While the mechanical properties of polymer gels are typically ascribed to the polymer network, the role of solvent dynamics-the majority component-remains elusive due to the lack of in-situ selective probing techniques. Here, by integrating operando Rheo-NMR with synchrotron radiation X-ray scattering (SRXS), we reveal a temperature-dependent coupling between macroscopic deformation and microscopic solvent confinement. Our results demonstrate a distinct bifurcation in behavior: at lower temperatures, the solvent dynamics remain relatively unperturbed as the network undergoes limited reorganization. However, at elevated temperatures (T >= 100 degrees C), a striking restriction of glycerol mobility is observed. In-situ SRXS uncovers the structural origin of this phenomenon: it stems from a competition between stretching-induced crystallite fragmentation and crystallization within the PVA network. At these elevated temperatures, crystallization is favored over fragmentation, resulting in a more constrained crystalline network environment that directly governs the solvent's rotational mobility. By establishing a direct correlation between stretching-induced structural evolution and solvent dynamics, this work offers a new perspective for designing high-performance soft materials through 'solvent engineering'.

Molecular chain defect engineering is a pivotal strategy for tailoring the macroscopic properties of polymeric materials. However, establishing a definitive relationship between molecular-level defects and bulk material performance remains challenging, due to the difficulty in precisely controlling not only the molecular architecture but also the subsequent chain packing, which critically governs material performance. In this work, we demonstrate that introducing ethylene units as chain defects into poly(vinyl alcohol) (PVA) enables precise modulation of the dichroism in iodine-doped PVA polarizers. This approach allows for concurrent control over the iodine-PVA complexation, the crystalline network and the mechanical properties. The dichroic behavior originates from the formation of oriented I3− and I5− species, with I3− absorbing between 400–520 nm and I5− between 520–780 nm. Therefore, optimizing optical performance—namely transmittance and polarization efficiency—requires careful tuning of the I3−/I5− ratio and their overall concentration. The incorporation of ethylene defects addresses this need through three synergistic effects: (1) It increases the I3−/I5− ratio by shortening the vinyl-alcohol sequence length in the amorphous regions, given that ethylene unit does not complex with iodine; (2) It reduces the overall crystallinity, as ethylene units are excluded from the crystalline domains; (3) It weakens intermolecular interactions (reflected by an increased Flory-Huggins parameter), which lowers the modulus but enhances drawability. This study illustrates how molecular-level defect engineering can be effectively translated into precise control over both chemical complexation and physical networks, thereby enabling the simultaneous manipulation of optical and mechanical properties in polymer materials.

The failure mechanism of acrylate copolymer waterproof composite films under sulfuric acid treatment is elucidated by time- and depth-resolved low-field single-sided nuclear magnetic resonance (NMR). The high depth sensitivity (10 μm) and large detection region (14 × 14 mm2) of single-sided NMR enable in situ tracking of porous structure formation under aqueous conditions. Both the pore size and interior surface wettability can be obtained through the proper selection of probe molecules, that is, water and ethanol, with different molecular sizes and surface tensions. A two-step erosion process is discovered over 7 days of treatment: Phase I (initial 4 days) primarily features calcite-to-gypsum transformation along with pore generation, and Phase II (final 3 days) involves slowing of pore propagation and copolymer matrix swelling. Numerical modeling confirms that such erosion inhibition arises from the interfacial stress concentration due to heterogeneous swelling of the acrylate copolymers.

Eco-friendly waterborne optical adhesives suffer from simultaneously achieving high interfacial adhesion and high bulk cohesion, alongside poor hydrothermal resistance. Here, we address this challenge by introducing Zn2+ coordination into a covalently cross-linked acetoacetylated poly(vinyl alcohol) (AAPVA) network. This synergistic multinetwork─comprising dynamic metal-ligand bonds, PVA crystallites, and covalent cross-links─dissipates energy to alleviate cohesive brittleness while providing new interaction sites at the adhesive-substrate interface. Consequently, the average peel strength is remarkably enhanced from 2.68 × 10-2 to 9.32 × 10-2 N mm-1, achieving optimal hydrothermal aging resistance at 0.22 wt % Zn2+. Furthermore, quantitative topological analysis via time-resolved low-field NMR, DSC, and FT-IR reveals that Zn2+ accelerates the initial cross-linking kinetics. Notably, the network constraint sites peak at 0.10 wt % Zn2+, while crystallization is completely suppressed above 0.64 wt %. This work provides a robust physical paradigm for utilizing dynamic metal coordination to decouple the adhesion-cohesion conflict in soft materials for demanding environments.

Understanding the film formation mechanism of waterborne latex is crucial for developing high-performance, eco-friendly coatings. However, the influence of various enviromental factors, i.e. temperature and wind, on spatiotemporal structure heterogeneity induced during drying complicates the establishment of the structure-process-property of coating. Here, we track a polyacrylate latex film formation using a custom-built single-sided nuclear magnetic resonance (NMR) hyphenated instrument. Two-dimensional correlation spectra reveal highly restricted water dynamics within the latex suspension, evidenced by a decreased self-diffusion coefficient D from 2.00×10−9 m2/s of pure water to 1.39×10−9 m2/s in suspension with a plummeted T1/T2 of 30, which is about 111 for pure water. For film drying under mild conditon (24 °C without airflow), dense particle packing induces strong capillary forces, generating anomalous fast-diffusion channels (D up to 31.05×10−9 m2/s) to accelerate water evaporation resulting in homogeneous structure along the thickness direction. Conversely, after introducing airflow, i.e. 35 °C with 10 L/min airflow, the accelerated drying rate (3.72 µm/min) drastically amplifies the spatiotemporal heterogeneity and triggers premature surface skinning. Such skin-core structure traps residual water inside and inhibit further coalescing of latex particles. The uncoalesced bottom layer thicknesses quantitatively predicted by non-destructive single-sided NMR (about 100, 200, and 400 µm), which is well consistent with SEM measurements (93, 240, and 409 µm, respectively). This work provides direct physical insights and theoretical guidance for the formulation and application of waterborne coatings during real service condition.

With the rapid advancement of flexible electronic technology, foldable displays have emerged as a leading application requiring highly reliable optical clear adhesives (OCAs). However, conventional OCAs lead to crease formation and interfacial failure on the screen under repeated folding. Here, a novel, flexible bilayer OCA with Janus feature in crosslinking density (v) is proposed, balancing high interfacial adhesion and high internal cohesion. The bilayer design enables a gradient v along the thickness direction, which is directly quantified by advanced unilateral NMR (UNMR). The optimized Janus OCA achieves comparable optical performance but superior mechanical properties compared to conventional OCA, effectively mitigating screen creases during dynamic folding test. Such enhanced performance originates from its asymmetric architecture, in which the low-v layer accommodates deformation on the compressive side, while the high-v layer maintains integrity on the tensile side. This design strategy offers a promising pathway toward next-generation flexible and foldable display technologies.

Calcium fluoride (CaF2) is a key functional material for next-generation lithography; however, limited understanding of its microscopic nucleation and growth mechanisms has led to continued reliance on empirical parameters during synthesis. To address this, we employ molecular dynamics (MD) simulations using a neuroevolution potential trained on ab initio MD data to investigate CaF2 crystallization, and analyze key kinetic and thermodynamic properties including species-resolved self-diffusion coefficients ( DCa and DF) and thermal conductivity. Based on these results, we show that temperature oscillation facilitates CaF2 crystallization and identify an effective temperature window of 800-1400 K, within which moderate atomic mobility and stable heat transport jointly promote abnormal grain growth. We further observe interface-induced growth and clarify anisotropic growth across the (100), (110), and (111) planes, with the (110) plane exhibiting faster growth at 1100 K, and propose an approximate method for evaluating growth rates. This work provides mechanistic insights into CaF2 crystallization and offers guidance for optimizing the synthesis of high-quality CaF2.

Owing to its low-cost maintenance and easy adaptability, low-field NMR (LF-NMR), which is developed based on permanent magnets, has attracted increasing attention in recent decades. It shows great potential for fundamental research as well as quality assessment and control in the industry. In this review, we first present the key hardware features of LF-NMR, including magnets, radiofrequency (RF) coils, spectrometers, and hyphenated units. Subsequently, commonly used pulse sequences and basic theoretical treatments are summarized. The applications of LF-NMR in polymer science are discussed in detail, including chain dynamics, polymer networks, and hierarchical morphologies. The multiphase and multicomponent features of polymers make polymer science a suitable area for developing new LF-NMR techniques. A personal perspective on the further development of LF-NMR is also presented.

In this study, the drying process of poly(vinyl alcohol)(PVA) aqueous solution under the coupled effects of wind field, temperature field, and concentration field was investigated using COMSOL software. A simplified multi-physics coupling model for flow, heat, and mass transfer was developed by integrating Fick's law, the free volume theory, and the Flory-Huggins theory. The mass transfer coefficient, initially calculated using boundary layer theory, was subsequently refined based on experimental data obtained from drying and weighing PVA aqueous solutions at varying air speeds (1.5-2.5 m/s). The findings reveal that the pressure at the interface between the film and the air undergoes minimal changes. This is attributed to the high Peclet number (Pe)calculated for hot air drying, indicating that the diffusion process of the PVA aqueous solution during the rapid drying phase is predominantly governed by convection. Furthermore, the modified mass transfer coefficient reaches its peak at an intermediate wind speed of 2.0 m/s, suggesting a nonmonotonic relationship between the mass transfer coefficient and wind speed. Through a combination of experimental methods and numerical [GRAPHICS] simulations, this study elucidates the mechanism by which wind speed influences the drying rate of polymer solutions. The insights gained provide a valuable foundation for optimizing the operational conditions for the drying and film formation of PVA aqueous solutions in engineering applications.

This study investigates the long-term failure mechanism of an iodine-doped poly(vinyl alcohol) (PVA) polarizer film under accelerated aging conditions of 85 degrees C and 85% relative humidity. The polarizer consists of seven layers: iodine-doped PVA sandwiched by triacetate cellulose (TAC) films as protective layers, poly(ethylene terephthalate) (PET) films as release layers, and pressure-sensitive adhesive (PSA) layers between TAC and PET. Optical microscopy and scanning electron microscope (SEM) reveal that failure initiates with air bubble growth at the film edges, propagating inward and causing PSA delamination. Optical measurements show a marked decrease in polarizing efficiency and color shifts linked to iodine species degradation, with Raman and UV-vis spectroscopy confirming a 2.8% reduction in I5 - species. Structural changes were characterized by two-dimensional (2D) wide-angle X-ray scattering (WAXS), showing a decrease in PVA crystallinity from 25% to 18% and a slight increase in the lamellar orientation factor. Low-field NMR indicates no significant change in chain mobility, while high-resolution solid-state NMR detects PSA hydrolysis through the appearance of methylene carbon. These findings emphasize the critical role of PSA degradation in polarizer failure and provide insight into the interplay among crystallinity, iodine stability, and adhesive integrity under harsh environmental aging.

The deformation mechanism of glycerol plasticized poly(vinyl alcohol) (PVA) with different hydrolyses (88

Understanding the deformation mechanism of the amorphous phase in semicrystalline polymers has been challenging due to the lack of a long-range ordered structure and chain dynamics heterogeneity. In this study, the amorphous chains' reorientation and dynamics change under uniaxial elongation of low-density polyethylene (LDPE) was investigated, utilizing H-1 time-domain nuclear magnetic resonance (H-1 TD-NMR) in combination with wide-angle X-ray scattering (WAXS). Depending on the chain dynamics difference, the amorphous phase can be decomposed into semirigid and mobile amorphous fractions, where the third rigid amorphous fraction appears under deformation. Such a rigid amorphous fraction, which is generated during necking (1.8 < lambda < 4.7), shows much slower dynamics (similar T-2 as the crystalline phase) as compared with the other two amorphous fractions. Moreover, strain-dependent H-1 TD-NMR and WAXS results clarify different structural transformation pathways for the rigid amorphous fraction. During the stress-softening (region II, 1.8 < lambda < 3.7), accompanied by decreasing crystallinity from 0.35 to 0.20 by WAXS, the rigid amorphous fraction is constantly formed (from 0 to 0.20), mainly at the compensation of the crystalline phase by lamellar fragmentation; and in the stress plateau (region III, 3.7 < lambda < 4.7) with constant crystallinity at 0.20, elongated and tightly packed semirigid amorphous chains are the main source of the rigid amorphous fraction (from 0.20 to 0.25). The rigid amorphous fraction generated by the former pathway exhibits more constrained chain mobility. The strain-dependent evolution of the rigid amorphous fraction is further supported by in situ H-1 TD-NMR results in addition to the ex situ process. Current work demonstrates H-1 TD-NMR as a promising technique for elucidating the amorphous chain reorientation and dynamics change upon deformation.

Understanding the molecular origin of stress softening in silica-reinforced polydimethylsiloxane remains a challenge. Here, we apply in situ elongational nuclear magnetic resonance (NMR) spectroscopy to selectively probe the polymer matrix under deformation. This allows us to address two key questions: how silica nanoparticles influence microscopic polymer deformation and the critical contribution of the interfacial layer to stress softening. By exploiting differences in chain dynamics, we selectively detect protons in the polymer network strands between topological constraints and the interfacial layer. Combining in situ NMR with numerical modeling based on the nonaffine tube model helps us decouple contributions of network strand deformation and orientation to the magnetic resonance signal. We show that nanoparticles significantly influence network deformation via strand reorientation at small strains. However, the strain-independent interfacial fraction indicates a minor role for the interfacial layer in stress softening during quasistatic loading-reloading tests. Stress softening in silica-filled polydimethylsiloxane poses challenges in understanding polymer matrix deformation. Here, the in situ elongational NMR spectroscopy and numerical modeling show that nanoparticle fillers significantly affect polymer network deformation, while the interfacial layer has minimal impact.

The molecular-level chain network evolution in sulfur cured natural rubber upon deformation is elucidated by the combination of in situ tensile instrument and time-domain (TD) nuclear magnetic resonance. Under active deformation, both the microscopic chain dynamics as reflected by proton T2 and the macroscopic stress-strain curves are obtained. In addition to the strain-induced restricted chain dynamics upon deformation, an abnormal strain-induced accelerated semi-restricted chain dynamics is observed when the stretching ratio is within 2.1 < λmac = (l0 + Δl)/l0 < 3.5. This is consistent with an almost invariant tensile modulus E of 0.42 MPa within this range. Such turning points (λmac = 2.1 and 3.5) are almost independent of measurement temperature (35-85 °C), as shown by the variable-temperature tensile NMR measurements. A strain-induced heterogeneous network deformation model is thus proposed: the network chains in the low cross-linking region start to relax at the intermediate stretching ratio (2.1 < λmac < 3.5 in the current study), while those in the highly cross-linking region continuously act as the force-bearing unit.

Polarizers are a key component of new display panels (i.e. liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs)), consisting of a polarizing film, support film, compensation film, and optical clear adhesives between the layers. The key functional layer is the iodine-doped polyvinyl alcohol (PVA) film. The processing of polarizers involves the synthesis of an optical-grade PVA resin, followed by the preparation of highly oriented iodine-doped PVA films, which includes the film casting, iodine doping, boric acid crosslinking, and post-stretching steps. Revealing the multi-scale structure and changes in chain dynamics during processing is crucial for establishing the structure-process-property relationship of PVA-based polarizers. The current work reviews the recent research progress in this direction, primarily including the following: (1) primary chemical structure of PVA, (2) solution casting of PVA films, (3) hierarchical structure and dynamics heterogeneity of plasticized PVA films, (4) formation mechanism of PVA-iodine complexes, and (5) crosslinking mechanism of boric acid in PVA.

A numerical simulation method, namely, SDNMR-WEBFIT, is reported for simulating proton spin diffusion NMR based on the Levenberg-Marquardt algorithm and a pseudo-2D diffusion model. This method is used for the precise quantification of dynamics heterogeneity of the interphase within multiphase polymer systems. The numerical simulation method provides measurements of spin-lattice relaxation time (T1), proton density (ρH), lamellar thickness (d), and spin diffusion coefficient (D) for each component. The pseudo-2D diffusion model is employed to simulate the proton spin diffusion build-up/decay curves, simultaneously calculating the lateral fraction of island-like structures (x-ratio). Such approach was successfully applied to various polymer systems, such as semi-crystalline polymer (Poly(ε-caprolactone), PCL), block copolymers (Styrene-butadiene-styrene triblock copolymer, SBS), and plasticized semi-polymers (Polvinyl alcohol, PVA).

The general development of Rheo-NMR during the last four decades as well as selective hyphenated apparatuses is presented. Based on different magnet types, the current review is divided into two categories, namely low-field and high-field NMR, while the time-domain NMR is normally applied in the former case and the frequency-domain NMR is adopted in the latter one. Depending on different rheometer cells, it can be further divided into tensile and shear mode Rheo-NMR. The combination of various rheometer cells and NMR facility guarantees our acquisition of molecular level structure and dynamics information under flow conditions, which is crucial for our understanding of the molecular origin of complex fluids. A personal perspective is also presented at last to highlight possible development in this direction.

Mechanical behavior of the cross-linked polymer system is modulated by various cross-linkings, i.e., chemical and physical cross-linking. The poly(vinyl alcohol) (PVA)-boric acid (BA) cross-linking system is known to exhibit cross-linking-induced stiffening behavior. In this study, the step-cycle mechanical tests reveal that the addition of BA not only enhances the chain modulus but also amplifies the mechanical resilience within a BA concentration range of 0.1-2.0 wt %. This structural origin is attributed to the effect of BA on the interpenetrated network consisting of (i) a crystallite-based network and (ii) a chain network in the amorphous domain. For the crystallite-based network, the lamella thickness of crystallites remains nearly constant at middle BA addition levels (0.1 wt % < c(BA) < 2.0 wt %), whereas the selective destruction of (100) and (200) planes over (101)/(10 (1) over bar) planes is observed, as evidenced by synchrotron radiation X-ray scattering (wide- and small-angle X-ray scattering). This preserves the skeleton of the crystallite-based network. Various time-domain nuclear magnetic resonance techniques, i.e., H-1 T-2 relaxometry and H-1 double-quantum NMR, quantitatively present the linear relationship between cross-linking density and modulus in the amorphous domain. These findings contribute to the understanding of the deformation mechanism of the PVA-BA cross-linking system during loading-unloading tests.

The crystallization behavior of silica-filled polydimethylsiloxane (PDMS) was investigated in detail by 1H solid-state nuclear magnetic resonance (1H SS-NMR) in combination with synchrotron radiation wide-angle X-ray scattering (WAXS), and temperature-modulated differential scanning calorimetry (TMDSC) techniques. For neat PDMS, no apparent difference is observed for the crystallinity characterized by 1H SS-NMR and WAXS at low-temperature regions. However, upon filler addition, a 15%-35% lower difference in crystallinity is observed measured by 1H SS-NMR compared to WAXS. The origin of such mismatch was explored through multi-component structural, dynamics, and chain-order analysis of PDMS samples with different filler fractions. The 1D integrated WAXS results of PDMS with different filler fractions at different temperatures show that the packing structure as well as crystal size basically remain unchanged, but as the filler fraction increases from 0 phr to 60 phr, the rigid component's dynamics order parameter Sr obtained by 1H SS-NMR decreases from 0.70 to 0.55. The filler fraction-dependent crystallinity calculated based on Sr was compared with experimental values, revealing a behavior of decreasing order in the crystalline region. Combining with the results of accelerated chain dynamics in crystalline region as reflected by T2 values, the molecular origin is attributed to the formation of CONDIS crystals, whose conformational order is lost but the position and orientation orders are kept. Such hypothesis is further supported by the TMDSC results, where, as the filler fraction increases from 0 phr to 60 phr, the melting range widens from 8.77 K to 14.56 K, representing a growth of 166%. In addition to previous reports related to the condition for forming CONDIS mesophase, i.e., temperature, pressure, and stretching, the nano-sized filler could also introduce the local conformational disorder for chain packing.

Multiscale structural evolution of conjugated polymer (CP) solutions from disorder to aggregation via environmental perturbations is a universal phenomenon in condensed matter physics. Here, we take poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as a model material and use Ultraviolet–Visible (UV–Vis) spectroscopy to study the hierarchical structure evolution during prolonged aging at relatively low temperature. Using in‐situ UV–Vis spectroscopy and the Franck‐Condon (FC) method, the dynamics of multiscale structural transitions in P3HT were elucidated. Hierarchical structural details can be extracted from the UV–Vis spectra, including the overall percentage of aggregates, conjugation length, degree of H‐/J‐type molecular packing, and site energetic disorder. Through covariance analysis of conformational disorder to aggregation transitions of conjugated polymers obtained under multiple conditions, we find that the trends of the above four key parameters are not consistent, which informs the unique evolution of the degree of ordering at different length scales within the aggregates. This work facilitates the scrutiny of the hierarchical structural transition from multi‐length scale perspective.