Surface Characterization of Oxyfluorinated Isotactic Polypropylene Films:  Scanning Force Microscopy with Chemically Modified Probes and Contact Angle Measurements

Abstract

The surface of isotactic polypropylene (iPP) films modified by oxyfluorination was studied by a combination of complementary techniques to elucidate the effect of the modification on the chemical composition, surface energy, and morphology. The elemental composition was measured by X-ray photoelectron spectroscopy (XPS), and the surface free energy was characterized by contact angle measurements with different liquids. Following the approach by Good and co-workers, the acid−base characteristics of the modified polymer surfaces were estimated. Subsequently, the modified iPP films were investigated by scanning force microscopy (SFM). In tapping mode SFM, the sample topography was imaged and the surface roughness was quantitatively determined. Gold-covered SFM probes modified with carboxylic acid and methyl terminated self-assembled monolayers of thiols were used to determine the pull-off force distributions in ethanol. The interaction of the treated polymer film surfaces with chemically functionalized SFM tips was shown to correlate with the surface tensions obtained by contact angle measurements. In particular, pull-off forces measured with carboxylic acid functionalized tips in ethanol depended approximately linearly on the basic part of the surface free energy of the polymer film surface.

Toward High Resolution Mapping of Functional Group Distributions at Surface-Treated Polymers by AFM Using Modified Tips

“…Previously we have reported that the average pull-off forces measured on flat, surface-treated polyolefins using for example −COOH-terminated tips in ethanol can be correlated with the surface energy of the polymer films. 10a-e These results correspond to average values obtained over the entire surface of the specimens. Because of the limited dynamic range of the pull-off forces measured in ethanol and the width of the force distributions, laterally resolved pull-off force measurements were inconclusive in the aforementioned studies.…”

Toward High Resolution Mapping of Functional Group Distributions at Surface-Treated Polymers by AFM Using Modified Tips

“…Previously we have reported that the average pull-off forces measured on flat, surface-treated polyolefins using for example −COOH-terminated tips in ethanol can be correlated with the surface energy of the polymer films. 10a-e These results correspond to average values obtained over the entire surface of the specimens. Because of the limited dynamic range of the pull-off forces measured in ethanol and the width of the force distributions, laterally resolved pull-off force measurements were inconclusive in the aforementioned studies.…”

Mapping Aging Effects on Polymer Surfaces: Specific Detection of Additives by Chemical Force Microscopy

“…The root-mean-square roughness measured on the polypropylene plates on 10 × 10 μm images was around 3−5 nm. Recently, Schönherr et al have investigated polymer film surfaces with a mean roughness of 8 to 20 nm and their results suggest that such a roughness does not significantly disrupt the pull-off forces measured by CFM. , Thus we do not expect influence of the sample topology on the adhesion force measurements in the present case.

1 Average adhesion forces (nN) measured with −CH 3 - and −OH-terminated tips on blank polypropylene (PP) and stabilized polypropylene (PP1 and PP2).

…”

Polymer-fluorinated silica composite hollow fiber membranes for the recovery of biogas dissolved in anaerobic effluent

“…This may be attributed to both insufficient hydrophobicity and a broad pore size distribution allowing water to seep into some large pores [31,32]. Note that our membranes exhibited higher water contact angles (123-125) than PVDF (92-100) [33,34] and PP membranes (100-118) [35][36][37] ,…”

Toward High Resolution Mapping of Functional Group Distributions at Surface-Treated Polymers by AFM Using Modified Tips

“…Previously we have reported that the average pull-off forces measured on flat, surface-treated polyolefins using for example −COOH-terminated tips in ethanol can be correlated with the surface energy of the polymer films. 10a-e These results correspond to average values obtained over the entire surface of the specimens. Because of the limited dynamic range of the pull-off forces measured in ethanol and the width of the force distributions, laterally resolved pull-off force measurements were inconclusive in the aforementioned studies.…”

Mapping Aging Effects on Polymer Surfaces: Specific Detection of Additives by Chemical Force Microscopy

“…The root-mean-square roughness measured on the polypropylene plates on 10 × 10 μm images was around 3−5 nm. Recently, Schönherr et al have investigated polymer film surfaces with a mean roughness of 8 to 20 nm and their results suggest that such a roughness does not significantly disrupt the pull-off forces measured by CFM. , Thus we do not expect influence of the sample topology on the adhesion force measurements in the present case.

1 Average adhesion forces (nN) measured with −CH 3 - and −OH-terminated tips on blank polypropylene (PP) and stabilized polypropylene (PP1 and PP2).

…”

Polymer-fluorinated silica composite hollow fiber membranes for the recovery of biogas dissolved in anaerobic effluent

“…This may be attributed to both insufficient hydrophobicity and a broad pore size distribution allowing water to seep into some large pores [31,32]. Note that our membranes exhibited higher water contact angles (123-125) than PVDF (92-100) [33,34] and PP membranes (100-118) [35][36][37] ,…”

Toward High Resolution Mapping of Functional Group Distributions at Surface-Treated Polymers by AFM Using Modified Tips

“…Previously we have reported that the average pull-off forces measured on flat, surface-treated polyolefins using for example −COOH-terminated tips in ethanol can be correlated with the surface energy of the polymer films. 10a-e These results correspond to average values obtained over the entire surface of the specimens. Because of the limited dynamic range of the pull-off forces measured in ethanol and the width of the force distributions, laterally resolved pull-off force measurements were inconclusive in the aforementioned studies.…”

Mapping Aging Effects on Polymer Surfaces: Specific Detection of Additives by Chemical Force Microscopy

“…The root-mean-square roughness measured on the polypropylene plates on 10 × 10 μm images was around 3−5 nm. Recently, Schönherr et al have investigated polymer film surfaces with a mean roughness of 8 to 20 nm and their results suggest that such a roughness does not significantly disrupt the pull-off forces measured by CFM. , Thus we do not expect influence of the sample topology on the adhesion force measurements in the present case.

1 Average adhesion forces (nN) measured with −CH 3 - and −OH-terminated tips on blank polypropylene (PP) and stabilized polypropylene (PP1 and PP2).

…”

Polymer-fluorinated silica composite hollow fiber membranes for the recovery of biogas dissolved in anaerobic effluent

“…This may be attributed to both insufficient hydrophobicity and a broad pore size distribution allowing water to seep into some large pores [31,32]. Note that our membranes exhibited higher water contact angles (123-125) than PVDF (92-100) [33,34] and PP membranes (100-118) [35][36][37] ,…”