No abstract

Studies of surface tension, adsorption parameters, and dynamic surface tension were performed on a series of bolaamphiphilic α,ω-(diammonium disulfato)poly(fluorooxetane)s of several perfluoroalkyl chain lengths. Similar measurements were performed on a small-molecule, anionic fluorosurfactant with a −C8F17 perfluoroalkyl group that is known to be an effective flow and leveling aid in aqueous coatings. Molecular area demands for the poly(fluorooxetane)s were found to be relatively small for a polymeric species and may indicate a change in conformation between bulk solution and interface. Other adsorption parameters were found to be similar to those of the small-molecule fluorosurfactant. Diffusion coefficients were found to be slightly smaller for the poly(fluorooxetane)s compared to the small-molecule fluorosurfactant.

An α,ω-dihydroxypoly(fluorooxetane) was prepared from a fluorinated oxetane monomer and characterized by matrix-assisted laser desorption ionization mass spectrometric (MALDI MS) and gel permeation chromatographic (GPC) methods. Estimated molecular weights were compared to those derived from NMR spectroscopic end-group analysis. The results of 2-D NMR spectroscopic analysis agreed well with 1-D NMR end-group analytical results and MALDI MS experiments. Because of the small molecular weight of the product, the results from the mass spectroscopic and NMR methods compared favorably. The overestimated molecular weights obtained from GPC are explained by aggregation of the amphiphilic poly(fluorooxetane) in a relatively poor solvent. The robustness of the methods was verified by fractionation of the polymer and subsequent analysis of the fractions by MALDI MS. In addition, information regarding product architecture and copolymerization with THF, which was used to complex the BF3 catalyst, was obtained using tandem mass spectrometry (MS/MS) methods.

Hybrid organic/inorganic acrylic nanostructured films were prepared by a UV/thermal dual‐curing process. The role of a fluorinated hydroxyl acrylate monomer (AF) as coupling agent was investigated. Increased Tg values and modulus of the dual‐cured films were achieved by increasing the TEOS inorganic precursor. The coupling agent deeply modified the surface properties of the cured films: the formation of hybrid films characterized by high hydrophobicity together with an increase on surface hardness was achieved. TEM analysis clearly evidenced the reducing of the nanosize dimensions of the inorganic silica domains by increasing the coupling agent content in the photocurable formulation.magnified image

Interfacial rheological studies were performed on a series of bolaamphiphilic R,ω-(diammonium disulfato)-poly(fluorooxetane)s of several perfluoroalkyl chain lengths. Similar measurements were performed on a small-molecule, anionic fluorosurfactant with a -C8F17 perfluoroalkyl group that is known to be an effective flow and leveling aid in aqueous coatings. Dilational viscoelasticities were measured for the fluorosurfactants as a function of concentration and oscillation rate. Elasticities were found to increase with increasing perfluoroalkyl chain length. All elasticities exhibited a strain rate dependence indicative of the influence of diffusional relaxation on elasticity values. Phase angles were found to be in the range for diffusional relaxation and decreased with increasing concentration and strain rate. Using interfacial rheological data, characteristic fluid dynamics numbers were calculated for the fluorosurfactants. Among these was the Marangoni number. Calculated Marangoni numbers for the poly(fluorooxetane)s were of the same order of magnitude as that for the small-molecule, long perfluoroalkyl chain surfactant. The poly(fluorooxetane)s all have equilibrium surface tensions greater than that of the small-molecule, long perfluoroalkyl chain surfactant, yet show similar abilities to aid in flow and leveling in aqueous coatings at comparable concentrations. Rheological measurements demonstrate that equilibrium surface tension alone is not enough to explain the fluid dynamics processes occurring during flow and leveling.