Mechanics of thermoresponsive polymer brush based soft materials: theory and experiments

Abstract eng:
Stimuli responsive soft nanomaterials are of growing scientific and technological interest. Polymer brushes are densely packed, surface tethered polymer chains. A brush behaves like an elastic surface layer with residual surface stress which produces deformation of the substrate. In a thermoresponsive brush, temperature reversibly changes the residual surface stress as well as the elastic modulus of the surface layer due to coil-globule phase transition in the brush. A mechanics model incorporating Young-Laplace effect is developed for high grafting density brush (graft density > 0.2) which produces large surface stress. The model is then applied to experiments on a poly(Nisopropylacrylamide)-co-Poly(N,N-Dimethylacrylamide) (PNIPAm-co-PDMA) polymer brush grafted on a plasticized poly(vinyl chloride) (pPVC) film using surface-initiated atom transfer radical polymerization (SI-ATRP). The model estimates effective surface stress due to the brush to be ∼ −10 N/m which can be halved by applying temperature.

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