Showing papers by "Michel Delamar published in 1999"

X-ray photoelectron spectroscopy characterization of submicrometer-sized polypyrrole-polystyrene composites

Abstract: The surface compositions of a series of five polystyrene−polypyrrole (PS−PPy) composites and three reference materials (the original poly(ethylene glycol) (PEG) stabilizer, the uncoated PEG-stabili

Tailored modification of quartz surfaces by covalent immobilization of small molecules (γ-aminopropyltriethoxysilane), monodisperse macromolecules (dendrimers), and poly(styrene/acrolein/divinylbenzene) microspheres with narrow diameter distribution

Abstract: Quartz plates were modified by consecutive immobilization of γ-aminopropyltriethoxysilane (APTS), phosphorus containing dendrimers with aldehyde groups (generation 5 – G5), Starburst PAMAM dendrimers generation 4 (G4-PAMAM), and poly(styrene/acrolein/divinylbenzene) microspheres [P(SAD)]. In this way surfaces with heterogeneity on molecular, macromolecular, and microscopic levels, and which were equipped with functional amino or aldehyde groups were obtained. Surface layers were characterized by X-ray photoelectron spectroscopy (XPS) and by contact-angle measurements. Analysis of XPS spectra revealed that the thickness of the layer of G5 on the SiO2-APTS substrate was 3.7 nm, i.e., the thickness was typical for macromolecular dimensions. The average thickness of the layer of PAMAM dendrimers on SiO2-APTS-G5 was found to be 0.35 and 0.29 nm, depending on whether calculations were based on attenuation of the intensity of the Si2p or the P2p signal respectively. This thickness was unreasonably low for a monolayer of PAMAM dendrimers and indicated that the surface of the SiO2-APTS-G5 substrate was incompletely covered with these macromolecules. The XPS method was also used for the determination of the degree of coverage of the surface of a SiO2-APTS-G5-PAMAM plate with P(SAD) microspheres. The degree of coverage was found to be 0.60 and approaches the maximum theoretically possible value (0.62) for microspheres attached chaotically and irreversibly to the surface in an arrangement one microsphere thick. Subsequent coverage of the SiO2-APTS-G5-PAMAM-P(SAD) substrate with PAMAM dendrimers resulted in the formation of a PAMAM adlayer 3.2 nm thick, close to the molecular dimensions of these dendrimers. Contact-angle measurements revealed considerable differences in the hydrophobicity of the surfaces of the quartz plates, depending on their modification. Hydrophobicity increased in the order SiO2 < SiO2-APTS-G5-PAMAM < SiO2-APTS ≤ SiO2-APTS-G5 < SiO2-APTS-G5-PAMAM-P(SAD).

Inorganic-organic systems with tailored properties controlled on molecular, macromolecular and microscopic level

Abstract: Methods suitable for modification of quartz and glass (plates and beads) on molecular, macromolecular and microscopic levels are described in this paper. The modifications led to composite materials with the core containing quartz (fused silica) or glass and outer shells composed of layers of γ-aminopropyltriethoxysilane (small molecules), dendrimers with aldehyde groups (G5) and/or Starburst PAMAM dendrimers with amino groups (macromolecules), and with one particle thick assemblies of poly(styrene–divinylbenzene–acrolein) microspheres with aldehyde groups at their surface (microscopic objects). Monitoring by AFM quartz plates with immobilized dendrimers revealed that their surfaces are relatively smooth with roughness parameter R g close to 2 nm and with diameters and maximal height of objects covering surface in form of bumps close to 4 nm, i.e. to diameters of single macromolecules of dendrimers. XPS studies of surfaces of modified quartz plates and glass beads unequivocally confirmed attachment of γ-aminopropyltriethoxysilane, dendrimers, and microspheres. Quantitative analysis revealed that dendrimer layers are 3.7 and 3.2 nm thick, for G5 and PAMAM dendrimers, respectively, indicating that these macromolecules form monolayer structures. XPS and SEM studies of quartz surface covered with layers of γ-aminopropyltriethoxysilane, G5 and PAMAM denrimers and subsequently with poly(styrene–divinylbenzene–acrolein) microspheres indicated that saturation of the surface coverage with these particles is achieved at the degree of coverage close to 0.60, i.e. to the maximal value attainable in the case of rapid covalent immobilization of spherical particles. Surfaces of quartz plates and glass beads, with outer layers containing G5 dendrimers and/or poly(styrene–divinylbenzene–acrolein) microspheres and thus, equipped with aldehyde groups, were used for covalent immobilization of human serum albumin (HSA). AFM studies revealed that macromolecules of HSA from dilute protein solution are attached onto surface of G5 dendrimers in such a way that they form clusters composed of not less than 50 protein macromolecules each. X-ray photoelectron spectroscopy used for monitoring of surfaces with immobilized poly(styrene–divinylbenzene–acrolein) microspheres which were subsequently exposed to contact with solution of HSA revealed that macromolecules of HSA are readily attached onto immobilized microspheres.

XPS and SERS evidence for iron nitride species responsible for the strong adhesion of polypyrrole to iron or steel treated with nitric acid

Abstract: The reason for the strong adhesion of polypyrrole (PPy) films to iron and mild steel surfaces pretreated with dilute nitric acid (HNO3) has been investigated by XPS and SERS techniques. It is shown that iron nitride (Fe≡N) species, arising from the reaction of HNO3 with the metal, are strongly grafted to the surface. These species could be responsible for the adhesion of PPy films to iron surfaces.