Under the joint supervision of Researcher Li Liangbin and Assistant Researcher Chen Jungeng, our Ph.D. candidate Tan Zhengqi and colleagues have developed and screened polyvinyl alcohol (PVA)-based modified materials for quarter-wave plate applications. Guided by theoretical calculations and verified through experiments, the team successfully obtained a series of biphenyl-aldehyde-modified materials and systematically investigated the regulation of their optical properties under different stretching conditions. This work also lays a solid foundation for the development of multi-side-group-modified PVA materials. The related study has been published in the journal Polymer.

In this article, Gaussian simulations were first employed to screen side groups with prominent polarizability, with biphenyl being particularly favored due to its molecular rigidity and high polarizability. In the experimental validation, the team identified suitable synthetic conditions where the molar acetalization degree of the products could be tuned (10%–50%) by adjusting the feed ratio and catalyst equivalents. A series of modified PVA materials were successfully obtained, and corresponding optical films were fabricated using solution casting. By inducing molecular chain orientation through uniaxial stretching, the researchers established the variation patterns of retardation and wavelength dispersion properties of the films under different stretching conditions. Based on these results, they determined the appropriate substitution ranges and stretching conditions for biphenyl-modified PVA materials, which also provide important insights for the future development of multi-side-group-modified PVA systems.

This work was supported by the Chinese Academy of Sciences (Grant JZHKYPT-2021-04), the Anhui Provincial Natural Science Foundation (Grant 2308085UM04), the Hefei Municipal Major Science and Technology Special “Revealing the List and Taking Command” Project (Grant 2022-SZD-005), and the Hefei Municipal Major Special Guidance and Entrustment Project “Research and Development of Polyvinyl Butyral (PVB) Films for Automotive Safety Glass” (Grant 2021DX005).

Tan Z, et al. Biphenyl acetalized polyvinyl alcohol optical films with excellent extraordinary wavelength dispersion [J]. Polymer,2025, 128780.

Under the joint guidance of Researcher Li Liangbin and Researcher Yu Wancheng, master's student Sun Shengyang and others in our team applied machine learning to the field of polymer density prediction and achieved accurate prediction of polymer material density through directed graph neural networks. The related work was published in the Journal of Chemical Physics.

The paper proposes a machine learning framework based on Graph Convolutional Neural Networks (GCNN) for accurate polymer density prediction. The study selected data of 1432 homopolymers from the PoLyInfo database and systematically compared the prediction performance of GCNN with other models such as neural networks, random forests, and XGBoost. The results show that the GCNN model combined with the Directed Message Passing Neural Network (D-MPNN) performs the best, with a mean absolute error (MAE) of 0.0497 g/cm³ and a coefficient of determination (R²) of 0.8097. Experimental verification showed that the predicted density of six polymers was highly consistent with the measured values, with a relative error not exceeding 4.8%. SHAP analysis and t-SNE visualization revealed the relationship between functional groups and density, enhancing the interpretability of the model. This research provides an efficient and accurate computational tool for high-throughput polymer screening, which helps promote the design and discovery of polymer materials.

This work was supported by the National Natural Science Foundation of China (No. U2430213) and the Chinese Academy of Sciences (JZHKYPT-2021-04).

S. Sun, F. Tian, C. Zhao, M. Xie, W. Li, W. Yu, K. Cui, and L. Li, Directed message passing neural networks enhanced graph convolutional learning for accurate polymer density prediction. The Journal of Chemical Physics 163(10),(2025)

Under the joint supervision of Researcher Liangbin Li and Postdoctoral Fellow Jungeng Chen, Ph.D. student Xueqing Han and colleagues from our team have innovatively proposed a new approach for synergistically modulating the optical properties of polyvinyl acetal (PVAc) films through molecular side-group chemical modification and sequential biaxial stretching.

By conducting acetalization reactions between polyvinyl alcohol (PVA) and benzaldehyde (BA), para-fluorobenzaldehyde (FBA), and para-methylbenzaldehyde (MBA), the team successfully synthesized a series of PVAc derivative films—namely PVBA, PVFBA, and PVMBA. During the biaxial stretching process, they revealed for the first time a three-dimensional refractive index modulation mechanism driven by the cooperative alignment of the polymer main chain and the molecular side groups.

This work addresses a long-standing challenge in PVA-based optical materials, where the high positive intrinsic birefringence of the hydroxyl groups limits tunability through mechanical deformation. By precisely introducing benzene ring substituents (–H/–F/–CH₃) with negative intrinsic birefringence and tuning the degree of acetalization (30%–50%), the team achieved a molecular-level dynamic balance between the positive birefringence of hydroxyl groups and the negative birefringence of aromatic rings.

In addition, the films overcome the limitation of conventional wavelength dispersion in PVA films: PVBA and PVFBA exhibit remarkably flat dispersion curves with slopes close to unity, while PVMBA displays anomalous wavelength dispersion behavior. The subsequent sequential biaxial stretching process enabled precise control of the internal two-dimensional stress field, leading to the synchronized modulation of main-chain orientation and side-group alignment in three-dimensional space. After stretching, the films exhibit anisotropy with n_x>n_y>n_z, meeting the optical compensation requirements for VA-LCD display applications.

Polarized infrared spectroscopy confirmed that this optical anisotropy arises from strain-induced planarization and reorientation of molecular chains under biaxial tension.

This research has been published in the journal ACS Applied Polymer Materials and was supported by the Institutional Platform Program of the Chinese Academy of Sciences (JZHKYPY-2021-04).

Han X, Tan Z, Fang X, et al. Modulating Birefringence and Wavelength Dispersion of Biaxially Stretched Poly (vinyl  acetal) Films[J]. ACS Applied Polymer Materials, 2025, 7, 8, 4992–5002

Under the supervision of Researcher Li Liangbin, our team’s master's student Liu Ziwei and collaborators conducted an in-depth investigation into the nonlinear stress response of polymer melts during uniaxial elongation using molecular dynamics simulations. The study elucidates the relationship between microscopic conformational changes and macroscopic mechanical properties, offering new theoretical insights for the field. The related work has been published in the Journal of Chemical Physics.

In the process of polymer processing, complex multiscale coupling phenomena such as necking and edge effects are commonly observed. The essence of these phenomena lies in the nonlinear dynamic response of polymer molecular chains under external fields. In this article, the research team conducted molecular dynamics simulations combined with the generalized Kraynik-Reinelt (KR) boundary condition to perform uniaxial stretching of polymer melts at equilibrium. They first systematically analyzed the evolution of stretch ratio, orientational order parameters, and entanglement state.

In addition, it was found that under nonlinear uniaxial elongational flow, the number of entanglement points exhibits a heterogeneous distribution across different chains as the stretching proceeds. Finally, the study showed that traditional stress prediction models based on average entanglement states deviate significantly at large strains, while the newly developed theoretical model—by introducing entanglement loss and the heterogeneous distribution of entanglement points—significantly improves the prediction accuracy of nonlinear rheological behavior. It is hoped that this work will attract further interest and reflection from researchers in the field.

This work was supported by the Fundamental Research Funds for the Central Universities (Grant No. WK2310000119), the China Postdoctoral Science Foundation (Grant No. 2023M743377), the Institutional Platform Program of the Chinese Academy of Sciences (Grant No. JZHKYPT-2021-04), the Hefei “揭榜挂帅” Major Science and Technology Special Project (Grant No. 2022-SZD-005), and the Hefei Municipal Commissioned Major Project: Research and Development of Polyvinyl Butyral (PVB) Films for Automotive Safety Glass Applications.

Liu Z, Xu T, Peng F, et al. Improved predictions of nonlinear uniaxial tensile stress in polymer melts by accounting for microscopic conformation and entanglement changes[J]. The Journal of Chemical Physics, 2025, 162(20).

Our doctoral student Zheng Huang, under the joint supervision of Researcher Liangbin Li and Postdoctoral Fellow Jungeng Chen, has conducted research on the processing of nanofiber membranes using high-temperature stretched PVA–glycerol hydrogel films. The study focused on the in-situ structural evolution and influencing factors of various hydrogel films stretched at different temperatures. The related work has been published in the journal Macromolecules.

In this article, in-situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) were employed to investigate the structural evolution of glycerol-containing PVA hydrogel films during stretching at different temperatures. SAXS and WAXS analyses revealed that uniaxial stretching induced melt-recrystallization of PVA lamellar crystals and the formation of nanofibers. The key factors driving structural evolution varied with stretching temperature. At lower temperatures, crystal disruption was primarily stress-induced. The reconstructed nanofibers could bear stress and feed back into the structural evolution process, thereby slowing crystal damage. Under high-temperature conditions, crystal disruption occurred mainly through melting, with a rapid decline in crystallinity under stress. However, stretching-induced recrystallization and nanofiber reconstruction were more readily achieved. In addition, the long period of lamellar crystals and nanofibers increased with the stretching temperature. Moreover, PVA porous nanofiber membranes with well-developed nanofiber networks and porous structures were obtained through biaxial stretching, solvent extraction, and drying.

This work was supported by the Major Science and Technology Project of Hefei City, Anhui Province (“Revealing the List and Taking Command,” Project No. 2022-SZD-005), and the Chinese Academy of Sciences (Grant No. JZHKYPT-2021-04).

Huang Z, Li W, Wan C, et al. Stretch-Induced Structure Evolution of Poly(vinyl alcohol)–Glycerol Gel Films: An In Situ Synchrotron Radiation X-ray Scattering Study [J]. Macromolecules, 2025.

Associate Researcher Hang Guo (currently Associate Professor at Xi’an Jiaotong University), Professor Kunpeng Cui, and Researcher Hongjun Zhang from the State Key Laboratory of Nuclear Detection and Electronics have systematically investigated the evolution of free volume voids in highly oriented isotactic polypropylene elastomers (HEPP) during tensile deformation, using an in-situ ultra-high count rate positron annihilation lifetime spectroscopy (PALS) technique developed through collaborative research.

By combining experimental results from in-situ synchrotron small-angle X-ray scattering (SAXS), the research team discovered that stretching induces the growth, coalescence, and redistribution of sub-nanometer-scale free volume voids within the interlamellar amorphous phase. They further proposed a reasonable physical model to explain this evolution process: stress-induced microphase separation in the interlamellar amorphous regions. This study was published in Macromolecules, a top-tier journal in the field of polymer science, and was selected as the front cover article for that issue.

This research considered the real-time evolution of free volume within the interlamellar amorphous phase under uniaxial tensile deformation, clarifying the mechanism of instability. In future work, the research team will focus on the structural evolution of HEPP and similar model semicrystalline polymers under various loading modes, including shear and combined shear-tensile loading, aiming to develop a comprehensive understanding of the deformation mechanisms at the lamellar cluster scale.

This work was supported by the National Natural Science Foundation of China (Grant Nos. 52303048, 12275270, 11975225) and the National Key R&D Program of China (Grant Nos. 2020YFA0405800, 2019YFA0210000).

Guo H, Luo M, Dong Y, et al. Evolution of Free-Volume Pores during Stretch-Induced Instability of the Interlamellar Amorphous Phase in Semicrystalline Polymers[J]. Macromolecules, 2025, 58(9),4645–4654

Under the joint supervision of Professors Li Liangbin and Cui Kunpeng, our postdoctoral researcher Zhang Yunhan and colleagues have, for the first time, unveiled the molecular dynamics of polyvinyl butyral (PVB)—the core material in automotive laminated glass—under mechanical stress. This study, published in the leading international journal Soft Matter, provides a new perspective on the evolution of hydrogen-bond networks in amorphous polymers under mechanical loading.

Using coarse-grained molecular dynamics simulations, the research team captured the dynamic changes of PVB during tensile deformation. Near the glass transition temperature, polymer chains were observed to undergo “slippage” under stress. This microscopic motion led to the breaking of intramolecular hydrogen bonds (“handshakes” within a chain), while unexpectedly promoting the formation of intermolecular hydrogen bonds (“handshakes” between chains)—a process akin to simultaneously “dismantling bridges” and “building new ones” at the molecular level.

By systematically varying three key parameters—vinyl alcohol (VA) content (which regulates hydrogen-bond density), block-structure regularity, and tensile strain rate—the researchers found that increasing VA content significantly enhances chain rigidity. During stretching, this rigidity facilitated more pronounced chain unfolding, which in turn strongly influenced hydrogen-bond lifetimes. The most groundbreaking discovery was that a net reduction in the total number of hydrogen bonds occurred just before fracture. However, after fracture, the hydrogen-bond network exhibited self-healing and reorganization through a mechanical–thermal coupling effect. This dynamic “destruction–reconstruction” balance mechanism provides a plausible explanation for the exceptional energy absorption capacity of PVB materials.

The study not only overcomes the technical challenge of monitoring hydrogen-bond dynamics in amorphous polymers but also establishes a quantitative predictive model linking molecular structure–hydrogen-bond networks–mechanical performance, laying a solid scientific foundation for the rational design of next-generation high-performance PVB films.

This work was supported by the China Postdoctoral Science Foundation (Grant 2023M743377), the Fundamental Research Funds for the Central Universities (Grant WK2310000119), the Hefei Municipal Major Special Guidance and Entrustment Project “Research and Development of Polyvinyl Butyral (PVB) Films for Automotive Safety Glass,” and the Hefei Municipal Major Science and Technology Special ‘Revealing the List and Taking Command’ Project (Grant 2022-SZD-005).

Y. Zhang et al. Investigating hydrogen bonding in poly(vinyl butyral) copolymers near glass-transition temperature under uniaxial stress: acoarse grained molecular dynamics study. Soft Matter, 2025,Advance Article