Cellulosic polymer colloids, polymers and polyelectrolytes

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An important contribution to the emerging bioeconomy is the conversion of biomass to useful products in environmentally friendly processes. About 5 years ago, we made a fascinating discovery. We discovered a novel type of nanocellulose (now called hairy nanocellulose, HNC), very different from the conventional cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF). The novel particle consists of a rod-shaped colloidal core and contains many polymeric or polyelectrolyte chains (the “hairs”). HNC particles belong to the class of polymer colloids. They can be produced by an aqueous process from delignified wood fibers (cellulose fibers) with a yield of about 50%. The other 50% consists of water-soluble cellulose derivatives. The research proposed here will address properties and applications of HNC and properties of the water soluble cellulosics and derivatives thereof. We propose to organize the research in 7 topics. In topic 1, “Characterization of HNC”, we will attempt imaging the hairs with three different techniques: (i) labeling the hairs with gold nanoparticles (AuNP), followed by TEM; (ii) imaging the hairs by AFM using chemically modified tips; (iii) by Stochastic Optical Reconstruction Microscopy (STORM). Topic 2 deals with HNC produced from CNC, and the liquid crystalline properties of right and left handed CNC. Topic 3 addresses the aggregation of trimmed HNC. We have shown that one can crosslink carboxylated crew cut HNC with a diamine (via bioconjugation or click chemistry), which results in end-to-end aggregation, since almost all the charges of HNC are located in the short hairs at both ends. It should also be possible to make long slender nanofibrils by mixing positively and negatively charged crew cut HNC, resulting in long fibrils in which the two types of HNC alternate. Topics 4 and 4 deal with antiscaling properties of HNC and antifouling membranes of polymer/HNC composites, to be measured by chronoamperometry. Finally topics 6 and 7 deal with the properties of cellulosic water-soluble polymers and polyelectrolyes respectively. Specifically, we propose to study cellulose derivatives with dialdehyde groups on the C2-C3 carbons of cellulose, with a degree of oxidation (DO) of about 1. We refer to these polymers as dialdehyde modified cellulose (DAMC), to distinguish them from dialdehyde cellulose (DAC), for which DO = 2. We propose to study the properties of DAMC and DAC, such as molecular weight, polydispersity in molecular weight and density of aldehyde groups, persistence length, Flory-Huggins - parameter (or polymer-solvent interaction parameter, etc.), as well as its long-time stability. Some of the techniques used will be GPC (gel permeation chromatography, static light scattering and osmotic pressure measurements. We will attach photoswitchable molecules to DAMC and image the polymeric chains with STORM.