Ultrathin Films of Variable Polarity and Crystallinity Obtained from 1,2-Polybutadiene Nanoparticle Dispersions

Abstract

Characterization of ultrathin films of different polymer nanoparticles obtained at room temperature via spin-coating of aqueous dispersions and their morphology are described. Very small nanoparticles of semicrystalline 1,2-polybutadiene (PB), noncrystalline poly(1-butene) (PH), and poly(1-butenal) (PHF) were prepared via catalytic emulsion polymerization and subsequent hydrogenation or hydroformylation. The prefabricated nanoparticles were used as building blocks. The thin films obtained are continuous and transparent (n=1.5; κ=0). The properties of these films, formed from different constituents, are analyzed. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images show that the PB-films are very smooth (rms roughness=10 nm) and polycrystalline. Recrystallization of these PB films reveals that edge-on lamellae are the constituent units. Films with very low roughness values (rms roughness <2 nm) are obtained with PH nanoparticles, due to the soft character of the nanoparticles. The AFM profile of the PHF films reveals that the surface remains structured after drying due to the high degree of the internal cross-linking that occurs in the nanoparticles. Quantification of the films' polarity (I(3)/I(1)=0.89, 1.3, and 2.1 for PHF, PB, and PH, respectively) agrees well with the previous values obtained for the polymer dispersions. Surfactant molecules are desorbed during the film formation; however, these aggregates can be removed by rinsing with water with no undesirable effects observed on the films.