Solubilization of lignin in copolymer micelles in aqueous solution

Abstract

The solubilization of lignin in self-aggregating triblock amphiphilic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) in aqueous solution has been studied utilizing liquid-state proton nuclear magnetic resonance spectroscopy (1 H NMR) and diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY NMR). Our hypothesis for copolymer micelle incorporation of lignaceous species includes a "hydrophilic-aromatic interaction model", in which lignin derivatives with amphiphilic characteristics, known to be abundant in the effluent from pulp mill and pretreatment of various lignocellulosic materials, have an affinity for these micelles, and tend to form relatively organized structures within them. Here we show how the chemical/structural features of lignin units and small molecule lignin models determine their solubilization behavior in the micelles. It was found that a buildup of concentration series of lignin and lignin-based model compounds guaiacol, eugenol, phenol, guaiacylglycerol-beta-guaiacyl ether, ferulic acid in Pluronic ® F68-deuterium oxide solution results in significant upfield chemical shifts of PEO-(CH 2-CH 2) and PPO-(CH 3) proton resonances, and at a critical guest concentration (CGC), dramatic upfield shifts due to gross structural transitions in the micelles. We present evidence that copolymer micelle-lignin interactions depend on both chemical functional group characteristics of solute (i.e., polarity, Hbonding ability) and π-π interactions between aromatic/conjugated groups. Our results demonstrate how the loci of incorporated solute in the block copolymer micelles are affected by these features.

Electrospun lignin-PVP nanofibers and their ability for structuring oil

“…Physicochemical properties of LSL/PVP solutions and effect on the morphology of electrospun nanostructures Surface tension, electrical conductivity and main shear and extensional rheological parameters of LSL/PVP solutions in DMF are collected in Table 2 as a function of total polymer concentration and LSL:PVP ratio. As can be seen, surface tension data remains roughly constant at around 35-37 mN/cm, in most cases lowering the surface tension of DMF (36.96 ± 0.02 mN/cm), according to a certain well-known amphiphilic character of both lignin [55][56][57] and PVP [58]. However, surface tension slightly increases with total polymer concentration and LSL:PVP ratio, as similarly reported for PVP-surfactants mixtures [59], lignin-surfactant mixtures [60] and lignin derivatives [61] above a critical aggregation concentration.…”

First Room Temperature Chiral Anionic Liquid Forming Micelles and Reverse Micelles

“…2D-ROESY data and the ring current effect associated with aromatic groups have been used to arrive at the architecture of micelles and biomembranes. − The ring current associated with phenyl ring of MBA can shield or deshield neighboring protons through space which would cause respective upfield or downfield chemical shift values (δ), revealing the conformation of the surfactants in micelles . The ring current effect is governed by eq . where “ i ” is a ring-current factor, B is the constant of proportionality, θ is the angle (between aromatic electron cloud and proton), and r is the distance (from aromatic ring to proton) The chemical shifts for methine (CH) and acetyl (OAc) protons of tartaric acid and for α-CH 2 and β-CH 2 protons of alkyl chain (Figures and SI.1) of T12M progressively shift upfield with increase in concentration from 5 to 200 mM indicating that these protons are in close proximity to MBA and present in the shielded region.…”

Improvement of Polypropylene Adhesion by Kraft Lignin Incorporation

“…ALK (pH 8.2) has a predominant hydrophilic behavior and partial water solubility, which might justify this behavior. Otherwise, despite its higher OH content, AC (pH 3.5) presents amphiphilic behavior and poor water solubility, due to its combination of aromatic and aliphatic bridges and a variety of oxygenated moieties 27 .…”