A series of acrylamide (AM) copolymers with various N-vinylpyrrolidone (NVP) contents were prepared by free radical solution polymerization. The chemical structures of polyacrylamide (PAM) and its copolymers were analyzed by Fourier transform infrared spectrometer (FTIR) and H NMR. Systematic investigations had been carried out to reveal the role of NVP in copolymer thermal degradation using a variety of techniques, such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermogravimetric analysis coupled Fourier transform infrared spectroscopy (TGA-FTIR). The DSC measurement showed an increase of 18 °C in the glass transition temperature (T_g) for the copolymer, meaning better thermal stability at 10% NVP content. TGA-FTIR analysis revealed that in the copolymer, low temperature pyrolysis products, such as ammonia and amides, were slowed down until NVP cleaved at about 400 °C. Furthermore, nitriles, which were derived from imide or isolated amide breakdown, were only detected in the copolymer over 350 °C, verifying that the amide or imide groups in the copolymer were also protected by NVP from another point of view. These results also revealed that NVP formed hydrogen bonds with amide groups and promoted the remote side group or inter-molecule crosslinking under heating.

Phospholipids and proteins were separately removed as the main non-rubber components to individually study their effect on the structure and properties of the rubber. Fourier Transform Infrared Spectroscopy (FTIR) and ¹H nuclear magnetic resonance spectroscopy (¹H-NMR) were used to characterize the chemical structure and the residual non-rubber component. A rheology study and stress relaxation measurements were used to study the role that non-rubber components play in natural networks. A rheological study showed that natural rubber (NR) and deproteinized natural rubber (DPNR) exhibited similar dynamic modulus at 170 °C. The lack of superposition in van Gurp–Palmen (vGP) curves at different temperatures for NR and DPNR, together with the shape of vGP curves, proved that long chain branching was mainly constructed by phospholipids. Stress relaxation measurements at room temperature were fitted with the Maxwell model and showed that the NR relaxation curve underwent a quick decrease and then came to an equilibrium stress retention of 58%, which is about 3 times higher than that of DPNR, indicating that proteins in NR contributed to the network structure at room temperature. Combining molecular dynamic studies, the interaction of proteins and phospholipids in non-rubber networks was proposed.

Inspired by the viscoelastic displacement theory and the advantages of preformed particle gels, we develop an innovative product called branched-preformed particle gel (B-PPG) for enhanced oil recovery.

Achieving high toughness and strength simultaneously in single-covalent-network hydrogels remains a longstanding challenge. Herein, we report a simple yet effective strategy to resolve this strength-toughness conflict by constructing polyacrylamide (PAAm) networks with abundant dangling chains that form transient entanglements. Unlike permanently trapped entanglements, these transient entanglements can slip and fully disentangle upon loading, enabling highly efficient energy dissipation and stress redistribution over a broad range of strains. Besides, these networks exhibit superior homogeneity compared to other structures, effectively mitigating stress concentration. As a result, our single-covalent-network hydrogels exhibit good mechanical properties, including a fracture strain of 5071%, a fracture strength of 1.06 MPa, a fatigue threshold of 1968 J·m⁻², and a fracture energy of approximately 60,000 J·m⁻². Moreover, these hydrogels feature low friction and high wear-resistance. Such a simple yet robust design paradigm effectively overcomes the longstanding strength–toughness trade-off without the complexity of multi-network architectures, opening avenues for next-generation hydrogels in biomedicine, wearable electronics, and other demanding environments.