophobic groups, opens a perspective for tuneable thickening performance.

Light-responsive polyurethanes: classification of light-responsive moieties, light-responsive reactions, and their applications

Stimuli responsiveness has been an attractive feature of smart material design, wherein the chemical and physical properties of the material can be varied in response to small environmental change. Polyurethane (PU), a widely used synthetic polymer can be upgraded into a light-responsive smart polymer by introducing a light-sensitive moiety into the polymer matrix. For instance, azobenzene, spiropyran, and coumarin result in reversible light-induced reactions, while o-nitrobenzyl can result in irreversible light-induced reactions. These variations of light-stimulus properties endow PU with wide ranges of physical, mechanical, and chemical changes upon exposure to different wavelengths of light. PU responsiveness has rarely been reviewed even though it is known to be one of the most versatile polymers with diverse ranges of applications in household, automotive, electronic, construction, medical, and biomedical industries. This review focuses on the classes of light-responsive moieties used in PU systems, their synthesis, and the response mechanism of light-responsive PU-based materials, which also include dual- or multi-responsive light-responsive PU systems. The advantages and limitations of light-responsive PU are reviewed and challenges in the development of light-responsive PU are discussed.