Degree Of Polymerization Research Articles

PRODUCTION OF SODIUM CARBOXYMETHYLCELLULOSE FROM PINE WOOD WASTE AND INVESTIGATION OF ITS PHYSICOCHEMICAL PROPERTIES

With the increasing use of wood resources, wood waste disposal is becoming a more pressing issue. Wood waste can be effectively processed and reused, thus reducing environmental impact. Our study proposes using wood waste to produce sodium carboxymethyl cellulose (Na-CMC) with enhanced physical and chemical properties. The paper explores a promising approach to processing Scots pine (Pinus sylvestris L.) wood waste via the suspension method to obtain the biopolymer Na-CMC. The ability to convert pine sawdust into Na-CMC meets the demand for high-quality wood raw materials, expands the biopolymer's applications, and reduces the environmental and economic burden of wood consumption. The aim of this study is to produce Na-CMC from Scots pine sawdust at 60°C and 80°C and investigate the biopolymer’s physical and chemical properties. In laboratory experiments, Na-CMC samples were synthesized at 60°C and 80°C using sodium hydroxide, propanol-2, and sodium monochloroacetate (Na-MCA). The physical and chemical properties of Na-CMC were studied such as functional groups (hydroxyl, methylene, carbonyl), alcohol and ether bonds by IR spectrophotometry; molecular mass, polymerization degree, and viscosity of polymer solutions by viscometry; carboxymethyl groups by conductometric titration; and product yield and solubility by gravimetry. The scientific and practical significance of the chemical modification of wood sawdust cellulose has been established, with carboxymethylation proving effective at 60°C

Copolymer Randomization by End‐Group Interchain Exchange Reactions

AbstractTheoretical analysis of the kinetic scheme describing formation and randomization of a binary copolymer due to end‐group interchange reactions is presented. Compact analytical expressions are obtained for the transient and equilibrium values of the copolymer degree of blockiness and fractions of active end‐groups of different types. The resulting copolymer is described by the first‐order Markov statistics, which can be rather far from the Bernoullian one. Its structure is determined by the composition of the system and a single combination of the rate constants of four elementary reactions. The kinetics includes fast and slow stages with characteristic time periods independent of and proportional to the average polymerization degree, respectively. During the fast stage, the initial polymers disappear, whereas the copolymer degree of blockiness is still very low. The distribution of units in the copolymer is Markovian, only if the initial polymers possess the most probable molar mass distributions. At the slow stage copolymer randomization gradually progresses, whereas the distribution of end groups may change in the opposite direction compared to the fast stage. The results can be used to analyze the experimental data on the chain structure of condensation, metathesis, and dynamic covalent polymers, where interchange reactions play a significant role.

Fresh, hardened properties and microstructural analysis on the effect of NaOH molarities of industrial by-products based self-compacting geopolymer concrete

AbstractThe sodium hydroxide (NaOH) molarity in Self-compacting geopolymer concrete (SCGC) is essential for activating the precursor and aggregate to develop strength, workability, and microstructure. In this study, SCGC mixes prepared with 50% fly ash (FA) and 50% ground granulated blast furnace slag (GGBS) to investigate fresh and hardened properties with NaOH molarities (M) ranges from 8 to 16, the ratio of Na2SiO3 to NaOH kept constant at 2.5 and ratio of alkaline solution to the binder at 0.45 with 2% SP for the polymerization process. SCGC workability studies indicate the NaOH concentration increased, the slump flow decreased, and 14 M was the optimum molarity. The compressive, split tensile, and flexural strength results showed 39.4 MPa, 4.72 MPa, and 5.91 MPa at 28 days. The C–S–H gel enhanced the strength qualities studied from Fourier transform infrared spectroscopy. The scanning electron microscope showed microstructural densification of the entire system, which improved with the NaOH concentration, and the strength increased with the degree of polymerization and polycondensation. Hence, based on workability, the optimized NaOH concentration is 14 M with binder contents of FA (50%) and GGBS (50%). This study helps to improve the microstructure and strength properties with potential cost implications of SCGC.

Light-induced transformation of a supramolecular gel to a stronger covalent polymeric gel.

A polymerizable diacetylene gelator, containing urea and urethane groups, that congeals various non-polar solvents was synthesized. The gelator molecules self-assemble forming non-covalent polymers through intermolecular hydrogen bonding, as evidenced from FT-IR and concentration-dependent 1H NMR spectroscopy. The self-assembly positions the diyne units of adjacent molecules at proximity and in a geometry suitable for their topochemical polymerization. UV irradiation of the gel resulted in topochemical polymerization, transforming the non-covalent polymer to a covalent polymer, in situ, in the gel state. The polymerization was confirmed by characterizing the polydiacetylene (PDA) using UV-Vis and Raman spectroscopy. Time-dependent rheological studies revealed gradual strengthening of the gel with the duration of irradiation, suggesting that the degree of polymerization increases with the duration of irradiation. The PDA formed is a semiconductor, which might be useful for various applications.

Catalytic Effect of Potassium Xanthates and Related Compounds on Disulfide Bond Enrichment of Polyalkylene Sulfides Synthesized in the Course of Episulfide Polymerization.

The original method for the preparation of high-molecular-weight polyalkylene sulfides was reported. Assuming anomalous peculiarities of the reaction (high polymerization rates, high degrees of polymerization, and huge discrepancy between the expected Mn values and the experimentally obtained values), the priority task was set to study the mechanism underlying the observed new type of polymerization. Thus, it was demonstrated that xanthate and related molecules could act as pure catalysts, facilitating both the chain-growth polymerization (ring-opening of episulfides) realized via an anionic route and the direct attack of the sulfur atom of one episulfide molecule on the methylene carbon atom of the second (neighbor) episulfide molecule, accompanied by the subsequent formation of a stable thiiranium-based zwitterionic adduct. The role of xanthate and related compounds as catalysts and stabilizing particles was further supplemented by modeling the attack of thiolate on the sulfur atom of a thiiranium-based adduct. The xanthate molecule acting as a catalyst was found to be involved in all stages of the process discussed by sharing the potassium atom with the sulfur atoms of active components of the system (the initial episulfide molecule, thiolate, and the zwitterionic intermediate). The subsequent analysis revealed the exceptional transparency of the materials obtained, which was found to exceed 99%. The pronounced self-healing ability was also found to be a distinctive feature of the synthesized high-molecular-weight polyalkylene sulfides enriched with disulfide bonds.

The general glycan profiling of Dendrobium officinale and their protective effects on MIN6 cells via ERK signaling pathway

Based on structural elucidation of natural and hydrolyzed glycans, the general glycans profiling of D. officinale were unequivocally established for the first time as follows: [Display omitted] The results indicated that the structure of D. officinale glycans with low degree of polymerization (DP ≤ 22) was linear α-D-1,4-glucan, whereas the structure of glycans with high degree of polymerization (DP > 24) was linear acetylated 1,4-glucomannan. The content of acetyl groups and mannose to glucose (M/G) ratio increased with the degree of polymerization of D. officinale glycans. In addition, this study showed that natural D. officinale glycans protected pancreatic β-cell damage induced by glucotoxicity through the extracellular signal–regulated kinase (ERK)1/2 pathway.

Chromatographic analysis of branched and debranched starch structure: Variability of their results

Starch structure determination is crucial for understanding its properties and applications. However, method-dependent variations in size determination can lead to ambiguous interpretations. This study investigates the ambiguities in starch structure determination by evaluating the variation in size of four commercial branched starches as determined by average molar mass, gyration radius, hydrodynamic radius, and chain-length distribution. The starches were analyzed using high-performance size-exclusion chromatography (HPSEC) coupled with multi-angle laser light scattering (MALLS) and refractive index detector (RI), and after debranching by HPSEC-RI and high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detector (PAD). MALLS-derived MW values for amylose and amylopectin were higher than those obtained using the hydrodynamic volume method. The molecular weight of amylopectin chains, determined by the degree of polymerization (DP), ranged between 2.1 and 2.9 × 103 g/mol for short chains, and between 4.1 × 103 and 1.1 × 104 g/mol for long chains. Differences in amylopectin chain content were observed between HPSEC-RI and HPAEC-PAD, highlighting the complementary nature of these techniques. The study underscores the need for standardizing chromatography-based methodologies in starch research, particularly with the advent of new technologies.

Mechanism of maltogenic α-amylase modification on barley granular starches spanning the full range of amylose

Amylopectin (AP)-only (APBS), normal (NBS), and amylose (AM) only (AOBS) barley starches were selected here to investigate catalysis pattern of maltogenic α-amylase (MA) on hydrolyzing AP and AM granular starches. MA shortened starch side chains with degree of polymerization (DP) 11–30. MA-treated APBS exhibited porous granular structures and dramatically increased degree of branching (DB, 17–20 %), and reduced ordered degrees, suggesting high hydrolysis and transglycosylation activities of MA. MA-treated NBS showed less pronounced porous structures and slightly increased DB (2–4 %), indicating high hydrolysis but low transglycosylation activities. AOBS displayed minimal changes in DB (0.2–0.3 %) and starch structures, implying low hydrolysis and transglycosylation activities. Therefore, MA preferred to attack the AP molecules with abundant glucan substrates with DP 11–30, while AM restricted MA activity likely by creating ineffective binding sites and undergoing rapid reorganization. These findings deepened the understanding of the mechanisms of MA in modifying granular starches with varying AM content.

Immobilization mechanism of heavy metals by crystals and liquid phase during melting treatment of MSWI fly ash

Melting treatment has emerged as a promising technology for managing municipal solid waste incineration (MSWI) fly ash owing to its advantageous features of effective detoxification and volume reduction. The melting treatment of MSWI fly ash involves the immobilization of heavy metals by crystals and liquid phase. Herein, the immobilization mechanism of heavy metals (Cu, Pb and Cd) by the crystals and the liquid phase was investigated using melting experiments, thermodynamic calculations and density functional theory (DFT) calculations. Results demonstrate that the immobilization of heavy metals is influenced by a combination of factors: the reaction of heavy metals, physical encapsulation ability of the liquid phase and chemical fixation ability of both the crystals and the liquid phase. An increase in the content of SiO2 and Al2O3 promotes the conversion of heavy metals oxides into heavy metals chlorides. Furthermore, an increase in the content and polymerization degree of the liquid phase facilitates the physical encapsulation of heavy metals chlorides. The chemical fixation ability of the crystals and the liquid phase differs for Cu and Pb, while Cd cannot be immobilized through chemical fixation. To enhance the immobilization of heavy metals during melting treatment, the chemical composition of MSWI fly ash should be adjusted within the anorthite region of the ternary phase diagram. This study provides valuable insights into the immobilization mechanism of heavy metals by the crystals and the liquid phase during the melting treatment of MSWI fly ash.

Microcrystalline Cellulose Extracted from Tissue Paper and its Comparison to Commercial Microcrystalline Cellulose

Introduction: Tissue paper has been utilized to extract Microcrystalline Cellulose (MCC) using sulphuric acid. The two approaches used for MCC extraction were with NaOH pretreatment (NaOH-EMC) and without NaOH (EMC). Method: The extracted MCC was characterized by FTIR, SEM, TGA, XRD, zeta potential, particle size, and degree of polymerization and then subsequently compared with the commercially available MCC(CMC). The particle size of the NaOH-EMC was lesser than the CMC, while the EMC had a larger size. The values recorded were respectively 1.322, 6.750, and 8.521 μm. The SEM images also supported the values reported by the particle size analyzer. Result: The distribution, however, was staggered for the prepared samples, as against the CMC. The prepared MCC suspensions were found to be more stable than the CMC based on the recorded zeta potential. The crystallinity for NaOH-EMC, EMC, and CMC was recorded to be 69.91, 68.59, and 70.89 percent, respectively, and the observations were not significantly different. Conclusion: The degree of polymerization of NaOH-EMC and EMC was 129 and 94, which was 189 lower than that of CMC, having the value of 178. The study successfully reports the extraction of MCC from the tissue paper as an alternative source.

Structural, molecular, and physicochemical properties of starch in high-amylose durum wheat lines

There is growing interest in the development of high-amylose cereals such as wheat due to their functional properties and nutritional value in foods. The increase in amylose content is associated with significant changes in the physicochemical, molecular, and structural characteristics of wheat starch which could affect its processing quality. The present study aimed to analyze the physicochemical, molecular, and structural characteristics of high-amylose starch from three durum wheat near isogenic lines (NILs), each obtained using three different recurrent parents. Morphology, granule size distribution, pasting and thermal properties, X-ray diffraction, and structural features were determined. The NILs showed the highest amylose content (65.3 and 69.8%), granules with an elongated shape, size between the wild-type and the mutant, restricted swelling in the pasting profile, the highest average and final gelatinization temperature, and B-polymorphism. The starches from the NILs showed the highest molar mass of amylopectin (AP) (7.0–7.6 × 107 Da) and the lowest amylose (AM) (1.1–1.8 × 106 Da), an issue associated with the biosynthesis of both components. The study on the debranched sample by high-performance size-exclusion chromatography showed that the high-amylose starch had the highest content of long B2 and B3 chains of AP (23.9–26.6%), which was corroborated with the high-performance anion-exchange chromatography analysis where the chains with degree of polymerization >37 had the highest content (18.3–19.1%). The PC1 is highly associated with the MwAM and the AM fraction in the debranched starch analyzed by HPSEC. Characterizing high-amylose durum wheat starch provides information to determine the structure-function relationship and design strategies to produce crosses with structural characteristics of AM and AP for specific applications.

Influence of Chemical, Morphological, Spectroscopic and Calorimetric Properties of Agroindustrial Cellulose Wastes on Drainage Behavior in Stone Mastic Asphalt Mixtures

New asphalt mixtures have been improved by using fibers (polypropylene, polyester, asbestos, carbon, glass, nylon, lignin, coconut, sisal, recycled rubber, PET, wood, bamboo, and cellulose), reducing the temperature and compaction energy for their collocation, minimizing the impact on the environment, increasing the tenacity and resistance to cracking of hot mix asphalt (HMA), preventing asphalt drainage in a Stone Mastic Asphalt (SMA). Hence, this paper aims to evaluate the influence of the chemical (lignin content, ash, viscosity, degree of polymerization, and elemental analysis), morphological (SEM), spectroscopic (FTIR-ATR and XRD), and calorimetric (ATG and DSC) properties of celluloses from bagasse Agave tequilana Weber var. Azul (ABP), corrugated paperboard (CPB) and commercial cellulose fiber (CC) as Schellenberg drainage (D) inhibitors of the SMA. The ABP was obtained through a chemical process by alkaline cooking, while CPB by a mechanical refining process. The chemical, morphological, spectroscopic, and calorimetric properties were similar among the analyzed celluloses, but CPB and ABP cellulose are excellent alternatives to CC cellulose for inhibiting drainage. However, CPB is the most effective at low concentrations. This is attributed to its morphology, which includes roughness, waviness, filament length, orientation, and diameter, as well as its lignin content and crystallinity.

Structure and bioactivity of tannin extracts from Taxodium ‘Zhongshanshan’

Abstract Taxodium ‘Zhongshanshan’ is a distinctive tree known for its rapid growth and robust stress resilience. To enhance the utilization of forestry resources, tannin extracts were procured from the barks (BE) and leaves (LE) of Taxodium ‘Zhongshanshan’. The tannin structures were characterized by FT-IR and MALDI-TOF MS, and found to be condensed tannin with a degree of polymerization not exceeding 6. The tannin extracts exhibited a potent ability to scavenge free radicals at capacities of 60–80 % compared to Vitamin C (VC). They inhibited the bacterial strains Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with a pronounced effect on the latter. Furthermore, tannin from Taxodium ‘Zhongshanshan’ appears benign and have no significant effect on cell activity.

Applications of regenerated bacterial cellulose: a review

AbstractWhilst synthetic polymers have changed the world in many important ways, the negative impacts associated with these materials are becoming apparent in waste accumulation and microplastic pollution due to lack of biodegradability. Society has become aware of the need to replace or substitute environmentally persistent synthetic polymers, and cellulose has received a large amount of attention in this respect. The mechanical properties of cellulose, its renewable nature and biodegradability are advantageous properties. Drawbacks exist for the use of plant cellulose (PC), including the water footprint of cotton, deforestation associated with wood/dissolving pulp, and the extensive processing required to refine plants and wood into pure cellulose. Bacterial cellulose (BC), also known as microbial cellulose, is gaining momentum in both academic and industry settings as a potential solution to the many drawbacks of plant-based cellulose. Compared to PC, BC has high purity, crystallinity and degree of polymerisation, and can be manufactured from waste in a way that yields more cellulose per hectare, per annum, and requires less intense chemical processing. Native bacterial cellulose can be formed and shaped to an extent and is found in a variety of commercial products. However, dissolving and regenerating bacterial cellulose is a potential avenue to broaden the applications available to this material. The aim of this study is to review the applications which utilize regenerated bacterial cellulose, with a focus on the dissolution/regeneration methods used and discussing the associated limitations and future outlook.

Synthesis and Solvent Free DLP 3D Printing of Degradable Poly(Allyl Glycidyl Ether Succinate)

AbstractDigital light processing (DLP) printing forms solid constructs from fluidic resins by photochemically crosslinking polymeric resins with reactive functional groups. DLP is used widely due to its efficient, high‐resolution printing, but its use and translational potential has been limited in some applications as state‐of‐the‐art resins experience unpredictable and anisotropic part shrinkage due to the use of solvent needed to reduce resin viscosity and layer dependent crosslinking. Herein, poly(allyl glycidyl ether succinate) (PAGES), a low viscosity, degradable polyester, was synthesized by ring opening copolymerization and used in combination with degradable thiol crosslinkers to afford a solvent free resin that can be utilized in DLP printing. Varying resin formulations of PAGES polymer are shown to decrease part shrinkage from 14 % to 0.3 %. Photochemically printed parts fabricated from PAGES possess tensile moduli between 0.43 and 6.18 MPa and degradation profiles are shown to vary between 12 and 40 days under accelerated conditions based on degree of polymerization and crosslink ratio.

Enhanced physical properties and water resistance of films using modified starch blend with poly(vinyl alcohol)

Research into sustainable biopolymer films is increasingly focused on finding viable alternatives to petroleum-based plastics. This study aims to address these challenges by examining the performance of a series of films prepared using polyvinyl alcohol (PVA) with varying degrees of saponification (DS) and polymerization (DP), combined with two modified starch: hydroxypropyl starch (HPS) and sodium octenylsuccinate starch (OctS). The findings demonstrate that increased PVA saponification and polymerization levels greatly improved the physical properties of the PVA/Starch blends because of the interactions and intermolecular entanglement between the PVA and starch chains. By altering the PVA and starch formulations, the blend films' tensile qualities and water resistance were greatly improved; at a 7:3 ratio, the highest tensile strength (TS) is ∼17.4 MPa, and elongation at break (EAB) is ∼476.8 %. The tensile properties and water resistance of the blend films were significantly enhanced by varying the PVA and starch formulations, achieving the highest tensile strength (17.4 MPa) and elongation at break (476.8 %) at a 7:3 ratio. Moreover, the PVA/OctS-7 blend exhibited superior water durability, and high transparency, with the lowest swelling (∼108.6 %) and certain wet strength, as well as varied solubility behaviors in different pH solutions, rendering it appropriate for use in packaging applications. As a result, PVA/Starch blend films' functional qualities can be significantly improved, making them appear as viable substitutes for petrochemical plastic packaging.

Integrated Analysis of Metabolome and Transcriptome Reveals the Effect of Burdock Fructooligosaccharide on the Quality of Chinese Cabbage (Brassica rapa L. ssp. Pekinensis)

Burdock fructooligosaccharide (BFO) is fructose with a low polymerization degree, which could improve the immunity to pathogens, quality, and stress resistance of vegetables. Still, there are no studies on applying BFO in Chinese cabbage. In this study, the effects of exogenous BFO sprayed with different concentrations (0, 5, 10, 20, 30 g·L−1) on the growth and soluble sugar content of Chinese cabbage seedlings were determined. The result showed that 10 g·L−1 was the appropriate spraying concentration. Based on metabolome analysis, a total of 220 differentially accumulated metabolites (DAMs) were found, among which flavonoid metabolites, glucosinolate metabolites, and soluble sugar-related metabolites were the key metabolites involved in improving the quality of Chinese cabbage caused by BFO. Further combination analysis with transcriptome, trans-cinnamate 4-monooxygenase (CYP73A5), and chalcone synthase 1 (CHS1) were more closely associated with the DAMs of flavonoid biosynthesis. Sulfotransferases 18 (SOT18), Branched-chain amino acid amino transferases 6 (BCAT6), and cytochrome P450 monooxygenase (CYP83A1) were the key genes in glucosinolate biosynthesis. Hexokinase (HxK1), beta-glucosidase 8 (BGL08), invertase 3 (INV3), beta-glucosidase 3B (BGL3B), and sucrose phosphate synthase 1 (SPS1) were significantly upregulated, potentially playing crucial roles in the soluble sugar metabolism. In conclusion, these results provided an understanding of the effects of BFO on the expression of genes and the accumulation of metabolites related to quality formation in Chinese cabbage.

Switchable pH-Responsive Morphologies of Coassembled Nucleobase Copolymers.

This work presents supramolecular coassembled nucleobase copolymers with transitional morphologies upon pH changes (from 7.4 to 10). Uracil- and adenine-containing copolymers were prepared by RAFT, which allowed us to finely tailor the polymerization degree and the composition. The coassembled formulations prepared in an aqueous buffer at two distinct pH (7.4 and 10) formed spherical morphologies at physiological pH. The increase of the pH induced the apparition of various large, irreversible anisotropic supramolecular architectures. Isothermal titration calorimetry revealed that the coassembly at pH 7.4 was mainly guided by H-bonds between complementary nucleobases, while the experiments conducted at pH 10 showed that the assemblies were mainly driven by hydrophobic interactions. These results highlight that the nature of supramolecular interactions (H-bonds or hydrophobic interactions) has a great influence on the morphology of nucleobase-containing coassemblies when changing the pH. These findings may provide further perspectives in the field of advanced nanomaterials.

Determination of Chain Transfer Constants of Alcohols for High‐Pressure Polyethylene Polymerization

AbstractIn low‐density polyethylene (LDPE) production, low‐molecular‐weight species are used as chain transfer agents (CTAs). They reduce the degree of polymerization, which has an impact on the polymer properties, such as processability. To specifically adjust the product properties, a detailed understanding of the transfer kinetics to CTAs is indispensable. Thus, the transfer activity of various primary, secondary, and tertiary alcohols as well as diols was investigated experimentally between 120 °C and 250 °C at 2000 bar. The results were evaluated using the Mayo and chain length distribution (CLD) method, and the latter was found to give more reliable results. It was observed that the hydroxy group systematically increases transfer activity compared to alkanes. Additionally, a linear increase of transfer activity with the number of hydrogen atoms is found.

Alkyl polyglycosides derived from α-olefins via Fisher glycosidation and their adsorption and aggregation behavior in aqueous solution

The effective and stable use of α-olefins is a topic of great research interest due to their abundant reserves, and the fact that the hydrolysis and epoxidation reaction of these substances produces hydroxyl group as a key linking group plays an important role in the synthesis of surfactants. Consequently, a series of alkyl polyglycosides (DC08PG, DC10PG, and DC12PG) were synthesized as non-ionic surfactants via the glycosidation reaction of long-chain 1, 2-vicinal diol with different carbon numbers and glucose. The results showed that 1, 2-vicinal diol exhibited increased reactivity in glycosidation due to their unique molecular structure. Furthermore, it was observed that the degree of polymerization (DP) achieved was notably elevated, registering at 1.63, surpassing the DP of 1.37 typically prepared using conventional methods. This enhancement was paralleled by a demonstrable increase in hydrophilicity, as evidenced by the hydrophile-lipophile balance number (HLB), resulting in a substantial improvement in the water solubility of the product, the transmission rate > 90 %. For adsorption and aggregation behavior, DC12PG showed a smaller cross-sectional area (Amin), larger saturation adsorption (Γmax), and could aggregate to form micelles at low concentrations, and short-term dynamic adsorption properties (DST) was prominent. At the same concentration, for foam properties, DC12PG with longer alkyl chains produced higher and more stable foam; for emulsification properties, the emulsification time was 298 s; for wetting properties, the contact angle was 61.59° in 30 s. This analysis will help to reveal the intrinsic connection between the molecular structure and properties of surfactants.