Cellulose dissolution in aqueous NaOH–ZnO: cellulose reactivity and the role of ZnO

Cellulose utilization at its full potential often requires its dissolution which is challenging. Aqueous NaOH is the solvent of choice due to the rapid, non-toxic, low cost and environmentally friendly dissolution process. However, there are several limitations, such as the required low temperature and cellulose´s moderately low degree of polymerization and concentration. Moreover, there is a tendency for gelation of semidilute solutions with time and temperature. The addition of ZnO aids cellulose dissolution and hinders self-aggregation in the NaOH solution; however, the exact role of ZnO has remained as an open question. In this work, we studied cellulose dissolution in the aqueous NaOH–ZnO system as well as the reactivity of the dissolved cellulose by oxidation with 4-AcNH-TEMPO+ (TEMPO+). Based on Raman spectroscopic studies and the TEMPO+-reactivities, we propose a new structure for cellulose dissolved in aqueous NaOH–ZnO. Graphic abstract

Synthesis of Narrowly Dispersed Block Copolymer of Butyl Acrylate and Acrylic Acid in a Solution Acquiring Colloidal Properties during Cooling

The homophase polymerization of acrylic acid is carried out in a solution of poly(butyl acrylate) trithiocarbonate (PBATC) in a mixed solvent 2-propanol–water. The phase diagram of the three-component PBATC-2-propanol–water system at 22°C is obtained. The homophase region of the compositions of semidilute solutions is determined. The homophase polymerization of AA in the three-component system at 70°C, in which the mixed solvent with respect to PBATC is similar in thermodynamic quality to the θ-solvent at 22°, yields solutions of the narrowly dispersed block copolymer butyl acrylate–acrylic acid. The content of the block copolymer in solutions is 15–23%, the MW of the copolymer is 10–20 × 103, and the polydispersity coefficient is 1.12–1.16. As evidenced by dynamic light scattering, under normal conditions, the solutions contain nanoparticles with a diameter of up to 50 nm with a narrow size distribution.

Influence of polymer flexibility on nanoparticle dynamics in semidilute solutions

The effects of polymer stiffness on nanoparticle dynamics in solution are probed using multi-particle collision dynamics simulations and mode-coupling theory.