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The colloidal layer formation on porous materials is a crucial step for printing and applying functional coatings, which can be used to fabricate anticounterfeiting paper. The deposition of colloidal layers and subsequent thermal treatment allows for modifying the hydrophilicity of the surface of a material. In the present work, wood-based colloidal inks are applied by spray deposition on spray-deposited porous cellulose nanofibrils (CNF) films. The surface modification by thermal annealing of the fabricated colloid-cellulose hybrid thin films is investigated in terms of layering and hydrophobicity. The polymer colloids in the inks are core-shell nanoparticles with different sizes and glass transition temperatures (T-g), thus enabling different and low thermal treatment temperatures. The ratio between the core polymers, poly(sobrerol methacrylate) (PSobMA), and poly(-butyl methacrylate) (PBMA) determines the T-g and hence allows for tailoring of the T-g. The layer formation of the colloidal inks on the porous CNF layer depends on the imbibition properties of the CNF layer which is determined by their morphology. The water adhesion of the CNF layer decreases due to the deposition of the colloids and thermal treatment except for the colloids with a size smaller than the void size of the porous CNF film. In this case, the colloids are imbibed into the CNF layer when T-g of the colloids is reached and the polymer chains transit in a mobile phase. Tailored aggregate and nanoscale-embedded hybrid structures are achieved depending on the colloid properties. The imbibition of these colloids into the porous CNF films is verified with grazing incidence small-angle X-ray scattering. This study shows a route for tuning the nanoscale structure and macroscopic physicochemical properties useful for anticounterfeiting paper., QC 20240604

Self-catalyzed hydrolysis upon storage of the common RAFT chain-transfer agent (CTA) 4-cyano-4-[(thiothiopropyl)sulfanyl] pentanoic acid (CTPPA) is confirmed, where the nitrile group is transformed into an amide by catalysis from the adjacent carboxylic acid moiety. The amide-CTA (APP) is found to poorly control molecular weight evolution during polymerization of two methacrylates, methyl methacrylate (MMA) and N,N-(dimethylamino)ethyl methacrylate (DMAEMA), likely due to poor reinitiation speed in the pre-equilibrium. However, when attached to a macromolecule, the impact of this amide moiety becomes insignificant and chain extension proceeds as expected with CTPPA. In light of CTPPA and similarly hydrolyzable CTAs being extensively employed for aqueous polymerizations of methacrylates, these findings highlight the importance of CTA purity when performing RAFT polymerizations., QC 20240604

QC 20230426

Correlating nanostructure and optical properties of thin hybrid films is the crucial ingredient for designing sustainable applications ranging from structural colors in anticounterfeiting to sensors. Here, the tailoring of the refractive index of hybrid cellulose nanofibril/water-dispersed colloidal ink thin films is presented. The authors apply scalable, layer-by-layer slot-die coating for preparing the cellulose nanofibril and hybrid thin films. Making use of the mobility of the polymer chains in the colloids upon annealing, the influence of the different colloid sizes and their glass transition temperature on the refractive index of the hybrid material is shown. The complex refractive indices of the thin films are characterized by spectroscopic ellipsometry and correlated to the different nanostructures of the thin films. The authors find that post-deposition annealing changes the colloidal nanostructure from particulate to agglomerates. Depending on the size of the colloids, imbibition of the colloids into the cellulose nanofibril template is observed. This scalable approach offers new avenues in structural color functional biomaterial hybrid layers., QC 20230725

Ultrasonication was used as a mean toincorporate glycerolor urea, yielding paper films with a ductility of up to 35%. Fiber-based materials are attractive sustainable alternativestofossil-based plastics, however, the lack of ductility (i.e., brittleness)limits their applicability in complex shapes as are often utilizedfor plastics. In this study, we hypothesize that it is possible toenhance the ductility of a cellulose-rich material by the incorporationof low molecular weight plasticizers (glycerol, urea, citric acid,and tannic acid). However, no significant effects could be observedafter swelling in the presence of plasticizers. To enhance any potentialeffect, it was decided to employ ultrasonication to mechanically disintegratethe fiber and aid the sorption of plasticizer prior to formation ofsheets from the treated fibers. Glycerol or urea in combination withultrasonication resulted in both internal and external fibrillationof the fibers, and it could be observed that the resulting fines createa film at the surface of the fibers in the formed sheets. Tensiletesting shows that this gives rise to a 100% increase in ductilitycompared to sheets from untreated fibers. The use of citric or tannicacid has the opposite effect, reducing ductility to a third of thatof the reference sheet. This is suggested to be due to the formationof covalent cross-links in the treated fibers, which also leads todifferent internal and external fibrillation mechanisms, as observedby scanning electron microscopy. The exceptionally high improvementof the strain-at-break for sheets from the glycerol- and urea-treatedfibers suggests that low molecular weight plasticizers affect theinternal properties of the fiber wall as well as the interactionsbetween the fine material forming in-between the fibers. The findingsfrom the current study suggest that the proposed approach to obtainductile cellulose-rich materials holds promise for the future, butit is also clear that more in-depth research is req, QC 20230630

The combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization with polymerization-induced self-assembly (PISA) is known to yield monodisperse nanolatexes. Interestingly, based on the results of the current study, reproducible bimodal nanolatexes were shown to be the result of chain extension of protonated poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) with methyl methacrylate (MMA) in water when aiming for a longer hydrophobic block, for which we provide the first imaging data to our knowledge. The bimodality was found to be induced by the hydrophilic Z-group of the RAFT agent, which has been reported in the literature to be the cause of bimodal molecular weight distributions in RAFT-mediated PISA in emulsion polymerization. Moreover, the advantages of such reproducible bimodal size distribution nanolatexes in coating applications were investigated briefly, underlining the possibilities of their one-pot synthesis. It was found that when bimodal nanolatexes are adsorbed onto cellulose filter paper, the contact angle against water is higher compared to chemically similar monomodal nanolatexes. Also, the morphological arrangement was found to be dependent on the drying protocol. This study aims to expand our understanding on bimodality and the identification of parameters that could promote it on demand to target high-end applications., QC 20230704

To address the increasing demand for biobased materials, lignin-derived ferulic acid (FA) is a promising candidate. In this study, an FA-derived styrene-like monomer, referred to as 2-methoxy-4-vinylphenol (MVP), was used as the platform to prepare functional monomers for radical polymerizations. Hydrophobic biobased monomers derived from MVP were polymerized via solution and emulsion polymerization resulting in homo- and copolymers with a wide range of thermal properties, thus showcasing their potential in thermoplastic applications. Moreover, divinylbenzene (DVB)-like monomers were prepared from MVP by varying the aliphatic chain length between the MVP units. These biobased monomers were thermally crosslinked with thiol-bearing reagents to produce thermosets with different crosslinking densities in order to demonstrate their thermosetting applications. The results of this study expand the scope of MVP-derived monomers that can be used in free-radical polymerizations toward the preparation of new biobased and functional materials from lignin., QC 20230607

In light of the need to redesign industrially produced materials by utilizing renewable resources, nanoscopic forms of cellulose are regarded as a valuable asset. In this work, the potential of cellulose nanofibrils (CNFs) as an unconventional nanoadditive for a polyester-melamine coil coating formulation is explored. CNFs, hydrophilic nanomaterials with high aspect ratios, were successfully incorporated in the solvent-borne formulation. Coatings were prepared with extremely low loadings of the nanoadditive (0.5 and 0.7 wt%). At these concentrations, the volume fraction of the nanofibrils in the coatings was calculated to be close to their percolation threshold. Two different pathways of CNF surface modification were applied to allow for a good compatibilization in the resin matrix, and the formulations were cured in two different settings. The effective compatibilization of the nano -additive led to a significant variation of the viscoelastic properties in the coatings containing CNFs. The results from dynamic mechanical analysis (DMA) highlighted the effect of CNFs on the crosslinked network at the nanoscale, resulting in an increase in Tg. Additionally, an increase in the stress at break and Young's modulus was determined by tensile testing, while satisfactory elongation at break was preserved. Other relevant effects induced by the presence of CNFs on the properties of the coatings were highlighted, such as a significant matt effect, increased surface roughness and lower scratch resistance. A preliminary evaluation of the water barrier properties by electrochemical impedance spectroscopy (EIS) is also presented, suggesting that the incorporation of a hydrophilic nanoadditive did not lead to a deterioration of the coatings' performance., QC 20230607

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., QC 20230327

Cellulose nanofibril (CNF)-networks are modified by the addition of small amounts (below 10 wt%) of well-defined cationic nanolatexes synthesized through reversible addition–fragmentation chain-transfer-mediated polymerization-induced self-assembly (PISA). Minute amounts of nanolatex inclusions lead to increased tensile and shear moduli, indicating that nanolatexes can act as bridging-points between CNFs. At higher nanolatex content, this stiffening effect is lost, likely due to interactions between nanolatexes leading to plasticization. The influence of nanolatex content and size on interparticle distance is discussed and is used as a tool to understand the effects observed in macroscopic properties. Upon annealing, the stiffening effect is lost due to the softening of the nanolatexes, indicating that the core–shell morphology is a prerequisite for this effect. These systems form a versatile platform to develop fundamental insights into complex condensed colloidal systems, to ultimately aid in the development of new sustainable material concepts., QC 20230228