Interface boundary interactions in polymer heterostructures with carbon nanotubes

This work presents a comprehensive spectroscopic study of a van der Waals heterostructure composed of a Poly(N-vinylcaprolactam-co-polyethyleneglycoldiacrylate) (PVCL-PEGDA) hydrogel at 8 % monomer concentration and 2 % PEGDA crosslinking, multiwalled carbon nanotubes (MWCNTs), and commercial medical-grade silicone. Using both Raman and FTIR spectroscopy, the individual components were first characterized, revealing distinct vibrational fingerprints that served as reliable references for the subsequent analysis of the assembled structure. Raman depth profiling enabled spatial resolution of the layers, showing that the hydrogel dominated the surface spectrum, CNT-related features appeared at intermediate depths, and the silicone substrate contributed at greater depths. The characteristic Raman bands, D (~1298 cm⁻¹) and G (~1585 cm⁻¹), confirmed the graphitic order and defect distribution within the CNTs, while the absence of the 2D (G′) band was attributed to the use of a 785 nm laser, which does not fulfill the optimal resonance conditions for its excitation. FTIR analysis provided complementary insights, demonstrating that the hydrogels retained their characteristic functional groups — C=O (amide), C–N, and CH stretching vibrations — under both dry and hydrated conditions, with noticeable water-induced broadening in the latter. The combined spectroscopic data confirmed the coexistence of vibrational signals from all materials, allowing the use of custom Python data processing to identify a well-defined interface region at 10–26 µm depth, where all three materials overlap, suggesting chemical interactions and partial doping at the boundary. Figures produced with the open-source visualization tool VisIt 3.4.1 enhanced the 3D visual analysis and validation of this non-destructive spectroscopic approach for complex soft-matter characterization, underscoring the potential of Raman spectroscopy for early-stage skin cancer detection.

• Autor principal: Loor Cabrera, Samantha Valeria (author)
• Format: bachelorThesis
• Publicat: 2025
• Matèries: Heteroestructuras; Hidrogeles; Espectroscopía Raman; Heterostructure; Hydrogel; Raman spectroscopy
• Accés en línia: https://repositorio.yachaytech.edu.ec/handle/123456789/1017