Antioxidant and dissociation behavior of polypropylene‐graft‐maleic anhydride

Abstract

Understanding the dissociation behavior of functional polymers can help tailor materials for performance in target applications. Polypropylene-graft-maleic anhydride (PP-g-MA) undergoes partial hydrolysis to form polypropylenegraft-succinic acid (PP-g-SA) due to trace atmospheric moisture during extrusion. While there have been reports on the relationship between interfacial and antioxidant properties for functional polymers, PP-g-SA's behavior has yet to be explored despite its widespread occurrence. Here, PP-g-MA was compounded with isotactic polypropylene (PP) in a twin-screw extruder and the influence of maleic anhydride (MA) content on interfacial behavior (dissociation constant and pH dependence of radical scavenging) was determined. Precise pK a bulk values of the PP-g-SA carboxylic acids were calculated using attenuated total reflection-Fourier-transform infrared spectroscopy (ATR-FTIR) titration and found to be $7.00-7.50 depending on MA content. The extinction coefficient ratio between the anhydride and carboxylic acids was reported for the first time, which was used to determine the increasing degree of hydrolysis with increasing alkalinity. pH-dependent radical scavenging capacity followed closely with dissociation results, with activity reaching up to 4.02 ± 0.23 Trolox Eq (nmol/cm 2 ), supporting the proposed radical scavenging mechanisms dependent on deprotonation of the carboxylic acids. This study demonstrates how dissociative properties of functional polymers can predict radical scavenging behavior in different environments.

Reactive Extrusion of Poly(lactic acid)-graft-Curcumin Antioxidant and Intelligent Packaging

“…20 Previous research has demonstrated the significance of pH conditions on radical scavenging kinetics. 66,67 Therefore, it is worth noting that the ABTS assay performed in this work was executed at pH 7.4, which is below the pK a value of curcumin's enolic hydrogen (7.8). 68 Consequently, curcumin was not deprotonated under these assay conditions, suggesting that ABTS radical scavenging by PLA-g-Cur films was limited to the HAT mechanism.…”

Reactive Extrusion of Nonmigratory Active and Intelligent Packaging

“…To facilitate homogenization of polymer pellets and reagent powders, isotactic PP and PP-g-MA were blended as described previously. 38 Briefly, PP was mechanically mixed with 50% w/w PP-g-MA and fed into a Process MA) through an attached volumetric feeder (11 mm volumetric single screw feeder for process 11 [MK2] by Thermo Electron, Germany) at 7% the maximum rate. Isotactic PP without blending was also prepared as a control for all analyses.…”

“…To facilitate homogenization of polymer pellets and reagent powders, isotactic PP and PP-g-MA were blended as described previously. 38 Briefly, PP was mechanically mixed with 50% w/w PP-g-MA and fed into a Process °C at the die. The extruded polymer filament was fed into a Vericut Pelletizer (ThermoFisher Scientific, Waltham, ME) using the L1 setting to form 0.5 mm granules of blended PP and PP-g-MA.…”

“…The carboxylic acids present in PP-g-MA have a lower pK a than that reported for the phenolic hydroxyls in curcumin, which could result in partial quenching of the ammonia. 38,62 In addition to demonstrating the application of this material as intelligent packaging, these results support that curcumin was not degraded during extrusion because possible degradation products such as ferulic acid and 4-vinyl guaiacol are incapable of this color change. 46 ■ CONCLUSION…”

Exploration of Optimal Reaction Conditions for Constructing Hydrophobic Polymers with Low Deformation to Facilitate the Dimensional Stability of Laminated Bamboo Lumber

“…The poplar cell wall was in situ polymerized with HEMA and 3-(methacryloxy) propyltrimethoxysilane (MAPTES) to improve its dimensional stability [ 21 ]. A functional monomer of unsaturated double bonds and polar carboxylic groups, maleic anhydride (MAh) is commonly used in grafting and copolymerization [ 22 , 23 ]. Lignocellulosic materials can attain higher hydrophobicity and dimensional stability by removing hydroxyl groups from wood polymers with organic anhydride.…”