Fluorescence properties of dansyl groups covalently bonded to the surface of oxidatively functionalized low-density polyethylene film

Abstract

The point of zero charge (PZC), the surface acidity constants pK1 and pK2, and the concentration of the charged surface groups A10H2+ and AlO" throughout the pH range 3.0-11.0 were determined by potentiometric acid-base titrations for a series of 7-aluminas used in industry as carriers which contain various amounts of sodium and silicon. Moreover, these surface parameters were determined for a modified carrier prepared by deposition of sodium on the 7-Al203 surface. It was found that the PZC, pKu pK2, and the concentration of the positively charged groups (A10H2+) at very low pH increased with sodium content whereas the concentration of the negative groups (AlO") decreased. The sodium effect was very pronounced when it was selectively concentrated on the surface of 7-Al203 particles. The consequences of the above phenomena are discussed in relation to the use of 7-aluminas for preparation of supported catalysts by deposition of active ion via adsorption of positive or negative species.

Estimation of the Surface Energy and Acid-Base Properties of Wood by Means of Wetting Method

“…In the sessile drop method, the penetration depth assumed to be < 1 nm and in the Wilhelmy plate wetting method, the absorption of liquids is assumed to be > 1 nm. This assumption of penetration depth is supported by a series of reports by Holmes-Farley and Whitesides (1986 and . According to the presented results, it is evident that the penetration enhances the basic and reduces the acid properties of wood.…”

Acid-base interactions in wetting

“…First, the titratable groups seem to comprise a single population: they fit a single titration curve with a single value of pK1/2 [23]. Second, a significant, non-zero PAC signal is observed for values of pH where no signal is expected, based on our previous observations [5]. The origin of this background is not presently understood.…”

“…1). For specificity, we will illustrate points using 'polyethylene carboxylic acid' (PE-Co2H), a material about which we have accumulated a substantial body of background information [2][3][4][5][6][7][8][9][10]. PE-CO,H is prepared by oxidation of lowdensity polyethylene film with chromic acid solution under specified conditions.…”

“…When the temperature of PE-Co2H is raised to a value close to the melting point of the polymer ( T= 100°C), functional groups migrate from the region of the interphase that determines the contact angle into deeper regions of the polymer [7,15]. In these regions, the functional groups may still be observed by penetrating forms of spectroscopy (IR [4,6], fluorescence [5], and to some extent XPS [4]), but they no longer influence wetting by water.…”

Effect of surface oxidation treatments on DC charge injection into polyethylene from aqueous electrolytes

“…The characteristic absorbance of hydroxyl group was not detected with attenuated total reflectance infrared spectroscopy (ATR-IR) [21], however Blais et al reported hydroxyl groups introduced with chromic acid etching [21]. It was also found in a different study that chromic acid treatment increased carbonyl concentration from 0.4% of surface carbons to 11% of carbon [23].…”