GPC Analysis Research Articles

Thermal stabilization of recycled PLA for 3D printing by addition of charcoal

Poly(lactic acid) (PLA) is one of the most widely used thermoplastic materials for 3D printing, particularly in the Fused Filament Fabrication technique. However, the printing process generates waste products and even though PLA is compostable, the possibility of recycling it provides ecological and economical benefits. In this work, a study on the stabilization of recycled PLA using charcoal (CC) was carried out, with the aim of overcoming the well-known problem of degradation (reduction in molecular weight) of PLA, during remelting. Microscopic investigations showed good dispersion of the filler in the polymer matrix, as well as better adhesion between the printed layers. Thermal analyses (Differential scanning calorimetry and thermogravimetry) indicate a stabilization of PLA waste because of the addition of small concentrations of CC to the recycled polymer matrix. These data are confirmed by GPC analyses, which show that the addition of filler is associated with higher molecular weight. Mechanical analysis indicated improved elongation at break and elasticity. Finally, a key ring was printed as an example of the better printability of the filament containing CC. The results indicate that a stabilization of the recycled PLA with a very low concentration of CC has been achieved. Improved 3D printability and properties of the 3D printed objects can be attained through recycling and recovery of wasted PLA, according to sustainability and circular economy matters.

Potential of Lauryl Gallate as Stability and Recyclability Improver of Poly (Butylene succinate-co-adipate)

In the present study, Lauryl Gallate (LG), a natural antioxidant, was used to improve polymer thermal stability and recyclability of a biodegradable polyester as poly(butylene succinate-co-adipate) (PBSA). Neat PBSA and PBSA/LG (0.5 wt% LG) blends were processed by melt extrusion and subjected to multiple consecutive extrusion cycles at 170 °C to prevent the occurrence of thermo-oxidative radical degradation processes of the polymer. Thermal, rheological, morphological, FTIR, and GPC analyses showed the beneficial effect of LG in delaying PBSA thermo-oxidative degradation, reducing polymer fragmentation at low-mid molecular weights compared to the reprocessed virgin PBSA. The use of LG limits the drop of both complex viscosity η* and zero-shear stress viscosity η0 as well as the reduction of crystallinity degree and the enhancement of melt flow rate (MFR). This molecular degradation produces low molecular weight polymer fractions and oligomers that solely affect molten PBSA fluidity. In the presence of 0.5 wt% of LG, the processability of PBSA doubles from six (neat PBSA) up to twelve extrusions until presenting the first signs of degradation of the molten polymer while preserving the mechanical characteristics at the solid state. These mechanical properties remain equivalent to the neat PBSA (Young’s modulus 0.33 GPa, yield strength 19.2 MPa, stress at break 24.4 MPa, and elongation at break 350%). Consequently, LG can be successfully employed as a natural PBSA stabilizer to extend the polymer lifecycle and contribute to the circular economy practice within the processing and manufacturing industry, particularly in the field of PBSA agricultural applications and injection moulded disposable products.

Red mud catalysts for hydrothermal liquefaction of alkali lignin: Optimization of reaction parameters

The aromatic enrichment structure of lignin shows its great potential for valuable chemicals, which could be a substitution for petrochemical raw materials. However, the selective breaking of its macromolecular structure is a key challenge in lignin valorization. This study examined hydrothermal liquefaction of alkali lignin with Zr, Mo, and Ce-impregnated red mud catalysts to achieve the maximum liquefaction and break down the sub-aromatic units into selective phenolics. 10 wt% Mo and 10 wt% Ce/RM exhibited the effective liquefaction tendency in ethanol solvent. With a C/F ratio of 1:5, the maximum bio-oil yield (81.8 wt%) was obtained with (5 wt%) Mo–Ce/RM catalyst, and maximum conversion (91.6%) was achieved with a 1:2 C/F ratio in 50E: 50W co-solvent. However, the C/F (1: 10) was found to be efficient towards the selective breaking of alkali lignin into guaiacol compounds with 65.4 area% selectivity of vanillin. The FTIR and 1H NMR analysis showed the actual breaking of lignin sub-aromatic structure into monomeric compounds. The results of GPC analysis validate the cleavage of lignin's structure with a significant reduction in the molecular weight of lignin from ∼28400 gm/mol to ∼485 gm/mol. The catalyst was highly recyclable as it maintained remarkable activity up to two successive catalytic cycles.

Mutagenesis enhances gellan gum production by a novel Sphingomonas spp.: upstream optimization, kinetic modeling, and structural and physico-functional evaluation.

Gellan gum (GG) has gained tremendous attention owing to its diversified applications. However, its high production and hence market cost are still a bottleneck in its widespread utilization. In the present study, high GG producing mutant of Sphingomonas spp. was developed by random mutagenesis using ethyl methylsulphonate (EMS) for industrial fermentation and identified as Sphingomonas trueperi after 16S rRNA and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) analysis. The fermentation conditions such as pH, temperature, and inoculum ratio were optimized by one factor at a time (OFAT) followed by screening of medium components by the Plackett-Burman statistical design. The most critical nutrients were further optimized by response surface methodology for maximizing GG production. The effect of dissolved oxygen tension in bioreactor on cell growth, substrate consumption, GG production, and batch productivity was elucidated. The highest GG titer (23 ± 2.4g/L) was attained in optimized medium at 10% inoculum (6.45 ± 0.5 log cfu/mL) under controlled fermentation conditions of pH (7), temperature (30°C), agitation (300-600rpm), and aeration (0.5-2.0 SLPM) at 22 ± 2% dissolved oxygen tension in a 10-L bioreactor. Kinetic modeling of optimized batch process revealed that logistic growth model could best explain biomass accumulation, while GG formation and substrate consumption were best explained by Luedeking-Piret and exponential decay model, respectively. Structural and physico-functional features of GG produced by mutant Sphingomonas spp. were characterized by HPLC, FTIR, NMR, DSC, TGA, GPC, SEM, and rheological analysis. The higher productivity (0.51g/L/h) under optimized fermentation conditions suggests potential consideration of mutant and process for commercial utilization.

Piezoelectric Zinc Oxides with High Polar Facets Ratios for Mechanically Controlled RAFT Polymerization†

Comprehensive SummaryMechanoredox chemistry that uses highly polarized piezoelectric materials as mechanoredox catalysts to promote redox reactions has emerged recently. It provides an alternative approach alongside the existing polymerization methods. Despite recent accomplishments, determining the quantitative relationship between the structure of ZnO and its catalytic performance for polymerization is still challenging. Herein, we prepared various ZnO crystals with different polar facets ratios to achieve efficient mechanically induced reversible addition‐fragmentation chain transfer polymerization (mechano‐RAFT). ZnO prepared from Zn(NO3)2 showed a high polar facet ratio of 1.66 and offered the highest catalytic activity among all ZnO samples. A near‐quantitative initiator efficiency of 99.5% and narrow molecular weight distribution were achieved for the polymerization of n‐butyl acrylate. Furthermore, the high chain‐end fidelity and chain extension capability were also evidenced by MALDI‐TOF MS and GPC analysis. This work highlighted the significant contribution of polar facets in ZnO to its catalytic activity and will guide the design of mechanoredox catalysis with superior catalytic performance in the future.

Metal free, white LED induced, room temperature degradation of methyl methacrylate - Methyl haloacrylate copolymers

Poly(methyl methacrylate) is a well-established and widely used commodity plastic. Since it only contains non-reactive CC bonds through the main chain, depolymerization and degradation conditions can be severe. As we are moving towards a self-sustainable world, requirements for new, green, and eco-friendly degradation methods emerge. Herein we utilize the efficient nature of light in the field of degradation and report a white LED-induced and metal-free method for the degradation of PMMA derivatives containing halogens at the main chain. As organodyes, erythrosin B, eosin Y and 10-phenylphenothiazine were employed and overall effects on degradation were examined and reported. The physical properties of synthesized copolymers and the kinetics of the method were investigated by DSC, TGA, 1H NMR and GPC analyses. Degradations up to 80% were observed at ambient temperature.

Imperative role of SBS molecular structure on the performance properties of modified binders and asphalt mixes

ABSTRACT The current study evaluates the impact of SBS molecular structure (L-SBS, B-SBS, HV-SBS, and DB-SB) and concentration on asphalt mix performance. Polymers were characterized using GPC, FTIR, melt rheology, and DSC analysis. GPC analysis indicates that BSBS has the highest molecular weight, while DB-SB has the lowest. FT-IR studies show differences in vinyl content among the four polymers. Asphalt mixture study resonated binder study where B-SBS polymer outperformed their counterparts. Results showed that compared to widely used L-SBS polymer, B-SBS copolymer generates ≈ 33 %, 26 % and 18 % more fatigue resistance, rutting resistance and stiffness behaviour, respectively, at a polymer content of 4.5 wt.%. The combined effect of higher molecular weight, triblock structure and the long-chain branching in B-SBS copolymer contributes to the discussed outcome which facilitates its utilization for high-stressed pavement sections at upper and intermediate service temperatures. However, L-SBS and HV-SBS polymers depict almost similar mixture performance due to their alike molecular structure. Moreover, the presence of a di-block structure and lower molecular weight results in inferior performance for mixes prepared with DB-SB polymer. The results clearly signify the dominance of polymer molecular structure in identifying the mixes’ performance properties at respective polymer content.

An environmentally benign approach for the synthesis of low molar mass polybutenes from mixed C4 monomers using AlCl3/ionic-liquid initiating systems

In this research, four novel ionic liquid compounds supported on boehmite were synthesized and employed along with AlCl3 to catalyze polymerization of Raffinate 1 (composed of C4 based mixed monomers) to polybutene, for oils viscosity improver applications. To characterize the supported ionic liquids, FTIR, XRD, TGA, EDS, SEM and Elemental Mapping analyses were employed. Furthermore, 1HNMR,13C NMR and DEPT-135, GC-MS and GPC analyses were performed to assess the effect of designed ionic liquids on the characteristics of obtained polybutenes. Notably, the introduction of the supported ionic liquids led to polybutenes with comparable Mn and Ð to blank AlCl3 system, but with lower exo-olefins content, which makes the final copolymer more suitable for target application. 13C NMR and GC-MS analyses confirmed the high participation of isobutylene units in the resulted polybutenes, 75–85%. As an outstanding remark, the suggested AlCl3/ionic liquid initiating system benefits greener polymerization strategy by halving the dosage of hazardous AlCl3 compared to blank system using neat co-initiator.

Performance improvement of a modified copolymer as an antiscalant and microbial growth inhibitor

Prevention and control of calcium sulfate scale formation and microbial growth accumulation in water handling systems is one of the challenging operations to avoid corrosion and flow restriction through equipment. This paper examines modified low-molecular-weight Maleic Anhydride (MAn) copolymerized by Acrylamide (AAm), which was successfully synthesized, developed, and analyzed as a multifunctional non-phosphorous antiscalant to overcome these problems. The structure, morphology, and thermal property of poly(MAn-co-AAm) were characterized. The intended structure and copolymerization were confirmed through GPC, FT-IR, SEM, and EDX analyses. The high thermal resistivity up to 400 °C was observed via TGA analysis. The standard NACE TM0374 methodologies were applied to evaluate the scale controlling capacity of poly(MAn-co-AAm) at various dosages (1–20 ppm), temperatures (50–90 °C), and regular intervals of 24–72 h. Interestingly, for low values of poly(MAn-co-AAm), efficiency was found 100% at the third level within the standard state. Further SEM and XRD analyses emphasized the validity of successful inhibition of calcium sulfate scale formation in comparison with other antiscalant agents, even at very low concentrations. In addition, antibacterial properties of poly(MAn-co-AAm) were investigated against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The results revealed that the developed copolymer possesses a wide antibacterial activity against both Gram-negative and Gram-positive bacteria. With this in mind, poly(MAn-co-AAm) is believed to be an effective and economical multifunctional antiscalant in cooling water treatment systems.

Preparation of CO2‐based poly(carbonate‐co‐lactide) with different porphyrin aluminum (III) catalysts

AbstractTwo‐component catalysts composed of tetra (para‐X substituted) phenylporphyrin aluminum (III) chloride, T (p‐X‐P)PAlCl, (where X = H, F, Cl, Br, CH3, OCH3, tert‐butyl), and cocatalyst bis(triphenylphosphine)imminium chloride (PPN+Cl−), could initiate the polymerization of propylene oxide (PO). And they could react with rac‐lactide, (rac‐LA), in the presence of propylene oxide (PO), to yield chains of enriched isotactic polylactide (PLA) with trace polyether segment. Also, these catalysts displayed different catalytic activity in the copolymerization of CO2 and PO, resulting in poly(carbonate‐co‐ether) copolymer with different carbonate unit content (CU%). Further, these catalysts could initiate one‐pot regio‐ and stereo‐ selective terpolymerization of rac‐LA, CO2 and rac‐PO, resulting in multi‐blocky poly(carbonate‐co‐lactide) with trace polyether segment. The structure of the products was verified by 1H NMR, 13C NMR, GPC, and DSC analysis, and it was found that variation of substitution groups in the periphery of porphyrin ligand would affect on the catalytic efficiency of ter‐polymerization, and the relative polymerization reaction ratio of the ring‐opening polymerization of LA (ROP) to the ring‐opening copolymerization of PO and CO2 (ROCOP), resulting in ter‐polymer with different contents of PLA segment and PPC segment. However, H‐T% in polycarbonate unit and Pi% in polylactide unit did not vary much with the change of catalysts.

Changes in structural parameters of SARA fractions during heavy oil hydrocracking using dispersed catalysts

Most of the characterization of SARA fractions of heavy crude oils during hydrocracking reactions is focused only on asphaltenes, and scarce works are devoted to analyze the differences in the structural parameters of all SARA fractions. In this work, a heavy crude oil is upgraded by non-catalytic and catalytic hydrocracking in a batch reactor at low severity conditions (3.9 MPa H2 pressure, 380 °C temperature, 800 rpm stirring rate, and 4 h reaction time). Three ore catalysts (hematite, magnetite and molybdenite) and one analytical grade catalyst (iron oxide) are employed. After reaction, the upgraded oils are first distilled and then separated into SARA fractions by the ASTM D86-16a and ASTM D2007-11 methods, respectively. NMR (1H and 13C), FTIR and GPC analyses are used to characterize SARA fractions before and after hydrocracking. The hydrocracking products exhibited a reduction in the average molecular weight of all SARA fractions as function of the hydrogenation capacity of each catalyst in the following order: Fe2O3 (analytical grade) > Molybdenite > Hematite > Magnetite. The structural parameters of saturates fraction remains unchanged except for the production of small length aliphatic chains from heavier fractions. For aromatics, resins and asphaltenes fractions, the number of aliphatic carbons is reduced due to dealkylation reactions increasing their aromaticity. For resins and asphaltenes fractions, hydrogenation and ring opening reactions are also carried out. Mo-based catalyst is mainly aimed at the conversion of asphaltenes, while the Fe-based catalysts focused on the conversion of resins.

Rheological and Aging Properties of Vegetable Oil-Based Polyurethane (V-PU) Modified Asphalt.

To study the rheological and aging properties of vegetable oil-based polyurethane (V-PU) modified asphalt, V-PU terminated with an -NCO group was synthesized from renewable castor oil, and liquefied MDI-100LL and 10-40 wt% V-PU modified asphalts were prepared. Temperature classification, multiple stress creep recovery (MSCR), and linear amplitude scanning (LAS) tests were carried out. The results showed that the modulus, the creep recovery rate (R), and the yield stress and yield strain of the V-PU modified asphalts significantly increased in the order: 0 wt% < 10 wt% < 20 wt% < 40 wt% < 30 wt%, while the phase angle and the unrecoverable creep compliance (Jnr) changed in the opposite order, and the high temperature grade of 30 wt% V-PU modified asphalt was 4 grades higher than that of the base asphalt, which indicated that the addition of V-PU enhanced the fatigue, permanent deformation, and recovery deformation resistance. The 30 wt% sample exhibited phase inversion had the best performance. Comprehensive FTIR, GPC, and fluorescence microscopy analyses showed that the molecular weight significantly increased and the V-PU molecules agglomerated after aging. The excess -NCO groups of V-PU prepolymer react with water in the air and the active hydrogen in the asphalt system and finally form a cross-linked three-dimensional network structure with the asphalt to improve performance. The mechanism of intramolecular cementation reaction and the aging process of V-PU modified asphalt was creatively derived.

Comparing the Properties of Bio-Polyols Based on White Mustard (Sinapis alba) Oil Containing Boron and Sulfur Atoms Obtained by Various Methods and Checking Their Influence on the Flammability of Rigid Polyurethane/Polyisocyanurate Foams.

The article compares the properties of bio-polyols obtained from white mustard (Sinapis alba) seed oil, which contain boron and sulfur atoms. Each of the bio-polyols was prepared by a different method of testing the efficiency of the incorporation of boron and sulfur atoms. All synthesis methods were based on the epoxidation of unsaturated bonds followed by the opening of epoxy rings by compounds containing heteroatoms. Two of the bio-polyols were subjected to additional esterification reactions of hydroxyl groups with boric acid or its ester. Three new bio-polyols were obtained as a result of the performed syntheses. The synthesized compounds were subjected to detailed physicochemical (physical state, color, smell, density, viscosity and pH), analytical (hydroxyl number, acid number, water content, content of C, H, N, S, O, B elements and GPC analysis), spectroscopic (FTIR, 1H NMR and 13C NMR) and thermal (DSC) tests. The obtained results allowed for a detailed characterization of the synthesized bio-polyol raw materials. Their suitability for obtaining polyurethane materials was also determined. The synthesized compounds have been found to be an interesting alternative to petrochemical polyols. The influence of the synthesized compounds on the flammability of polyurethane materials was tested experimentally. On the basis of this testing, a number of rigid polyurethane/polyisocyanurate foams were obtained, which were then subjected to flammability tests with the methods of horizontal and vertical burning, limiting oxygen index (LOI) and using the cone calorimeter. Based on this research, it was found that the presence of sulfur and boron heteroatoms reduced the flammability of polyurethane materials based on synthesized bio-polyols.

NMR and GPC Analysis of Alkyd Resins: Influence of Synthesis Method, Vegetable Oil and Polyol Content.

Alkyd resins are oil-based polymers that have been widely used for generations in the surface coating industry and beyond. Characterization of these resins is of high importance to understand the influence of its components on its behavior, compatibility with other resins, and final quality to ensure high durability. Here, NMR spectroscopy and GPC were used for characterizing differences in the chemical structure, molecular distribution, and dispersity between oil-based and fatty acid-based alkyd polymers made from sacha inchi and linseed oils. Sancha inchi (Plukentia volubilis L.) is a fruit-bearing plant native to South America and the Caribbean, and has a rich unsaturated fatty acid content. The effect of vegetable oil and polyol selection on the synthesis of alkyd resins for coating applications was analyzed. The influence of two different synthesis methods, monoglyceride and fatty acid processes, was also compared. Important structural differences were observed using NMR: one-dimensional spectra revealed the degree of unsaturated fatty acid chains along the polyester backbone, whereas, 2D NMR experiments facilitated chemical shift assignments of all signals. GPC analysis suggested that alkyd resins with homogeneous and high molecular weights can be obtained with the fatty acid process, and that resins containing pentaerythritol may have uniform chain lengths.

Production of biocrude oils from various bio-feedstocks through hydrothermal liquefaction: Comparison of batch and continuous-flow operations

Laboratory- and pilot-scale hydrothermal liquefaction (HTL) of biomass has predominantly been carried out in batch reactor systems. However, the development of continuous-flow reactor systems is critical for industrial deployment of HTL technology in a cost-competitive manner. In this study, a continuous-flow HTL system (with a feed capacity up to 6 kg/h) was developed and employed to convert various types of bio-feedstocks (wood sawdust, cornstalk, and black liquor) into biocrudes in the presence of K2CO3 catalyst at 300 °C for 12 min. The produced biocrude oils were characterized in detail by using GC-MS, FT-IR, GPC, and elemental analysis. This work compared the performance of the continuous-flow HTL process with that of a batch HTL process under the same conditions in terms of the yields and chemistry of the biocrude products as well as the energy recovery potential. The results indicated that HTL of different bio-feedstocks, particularly cornstalk and pinewood, in the continuous-flow reactor led to a higher yield of biocrude (32.4 and 34.5 wt %, respectively) with lower molecular weights and less solid residue (2.9 and 4.6 wt%, respectively) as well as a higher energy recovery rate (53.3 and 52.0%, respectively) compared with those in the batch reactor (Cornstalk: 23.8 wt%, 6.2 wt% and 46.5%; Pinewood: 28.5 wt%, 10.3 wt% and 50.8%, respectively). These promising results shall advance the future development and deployment of the HTL technology in Canadian and global bioenergy sectors.

Synthesis of Polytitanocarbosilane and Preparation of Si–C–Ti–B Fibers

Continuous SiC fiber is a kind of high–performance ceramic fiber that combines many advantages, such as high strength, high modulus, high hardness and low density. It has excellent mechanical properties, high–temperature and oxidation resistance, which could be applied as essential reinforcement in advanced ceramic matrix composites (CMCs) in the fields of aerospace and advanced weaponry. Melt–spinnable polytitanocarbosilane (PTCS) is an important precursor, which can be used to prepare continuous SiC fibers through a precursor–derived method. In this work, low–softening–point polycarbosilane (LPCS) and tetrabutyl titanate were used to prepare polytitanocarbosilane with a ceramic yield of 67.5 wt% at 1000 °C. FT–IR, TGA, GPC, 1H NMR, 29Si NMR, and elemental analysis were used to analyze the composition and structure of the PTCS precursor. Finally, Si–C–Ti–B fibers with an average tensile strength of 1.93 GPa were successfully prepared by melt spinning, pre–oxidation, pyrolysis, and high–temperature sintering of the PTCS precursor. The strength retention rates were 71.5% and 79.8% after heat treatment at 1900 °C and 2000 °C under an argon atmosphere for 1 h, respectively. The strength retention rates of Si–C–Ti–B fibers are higher than those of commercial Hi–Nicalon fibers, Tyranno ZMI fibers and Hi–Nicalon S fibers. This work can lay a theoretical foundation and technical support for developing high-performance SiC ceramic fibers containing titanium and their ceramic matrix composites.

Preparation and evaluation of injectable microsphere formulation for longer sustained release of donepezil.

In this study, donepezil-loaded PLGA and PLA microspheres (Dp-PLGA-M/Dp-PLA-M) and Dp-PLA-M wrapped in a polyethylene glycol-b-polycaprolactone (PC) hydrogel (Dp-PLA-M/PC) were prepared to reduce the dosing frequency of injections to treat Alzheimer's disease patients. Dp-PLGA-M and Dp-PLA-M with a uniform particle size distribution were repeatably fabricated in nearly quantitative yield and with high encapsulated Dp yields using an ultrasonic atomizer. The injectability and in vitro and in vivo Dp release, biodegradation, and inflammatory response elicited by the Dp-PLGA-M, Dp-PLA-M, and Dp-PLA-M/PC formulations were then compared. All injectable formulations showed good injectability with ease of injection, even flow, and no clogging using a syringe needle under 21-G. The injections required a force of <1N. According to the biodegradation rate of micro-CT, GPC and NMR analyses, the biodegradation of Dp-PLA-M was slower than that of Dp-PLGA-M, and the biodegradation rate of Dp-PLA-M/PC was also slower. In the Dp release experiment, Dp-PLA-M sustained Dp for longer compared with Dp-PLGA-M. Dp-PLA-M/PC exhibited a longer sustained release pattern of two months. In vivo bioavailability of Dp-PLA-M/PC was almost 1.4 times higher than that of Dp-PLA-M and 1.9 times higher than that of Dp-PLGA-M. The variations in the Dp release patterns of Dp-PLGA-M and Dp-PLA-M were explained by differences in the degradation rates of PLGA and PLA. The sustained release of Dp by Dp-PLA-M/PC was attributed to the fact that the PC hydrogel served as a wrapping matrix for Dp-PLA-M, which could slow down the biodegradation of PLA-M, thus delaying the release of Dp from Dp-PLA-M. Dp-PLGA-M induced a higher inflammatory response compared to Dp-PLA-M/PC, suggesting that the rapid degradation of PLGA triggered a strong inflammatory response. In conclusion, Dp-PLA-M/PC is a promising injectable Dp formulation that could be used to reduce the dosing frequency of Dp injections.

Changing the ratio of phenolic compounds to saccharides is an approach to the regulation of antioxidant properties of polysaccharides

Rice straw is an agricultural waste rich in lignocellulose. Soluble polysaccharides (SPs) and phenolic compounds are released from rice straw during bioethanol production. In this study, the composition of the SPs was analyzed using HPLC. It was found that phenolic compounds were another major component in the SPs besides saccharides. FT-IR of the SPs indicates that the phenolic compounds were covalently linked to the SPs in the form of ester or ether bonds. GPC analysis showed that the ratio of phenolic compounds to saccharides (P/S) was related to the molecular weight. The SPs with higher P/S exhibit stronger antioxidant capacities. The relationships between the molecular weight, P/S, and antioxidant capacity were identified by regulating the P/S of the SPs using a laccase oxidation method. The results indicate that the oligosaccharides in the SPs have a higher P/S and were the major contributor to the antioxidant capacity. The SPs derived from rice straw exhibit much higher antioxidant capacities than commercial SPs, suggesting that lignocellulosic biomass is a suitable material for the preparation of SPs with high antioxidant properties.

Analytical Method Cluster Development for Comprehensive Characterisation of Suberinic Acids Derived from Birch Outer Bark.

Suberin is a complex polyester biopolymer, and it is practically impossible to estimate the real content of suberin in suberised plant tissues. This indicates the importance of the development of instrumental analytical methods for the comprehensive characterisation of suberin derived from plant biomass for the successful integration of suberinic products into biorefinery production chains. In this study, we optimised two GC-MS methods-one with direct sylilation, and the second with additional depolymerisation, using GPC methods with RI detector and polystyrene calibration and with a three-angle light scattering detector and an eighteen-angle light scattering detector. We also performed MALDI-Tof analysis for non-degraded suberin structure determination. We characterised suberinic acid (SA) samples obtained from birch outer bark after alkaline depolymerisation. The samples were particularly rich in diols, fatty acids and their esters, hydroxyacids and their corresponding esters, diacids and their corresponding esters, as well as extracts (mainly betulin and lupeol) and carbohydrates. To remove phenolic-type admixtures, treatment with ferric chloride (FeCl3) was used. The SA treatment with FeCl3 allows the possibility to obtain a sample that has a lower content of phenolic-type compounds and a lower molecular weight than an untreated sample. It was possible to identify the main free monomeric units of SA samples by GC-MS system using direct silylation. By performing an additional depolymerisation step before silylation, it was possible to characterise the complete potential monomeric unit composition in the suberin sample. For the molar mass distribution determination, it is important to perform GPC analysis. Even though chromatographic results can be obtained using a three- laser MALS detector, they are not fully correct because of the fluorescence of the SA samples. Therefore an 18-angle MALS detector with filters was more suitable for SA analysis. MALDI-Tof analysis is a great tool for the polymeric compound structural identification, which cannot be done using GC-MS. Using the MALDI data, we discovered that the main monomeric units that makes up the SA macromolecular structure are octadecanedioic acid and 2-(1,3-dihydroxyprop-2-oxy)decanedioic acid. This corresponds with GC-MS results, showing that after depolymerisation hydroxyacids and diacids were the dominant type of compounds found in the sample.

Effects of enzymatic hydrolysis and physicochemical properties of lignocellulose waste through different choline based deep eutectic solvents (DESs) pretreatment

DESs are promising green solvents in lignocellulose pretreatment. In this work, four choline chloride based DESs were synthesized and their physicochemical properties were evaluated. Herbaceous lignocellulose (wheat straw, sorghum straw) and woody lignocellulose biomass (poplar wood, pine wood) were selected as pretreated substrates. In order to reveal the mechanism that pretreatment can improve the efficiency of enzymatic hydrolysis, the pretreated lignocellulose and lignin were analyzed. SEM, FT-IR and XRD characterization revealed the microstructural changes of pretreated lignocellulose, including the increase of surface roughness and pore erosion, changes of polysaccharide/lignin chemical groups, the increase of CrI. The efficient delignification increased the accessibility of enzyme to cellulose, the lignin content negatively affected enzymatic hydrolysis conversion. Furthermore, GPC analysis showed that the polydispersity of sulfonated lignin was reduced after pretreatment, lignin had more homogeneous molecular structures. The degree of unsaturation was calculated according to the elemental composition of sorghum straw and lignin. The unsaturation of pretreated sorghum straw decreased, that may be due to the removal of partial lignin. The elemental composition of acid insoluble lignin (separated from sorghum straw) reflects the increase of unsaturation of lignin after pretreatment.