Topographical and chemical characterization of polymer surfaces modified by physical and chemical processes

Abstract

Nanoscale changes to the surface of polymeric materials enables changes in materials' adhesion, wettability, printability, chemical functionality, and bioactivity, while maintaining desirable bulk properties. Polymer surface modification is therefore used in applications such as antimicrobial or non-fouling materials, biosensors, and active packaging. The range of available modification and analytical techniques used across laboratories prevents accurate comparison of techniques in terms of their effects on surface chemistry and topography. It was therefore our goal to evaluate the effects of four surface modification techniques (chromic acid, piranha solution, ultraviolet irradiation, and oxygen plasma) on polyethylene films. Changes in surface chemistry and topography were quantified using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), contact angle measurement, and direct measurement of available surface carboxylic acids. Roughness increased in the order: piranha (57.7 nm); oxygen plasma (76.3 nm); UV irradiation (76.4 nm); chromic acid (120 nm). Hydrophobicity decreased in the order: piranha (77.20), chromic acid (73.50), oxygen plasma (61.70), UV irradiation (58.70). Functionalization (by IR absorbance intensity between 1680-1780 cm À1 ) increased in the order: oxygen plasma (0.06), piranha (0.09), chromic acid (0.34), UV irradiation (0.50). By analyzing these methods using consistent analytical techniques, side-by-side comparisons have been accurately made.

Active Packaging Coatings

“…Physical methods include flame, corona discharge, UV radiation, and plasma [5,15,17]. Wet methods involve the use of corrosive liquids to which the polymer substrates are directly exposed, like piranha solution (dissolved hydrogen peroxide and sulfuric acid), combined sodium hydroxide and sulfuric acid, chromic acid, potassium permanganate, and nitric acid [18][19][20][21][22]. The main effect of these surface activation methods is the formation of reactive oxygenated species on the polymer surface like carbonyl, hydroxyl and carboxylic acid groups [21,22].…”

“…Wet methods involve the use of corrosive liquids to which the polymer substrates are directly exposed, like piranha solution (dissolved hydrogen peroxide and sulfuric acid), combined sodium hydroxide and sulfuric acid, chromic acid, potassium permanganate, and nitric acid [18][19][20][21][22]. The main effect of these surface activation methods is the formation of reactive oxygenated species on the polymer surface like carbonyl, hydroxyl and carboxylic acid groups [21,22]. Some methods of industrial relevance to activate the surface of polymeric packaging materials are flame, corona, and atmospheric or vacuum plasma [23], which remove contaminants from the surface of polymer films, increase their surface energy and wettability (in order to apply coatings of different types, like inks for printing or metallic coatings), and increase the level of oxygen on their surface.…”

Manipulating interactions between functional colloidal particles and polyethylene surfaces using interfacial engineering

“…Cleaned films were dried using pure nitrogen gas and stored in clean glass petri dishes prior to use. Polyethylene films were modified by UV-ozone treatment as previously described by Barish and Goddard [16] using a Model 42 UVO Cleaner (Irvine, CA, USA), which emits 28 mW/cm 2 light at 254 nm at a distance of 2 cm. After a 5-min warm up time, the samples were treated for a period of 15 min.…”

Development of active, nanoparticle, antimicrobial technologies for muscle-based packaging applications

“…In these chemical treatments, however, a longer period of treatment can affect/deteriorate their bulk properties as compared to shorter treatment periods (< 1 hr) which produce only surface effects (Barish & Goddard, 2011). Finally, though these treatments show good surface activation potential, they are not favoured in industrial processes owing to their negative environmental effects.…”

“…Piranha solution: A mixture of H 2 O 2 (30 %), H 2 SO 4 and water in a suitable proportion (Barish & Goddard, 2011).…”