For sustainable polymer nanocomposites, wood-based polymeric materials are ideally suited to serve as both matrix and functional entity. The major components, being at the same time the two most abundant biomaterials, are cellulose and lignin. Due to its aromatic structure, lignin is well-suited to serve as aromatic building block in macromolecular materials for polymeric materials, e.g. thermosets [1]. Here, the aromatic structure determines the physico-chemical properties. The arrangement of the phenyl rings can be tailored by the choice of cross-linkers and wood source and is directly visualized by X-ray scattering. Making use of the UV-absorption of lignin due to the large number of phenolic groups, the combination with nanofibrillar cellulose as structure-directing matrix allows for developing a sustainable UV protective thin film nanocomposite with tailorable transmission [2]. In terms of sustainable processing, spray deposition allows for facile scalability and the use of low-viscous aqueous solutions [3]. Using semiconducting and water-soluble polymers, functional polymer inks incorporating cellulose allow for installing thin film organic electronics [3,4]. To retain its functionality, long term-stability under varying environmental conditions is crucial. Hence, neutron scattering allows for correlating nanostructural changes during humidity cycling with their functionality, e.g. as polymeric electrodes [5]. Especially the use of in situ methods using X-rays and neutrons will be highlighted.

Neutron scattering is a powerful technique for investigating the structure and dynamics of materials across multiple length and time scales. Its unique interaction with matter provides essential insights into polymers and soft materials, making it highly complementary to other experimental techniques. Methods such as quasielastic neutron scattering (QENS), neutron spin-echo (NSE), and small-angle neutron scattering (SANS) allow researchers to study molecular motion, self-diffusion, and viscoelastic behavior [1].
For structural characterization, neutron techniques complement X-ray scattering and microscopy methods like atomic force microscopy (AFM), revealing material organization from atomic arrangements to larger morphologies, particularly in nanostructured and self-assembled systems [2]. In the study of dynamics, neutron scattering works alongside calorimetry, dielectric spectroscopy, and rheology, providing complementary insights into relaxation processes and viscoelastic behavior. Together, these approaches link molecular-scale interactions with macroscopic properties for a more comprehensive understanding of materials [3,4].
A major advantage of neutron techniques is their ability to selectively probe different components through isotopic substitution, enabling precise studies of polymer dynamics in various environments. This has driven advancements in energy applications, such as ion transport in polymer electrolytes, as well as in medicine and biomaterial research. Neutron scattering has also played a crucial role in understanding protein-polymer interactions and membrane dynamics in biological systems [5].
Here, we illustrate these capabilities through various experimental cases, highlighting different materials, techniques, and applications. By examining real-world examples across multiple fields, we aim to demonstrate how neutron scattering, in combination with other methods, enhances our understanding and drives the advancement of functional materials.

The structural characterization of polymer films and membranes under controlled humidity (RH) and temperature (T) conditions has received considerable attention, particularly in energy-related studies. Small-angle neutron scattering (SANS) is an analysis method specifically suitable for such systems, as neutrons offer the unique ability to vary the scattering contrast between different components of a complex multi-component hydrocarbon sample by selective deuteration. Proton and anion exchange polymer membranes with improved conductivity under different T and RH conditions or durability after exposure to application conditions have been extensively studied using SANS. However, most studies have focused on membranes equilibrated in H2O, D2O or mixtures to vary the neutron contrast to obtain a much clearer view of the structure and morphology of the crystalline and amorphous polymer regions and the water domains. Until recently, fewer studies have addressed the in-beam variation of RH, T or neutron contrast on the sample due to the lack of a dedicated sample environment that would allow complete control of the in-situ variation of these parameters over a long period of time during a SANS measurement with multiple samples in the beam. With the increasing search for non-hazardous and environmentally friendly alternatives to perflourinated Nafion, the demand for such a versatile in-situ sample treatment for SANS studies, which can be complemented by in-beam conductivity monitoring, has increased. I report here how such detailed in situ sample characterization and treatment can now be achieved on conducting polymer membranes during extended Q-range SANS, with examples on Nafion and functionalized syndiotactic polystyrene.

Lignin is a renewable biopolymer being investigated worldwide as an environmentally benign antioxidant for use in food preservation, pharmaceuticals, and materials science. For its successful implementation into process streams, a quick, easy, and reliable method is needed for the antioxidant capacity determination.
A method using ¹H NMR spectra of benchtop as well as high-field NMR systems in combination with partial least squares (PLS) regression is presented to determine lignin’s antioxidant capacity using various metrics derived from antioxidant assays (DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric ion reducing antioxidant potential) and FC (Folin-Ciocalteu). The PLS regression was calibrated and validated by performing these wet-chemical photometric assays on a set of 53 organosolv lignin samples. External validation errors between 4 % and 11 % were achieved on all NMR devices (43, 60, 500 and 600 MHz), except for the DPPH models which lead to significantly higher errors. Surprisingly, no significant differences in the performance of the benchtop and high-field devices were found. The larger DPPH model errors can be explained due to the DPPH assay already showing larger variances in the reference measurement.¹
Furthermore, the calibration transfer between the spectrometers, also between benchtop and high-field NMR was explored. Despite the substantial resolution difference between high- and low-field NMR, the results confirm the feasibility of calibration transfer between benchtop and high-field NMR spectra. This expands the possibilities for benchtop NMR in chemometric analysis and in transferring calibrations from costly high-field to affordable benchtop instruments.