The morphology of layer-by-layer films of polymer/polyelectrolyte studied by atomic force microscopy

Abstract

Layer-by-layer (LBL) films of a semiconducting polymer (POMA) alternated with a polyelectrolyte (PVS), adsorbed onto silicon oxide, mica, ITO/glass, Au/Cr/glass, hydrophilic and hydrophobic glass were studied by atomic force microscopy (AFM). The samples were characterized LBL with the AFM operating in the contact, friction and tapping modes, which allowed us to determine their morphological surface properties such as roughness, mean grain size, grain boundaries and power spectrum density. Their film thickness was measured by AFM using the tip as a scraping tool. Surface roughness increases with the number of bilayers until a constant value is reached. This is in agreement with the observed increase in the adsorbed amount (per layer) of POMA as the number of bilayers is increased, which also saturates after several bilayers. It is shown that the 3D growth behaviour indicates a similar microscopic mechanism for all systems under study, pointing to a stochastic growth process of the Eden model type, but strongly influenced by initial roughness and water affinity of the virgin substrates. The crystalline or amorphous nature of the substrates does not seem to influence the growth process.

Functionalised nanoscale coatings using layer-by-layer assembly for imparting antibacterial properties to polylactide-co-glycolide surfaces

“…Dark zones probably correspond to residual alcohol groups from the aminolysis treatment (Figure 6a). With increasing the layer number, the roughness of coated surface is increased, as also reported in literature [36][37][38] In particular, Guo et al [36] obtained a similar rather smooth coated surfaces after deposition of 10 layers, when PAH-PAA (poly(acrylic acid)) complexes were the outmost layer. In contrast, they observed a rough surface morphology when PSS was the outmost layer.…”

Study of the growth process of in situ polyaniline deposited films

“…Higher concentrations of aniline in the solution lead to higher absorbance, i.e., larger film thickness, in addition to a faster increase. The film thickness was measured with the AFM using the tip as a scraping tool [29]. As Table 1 shows, the thickness of in situ PAni films (average of three values) increased with the concentration of aniline in the reaction media, being of the order of 200 nm for the highest aniline concentra- tion used.…”

Nanocompósitos eletroativos de poli-o-metoxianilina e polissacarídeos naturais

“…Também para a POMA, a forma esmeraldina é a mais comumente utilizada. A POMA vem sendo bastante estudada [14][15][16][17] na forma obtida via síntese química (pó) ou via eletroquímica (filme) [18][19][20] com a finalidade das mais diversas aplicações, tais como em conjunto com DNA para fins biomédicos 21 ou na fabricação de filmes automontados [22][23][24][25] . Sousa e co-autores 22 estudaram os processos de adsorção na preparação de filmes automontados de POMA com poli(vinil sulfonato de sódio) (PVS) empregando um método estatístico para tratar as propriedades morfológicas dos filmes.…”