Gas transport in surface grafted polypropylene films with poly(acrylic acid) chains

Surface Modification of Polypropylene Membrane Using Biopolymers with Potential Applications for Metal Ion Removal

This work aims to present the modification of polypropylene (PP) membranes using three different biopolymers, chitosan (CHI), potato starch (PS), and cellulose (CEL), in order to obtain three new materials. The modified membranes may be degraded easier than polypropylene ones and could be used as selective membranes for metal ions removal, among other applications. For this purpose, the UV energy induced graft copolymerization reaction among polypropylene membrane, acrylic acid, benzophenone (as photoinitiator), and the biopolymer (CHI, PS, or CEL) was conducted. The results of FT-IR-ATR, XRD, TGA, DSC, SEM, BET, and AFM analyses and mechanical properties clearly indicate the successful modification of the membrane surface. The change of surface wettability was monitored by contact angle. The grafting reaction depends on natural polymer, reaction time, and concentration. In order to prove the potential application of the modified membranes, a preliminary study of sorption of metal ion was carried out. For this purpose, the PP-CHI membrane was chosen because of the high hydrophilicity, proportionate to -OH and NH2; these groups could act as ligands of metal ions, provoking the interaction between PP-CHI and M+ (PP-CHI-M+) and therefore the metal ion removal from water.

Fourier transform infrared studies on the dissociation behavior of metal-chelating polyelectrolyte brushes

The dissociation behavior of surface-grafted polyelectrolytes is of interest for the development of stimuli-responsive materials. Metal-chelating polyelectrolyte brushes containing acrylic acid (PAA) or hydroxamic acid (PHA) chelating moieties were grafted from the surface of polypropylene (PP). Fourier transform infrared (FTIR) spectroscopy was used to determine the effective bulk pKa of the polyelectrolyte brushes (pKa(bulk)) and to characterize metal-chelating behavior. The pKa(bulk) values of PP-g-PAA and PP-g-PHA were 6.45 and 9.65, respectively. Both PP-g-PAA and PP-g-PHA exhibited bridging bidentate and chelating bidentate iron chelation complexes. This is the first reported determination of the pK(a,bulk) of surface-grafted poly(hydroxamic) acid.

Immobilization of caffeic acid on a polypropylene film: synthesis and antioxidant properties

The immobilization of caffeic acid (CA) on a polypropylene (PP) film was successfully performed through the covalent binding of the caffeoyl chloride on a modified polymeric surface of PP films grafted with hydroxyethyl methacrylate as monomer (PP-g-HEMA). The different reaction steps were monitored by FT-IR spectroscopy. The synthesized films were characterized by Folin-Ciocalteu method by measuring the available phenolic groups as caffeic acid equivalents linked to the surface. The antioxidant efficiency of the modified polymers was evaluated by typical spectrophometric methods, such as the bleaching of radicals DPPH(•) and ABTS(•+), and the inhibition of the enzymatically induced coupled oxidation of linoleic acid and betacarotene. The available phenolic groups on the modified film presented a good correlation with the antiradical activity toward DPPH(•). Moreover, the polymer synthesized in this work showed a good protective activity against ascorbic acid oxidation in real samples of orange juice.