The increasing prevalence of electronic devices and the development of “smart buildings” have intensified the problem of electromagnetic interference (EMI) pollution. Consequently, there is a pressing need for advanced EMI shielding materials. Graphene‐based polymer nanocomposites are exceptionally promising for this role, owing to graphene’s outstanding electrical and structural characteristics. However, the effectiveness of these composites is highly dependent on the quality of the graphene and its dispersion within the polymer matrix. The synthesis method of graphene, therefore, plays a crucial role in determining the final properties of the nanocomposite. In this study, we report the design and characterization of polymer‐based nanocomposite films based on poly(methyl methacrylate) (PMMA) and incorporating different types of graphene, prepared by a solution casting method. Various graphene samples (NG5–NG10) were obtained by molten salt electrolysis performed at different temperatures (330°C–390°C) and voltages (10–15 V), using the nonstationary current regimes. The obtained nanocomposite films were studied with SEM and TEM microscopy, Raman and XRD spectroscopy, and conductivity measurements. PMMA/nanostructured graphene (NG) exhibited structural parameters depending on the used graphene type and synthesis voltage. Also, PMMA/NG nanocomposites demonstrated changes in electrical resistivity response. The incorporation of just 1 wt% of graphene into the PMMA matrix resulted in a dramatic improvement in electrical properties. Specifically, the electrical resistivity was reduced by seven orders of magnitude for neat PMMA versus the PMMA/NG5 nanocomposite. These findings demonstrate that tuning the electrochemical synthesis parameters is a critical strategy for optimizing the properties of graphene and developing effective PMMA‐based nanocomposites for EMI shielding applications.

Both the electrical conductivity and tailored mechanical characteristics—showing flexibility and structural integrity—are key properties of polymer composites. In this work, a novel, simple, and water-based strategy for synthesizing rGO-MWCNT/polymer composites was developed. Namely, carbon nanofillers in a mixture of reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) were incorporated in a waterborne methacrylic polymer matrix at loadings of 0.25, 0.5, and 1.0 wt.% nanofiller, and with rGO-to-MWCNT ratios of 10:1, 1:1, and 1:10 (w/w) at room temperature. Electrically conductive composites were obtained with all tested filler rates showing the highest conductivity (up to 8.2 × 10⁻³ Sm⁻¹) for the MWCNT-rich filler due to the formation of a segregated network of the filler in the matrix. The mechanical properties of the composites—characterized by their Young’s modulus and elongation at break—strongly depended on both the filler incorporation rate and the rGO:MWCNT ratio. For instance, soft and flexible composites were obtained by incorporating 0.25 wt.% of the MWCNT-rich filler, which increased the elongation at break from 154.2% (neat polymer) to 252.4%. Overall, this study emphasizes the sensitive interplay between carbon filler introduction incorporating conductivity and the fillers’ impact on the mechanical properties of a polymer composite, both necessitating careful optimization for applications, e.g., in flexible electronics.

Improving the sustainability of polymer composites is a pressing priority, particularly in reducing reliance on fossil-derived components and minimizing environmental impact during synthesis. Lignin, an abundant and renewable natural polymer, offers significant potential as a bio-based additive due to its aromatic structure and intrinsic functionality. Conventional methods for incorporating lignin into polymer matrices often rely on non-sustainable, solvent-based routes, leading to poor dispersion and aggregate formation due to lignin’s incompatibility with polymers. This study presents a more sustainable approach using waterborne, in-situ semicontinuous miniemulsion polymerization to integrate lignin (0.5–1 wt%) into (meth)acrylic matrices. The resulting composite films, formed via water evaporation, exhibited enhanced UV and visible light absorption, improved mechanical strength, particularly at 1 wt% lignin and increased thermal stability even at low loadings. Despite lignin’s hydrophilicity, the composites demonstrated reduced water permeability. UV degradation studies showed that lignin’s chromophoric groups generate free radicals under UV exposure, triggering controlled photodegradation of both lignin and polymer phases. This controlled breakdown combined with the composite’s enhanced structural integrity highlights lignin’s dual function: reinforcing the material under standard conditions while enabling degradation under specific environmental stimuli.