Biobased and Sustainable Alternative Route to Long-Chain Cellulose Esters

Polysaccharide of sunflower (Helianthus annuus L.) stalk pith inhibits cancer proliferation and metastases via TNF-α pathway

The decoctions of sunflower (Helianthus annuus L. HAL) stalk pith have been used to treat advanced cancer, and polysaccharide of sunflower stalk pith (HSPP) was key ingredient of the decoctions. To forage specially structured HSPP with anti-tumor effects and to uncover its mechanisms of anticancer activity, syngeneic mouse model of lung carcinoma metastasis was established and the HSPP was found to contain long-chain fatty acid. Encouragingly, the mean survival of the polysaccharide group (47.3 ± 12.8 d) and its sub-fractions group HSPP-4 (50.7 ± 13.0 d) was significantly increased compared with control group (38.7 ± 12.7 d) or positive control group (41.8 ± 13.4 d), (n = 20, P < 0.01 vs. the control group or positive control group). Furthermore, the HSPP exerted inhibitory effects on the tumor cells' metastasis. Eventually, it is postulated that the polysaccharide could inhibit tumor proliferation and metastasis by reduction of TNF-α from the macrophage.

Insight into the Feasibility of Fatty Acyl Chlorides with 10-18 Carbons for the Ball-Milling Synthesis of Thermoplastic Cellulose Esters

Fatty acid cellulose esters (FACE) are common cellulose-based thermoplastics, and their thermoplasticity is determined by both the contents and the lengths of the side chains. Herein, various FACE were synthesized by the ball-milling esterification of cellulose and fatty acyl chlorides containing 10-18 carbons, and their structures and thermoplasticity were thoroughly studied. The results showed that FACE with high degrees of substitution (DS) and low melting flow temperatures (Tf) were achieved as the chain lengths of the fatty acyl chlorides were reduced. In particular, a cellulose decanoate with a DS of 1.85 and a Tf of 186 °C was achieved by feeding 3 mol of decanoyl chloride per mole anhydroglucose units of cellulose. However, cellulose stearate (DS = 1.53) synthesized by the same protocols cannot melt even at 250 °C. More interestingly, the fatty acyl chlorides with 10 and 12 carbons resulted in FACE with superior toughness (elongation at break up to 94.4%). In contrast, due to their potential crystallization of the fatty acyl groups with 14-18 carbons, the corresponding FACE showed higher tensile strength and Young's modulus than the others. This study provides some theoretical basis for the mechanochemical synthesis of thermoplastic FACE with designated properties.

Structure-Property Relationships of Short Chain (Mixed) Cellulose Esters Synthesized in a DMSO/TMG/CO2 Switchable Solvent System

Increasing environmental pollution and petroleum resource depletion are important indicators for the necessary and inevitable replacement of fossil-based polymeric materials with more sustainable counterparts. Hence, the development of bio-based materials from renewable resources, such as cellulose, is of great importance. Herein, we introduce a rapid and homogeneous microwave assisted synthesis of high molecular weight (59 kDa ≤ Mn ≤ 116 kDa) short chain (mixed) cellulose esters (CEs) with variable acyl side chain length (2 ≤ C ≤ 8) by using a DMSO/TMG/CO2 switchable solvent system. Accordingly, (mixed) CEs were synthesized by implementing tetramethylguanidine (TMG) into a switchable solvent system (DMSO/TMG/CO2), followed by in-depth structural characterization via IR, 1H NMR, 13C NMR, and SEC. Examination of the structure-property relationships revealed a decrease in the glass transition temperature (177 °C ≤ Tg ≤ 204 °C), an increase in surface hydrophobicity, i.e., water contact angle (WCA) (65° ≤ WCA ≤ 98°), and a decrease of Young's modulus (7.51 MPa ≤ E ≤ 13.6 MPa), with longer alkyl side chains.

Hydrophobic carboxymethyl cellulose as a clean-up sorbent in the determination of nitrofuran metabolites in animal-fat samples

Hydrophobic carboxymethyl cellulose (CMC) biopolymers were fabricated for the removal of fat from food sample matrices. The hydrophobic CMCs were synthesised via the esterification of CMC with three alcohols with carbon chains of different lengths, methanol, butanol, and octadecanol, in the presence of sulfuric acid. The structure of the three synthesised hydrophobic CMCs was verified using FT-IR, and the physicochemical properties were investigated by TGA, SEM, and X-ray. Characterization confirmed the successful synthesis of the hydrophobic CMCs and that the hydrophobic groups are embedded in the sorbent biopolymer to interact with fat and reduce the fat content of the sample extract. Moreover, the performance of the fabricated hydrophobic CMCs was studied in two applications: fat removal and the determination of nitrofuran (NF) metabolites in fat samples. In the first application, excellent results were observed for fat removal; the highest percentage of fat removed from food sample extracts was 94.2% and the lowest was 88.5%. Successful results were also observed in the determination of NF metabolites in fat samples, as the final extract was clear and pure using the hydrophobic CMCs, while it was turbid for the control sample. In addition, the recovery of four NF metabolites was in the range of 97-117%. In general, the hydrophobic CMCs showed promising and satisfactory results, with CMC-C18 exhibiting the best results. The NF detection method was validated using CMC-C18 in three spiking levels; 0.5, 1.0 and 1.5 μg kg-1. The average recoveries of NF range between 83.3 to 104.3%, and the intra-day precision was determined by coefficient of variation, which was below 10% for all NF. The limit of detection and limit of quantification were between 0.6 to 0.9 and 0.20 to 0.28 μg kg-1 respectively. For linearity, the correlation coefficient (r2) was higher than 0.99 for NF metabolites. Overall, the hydrophobic CMCs can be further developed and safely used as green sorbents in food analysis applications.

Effect of cellulose materials on the mechanochemical-assisted reaction system with oleic acid

As the most abundant natural polymer in nature, cellulose has become the promising alternative raw material to replace fossil-based polymer. Owing to the presence of innumerable hydroxyl groups, various approaches are employed to render processability of cellulose. Herein, a sustainable esterification strategy, mechanochemical-assisted esterification, was developed to produce cellulose oleate (CO) with only a small amount of solvent. The differences in reactivity between all types of cellulose were elucidated. According to thermal stability analysis, the degradation temperature decreased after modification due to the substitution of the long oleoyl group. High degree of substitution (DS) of CO also possessed glass transition temperature (Tg) based on differential scanning calorimetry (DSC) analysis. Herewith, the processability of cellulose was introduced after modification. In this study, bamboo waste cellulose nanofiber oleate (BW CNF-OA) showed the highest DS (2.28) among the COs. Its higher surface reactivity due to the high surface aspect ratio led to a higher quantity of fatty acids attached to the cellulose. For the mechanical properties, low DS of COs exhibited higher tensile strength values. In a nutshell, this greener approach is more favorable than conventional chemical esterification in terms of reduced solvent dosage and improved sustainability.

Synthesis and mechanical performance of thermoformable cellulose fatty acid esters using natural soap

A cellulose fatty acid ester consisting solely of natural organic compounds is synthesized by heterogeneous esterification. Solid soap, a natural product-based compound, is used as a mixed fatty acid source. The synthesized cellulose ester can be readily processed into a semi-transparent film. Mechanical properties of the cellulose ester are also investigated.

Reductive Amination of Dialdehyde Cellulose: Access to Renewable Thermoplastics

The reductive amination of dialdehyde cellulose (DAC) with 2-picoline borane was investigated for its applicability in the generation of bioderived thermoplastics. Five primary amines, both aliphatic and aromatic, were introduced to the cellulose backbone. The influences of the side chains on the course of the reaction were examined by various analytical techniques with microcrystalline cellulose as a model compound. The obtained insights were transferred to a 39%-oxidized softwood kraft pulp to study the thermal properties of thereby generated high-molecular-weight thermoplastics. The number-average molecular weights (M_n) of the diamine celluloses, ranging from 60 to 82 kD, were investigated by gel permeation chromatography. The diamine celluloses exhibited glass transition temperatures (T_g) from 71 to 112 °C and were stable at high temperatures. Diamine cellulose generated from aniline and DAC showed the highest conversion, the highest T_g (112 °C), and a narrow molecular weight distribution (D̵ of 1.30).

Esterification of Cellulose with Long Fatty Acid Chain through Mechanochemical Method

Mechanochemical reaction, a green synthetic esterification route was utilized to prepare long-chain cellulose esters from microcrystalline cellulose. The influence of reaction conditions such as reaction temperature and time were elucidated. Only low dosage of oleic acid, 1-butyl-3-metylimidazolium acetate, and p-toluenesulfonyl chloride were required. The success of modification reaction was confirmed by Fourier transforms infrared spectroscopy as a new absorbance peak at 1731 cm⁻¹ was observed, which indicated the formation of carbonyl group (C=O). Solid-state nuclear magnetic resonance was also performed to determine the structural property and degree of substitution (DS) of the cellulose oleate. Based on the results, increasing reaction temperature and reaction time promoted the esterification reaction and DS. DS values of cellulose oleates slightly decreased after 12 h reaction time. Besides, X-ray diffraction analysis showed the broadening of the diffraction peaks and thermal stability decreased after esterification. Hence, the findings suggested that grafting of oleic acid’s aliphatic chain onto the cellulose backbone lowered the crystallinity and thermal stability.

Sustainable Fatty Acid Modification of Cellulose in a CO2-Based Switchable Solvent and Subsequent Thiol-Ene Modification

Searching for more sustainable materials as an alternative to petroleum-based products is of increasing interest due to different environmental issues. Cellulose and fatty acids are two very promising candidates for biobased material design. Herein, we report a sustainable synthesis of fatty acid cellulose esters (FACEs) via transesterification of cellulose with methyl-10-undecenoate in a CO₂-based switchable solvent system. FACEs with a degree of substitution between 0.70 and 1.97 were synthesized by simple variation of reaction parameters and characterized in detail. Subsequently, a FACE with a degree of substitution (DS) of 0.70 was modified via thiol-ene reaction, demonstrating an efficient and versatile method to tune the structure and properties of the new cellulose derivatives. Films were produced from each sample via solvent casting, and their mechanical properties were examined using tensile tests. Elastic moduli (E) ranging from 90 to 635 MPa and elongations at break between 2 and 23% were observed, depending on the DS of the FACE and the type of thiol employed for the modification. Finally, contact angle measurements confirmed an increase in the surface hydrophobicity (75-91°) for the thiol-ene-modified samples.

Dual Activity of Grubbs-Type Catalyst in the Transvinylation of Carboxylic Acids and Ring-Closing Metathesis Reactions

The development of a multifunctional catalyst, which mimics the promiscuity of enzymes, that would catalyze more than one chemical transformation in a single reaction vessel is one of the key points of modern sustainable chemistry. The results of our experiments indicated that Grubbs-type catalysts possess such multitask activity, catalyzing the transvinylation reaction of carboxylic acids without losing their original metathetic activity. This new activity of Grubbs catalysts was evidenced on several examples. It allows us to design a transvinylation/ring-closing metathesis (RCM) cascade reaction leading to the formation of endocyclic enol lactones from unsaturated carboxylic acids in an one-pot procedure. This unique ability of Grubbs catalyst to catalyze multiple mechanically distinct cascade reactions in a chemoselective way offers the new possibility for the synthesis of complex compounds from simple, easily accessible substrates.

Evaluation of esterification routes for long chain cellulose esters

Long chain cellulose esters are internally plasticized bio-based materials, which have good future potential in several applications such as coatings, films and plastics. The long chain cellulose esters with different side chain lengths were synthesized using different esterification methods. When homogeneous esterification was used, the acyl chloride method was the most effective esterification method and cellulose esters prepared using this method have the highest degree of substitution values (DS). In this case, the long chain cellulose esters showed DS values from 0.3 to 1.3 depending on the side chain length of cellulose esters. CDI activation, vinyl transesterification and anhydride routes resulted in somewhat lower DS values. The cellulose was also pretreated with ozone, which decreased cellulose molar mass, and resulted in synthesized cellulose esters having higher DS and better reaction efficiency than untreated cellulose. When heterogeneous esterifications were used, only acyl chloride method seemed to work.

Preparation and Properties of Jute Fiber Long-Chain Fatty Acid Esters in Supercritical Carbon Dioxide

A two-step method involving continuous screw-extrusion steam explosion (CSESE) pretreatment and esterification in supercritical carbon dioxide (scCO₂) is used to prepare long-chain fatty acid-modified jute fiber. The weight gain percentage (WG %) of CSESE-pretreated jute laurate (JL) was 110.7% when esterification was carried out in scCO₂ at 14 MPa and 100 °C for 2 h. The corresponding WG % was 105.5% when esterification was instead carried out in pyridine at 100 °C for 2 h. Scanning electron microscopy and X-ray diffraction indicated that CSESE pretreatment enhanced the reactivity of jute fiber, with esterification in scCO₂ simultaneously occurring on the fibers surface and internal walls. The glass transition temperature of esterified jute was approximately 119 °C, indicating that it could be hot processed over a wide temperature range. The esterified jute had an oil absorption ratio of 17.01 g/g, so it can be used as an oil absorption material.

Fatty Acid-Based Radically Polymerizable Monomers: From Novel Poly(meth)acrylates to Cutting-Edge Properties

The increasing price of barrels of oil, global warming, and other environmental problems favor the use of renewable resources to replace the petroleum-based polymers used in various applications. Recently, fatty acids (FAs) and their derivatives have appeared among the most promising candidates to afford novel and innovative bio-based (co)polymers because of their ready availability, their low toxicity, and their high versatility. However, the current literature mostly focused on FA-based polymers prepared by condensation polymerization or oxypolymerization, while only a few works have been devoted to radical polymerization due to the low reactivity of FAs through radical process. Thus, the aim of this Review is to give an overview of (i) the most common synthetic pathways reported in the literature to provide suitable monomers from FAs and their derivatives for radical polymerization, (ii) the available radical processes to afford FA-based (co)polymers, and (iii) the different applications in which FA-based (co)polymers have been used since the past few years.

Effects of Fatty Acid Anhydride on the Structure and Thermal Properties of Cellulose-g-Polyoxyethylene (2) Hexadecyl Ether

Cellulose was premodified by short-chain fatty acid anhydrides, such as acetic anhydride (CA), propionic anhydride (CP), and butyric anhydride (CB), followed by grafting of polyoxyethylene (2) hexadecyl ether (E₂C₁₆) using toluene-2,4-diisocyanate as a coupling agent. The feeding molar ratio of E₂C₁₆ and the anhydroglucose unit (AGU) was fixed at 4:1, and then a series of CA-g-E₂C₁₆, CP-g-E₂C₁₆, and CB-g-E₂C₁₆ copolymers were successfully prepared. The structures and properties of the copolymers were characterized using FTIR (fourier transform infrared spectra), ¹H-NMR (Proton nuclear magnetic resonance), DSC (Differential scanning calorimeter), POM (polarized light microscopy), TGA (thermogravimetric analysis) and WAXD (wide-angle X-ray diffraction). It was shown that with the anhydride/AGU ratio increasing, the degree of substitution (DS) value of E₂C₁₆ showed a trend of up first and then down. With the carbon chain length increasing, the DS value of E₂C₁₆ continuously increases. The phase transition temperature and thermal enthalpy of the copolymers increased with an increasing DS value of E₂C₁₆. When the ratio of CB/AGU was 1.5:1, the DS of E₂C₁₆ was up to the maximum value of 1.02, and the corresponding melting enthalpy and crystallization enthalpy were 32 J/g and 30 J/g, respectively. The copolymers showed solid–solid phase change behavior. The heat resistant temperature of cellulose-based solid–solid phase change materials was always higher than 270 °C. After the grafting reaction, the crystallinity of E₂C₁₆ decreased, while the crystal type was still hexagonal.

Thermal and mechanical properties of tailor-made unbranched α-1,3-glucan esters with various carboxylic acid chain length

The convenient and environmentally friendly method for in vitro polymerization catalyzed by glucosyltransferase, designated as GtfJ, extracted from recombinant E. Coli was used to synthesize tailor-made α-1,3-glucan (α-1,3-d-glucan) having moderate molecular weight (M_w=2.0×10⁵) and no branches. With the aim to improve thermoplasticity of this polysaccharide, after in vitro synthesis, chemical modification by acylation was selected and then fully substituted α-1,3-glucan esters were successfully obtained via both homogeneous and heterogeneous methods. Thermal degradation temperature of α-1,3-glucan esters was improved after esterification and dependent on neither side chain length nor synthesis methods. DSC curves suggested a presence of crystal structure in α-1,3-glucan acetate, propionate, butyrate, valerate and hexanoate due to detectable melting endotherm, whereas octanoate exhibited amorphous behavior. T_m's of α-1,3-glucan esters were relatively high, more than 200°C, in comparison with commercial plastics. The shorter chain length of acid component, the higher T_m and T_g ester products exhibited. In addition, tensile strength of α-1,3-glucan esters decreased in contrast with elongation at break with an increase in alkyl chain length of an acid component. Thus, crystalline and amorphous α-1,3-glucan esters with adjustable thermal and mechanical properties obtained from this research are promising materials for continuing applied researches and contemplating the future application in bio-based thermoplastic materials.