We report the depolymerization of high molecular weight lignin (60 000 Da) over various recyclable solid base catalysts at 250 °C over 1 h.

Poly(acrylic acid) consisting of 25 monomer units (PAA 25 ) was used to stabilize nanoparticle aggregates (NPAs) consisting of either NaGdF 4 or 50/50 mixtures of GdF 3 and CeF 3 . The resulting polymer-stabilized nanoparticle aggregates (NPAs) were developed and tested for their application as contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT). The PAA 25 -stabilized NPAs exhibit low polydispersity and are colloidally stable at concentrations of 40 mg/mL, while their sizes can be be controlled by choosing a specific ratio of Gd 3þ to Ce 3þ . Scanning transmission electron microscopy (STEM) reveals that NaGdF 4 NPAs possess an average diameter of 400 nm. High-resolution STEM and powder X-ray diffraction (XRD) both show that these NPAs consist of a stable aggregate of smaller NPs, whose diameters are 20-22 nm. PAA 25stabilized NPAs consisting of a 50/50 mixture of GdF 3 and CeF 3 possess an average diameter of 70 nm, while the fundamental unit size is estimated to be 10-12 nm in diameter. The PAA 25 -stabilized GdF 3 /CeF 3 NPAs possess mass relaxivities of 40 ( 2 and 30 ( 2 s -1 (mg/mL) -1 at 1.5 T and 3.0 T, respectively. Their effectiveness as contrast agents for CT X-ray imaging at various X-ray energies was also tested and compared to that of equivalent mass concentrations of Gd 3þ -diethylene triamine pentaacetic acid (Gd 3þ -DTPA) and iopromide. Gd-based NPAs exhibit superior CT contrast to equal-mass concentrations of either iopromide or Gd 3þ -DTPA below 30 keV and above 50 keV. Finally, PAA 25 was functionalized by folic acid to explore targeted imaging. Confocal microscopy revealed that, by functionalizing the PAA 25 -stabilized NaGdF 4 :Tb 3þ NPAs with ∼0.8 folates per polymer, binding and endocytosis occurred in SK-BR-3 human breast cancer cells. The utility of the PAA 25 -stabilized GdF 3 /CeF 3 NPAs for MRI is demonstrated in rat perfusion MRI experiments, where T 1 -weighted MRI images of equivalent concentrations of either Gd 3þ -DTPA or the above NPAs are directly compared. The high relaxivities provide an opportunity to conduct perfusion MRI experiments with significantly lower concentrations than those needed for current commercial agents.

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offers a non-contact method of curing, with minimal substrate heating. Early attempts at AMF methods employed ferric oxide nanoparticles that were prone to aggregation and scorching of the resins. [5] This limited the technology to water-based formulations. Magnetocuring advances AMF induction through incorporation of Curie temperature (T c ) controlled modifiers, also known as Curie magnetic nanoparticles (CNP). Our previous magnetocuring work explored the adhesion strength for different substrates, adhesives, CNP loading, and heating properties of CNP. [1] One of the key advances in our magnetocuring methodology is preventing overheating, the main disadvantage of ferric oxide nanoparticles. Resin scorching is prevented by matching the T c of CNP to the resin activation temperature. As T c is approached, CNP's lose their ferromagnetic properties. [6] The resin temperature cannot extend beyond T c , which can be tuned by adjusting the CNP's chemical composition. However, heating rates are limited to 1.2 °C s −1 and tuneable T c are needed to pair with thermosets possessing variable temperature activation-from 80-200 °C. High saturation magnetization (M s ) is an important parameter required to obtain high heating rate. [7] However, tuning T c may result in undesirable changes in M s . [1,8] Optimization of heating rates and tuneable T c need to be compatible with good mechanical strength and nanoparticle colloidal stability within the organic resins.Generally, the heating rates of CNP can be tuned through composition, surface coatings, particle size, and percent loading. [9] However, these factors may lead to undesirable shifts in material parameters of CNP magnetic anisotropy, magnetization, and Curie temperature. Hence, other methods of temperature control were explored, that is, increasing thermal conductivity of the resin by addition of carbon allotropes. Carbon allotropes such as carbon nanotubes (CTUBE) and carbon nanocoils (CCOIL) can increase modulus and impart electromagnetic shielding. [10] Reinforcement of epoxy nanocomposites by the addition of carbon allotropes increases mechanical strength, thermal/electrical conductivity, and electromagnetic wave absorption. [10c,11] CTUBEs are composed of hexagonal rings of carbon atoms; helical variants are referred to as CCOIL. CCOIL possess additional non-hexagonal cycle carbon, such as cyclopentadiene and Magnetocuring of adhesives refers to the curing of an epoxy + Curie temperature controlled magnetic nanoparticles (CNP) composite using a suitable alternating magnetic field. The controlled heating of the CNP results in remote, wireless curing without resin overheating. However, typical CNP possess only a fraction of the heat output of ferric oxide nanoparticles, quantified as the specific absorption rate (SAR). Previous investigations of epoxy + CNP adhesives revealed a SAR of 5 W.g −1 , which is 10-100× less than that of ferric oxides. Here, it is demonstrated that SAR can be improved to up to 60 W.g −1 by tuning CNP composition and by the addition of c...

Lignin extraction from lignocellulosic biomass has attracted considerable attention for an alternative production of sustainable fuels and chemicals. We report the lignin isolation from coconut coir using Klason, organosolv, and soda methods and the depolymerization of isolated lignin to value-added chemicals using a solid base catalyst. The yield of isolated lignin by the Klason method was found to be about 4 to 6 times higher than that by other methods. The structure of isolated Klason lignin (CC-KL), organosolv lignin (CC-ORGL), and soda lignin (CC-SL) was studied using attenuated total reflection (ATR), NMR, microanalysis, and so forth. The monomer molecular formula derived from microanalysis suggested that coir lignin is rich in guaiacyl units. ATR and 13C NMR clearly indicate that CC-ORGL contains more C–C bonds compared to CC-KL and CC-SL. Subsequently, these isolated lignins were depolymerized over a solid base catalyst (NaX) under atmospheric pressure. CC-SL shows a high yield of aromatic products (28%) compared to CC-ORGL and CC-KL. In order to develop a sustainable future technology, one-pot depolymerization of coconut coir was performed which resulted in a high yield (64%) of aromatic products.

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