Ying-Ling Liu

Debondable adhesion is highly attractive in the development of high-performance adhesives, particularly for sustainability initiatives requiring material recycling and reuse. Vitrimers, which possess dynamic features under specific conditions─typically at elevated temperatures─have been widely studied for the development of debondable adhesives. This work demonstrates an alternative approach to achieving debondable adhesion by establishing thin vitrimer layers on substrate surfaces via chemical modification. Poly(ethylene terephthalate) (PET) films, surface-modified with diketoenamine (DKA)-based vitrimers, were prepared to demonstrate the proposed strategy. When a commercial epoxy AB glue was utilized as the adhesive, pristine PET films did not exhibit debondable behavior. In contrast, the vitrimer-modified PET films demonstrated debonding capabilities at 50 °C, evidenced by a reduction in lap shear strength from 8.2 ± 0.9 MPa to 3.3 ± 0.9 MPa. Furthermore, acid-catalyzed hydrolysis of the DKA layers in the adhered samples resulted in a reduction in lap shear strength from 4.9 ± 0.5 MPa to 1.8 ± 0.5 MPa. This study demonstrates a highly effective approach for engineering debondable interfaces that is readily applicable to commercial adhesive systems.

Elemental sulfur has been widely utilized as a sustainable feedstock for the synthesis of sulfur‐modified and sulfur‐rich polymers. This study aims to extend the sulfur chemistry to surfaces vulcanization of polymer films. The process involves the infiltration of molten sulfur into the polymer film from surface, followed by in situ vulcanization. The surface vulcanization yields a vulcanized polymer layer on the top portion of the polymer film, resulting in an asymmetric structure. To demonstrate this synthetic route, a mainchain polybenzoxazine (PBz) film is employed. The resulting surface vulcanized and crosslinked PBz films are characterized using a scanning electron microscopy equipped with an energy‐dispersive X‐ray, an X‐ray photoelectron spectroscopy, and a Fourier transform infrared spectroscopy. The surface vulcanization strategy establishes a platform for the development of preparation of a new class of sulfur‐containing materials.

Based on the concept of green chemistry and synthesis of new functional materials, elemental sulfur is employed as the feedstock for the preparation of nanohybrid materials of carbon nanotubes (CNT) and sulfur. Referring to the radical reaction-based inverse vulcanization process, 2 reaction routes are conducted in this work. In the first approach elemental sulfur is directly reacted with CNTs through the addition reaction between sulfur radicals and the CC bonds of CNT surfaces. The obtained CNT-sulfur nanohybrids possess 23.2 wt % polysulfide segments chemically bonded to the outer surfaces of CNTs. The second route involves 2-step reactions, including the incorporation of poly-(glycidyl methacrylate) (PGMA) to CNTs through a surface-initiated atom transfer radical polymerization followed by an inverse vulcanization reaction between the PGMA-functionalized CNTs and elemental sulfur. 31.3 wt % polysulfide segments are chemically bonded to the PGMA-functionalized CNTs. The CNT-sulfur nanohybrids are subjected to metal ion absorption. The sample from route 2 exhibits an absorption capacity of 16 mg g^-1 for Fe³⁺, which is several times higher than the values reported for sulfur polymers from inverse vulcanization. The inverse vulcanization-like process provides an effective platform for the synthesis of CNT-sulfur nanohybrids exhibiting high absorption capacity for metal ions.

This work reports the preparation of environmentally benign polymeric materials by employing biomass-based raw materials in the synthesis of recyclable thermosetting resins. With water-soluble lignin (possessing −COOH groups) as a feedstock, lignin-triketone (OL-TK) is prepared and cross-linked with tris­(2-aminoethyl)­amine (TREN) to result in the corresponding lignin-based diketoenamine resins. The resin shows a glass transition temperature (T _g ) of about 165 °C, which is higher than the values reported for other diketoenamine resins and other lignin-based vitrimers due to the relatively rigid structure of lignin and diketoenamine groups. Nevertheless, the lignin-based diketoenamine resin shows high brittleness, leading to failure in the mechanical tests. Further studies employ OL-TK as a reactive modifier for a furanic dicarboxylic acid (FDCA)-based diketoenamine resin. The lignin-containing diketoenamine resins exhibit some features of vitrimers, including satisfactory stress relaxation at 180 to 220 °C, thermal recycling ability, and chemical degradation/recycling characteristics. The addition of 3 wt % OL-TK brings positive effects on enhancing the mechanical properties and suppressing the creep at high temperatures of the pristine resin and does not alter its thermal properties and thermal recycling and reprocessing features. A high OL-TK fraction of 7 wt %, although further increasing the mechanical property and stress relaxation of the vitrimers, would result in lignin aggregation in the thermally recycled sample. High OL-TK content is negative for the recycling performance of the vitrimers.

Nanocomposites of single-ion-conducting polyelectrolyte (SICP) and SICP-functionalized carbon nanotubes provide a platform for the preparation of polymer electrolytes with enhanced lithium-ion conductivities and high lithium transference numbers.

Reactive polymers are attractive precursors for the synthesis of functional polymers and the preparation of crosslinked polymers. This work reports an effective approach for the synthesis of reactive polyesters with pendant phenol groups employing a newly synthesized Meldrum's acid derivative (MAHP) as the monomer through a selective ketene/hydroxyl addition reaction. The MAHP‐based polyester (P‐MAHP) shows an inherent viscosity of 0.123 dL g⁻¹ (measured in 1‐methyl‐2‐pyrrolidinone), a glass transition temperature (T_g) of 30°C (measured with a differential scanning calorimeter), and a thermal stability of about 240°C. P‐MAHP, like phenolic novolac (PN), is utilized as a crosslinking agent for epoxy compounds. In dynamic mechanical analysis, the P‐MAHP‐crosslinked epoxy resin (ER_P‐MAHP) exhibits a T_g of 102°C (lower than the value of 155°C founded with the PN‐crosslinked analogue (ER_PN)) and a storage modulus of 2.37 GPa (higher than the value of 1.85 GPa found with ER_PN). Moreover, based on the dynamic ester bonds, ER_P‐MAHP possesses associactive covalent adaptable networks exhibiting stress relaxation and physical recycling features. The results demonstrate a significant progress on polymer chemistry and synthesis of polymeric materials.