Effect of Varying Chain Length and Content of Poly(dimethylsiloxane) on Dynamic Dewetting Performance of NP-GLIDE Polyurethane Coatings.

Abstract

Polyurethane coatings containingnanopools of a grafted lubricating liquid ingredient for dewetting enablement (NP-GLIDE)are prepared by curing a commercial polyol P0, a hexamethylene diisocyanate trimer, and P1- g-PDMS, which is a graft copolymer consisting of a polyol backbone P1 bearing poly(dimethylsiloxane) (PDMS) side chains. These materials are known as NP-GLIDE because most test liquids have no problem to cleanly glide off them and because segregated nanopools of the grafted lubricating ingredient (PDMS) for dewetting enablement are dispersed throughout the coating matrix. To optimize the dewetting performance of the NP-GLIDE coatings, the molecular weights of the PDMS side chains in the P1- g-PDMS samples were increased from 1.0 kDa (1k) to 5.0 kDa (5k) and 10.0 kDa (10k). A comparative study of the coatings containing three different P1- g-PDMS samples at a constant PDMS mass fraction of either 6.0 or 2.00% (m/m) showed that P1- g-PDMS5k-based coatings exhibited the best dewetting properties. These properties included the lowest sliding angles for test liquids that were incompatible with PDMS and the fastest and most effective contraction of marker ink traces and a paint. Coatings containing 0.50 and 1.00% (m/m) of PDMS5k were also prepared from P1- g-PDMS5k and compared with those containing 2.00 and 6.0% (m/m) of PDMS5k. The coatings were shown to retain their dewetting properties with the PDMS contents as low as 1.00% (m/m). Although the results of this study provided valuable insight into the design of future practical NP-GLIDE coatings, a model has also been proposed for the surface structure of the coatings to justify our observations.