The strength of interfacial attractions between polymer chains and nanoparticles is known to control the mobility of chains and viscoelastic properties in polymer nanocomposites. We chose the interfacial layers around magnetic nanoparticles to consist of two different miscible polymers and measured the energy absorption rates as particles dissipate energy while they rotate under a high-frequency alternating magnetic field. Local viscosities were calculated from the measured rotational relaxation times using the classical absorption model. The changes in local viscosities were attributed to the rigidity of adsorbed polymers and chemical heterogeneities of their interfacial layers. The highest viscosity was measured with the flexible, shorter adsorbed poly(methyl methacrylate) chains. The weak interphases between poly(methyl acrylate) and highly rigid polymers such as poly(2-vinyl pyridine), and poly(bisphenol A carbonate) allowed particles to rotate easily in a diffusive mode, yielding the lowest viscosity that matched to the viscosity prediction of an unentangled matrix polymer. Chemical and dynamic heterogeneity of interfacial layers around nanoparticles highly depend on the rigidity of chains. Measuring the local viscosity of interfacial polymer layers is essential for interfacial layer-controlled mechanisms of stress transfer, reinforcement, and thermal conductivity in polymer nanocomposites.

Micromolding of UV-curable materials is a patterning method to fabricate microstructured surfaces that is an additive manufacturing process fully compatible with roll-to-roll systems. The development of micromolding for mass production remains a challenge because of the multifaceted demands of UV curable materials and the risk of demolding-related defects, particularly when patterning high-aspect-ratio features. In this research, a robust micromolding approach is demonstrated that integrates thiol-ene polymerization and UV LED curing. The moduli of cured thiol-ene coatings were tuned over 2 orders of magnitude by simply adjusting the acrylate concentration of a coating formulation, the curing completed in all cases within 10 s of LED exposure. Densely packed 50-μm-wide gratings were faithfully replicated in coatings ranging from soft materials to stiff highly cross-linked networks. Further, surface energy was modified with a fluorinated polymer, achieving a surface energy reduction of more than a half at a loading of 1 wt %, and enabling tall (100 μm) defect-free patterns to be attained. The demolding strengths of microstructured coatings were compared using quantitative peel testing, showing its decrease with decreasing surface energy, coating modulus, and grating height. This micromolding process, combining tunability in thermomechanical and surface properties, makes thiol-ene microstructured coatings attractive candidates for roll-to-roll manufacture. As a demonstration of the utility of the process, superhydrophobic surfaces are prepared using the system modified by the fluorinated polymer.

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