Amphiphilic cationic polymethacrylates: synthesis, characterization and interactions with cellulose

Abstract

Amphiphilic cationic co-polymers, containing poly([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide) (polyMETAI) or poly[2-(dimethylamino) ethyl methacrylate] (PDM) segment, were synthesized through two different main routes. Block co-polymers containing poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) were synthesized with oxyanionic polymerization, whereas radical polymerization was used to obtain statistical co-polymers with stearyl methacrylate (SMA) and fluorodecyl methacrylate (FMA). The melt and thermal transition properties of the polymers were studied with dynamic scanning calorimetry and rheometry. PDM decreased crystallinity of the polymer and increased the melt strength of the polymers. The solution properties were studied with a surface tension measurement, with dynamic light scattering equipment, and with rheometry. Polymers containing highly hydrophobic segments, such as stearyl, formed charge stabilized aggregates in a water solution, whereas polymers with a less hydrophobic block, such as PEO, formed a micellar structure. The suitability of the prepared polymers, as well as a set of commercial polymers, on cellulose fiber systems was studied. The polymers containing a cationic segment formed permanent adhesion on the anionic surface, and strong bonding with the cellulose fibers. The mechanical strength of the cellulose fiber sheets was increased more with polymers containing cationic segments than the ones with corresponding nonionic segments. Strain hardening behaviour was introduced into the fiber-polymer sheets that did not contain cationic segments and the bonding between the fiber and the polymer was weak enough. A mechanically strong cellulose fiber network could also be prepared with a hydrophobic cationic polymer, but the strength was decreased with the high density of the hydrophobic side group in the polymer. The polymers containing a highly hydrophobic segment formed a thin layer coating on the paper surface and a small amount of polymer was enough for a complete thin layer coverage of the surface. Additionally, the higher amount of the polymer did not change the chemical or physical properties of the surface, which supported the assumption of a nanolayer formation.