Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is currently used for a wide range of applications, often involving the synthesis of block copolymers. Here, an in-depth characterization of PDMAEMA prepared by atom transfer radical polymerization (ATRP) is reported, with a focus on end group analysis. The structure of the polymer was elucidated by one- and two-dimensional NMR spectroscopy, which assessed the presence of deactivated chains and allowed for a quantification of their fraction. Detailed characterization by MALDI-TOF MS further provided insightful information about the chain end fidelity. On this basis, termination by disproportionation was found to be the main mechanism for the loss of active chain ends. The detailed characterization allowed for an estimation of the preserved chain end functionality (CEF) of PDMAEMA. Additionally, a chain extension experiment was conducted, using PDMAEMA as a macroinitiator for the polymerization of methyl methacrylate (MMA) by ATRP. The results of chain extension supported the estimation of CEF based on the data provided by NMR and MS. Although assessing the degree of polymerization of a block copolymer proves challenging when the amount of the initial block able to act as a macroinitiator is not known a priori, an accurate estimation of the DP and M-n of the obtained block copolymer was possible by total nitrogen analysis. The tools here provided for the characterization of PDMAEMA and its block copolymer architectures allow the obtainment of essential information about the extent of control over the homo- and copolymerization. Therefore, they are of high importance when well-defined structures are aimed for.

Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods. Graphic abstract: [Figure not available: see fulltext.]

The potential for large-scale applications of cellulose nanofibrils (CNFs) is limited by the high water content of the starting material, which leads to high transportation costs and undesirable environmental impact. However, drying of CNFs results in loss of their nanoscopic dimensions leading to deterioration of their unique inherent mechanical properties. Herein, thorough redispersion studies of both fundamental and applied nature have been conducted in order to evaluate the effect of charge, redispersing agent, and drying method. Freeze-dried CNF dispersions were successfully redispersed by either increasing the charge density or adding redispersing agents. The greatest effect on redispersibility was achieved with fractionated LignoBoost lignin as redispersing agent, and this is attributed to steric repulsion during water removal and reduced CNF adhesion. Furthermore, the results unexpectedly show that redispersion is easier when the CNFs are dried in the form of nanopapers. By using this approach, excellent redispersibility was achieved even without a redispersing agent. Nanopapers formed from the redispersed CNFs was found to have essentially the same mechanical properties as those made from never-dried CNFs. Hence, this work suggests solutions for making CNFs viable for large-scale application while maintaining their nanoscale dimensions and their ability to create nanopapers with excellent mechanical properties.

This study highlights the beneficial role of cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) as components in functional membranes. The approaches of the use of CNF and CNC as membrane materials Ibr water purification have been studied extensively during the past decades. This is due to their inherent abundance, renewability, sustainability and unique properties such as high aspect ratio, high surface area, high crystallinity, and high mechanical properties. The performance of CNF- and CNC-based membranes especially in treating actual water samples were also highlighted in this review to give a better overview of the behavior of these nanocellulose as membrane materials. The challenges of using CNFs and CNCs and the needfor improvements for the future development of membrane materials are also discussed.

An all-water-based procedure for "controlled" polymer grafting from cellulose nanofibrils is reported. Polymers and copolymers of poly(ethylene glycol) methyl ether methacrylate (POEGMA) and poly(methyl methacrylate) (PMMA) were synthesized by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) from the cellulose nanofibril (CNF) surface in water. A macroinitiator was electrostatically immobilized to the CNF surface, and its amphiphilic nature enabled polymerizations of both hydrophobic and hydrophilic monomers in water. The electrostatic interactions between the macroinitiator and the CNF surface were studied by quartz crystal microbalance with dissipation energy (QCM-D) and showed the formation of a rigid adsorbed layer, which did not desorb upon washing, corroborating the anticipated electrostatic interactions. Polymerizations were conducted from dispersed modified CNFs as well as from preformed modified CNF aerogels soaked in water. The polymerizations yielded matrix-free composite materials with a CNF content of approximately 1-2 and 3-6 wt % for dispersion-initiated and aerogel-initiated CNFs, respectively.

A molecularly engineered water-borne reactive compatibilizer is designed for tuning of the interface in melt-processed thermoplastic poly(caprolactone) (PCL)-cellulose nanocomposites. The mechanical properties of the nanocomposites are studied by tensile testing and dynamic mechanical analysis. The reactive compatibilizer is a statistical copolymer of 2-(dimethylamino)ethyl methacrylate and 2-hydroxy methacrylate, which is subsequently esterified and quaternized. Quaternized ammonium groups in the reactive compatibilizer electrostatically match the negative surface charge of cellulose nanofibrils (CNFs). This results in core-shell CNFs with a thin uniform coating of the compatibilizer. This promotes the dispersion of CNFs in the PCL matrix, as concluded from high-resolution scanning electron microscopy and atomic force microscopy. Moreover, the compatibilizer "shell" has methacrylate functionalities, which allow for radical reactions during processing and links covalently with PCL. Compared to the bio-nanocomposite reference, the reactive compatibilizer (<4 wt %) increased Young's modulus by about 80% and work to fracture 10 times. Doubling the amount of peroxide caused further improved mechanical properties, in support of effects from higher cross-link density at the interface. Further studies of interfacial design in specific nanocellulose-based composite materials are warranted since the detrimental effects from CNFs agglomeration may have been underestimated.