A novel self-colored waterborne polyurethane (SCPU) was synthesized and used in the preparation of a microfiber synthetic leather (MS-Leather) base in order to reduce the pollution caused by N,N-dimethylformamide (DMF) and dyes. The SCPU was prepared using the reaction of a reactive brilliant red K-2G with a waterborne polyurethane which was then extended via a first generation of hyperbranched poly(amine-ester). With the introduction of the dye, new absorption peaks at 1118 cm⁻¹ [S=O], 1413 cm⁻¹ [N=N], and 1635 cm⁻¹ [C=N] appeared in the Fourier transform infrared (FTIR) spectrum of SCPU, and SCPU mean particle size increased to 162 nm. The X-ray diffraction (XRD) peak intensity of SCPU at 19.27° was 1310 cts. The thermal stability of SCPU at 200–280 °C was inferior to that of the control sample; however, it improved at temperatures above 360 °C. Finally, a free-dyeing MS-Leather base prepared by using SCPU without DMF was manufactured. It was found that the dyes were distributed mainly in the polyurethane matrix rather than in the microfibers. Moreover, the color changes of the base before and after being washed in both a water and a soap solution were 0.93 and 4.21, respectively. This indicated that the base’s washing color fastness to water was better than to a soap solution.

Despite its potential as a metal-free tanning agent capable of eliminating Cr pollution in the leather industry, the conventional preparation of poly(carbamoyl sulfonate) faces challenges, such as the extensive use of low-boiling organic solvents and low blocking ratios of –NCO groups. Herein, a liquid sulfonate chain extender, 2,3-dihydroxypropanesulfonic acid triethylamine salt (DHPSTEA), was initially synthesized. A series of poly(carbamoyl sulfonate) tanning agents (CTAS) were then synthesized using DHPSTEA and various diisocyanates as reaction monomers, with sodium bisulfite serving as the blocking agent and without utilizing organic solvents. CTAS demonstrated a blocking ratio of > 99% and satisfactory stability under acidic conditions at room temperature. Application experiments revealed that CTAS exhibited excellent tanning performance, with the parent diisocyanate monomer markedly influencing their tanning properties. CTAS synthesized with dicyclohexylmethane-4,4′-diisocyanate resulted in optimal product performance, yielding a shrinkage temperature of 83.2 °C at a 6% dosage. CTAS-tanned leather displayed excellent collagen fiber dispersion, yellowing resistance and mechanical properties. Additionally, CTAS is easy to biodegrade (BOD₅/COD > 0.45). Thus, this novel metal-free tanning agent holds a great potential as a sustainable alternative to traditional chrome tanning agent. Graphical Abstract

A self-switchable polymer reactor with a hyperbranched structure for controlled catalytic chemistry processes is reported. This polymer reactor was made of silver nanoparticles and a polymer carrier consisting of hyperbranched polyethylenimine and hydroxyethyl acrylate that behaved as thermally switchable domains. Below the transfer temperature, relatively strong catalytic reactivity was demonstrated due to the leading role of hydrophilic groups in the switchable domains, which opened access to the substrate for the packaged silver nanoparticles. In contrast, it showed weak catalysis at relatively high temperatures, reducing from the significantly increased hydrophobicity in the switchable domains. In this way, the polymer reactor displays controllable, tunable, catalytic activity based on this approach. This novel design opens up the opportunity to develop intelligent polymer reactors for controlled catalytic processes.

In order to elucidating the exact effect mechanism of polyphenols on the assembly of collagen, the assembled architectures of collagen treated with different amounts of procyanidin (PA) were investigated in details. The assembled morphologies of collagen were greatly influenced by the content of PA according to atomic force microcopy (AFM) images. When the content of PA was more than 20% (w/w), the fibrillar morphologies were substituted by globular aggregates, which were driven by the intense hydrogen bonding action originating from PA. While the formation of the non-fibrous aggregates was due to the coiling and entangling of flexible collagen molecules rather than their gelatinization based on the appearance of typical adsorption peaks at 222nm and 197nm on circular dichroism (CD) spectra. After being crosslinked by glutaraldehyde (GA), not only the diameters but also the lengths of fibrils increased. Unfortunately, the fibrillogenesis was still inhibited when the collagen suffered from 20% PA firstly and then 4% GA. Conversely, the fibrous morphologies of the fibrils stabilized by 4% GA and then underwent 20% PA maintained well, in spite of accompanying with grievous intertwining. This difference was derived from the change of flexibilities of collagen before and after being crosslinked by GA. Additionally, the differential scanning calorimeter (DSC) analysis confirmed the PA had no positive effect on the improvement of thermal stability of hydrous collagen, whereas the denaturation temperature of hydrated collagen stabilized by 4% GA increased from 40 °C to 80 °C.