Bottlebrush polymers are macromolecules with densely grafted polymeric side chains on a linear backbone. The highly branched architecture leads to unusual physics in polymer blends, such as limited miscibility with long linear polymers and a strong entropic attraction to surfaces and interfaces. The strong tendency for bottlebrush accumulation at interfaces can be leveraged for the design of functional coatings. In this study, we examine the phase behavior of bottlebrush poly (styrene-r-deuterated styrene) (PS-r-dPS) in thin film blends with linear PS. The bottlebrush side chain length (Nsc) and linear PS length (Nm) were systematically varied to examine their impacts on film structure. Thin films were prepared by flow coating from chlorobenzene, and the through-film structure was measured after thermal annealing with time-of-flight secondary ion mass spectrometry (TOF-SIMS). The as-cast films exhibited a strong surface excess and weak substrate excess for nearly all bottlebrush architectures, demonstrating that surface properties can be tuned during film casting. However, after thermal annealing, the equilibrated film structures strongly depended on bottlebrush architecture: At fixed Nsc, the segregation of the bottlebrush polymers at both the surface and substrate interfaces increases with increasing Nm. At fixed Nm, the enrichment of the bottlebrush polymers at the free surface increases with decreasing Nsc. These studies provide guidelines for the design of surface-active bottlebrush additives, and show how segregation is controlled through architecture and processing

Bottlebrush polymers as surface active additives in thin polymer films

255th National Meeting (2018)

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