Processing strategies are fundamental to the development of advanced functional polymers, serving as the link between their microstructure and macroscopic performance. Within the framework of the structure–processing–property paradigm, external force fields such as thermal, mechanical, magnetic, electrical, or optical stimuli can be incorporated during the processing of polymers/polymer composites to fine-tune their morphology and achieve targeted functionality. This work investigates two such strategies: (i) magnetic field-assisted alignment, and (ii) uniaxial mechanical deformation, to understand the underlying physical mechanisms that govern structural evolution and performance in two distinct polymer systems.

 

First, the elements of processing science are addressed in the context of roll-to-roll fabrication of anisotropic piezoresistive films via magnetic field assisted alignment of ferromagnetic Ni particles aligned in the z-axis of a flexible polymer matrix. A mechanistic framework was developed to quantify the particle alignment kinetics, polymer crosslinking, changing magnetic field, and temperature evolution which were further correlated to formation of micro-columnar morphology in relation to the line speeds. The resulting anisotropic films were demonstrated as piezoresistive sensors, exhibiting tunable sensitivity over a broad pressure range (up to 1.2 MPa), with fast response times (<100 ms), and excellent mechanical robustness. A 15 × 15 cm large-area unitary sensor with an array of 100 sensing points was fabricated, showing real-time spatial mapping capabilities with minimal signal cross-talk—enabled by the anisotropic microstructure.

 

In the second topic, the effect of different process parameters on the solvent evaporation of solution cast Polyvinyl alcohol (PVA) is addressed. Polymer chains preferentially align in the in-plane due to restricted relaxation and higher plane stresses with increasing molecular weight which is identified by an increase in out-of-plane birefringence. Uniaxial tensile stretching at various temperatures levels indicated that stretching at elevated temperatures below the onset of Tm resulted in higher elongation to break. Real-time birefringence measurements are conducted during stretching and stress-optical and strain-optical behavior is characterized. These studies revealed that optimum stretching of PVA films is achieved at higher temperatures (below partially molten) where the reduction in H-bonding strength facilitates molecular mobility while the structural interconnectivity is still maintained through both entanglements and remaining oriented crystalline domains.