Temperature Responsive Cellulose-graft-Copolymers via Cellulose Functionalization in an Ionic Liquid and RAFT Polymerization

Abstract

Well-defined cellulose-graft-polyacrylamide copolymers were synthesized in a grafting-from approach by reversible addition-fragmentation chain transfer polymerization (RAFT). A chlorine moiety (degree of substitution DS(Cl) ≈ 1.0) was introduced into the cellulose using 1-butyl-3-methylimidazolium chloride (BMIMCl) as solvent before being substituted by a trithiocarbonate moiety resulting in cellulose macro-chain transfer agents (cellulose-CTA) with DS(RAFT) of 0.26 and 0.41. Poly(N,N-diethylacrylamide) (PDEAAm) and poly(N-isopropylacrylamide) (PNIPAM) were subsequently grafted from these cellulose-CTAs and the polymerization kinetics, the molecular weight characteristics and the product composition were studied by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and size exclusion chromatography of the polyacrylamides after cleavage from the cellulose chains. The number-average molecular weights, Mn, of the cleaved polymers ranged from 1100 to 1600 g mol(-1) for PDEAAm (dispersity Đ = 1.4-1.8) and from 1200 to 2600 g mol (-1) for PNIPAM (Đ = 1.7-2.1). The LCST behavior of the cellulose-graft-copolymers was studied via the determination of cloud point temperatures, evidencing that the thermoresponsive properties of the hybrid materials could be finely tuned between 18 and 26 °C for PDEAAm and between 22 and 26 °C for PNIPAM side chains.

Thermoresponsive and biocompatible poly(vinyl alcohol)‐graft‐poly(N,N‐diethylacrylamide) copolymer: Microwave‐assisted synthesis, characterization, and swelling behavior

“…35 The LCST values of graft copolymers were determined at a fixed wavelength using a UV-vis spectrophotometer, and the variation of transmittance with temperature is exhibited in Figure 12. The thermoresponsivity of PVA-g-PDEAAm copolymer in distilled water was studied via transmittance measurements.…”

Rapid pretreatment of Miscanthus using the low-cost ionic liquid triethylammonium hydrogen sulfate at elevated temperatures

“…7 This has opened up new processing options for biomass, including one-pot biofuel production, 2,17 the Ionocell-F spinning of cellulose fibres for fabrics, 38 production of thermally responsive cellulose composites, 39 and production of cellulosic films. 40 Cellulose dissolving ILs have been reported to be amongst the highest-yielding and most feedstock-independent lignocellulose pretreatment technologies, 41 however, the high cost of the required ILs as well as their low thermal stability and their requirement for dry conditions is turning out to be generally prohibitive for biofuel and bulk chemical applications.…”

Effect of the Molecular Structure of Acylating Agents on the Regioselectivity of Cellulosic Hydroxyl Groups in Ionic Liquid

“…The stretching vibration band of the C-Br group in the 2-bromoisobutyryl moiety appeared at 664 cm -1 in the spectrum of the cellulose-BiB (c). An additional signal at 763 cm -1 indicated the presence of C-Cl in the cellulose-BiB, which was explained by the partial replacement of the bromide moieties by the chlorine anions from the solvent in a nucleophilic substitution reaction (Hufendiek et al 2014). In the cellulose-CPAC spectrum (d), the presence of a peak at 3070 cm -1 for the benzene ring C-H stretching ) and the stretching vibration absorption peak of C-Cl at 730 cm -1 provided clear evidence of the introduction of 2-chloro-2-phenylacetyl moiety in the cellulose-CPAC.…”