High Molar Mass Research Articles

Influence of the cationic degree and molar mass of modified starches on their physicochemical properties and capability to enhance the oil recovery process

Polysaccharides and their derivatives are used as additives in numerous petroleum industrial processes, especially in enhanced oil recovery (EOR). There exists however, a lack of studies concerning how their physicochemical properties affect the oil recovery process. This work presents an investigation of a series of 2-hydroxy-3-(trimethylammonium)propyl starches (HTPS) with different molar masses and cationic degrees that are potentially useful for EOR. It was investigated surface/interfacial tensions, rheological profile, emulsion index and wettability alteration. The results provide experimental evidence that the HTPS intrinsic properties affect the measured properties. The HTPS solution/oil interfacial tension (IFT) ranged from a low value of 19.0 to a high value of 34.0 mN/m and correlates positively with the molar mass of the HTPS. In contrast, the rheological behavior displays correlations with the molar mass and the degree of cationization. Furthermore, the 1 % HTPS solutions presented around 10 % of viscosity increase in comparison to brines typically used in waterflooding. The derivative with a higher molar mass and intermediate degree of cationization (HTPS 2) was more effective in changing the wetting condition of an aged limestone with a wettability alteration index (WAI) of 52 % while the commercial surfactant cetyltrimethylammonium bromide (CTAB) presented a WAI of 32.6 %.

Enhanced biodegradation of phenanthrene and anthracene using a microalgal-bacterial consortium.

Polycyclic aromatic hydrocarbons (PAHs) are chemicals that are released into the environment during activities of the petroleum industry. The bioaccumulation, carcinogenic and mutagenic potential of PAHs necessitates the bioremediation of these contaminants. However, bioremediation of PAHs has a number of limitations including the inability of a single microbe to degrade all of the PAH fraction's environmental constituents. Therefore, a different paradigm, employing microalgal-bacterial consortium (MBC), may be used to effectively remove PAHs contaminants. In this type of interaction, the microalgae and bacteria species in the consortium work together in a way that enhances the overall performance of the MBC. Bacterial species in the consortium provide essential nutrients or growth factors by degrading toxic substances and provide these to microalgae, while the microalgae species provide organic carbon for the bacterial species to grow. For the first time, the ability of Gonium pectorale (G. pectorale) microalgae to break down phenanthrene (PHE) and anthracene (ANT) was investigated. Phenanthrene was shown to be more effectively degraded by G. pectorale (98%) as compared to Bacillus licheniformis (B. licheniformis) 19%. Similarly, G. pectorale has effectively degrade anthracene (98%) as compared with B. licheniformis (45%). The consortia of G. pectorale and B. licheniformis has shown a slight increase in the degradation of PHE (96%) and ANT (99%). Our findings show that B. licheniformis did not inhibit the growth of G. pectorale and in the consortia has effectively eliminated the PAHs from the media. Therefore G. pectorale has a tremendous potential to remove PAHs from the polluted environment. Future research will be conducted to assess Gonium's capacity to eliminate PAHs that exhibit high molar masses than that of PHE and ANT.

Ancillary Ligand Lability Improves Control in Cyclic Ruthenium Benzylidene Initiated Ring-Expansion Metathesis Polymerizations.

The synthesis of well-defined cyclic polymers is crucial to exploring applications spanning engineering, energy, and biomedicine. These materials lack chain-ends and are therefore imbued with unique bulk properties. Despite recent advancements, the general methodology for controlled cyclic polymer synthesis via ring-expansion metathesis polymerization (REMP) remains challenging. Low initiator activity leads to high molar mass polymers at short reaction times that subsequently "evolve" to smaller polymeric products. In this work, we demonstrate that in situ addition of pyridine to the tethered ruthenium-benzylidene REMP initiator CB6 increases ancillary ligand lability to synthesize controlled and low dispersity cyclic poly(norbornene) on a short time scale without relying on molar mass evolution events.

Chitin biochar as an effective and low-cost alternative for improving electron charge transfer of supported ZnFe2O4 during catalytic oxidation of high molar mass pollutants

In this work, a novel photocatalyst was prepared by supporting ZnFe2O4 onto chitin biochar. The novelty of this work lies in being the first report of ZnFe2O4 supported on biochar obtained from chitin residues, with a complete investigation of its efficiency carried out in two model pollutant molecules, namely ponceau and methylene blue dyes, using the mechanisms that rule heterogeneous photo-Fenton processes. Different ratios of biochar to metal oxide were tested, and it was observed that the electron/hole recombination rate decreased in the composite with equal amounts of each component, named Zn50B. The catalytic process for ponceau red and methylene blue degradation best fit the first-order kinetic model, with a degradation rate at least 26 times faster than the values reported in the literature, with complete removal after 15 and 60 min, respectively. According to radical scavenging experiments and quantum chemical calculations, the degradation mechanism behind Zn50B efficiency consists on the generation of highly oxidizing •OH(aq) and •O2-(aq) species, and its surface plays a minor role by attracting the studied molecules to near radical-generating active sites. Therefore, Zn50B composite is a promising novel photocatalyst, with proven high stability in up to 8 sequential recycles.

Upgrading of kraft lignin with phosphoric acid purification: A promising route for the synthesis of renewable epoxy resins

Obtaining bioproducts of industrial interest from kraft lignin not only adds value to this residual biomass while reducing environmental impact, but also fosters the circular economy and promotes sustainable development. However, its use without the removal of ash, metals, sulfur, and nitrogen implies a reduction in the final product properties, limiting its applications. This study aims to present a simple and efficient route for the production of purified kraft lignin (LKP) with low ash 0.51% and total sulfur 0.74% content. It is produced from impure kraft lignin (LKI), with high ash 9.74% and total sulfur 1.39% content which was treated with hot H3PO4/H2O solution (dilute acid purification), aiming at the synthesis of lignin-based epoxy resins. Elemental Analysis of carbon (C), hydrogen (H), and nitrogen (N) (wt%); ash (wt%); total sulfur (wt%); moisture contents (wt%); X-ray Fluorescence; X-ray Diffraction; Infrared Spectroscopy; Thermogravimetric Analysis; and Differential Scanning Calorimetry showed that LKP improved its structural, functional; and chemical properties, particularly thermal properties: 17% increase initial decomposition temperature (Tonset), 18% decrease final decomposition temperature (Tendset), 14% increase maximum decomposition temperature (Tdmax.), 35% increase carbonaceous residue (CR) and 8% increase in the value of glass transition temperature (Tg). The limiting oxygen index (LOI) calculated for this sample was around 34%, thus configuring a “self-extinguishing” material. Moreover, its high phenolic and aliphatic hydroxyl content 8.02 mmol L−1, high aromaticity (H/C = 1.11), high weight average molar mass (Mw̅≅1900g mol−1), and ash and total sulfur low contents justify its use in the synthesis of lignin-based epoxy resins. A sample of LKP was tested in a classic epoxidation reaction to obtain the prepolymer denominated of lignin-based epoxy resin (E-LKP), whose epoxy equivalent weight (EEW) was around 3500 g mol−1, which is similar to that of the high molar mass epoxy resin, D.E.R. 668-20 2000, commercialized by Dow Chemical Company®. E-LKP was polymerized with a conventional curing agent (polyetheramine) to produce the cured lignin-based epoxy resin (R-ELKP) with good physical-chemical properties. The high glass transition temperature (Tg2 = 133 ºC), a good limiting oxygen index (LOI = 27%), and excellent aesthetic characteristics (homogeneity and high brightness) stand out. These promising results suggest that it is possible to develop cured lignin-based epoxy resin with properties comparable to cured petroleum-based epoxy resin. The use of purified kraft lignin to obtain materials (prepolymers and polymers epoxy, among others) will also favor the environment, developing greener and renewable products.

One Step Closer to Coatings Applications Utilizing Self-Stratification: Effect of Rheology Modifiers.

Self-stratification of model blends of colloidal spheres has recently been demonstrated as a method to form multifunctional coatings in a single pass. However, practical coating formulations are complex fluids with upward of 15 components. Here, we investigate the influence of three different rheology modifiers (RMs) on the stratification of a 10 wt % 7:3 w:w blend of 270 and 96 nm anionic latex particles that do not stratify without RM. However, addition of a high molar mass polysaccharide thickener, xanthan gum, raises the viscosity and corresponding Péclet number enough to achieve small-on-top stratification as demonstrated by atomic force microscopy (AFM) measurements. Importantly, this was possible due to minimal particle-rheology modifier interactions, as demonstrated by the bulk rheology. In contrast, Carbopol 940, a microgel-based RM, was unable to achieve small-on-top stratification despite a comparable increase in viscosity. Instead, pH-dependent interactions with latex particles lead to either laterally segregated structures at pH 3 or a surface enrichment of large particles at pH 8. Strong RM-particle interactions are also observed when the triblock associative RM HEUR10kC12 is used. Here, small-on-top, large-enhanced, and randomly mixed structures were observed at respectively 0.01, 0.1, and 1 wt % HEUR10kC12. Combining rheology, dynamic light scattering, and AFM results allows the mechanisms behind the nonmonotonic stratification in the presence of associative RMs to be elucidated. Our results highlight that stratification can be predicted and controlled for RMs with weak particle interactions, while a strong RM-particle interaction may afford a wider range of stratified structures. This takes a step toward successfully harnessing stratification in coatings formulations.

Superbase‐enabled anionic polymerization of poly(alkyl cyanoacrylate)s: achieving well‐defined structures and controlled molar masses

AbstractPoly(alkyl cyanoacrylate)s (PACAs) find extensive use as adhesives in engineering and medicine. However, their high reactivity often leads to wide molar mass dispersity and uncontrolled chain‐end functionalities. Achieving precise polymer structures is crucial, particularly for medical applications to prevent oligomer toxicity. The conventional anionic polymerization of cyanoacrylates initiated by water results in high molar mass dispersities (Ð) and low end‐group functionalities. Nonetheless, under specific conditions, anionic polymerization holds the potential for controlling the molar mass and Ð of PACAs. Here, we demonstrate the synthesis of well‐defined PACAs by employing minute quantities (1%) of superbases to activate a functional thiophenol (PhSH) initiator. This strategy enables the attainment of adjustable molecular weights (Mn > 20 kg mol−1) and moderate dispersities (Ð < 1.4) for homopolymers and block copolymers. The selective initiation by thiophenol is confirmed through 1H DOSY NMR analysis. Furthermore, the controlled homo‐ and copolymerization of ACA derivatives highlights the remarkable performance of the superbase in conjunction with PhSH. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

β-(1 → 3)(1 → 6)glucan from Schizophyllum commune 227E.32: High yield production via glucose/xylose co-metabolization

A co-metabolization of xylose and glucose by Schizophyllum commune 227E.32 wild mushroom for exopolysaccharide (EPS) production is presented. Cultivations performed with S. commune 227E.32 at different xylose concentrations demonstrated that the concentration of 50 g·L−1 of xylose achieved the highest EPS production, around 4.46 g·L−1. Scale-up in a stirred tank reactor (STR) was performed. 10 % inoculum showed the highest cost/benefit ratio regarding sugar conversion and EPS production (Y P/S = 0.90 g·g−1), achieving 1.82 g·L−1 of EPS. Isolation, purification, and characterization were conducted with EPS produced in flasks and STR. GC–MS analysis showed glucose as main monosaccharide constituents for both isolates. 13C NMR and HSQC-edited showed that both EPS isolated consisted of a β-D-Glcp (1 → 3) main chain, partially substituted at O-6 with nonreducing β-D-Glcp ends on every third residue, similar to β-D-glucan isolated from S. commune basidiomes known as schizophyllan (SPG). The Mw was determined by GPC to 1.5 × 106 Da (flasks) and 1.1 × 106 Da (STR). AFM topographs revealed a semi-flexible appearance of the β-D-glucan, consistent with the triple helical structures adopted by SPG and overall contour length consistent with a high molar mass.

Cyanocobalamin (VB12) Bionic Enzyme-Assisted Photocatalytic Chain-Growth Polymerization for Detection of Lung Cancer Biomarkers.

Cobalt-mediated radical polymerization is noted for its great level of control over the polymerization of acrylic and vinyl esters monomers, even at high molar mass. Vitamin B12, a natural bionic enzyme cobalt complex, involves the conversion of organic halides to olefins through chain-growth polymerization. In this work, the notion of R-Co(III) free radical persistent free radical effect and vitamin B12 circulation were first reported for the perception of ultralow abundance of microRNA-21, a lung cancer biomarker. Indeed, most Co-containing catalytic reactions can occur under mild conditions due to their minimal bond dissociation of the C-Co bond, with blue light irradiation. Based on the intrinsic stability of the vitamin B12 framework and recycling of the catalyst, it is evident that this natural catalytic scheme has potential applications in medicinal chemistry and biomaterials. In addition, this strategy, combined with highly specific recognition probes and vitamin B12 circulation-mediated chain-growth polymerization, has a detection limit as low as 910 aM. Furthermore, it is sensitive for sensing in serum samples containing biomarkers and shows great potential for RNA selection and amplification sensing in clinical samples.

Asymmetrical Flow Field Flow Fractionation for Molar Mass Characterization of Polyethylene Oxide in Abuse-Deterrent Formulations

High molar mass polyethylene oxide (HM-PEO) is commonly used to enhance the mechanical strength of solid oral opioid drug products to deter abuse. Because the properties of PEO depend on molar mass distribution, accurately determining the molar mass distribution is a necessary part of understanding PEO's role in abuse-deterrent formulations (ADF). In this study, an asymmetrical flow field-flow fractionation (AF4) analytical procedure was developed to characterize PEO polymers with nominal molar masses of 1, 4 or 7 MDa as well as those from in-house prepared placebo ADF. The placebo ADF were manufactured using direct compress or hot-melt-extrusion methods, and subjected to physical manipulation, such as heating and grinding before measurement by AF4 were performed. The molar mass distribution characterized by AF4 revealed that PEO was sensitive to thermal stress, exhibiting decreased molar mass with increased heat exposure. The optimized AF4 method was deemed suitable for characterizing HM-PEO, offering adequate dynamic separation range for PEO with molar mass from 100 kDa to approximately 10 MDa.

Revealing the Monomer Gradient of Polyether Copolymers Prepared Using N‐Heterocyclic Olefins: Metal‐Free Anionic versus Zwitterionic Lewis Pair Polymerization

AbstractN‐Heterocyclic olefin (NHO)‐based polymerization pathways for the copolymerization of ethylene oxide (EO) and propylene oxide (PO) are investigated in detail. Employing in situ 1H NMR spectroscopy, both an organocatalytic, anionic polymerization setup (system A) and a zwitterionic, Lewis pair‐type approach (system B) are studied comparatively. The obtained kinetics data are fitted to the non‐terminal model (Jaacks and Ideal Integrated) and terminal Mayo–Lewis model (Meyer Lowry) to determine the reactivity ratios, revealing striking differences in copolyether microstructure and achievable molar masses. While for the metal‐free catalysis (system A) reactivity ratios of rEO = 3.4 and rPO = 0.30 are found, indicating a soft gradient structure, the presence of Mg(HMDS)2 (system B) entails exclusively zwitterionic propagation. This results in enhanced selectivity, displaying corresponding parameters of rEO = 7.9 and rPO = 0.13, in line with the proposed monomer‐activated mechanism. The block‐like, strongly tapered copolyether microstructure is also reflected in the thermal properties, showing a melting point for the latter sample and much higher molar masses (Mn >50 000 g mol−1). Notably, this study not only identifies capable polymerization systems for EO/PO, but also underlines that via in situ 1H NMR kinetics key questions regarding the polymerization mechanism can be illuminated quickly and reliably, simplifying access to essential structure‐property relations.

Toughening and Stiffening in Thermoreversible Diels–Alder Polymer Network Blends

The thermophysical properties, mechanical behavior, and healing performance of Diels–Alder-based polymer networks can be tuned widely by changing the molar mass, functionality, and stoichiometric ratio of the multifunctional diene (e.g., furan) and dienophile (e.g., maleimide) monomers. Blending furan-functionalized monomers with a high and low molar mass opens a new dimension in tuning the properties of the resulting reversible polymer network blends (RPNBs), containing different ratios of elastomeric and thermoset phases, with low and high crosslink densities and glass transitions below and above room temperature, respectively. Increasing the thermoset content up to 20 wt % raises the gel transition temperature (Tgel), relaxation time (τ), rubbery plateau modulus, ultimate stress, and Young’s modulus of the stiffened elastomers, while the strain at fracture and self-healing efficiency remained mostly unchanged. Conversely, the addition of up to 20 wt % of the elastomer phase drastically toughens the thermosets because of stress dissipation, which can suppress the stress concentration in the phase-separated network blends. The blends showed higher stress and strain at break while retaining similar Young’s moduli. The toughness increases up to an order of magnitude at 50 wt %, compared to the pure thermoset. The phase-separated morphologies were evidenced by the presence of the Tg’s of the pure networks in DSC and DMA.

Kinetic Modeling of the Synthesis of Poly(4-vinylpyridine) Macro-Reversible Addition-Fragmentation Chain Transfer Agents for the Preparation of Block Copolymers

Reversible addition-fragmentation chain transfer (RAFT) polymerization is one of the most common controlled polymerization techniques to prepare well-defined, rather narrow dispersed polymers due to reduced demands in reactant preparation. Despite these advantages, RAFT polymerization was so far primarily utilized on small laboratory scales. This study presents a first step to a scaled-up RAFT polymerization by developing and experimentally validating a kinetic model on the example of the polymerization of 4-vinylpyridine (4VP), which to date is not described in the literature. With the implementation of the results from modeling, the synthesis process was extended to a medium scale (from 6 to 36 g), while the same high conversions, molar mass, and low dispersity as in the smaller scale were achieved. The process is also optimized regarding the high degree of livingness necessary for using the 4VP polymers as a macro-RAFT agent in the subsequent reaction step for the synthesis of poly(4-vinylpyridine)-b-polystyrene diblock copolymers by RAFT dispersion polymerization.

Effect of Poloxamer Binding on the Elasticity and Toughness of Model Lipid Bilayers.

Poloxamers, also known by their trade name, Pluronics, are known to mitigate damage to cellular membranes. However, the mechanism underlying this protection is still unclear. We investigated the effect of poloxamer molar mass, hydrophobicity, and concentration on the mechanical properties of giant unilamellar vesicles, composed of 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine, using micropipette aspiration (MPA). Properties including the membrane bending modulus (κ), stretching modulus (K), and toughness are reported. We found that poloxamers tend to decrease K, with an impact largely dictated by their membrane affinity, i.e., both a high molar mass and less hydrophilic poloxamers depress K at lower concentrations. However, a statistically significant effect on κ was not observed. Several poloxamers studied here showed evidence of membrane toughening. Additional pulsed-field gradient NMR measurements provided insight into how polymer binding affinity connects to the trends observed by MPA. This model study provides important insights into how poloxamers interact with lipid membranes to further understanding of how they protect cells from various types of stress. Furthermore, this information may prove useful for the modification of lipid vesicles for other applications, including use in drug delivery or as nanoreactors.

Mechanism of βα recrystallization in isotactic polypropylene

βα recrystallization refers to a process of melting of the β crystallites followed by a recrystallization into α phase in isotactic polypropylene (iPP). It is normally observed only after cooling down the β-nucleated iPP (β-iPP) from the crystallization temperature to below 100 °C before heating. In this work, several β-iPP with different molecular weights were employed to investigate the βα recrystallization in the heating process starting at the crystallization temperature (Tc). It turned out that the non-cooled β-iPP with a molar mass of about 12 kg/mol (β-iPP12K) showed a βα recrystallization during slowing heating. The extent of the βα recrystallization gradually reduced with the increase of the Tc of the β-iPP12K. This peculiar behavior of β-iPP12K can be assigned to the existence of less stable β-crystallites which are susceptible to βα recrystallization. The β-iPP12K preferred to crystallize into thin β-crystallites with low stability which could be melted at low temperatures to form “amorphous self-nuclei” during slow heating. These local ordered amorphous phase would serve as nucleation-sites for α growth in a favorable temperature range. With respect to the β-iPP with high molar mass, although the “amorphous self-nuclei” could be induced at a certain temperature, this temperature was already beyond the appropriate temperature for α growth.

ONE-POT SYNTHESIS OF NORBORNENE-CYCLOOCTENE COPOLYMERS

The one-pot synthesis of random multiblock copolymers of norbornene and cyclooctene has been performed for the first time. It is shown that the first generation Grubbs Ru-carbene complex makes it possible to obtain these copolymers directly from monomers. In the course of one-pot synthesis, the metathesis polymerization of norbornene, which has a markedly higher ring strain, occurs first. Then, cyclooctene polymerizes and simultaneously an interchain cross-metathesis reaction takes place, during which the block structure of the copolymer is formed. Compared to the previously studied interaction of polynorbornene and polycyclooctene, the one-pot method makes it possible to obtain copolymers with a higher molar mass at a lower catalyst consumption.

All-Polyhydroxyalkanoate Triblock Copolymers via a Stereoselective-Chemocatalytic Route

Biodegradable polyhydroxyalkanoate (PHA) homopolymers and statistical copolymers are ubiquitous in microbially produced PHAs, but the step-growth polycondensation mechanism the biosynthesis operates on presents a challenge to access well-defined block copolymers (BCPs), especially higher-order tri-BCP PHAs. Here we report a stereoselective-chemocatalytic route to produce discrete hard-soft-hard ABA all-PHA tri-BCPs based on the living chain-growth ring-opening polymerization of racemic (rac) 8-membered diolides (rac-8DLR; R denotes the two substituents on the ring). Depending on the composition of the soft B block, originated from rac-8DLR (R = Et, nBu), and its ratio to the semicrystalline, high-melting hard A block, derived from rac-8DLMe, the resulting all-PHA tri-BCPs with high molar mass (Mn up to 238 kg mol-1) and low dispersity (Đ = 1.07) exhibit tunable mechanical properties characteristic of a strong and tough thermoplastic, elastomer, or a semicrystalline thermoplastic elastomer.

A circular bioprocess application of algal-based substrate for Bacillus subtilis natto production of γ-PGA.

Poly-γ-glutamic acid (γ-PGA) is a bio-derived water-soluble, edible, hydrating, non-immunogenic polymer. Bacillus subtilis natto is a wild-type γ-PGA producer originally isolated from Japanese fermented natto beans whose activity has been shown to be enhanced through ion-specific activation of Extrachromosomal DNA maintenance mechanisms. Being a GRAS γ-PGA producer, this microorganism has attracted great interest in its use within an industrial context. Here we successfully synthesised amorphous, crystalline and semi-crystalline γ-PGA between 11-27g/L. In line with circular economy principles, scalable macroalgal biomass has been evaluated as substrate for γ-PGA, displaying great potential in both yields and material composition. In this study whole cell, freeze dried seaweed -namely Laminaria digitata, Saccharina latissima and Alaria esculenta-were pre-treated by means of mechanical methods, sterilised and subsequently inoculated with B. subtilis natto. High shear mixing was found to be the most suitable pre-treatment technique. Supplemented L. digitata (9.1g/L), S. latissima (10.2g/L), A. esculenta (13g/L) displayed γ-PGA yields comparable to those of standard GS media (14.4g/L). Greatest yields of pure γ-PGA were obtained during the month of June for L. digitata (Avg. 4.76g/L) comparable to those obtained with GS media (7.0g/L). Further, pre-treated S. latissima and L. digitata complex media enabled for high molar mass (4,500kDa) γ-PGA biosynthesis at 8.6 and 8.7g/L respectively. Compared to standard GS media, algal derived γ-PGA displayed significantly higher molar masses. Further studies will be necessary to further evaluate the impact of varying ash contents upon the stereochemical properties and modify the properties of algal media based γ-PGA with the aid of key nutrients; however, the material synthesised to date can directly displace a number of fossil fuel derived chemicals in drug delivery applications, cosmetics, bioremediation, wastewater treatment, flocculation and as cryoprotectants.

Effect of enzymatic polymerization on the thermal stability of flavonoids

The mechanisms of the enzymatic polymerization of flavonoids, including quercetin, rutin and catechins, have been fairly well researched, but the properties of polymeric forms of flavonoids still require in-depth analysis. The products of enzymatic polymerization are oligomeric flavonoids. The antioxidant and antimicrobial properties of many oligomeric flavonoids have been described in the literature. However, data on the thermal properties of oligomeric flavonoids are lacking and the supplementing of these deficiencies is a scientific novelty of this work. The aim of this study is to determine the effect of enzymatic polymerization on thermal stability of oligomeric flavonoids. As part of the work, oligomeric quercetin, rutin and catechin were prepared by the enzymatic polymerization reaction with laccase and horseradish peroxidase enzymes. The oligomeric structure of the flavonoids was confirmed by spectroscopic (Fourier transform infrared spectroscopy (FTIR) and UV–visible spectroscopy (UV–Vis)) as well as chromatographic (ultra-performance liquid chromatography (UPLC) and gel permeation chromatography (GPC)) methods. Thermal properties of oligomeric flavonoids were investigated using differential scanning calorimetry (DSC) and thermogravimetry (TG). Moreover, the antioxidant and antimicrobial properties of oligomeric forms of selected polyphenols were investigated. Based on DSC analysis, it was found that the common feature of all oligomeric flavonoids was a higher final oxidation temperature and a higher oxidation enthalpy than the reference flavonoids. Thermogravimetric analysis showed that oligomeric poly(flavonoids)-laccase had better thermal stability, which correlated with higher molar mass.

Changes in chemical structures and molar mass parameters of birch wood powder by ethylene diamine treatment

It is necessary to delignify wood samples and treat them with ethylene diamine (EDA) before they are dissolved in 8% (w/v) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) prior to size-exclusion chromatography (SEC) analysis. In the present study, the effects of delignifying birch wood powder 0–3 times with NaClO2 and subsequently treating it with EDA on its solubility in 8% (w/v) LiCl/DMAc and its SEC data. The neutral sugar composition of the birch powder was almost unaffected by either delignification or treatment with EDA. Treatment of the birch powder with EDA resulted in 28% solubilities in 8% (w/v) LiCl/DMAc. Approximately 11% of cellulose molecules in the birch wood powder was dissolved, and detected as a high-molar-mass (HMM) fraction in the SEC elution pattern. Each single delignification treatment increased the solubility in 8% (w/v) LiCl/DMAc to 68–74% after EDA treatment. Based on the glucose contents of the delignified samples, almost all cellulose molecules in the delignified samples were dissolved in 8% (w/v) LiCl/DMAc after EDA treatment, and detected as the HMM fractions in the SEC elution patterns. The HMM cellulose molecules in the EDA-treated birch powder had linear random-coil conformations in 1% (w/v) LiCl/DMAc. However, the SEC data suggest that there probably were some chemical linkages between the HMM cellulose molecules and lignin or NaClO2-treated lignin fragments in the HMM fractions.