High Intrinsic Viscosity Research Articles

Synthesis, crystallization behavior and mechanical property of biodegradable Poly(butylene succinate-co-2-methyl succinate) copolyesters

In this research, a series of biodegradable poly(butylene succinate-co-2-methyl succinate) (PBSMS) random copolyesters with butylene 2-methyl succinate (BMS) unit content from about 10 to 90 mol% were successfully synthesized. Both the homopolymers poly(butylene succinate) (PBS), poly(butylene 2-methyl succinate) (PBMS), and PBSMS copolyesters showed relatively high intrinsic viscosity values of over 0.8 dL/g. The basic thermal parameters, crystallization behavior, crystal structure, spherulitic morphology and growth rate, and mechanical properties of PBSMS copolyesters were extensively studied and compared with those of PBS. The incorporation of methyl group not only effectively increased the toughness of PBSMS copolyesters but also significantly restrained the crystallizability of these copolyesters, showing that PBSMS copolyesters with the BMS unit content higher than 50 mol% were amorphous. Among these copolyesters, PBSMS30 (BMS unit content = 30 mol%) exhibited the most outstanding mechanical properties, with a Young's modulus of 188.0 ± 19.1 MPa, a tensile strength of 19.1 ± 1.8 MPa, and an elongation at break of 714.5 ± 23.2 %. By randomly introducing methyl as a side group into the PBS main chain, the mechanical properties of PBSMS copolyesters have been significantly improved. From the perspective of structure and properties, this study should be interesting and crucial for the development and research of biodegradable polymers.

Chemical upcycling of poly(ethylene terephthalate) with binary mixed alcohols toward value-added copolyester by depolymerization and repolymerization strategy

The glycolysis is one of the most promising chemical ways for the disposal of waste Poly(ethylene terephthalate) (PET) due to the relative mild conditions. However, several serious issues still remain to be solved, including complex monomer purification, elusive product components, and ambiguous depolymerized mechanism. Herein, the depolymerization-repolymerization strategy of PET with ethylene glycol (EG)/cyclohexane-1,4-dimethanol (CHDM) binary mixed alcohols was proposed to prepare the value-added Poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG/PCTG). Based on the one-pot depolymerization-repolymerization process, a series of amorphous PETG/PCTG with high molecular weight (Mn > 25,000 g/mol) and glass transition temperature can be prepared. The controlled depolymerization of PET into oligomers with higher molecular weight is of great importance to obtain high molecular weight PETG copolyesters according to the hierarchical process. The depolymerization mechanism of PET with mixed EG/CHDM was deeply elucidated, in which EG depolymerizes PET chains into the short ones, and CHDM undergoes transesterification with ester group on the end group of BHET monomers and oligomers with different molecular weight to substitute the ethylene glycol terephthalate (ET) units into 1,4-cyclohexanedimethanol terephthalate (CT) units. For post-consumer PET, the depolymerization-repolymerization of colorless PET bottle can form the rPETG with higher intrinsic viscosity, molecular weight, and thermal properties, superior to the PET film and colored bottles. The information in this work is of great importance for the upcycling of PET waste.

A green and cost-effective zinc-biphenol hybrid flow battery with eutectic electrolyte

Eutectic electrolytes have been widely used in redox flow batteries (RFBs) due to their unique features such as abundant availability, biodegradability, and low cost, as well as their excellent dissolution ability for redox-active substances. Despite these advantages, eutectic electrolytes still have some limitations in important aspects such as reaction kinetics, mass transport and ionic conductivity due to their relatively high intrinsic viscosity. In this work, we explore a green and cost-effective zinc-based eutectic electrolyte containing small molecules additives, which not only has elevated ionic conductivity, but also can dissolve organic cathode materials 3,3′,5,5′-tetramethylaminemethylene-4,4′-biphenol (TABP) at high concentrations. In this zinc-based eutectic electrolyte, TABP exhibits a highly positive redox potential (1.50 V versus Zn/Zn2+), quasi-reversible redox reaction kinetics and good redox stability. When operated in a practical hybrid flow battery, the Zn-TABP cell based on this eutectic electrolyte exhibits excellent rate performance, high capacity utilization, and low capacity decay rate (0.119 % per cycle). Post-analysis for the TABP catholyte suggests that the Michael side reaction rate of TABP in electrochemical cycling appears to depend upon its concentration.

Extraction, characterization and concentration regimes of the natural gum from Triumfetta cordifolia stem bark

Gum extracted from the Triumfetta. cordifolia plant is traditionally used for its impressive and versatile properties, but many of its intrinsic characteristics still remain poorly documented. This article presents the extraction, purification and physicochemical characterization of the gum present in the stem bark of the plant on the one hand, and the delineation of its concentration regimes in solution on the other. To this end, fresh stem bark was collected and cold extracted in distilled water, followed by ethanol precipitation. The gum was then characterized by elemental analysis, ICP-AES, FT-IR, ATG and GC-FID. Finally, the intrinsic viscosity was determined and concentration regimes delineated using both capillary viscometry and rheometry. Results revealed a monosaccharide composition rich in uronic acids, making T. cordifolia gum a polyelectrolyte, with a high mineral charge, and physicochemical properties similar to those of other polyelectrolyte gums. T. cordifolia gum solutions showed a relatively high intrinsic viscosity (24.3 ± 2.3 dL g−1) and exhibited three distinct concentration regimes (namely dilute, semi-dilute and concentrated) separated by two critical concentrations (C* = 0.3 g L−1 and C** = 1.4 g L−1). These properties open up new prospects for the use of T. cordifolia gum as a texturizing and structuring agent for a variety of mixtures and complex preparations such as emulsions.

Bacterial capsular polysaccharides with antibiofilm activity share common biophysical and electrokinetic properties

Bacterial biofilms are surface-attached communities that are difficult to eradicate due to a high tolerance to antimicrobial agents. The use of non-biocidal surface-active compounds to prevent the initial adhesion and aggregation of bacterial pathogens is a promising alternative to antibiotic treatments and several antibiofilm compounds have been identified, including some capsular polysaccharides released by various bacteria. However, the lack of chemical and mechanistic understanding of the activity of these polymers limits their use to control biofilm formation. Here, we screen a collection of 31 purified capsular polysaccharides and first identify seven new compounds with non-biocidal activity against Escherichia coli and/or Staphylococcus aureus biofilms. We measure and theoretically interpret the electrophoretic mobility of a subset of 21 capsular polysaccharides under applied electric field conditions, and we show that active and inactive polysaccharide polymers display distinct electrokinetic properties and that all active macromolecules share high intrinsic viscosity features. Despite the lack of specific molecular motif associated with antibiofilm properties, the use of criteria including high density of electrostatic charges and permeability to fluid flow enables us to identify two additional capsular polysaccharides with broad-spectrum antibiofilm activity. Our study therefore provides insights into key biophysical properties discriminating active from inactive polysaccharides. The characterization of a distinct electrokinetic signature associated with antibiofilm activity opens new perspectives to identify or engineer non-biocidal surface-active macromolecules to control biofilm formation in medical and industrial settings.

Comparative analysis of exopolysaccharide-producing Lactiplantibacillus plantarum with ropy and non-ropy phenotypes on the gel properties and protein conformation of fermented milk

In this study, we evaluated the impact of Lactiplantibacillus plantarum (L. plantarum) with ropy and non-ropy phenotypes on gel structure and protein conformation of fermented milk. Ropy L. plantarum (T1 & CL80) secreted EPS with high molecular weight (1.41 × 106, 1.19 × 106 Da) and intrinsic viscosity (486.46, 316.32 mL/g), effectively enhances fermented milk viscosity and water holding capacity (WHC) (65.4%, 84.6%) by forming a dense gel structure. Non-ropy L. plantarum (CSK & S-1A) fermented milk gel’s high surface hydrophobicity and free sulfhydryl content caused high hardness and low WHC. Raman spectroscopy combined with circular dichroism analysis showed that high levels of α-helix (29.32–30.31%) and random roil (23.06–25.36%) protein structures are the intrinsic factors that contribute to the difference among fermented milk gels of ropy and non-ropy strains. This study provides a basis for understanding the structural variability of fermented milk gels using ropy or non-ropy lactic acid bacteria.

Insight into the purification of algael water by a novel flocculant with enhanced branched nanochitosan structure

For improving inadequate nanostructural stability and promote algal removal efficiency, a novel nanochitosan-grafted flocculant (PAD-g-MNC) with an enhanced branched nanostructure and high molecular weight (MW) was fabricated via maleic anhydride acylation polymerization. Characterization results verified the successful synthesis of the flocculant and the formation of an irregular particle nanostructure. PAD-g-MNC exhibited superior algal and extracellular organic matter (EOM) removal and obtained the turbidity and chlorophyll-a removal rates of 93.46%–95.39% and 95.10%–97.31%, respectively, at the dosage of 4–5 mg L−1. The growth rate, strength factor, and recovery factor of algal flocs flocculated by PAD-g-MNC were 90.36, 0.63, and 0.27 (100 rpm), respectively, and were higher than other flocculants prepared through conventional methods. Results indicated that the high intrinsic viscosity and stability branched nanostructure promoted the formation of stable flocs and regeneration ability of flocs. MW distribution and three-dimensional fluorescence analyses revealed that the special structure of PAD-g-MNC was beneficial to the removal of tryptophan-like proteins in EOM. Strong adsorption–adhesion and bridging–netting effects of the nanostructure chain were the dominated mechanisms in the improvement of flocculation efficiency. This study provided theoretical and experimental guidance for the design of flocculants with superior performance and efficient algal water purification performance.

Sulfur polymerization strategy based on the intrinsic properties of polymers for advanced binder‐free and high‐sulfur‐content Li–S batteries

AbstractLithium–sulfur (Li–S) batteries are the promising next‐generation secondary energy storage systems, because of their advantages of high energy density and environmental friendliness. Among numerous cathode materials, organosulfur polymer materials have received extensive attentions because of their controllable structure and uniform sulfur distribution. However, the sulfur content of most organosulfur polymer cathodes is limited (S content <60%) due to the addition of large amounts of conductive agents and binders, which adversely affects the energy density of Li–S batteries. Herein, a hyperbranched sulfur‐rich polymer based on modified polyethyleneimine (Ath‐PEI) named carbon nanotube‐entangled poly (allyl‐terminated hyperbranched ethyleneimine‐random‐sulfur) (CNT/Ath‐PEI@S) was prepared by sulfur polymerization and used as a Li–S battery cathode. The high intrinsic viscosity of Ath‐PEI provided considerable adhesion and avoided the addition of PVDF binder, thereby increasing the sulfur content of cathodes to 75%. Moreover, considering the uniform distribution of elemental sulfur by the polymer, the utilization of sulfur was successfully improved, thus improving the rate capability and discharge capacity of the battery. The binder‐free, sulfur‐rich polymer cathode exhibited ultra‐high initial discharge capacity (1520.7 mAh g−1 at 0.1 C), and high rate capability (804 mAh g−1 at 2.0 C). And cell‐level calculations show that the electrode exhibits an initial capacity of 942.3 mAh g−1electrode, which is much higher than those of conventional sulfur‐polymer electrodes reported in the literature.

Synthetic and biopolymers for lake restoration – An evaluation of flocculation mechanism and dewatering performance

In the frame of the global phosphorus (P) crisis and ongoing eutrophication issues in the environmental sector, lake sediment can be considered as an alternative P source after its removal from eutrophic lakes. However, high water contents make sediment dewatering a crucial step towards the efficient reusability of remaining solids. The application of polymeric substances facilitates solid-liquid separation by flocculation of suspended particles. To lower the environmental risk of contamination with toxic, non-biodegradable monomeric residues during and after the application of synthetic polyacrylamide(PAM)-based polymers, switching to natural polymeric substances (biopolymers), e.g., starch- or chitosan-based, is increasingly emphasized. The dewatering performance of four conventional PAM-based polymers was compared to two starch- and one chitosan-based biopolymer. Laboratory experiments were conducted to determine the dewatering rate, floc size and strength, and reject water quality. Biopolymers generally caused the formation of smaller but less shear-sensitive flocs, and lower P levels in the reject water compared to synthetic polymers. Dewatering performance was correlated to the most important functioning influencing polymer-specific properties intrinsic viscosity (polymer extension) and surface charge density (CD). Due to the high CD and low intrinsic viscosity of the biopolymers, electrostatic patch flocculation seems to be the favored flocculation mechanism, while for synthetic polymers bridging seems to be dominating. Solid-liquid separation technologies should be adjusted to the resulting floc size and structure, while surface CD and intrinsic viscosity are important properties for the choice of biopolymer. Overall, biopolymers can function as a more environmentally friendly alternative to synthetic products for lake sediment dewatering accompanied by the potential for P recovery.

Synthesis, thermal, and mechanical properties of fully biobased poly(hexamethylene 2,5-furandicarboxylate-co-diglycolate) copolyesters

In this research, a series of fully biobased poly(hexamethylene 2,5-furandicarboxylate-co-diglycolate) (PHFDG) copolyesters with hexamethylene diglycolate (HDG) unit contents from about 10 to 90 mol% were successfully synthesized through a two-stage melt polycondensation method. The basic thermal parameters, crystal structure, crystallization behavior, melting behavior, mechanical property, and hydrophobicity or hydrophilicity of the PHFDG copolymers were extensively studied and compared with those of the parent homopolymers poly(hexamethylene 2,5-furandicarboxylate) (PHF) and poly(hexamethylene diglycolate) (PHDG). Both the homopolymers and the copolyesters had relatively high intrinsic viscosity values. The physical properties of PHFDG copolymers displayed an obvious HDG unit content dependence. When the HDG unit content was not higher than 30 mol%, the copolymers showed a high melting temperature of about 116 °C and above. Depending on the HDG unit content, the copolymers displayed different crystal structures as that of PHF or that of PHDG. PHFDG copolymers displayed excellent mechanical properties. For instance, PHFDG20 (HDG unit content = 20 mol%) showed a Young's modulus of 500.9 ± 29.8 MPa, a tensile strength of 34.6 ± 2.3 MPa, and an elongation at break of 403.3 ± 10.5%. The hydrophilicity of PHFDG copolymers obviously increased with increasing the HDG unit due to the presence of ether oxygen. In sum, the PHFDG copolymers with low HDG unit content of 30 mol% and below may show comparable or even better thermal and properties than those of commercial biodegradable polymers, such as poly(butylene succinate) and poly(butylene adipate-co-terephthalate) and may thus find similar final end uses in the packaging materials field due to both the good thermal, mechanical, and barrier properties and the enhanced hydrophilicity.

Efficient Synthesis of Itaconate Polyesters with Amine-Triggered Rapid Degradation and Outstanding Mechanical Properties: An Experimental and Theoretical Study on Degradation Mechanisms

A range of degradable polyesters have been developed as sustainable alternatives for commercial plastics; however, limitations of composting facilities and uncontrolled degradation in the environment hindered their viability. In this study, biobased itaconic acid was selected as an active site to control the degradation of polyesters. A series of PBXI copolyesters with Mw’s ranging from 4.86 to 8.31 × 104 g/mol and high intrinsic viscosities of more than 1.15 dL/g were successfully synthesized without any cross-linking by selecting appropriate reaction conditions, including condensation temperature and vacuum, effective inhibitor, and catalyst. The obtained copolyesters were semicrystalline, and their Tm’s could be regulated from 42.5 to 179.5 °C. They exhibited outstanding elastic modulus (120–598 MPa) and tensile strength (17.9–51.4 MPa) among degradable polymers. Degradation experiments demonstrated that the incorporation of itaconate segments could facilitate both the hydrolysis and enzymatic degradation of polyesters. The state-of-the-art computation and analysis via molecular dynamics (MD) simulations of PBXI–CALB complexes elucidated the enzymatic degradation mechanism. Experimental results proved that, at room temperature, the degradation could be stimulated and regulated by amines without a catalyst and the Mn’s of lactamization products rapidly decreased to less than 5000 g/mol within 24 h. Moreover, the copolymerized structure of copolyesters and solvent factors could influence the aza-Michael addition between amines and itaconate units. This work provides a strategy to synthesize biodegradable copolymers with the potential to undergo controlled and rapid in vivo degradation with outstanding mechanical properties.

Biodegradable Poly(butylene succinate) Copolyesters Modified by Bioresoured 2,5-Tetrahydrofurandimethanol

The problems of fossil-based resources and pollution caused by traditional nondegradable polymers have led to the need for biobased monomers and polyesters, presenting more environmentally friendly features. 2,5-Tetrahydrofurandimethanol (THFDM), a biobased monomer containing an aliphatic ring structure and an ether group, was introduced into the molecular chain of polybutylene succinate (PBS) as a sustainable unit to optimize its performance and improve its sustainability. The poly(butylene-co-tetrahydrofurandimethylene succinate) (PBTS) copolyesters were synthesized using a melt polycondensation method. The copolyesters exhibited relatively high intrinsic viscosity (1.03–1.71 dL/g). The Tg values of PBTS copolyesters increased significantly along with the introduction of THFDM (from −32.2 to −12.9 °C). According to the investigation using WAXD (wide-angle X-ray diffraction) analysis and successive self-nucleating annealing (SSA) measurement, it was revealed that the introduction of THFDM reduced the crystallization ability of PBTS while increasing its crystal content with relatively low lamella thickness. This phenomenon was mainly attributed to the aliphatic rings, which limited the movement and regular stacking of the molecular chains. The degradation rate and toughness of the copolyesters improved due to the decrease of crystallization degree. Meanwhile, the gas barrier property of PBTS slightly decreased but remained at a relatively high level. The permeabilities of O2 and CO2 were lower than that of commercially available PBAT. In summary, the introduction of THFDM not only improved the biobased resources content and the sustainability of copolyesters but also improved the toughness and degradation performance without sacrificing gas barrier performance.

Dynamics of methane hydrate particles in water-dominant systems during transient flow

Natural gas hydrates are expected to be a new energy resource due to their diverse geographic distribution with huge potential for energy recovery. Test production systems for these resources typically consist of separate gas and water production lines. While this should limit the possibility of re-association during transit, the water lines may suffer from gas breakthrough. Hydrate formation and agglomeration in these water-dominant conditions is not well understood, but may lead to bedding, and, ultimately, plug formation. In this work, we interrogate the dynamics of agglomerating methane hydrate particles experiencing a change in flow conditions using a flowloop instrumented with an in-line video camera under two sets of conditions: i) a sudden stop; and ii) a stepwise decrease in the flow velocity. Particle size distributions were observed using the camera, where the size, number, andrateof particle transition were all explored. The particle size was sensitive to flow velocity, where changing shear conditions led to a new size distribution being established within seconds. This indicates that hydrate agglomeration takes place rapidly, which is an important insight for transient simulations. An associated change in slurry rheological properties was observed, where large, agglomerated particles were typically rough and irregular, suggesting a high intrinsic viscosity. Finally, a conceptual model for hydrate blockage formation in water-dominant systems was developed, offering a new microscopic view of hydrate particles and their agglomeration that incorporates the roles of particles spanning different size categories. This will be of particular use not only in evaluating the risks of re-association in production lines for hydrate reservoirs, but in understanding the dynamics associated with potential hydrate formation in CO2sequestration applications.

Immunoglobulin M Monoclonal Gammopathies of Clinical Significance.

Immunoglobulin M monoclonal gammopathy of undetermined significance (MGUS) comprises 15-20% of all cases of MGUS. IgM MGUS is distinct from other forms of MGUS in that the typical primary progression events include Waldenstrom macroglobulinaemia and light chain amyloidosis. Owing to its large pentameric structure, IgM molecules have high intrinsic viscosity and precipitate more readily than other immunoglobulin subtypes. They are also more commonly associated with autoimmune phenomena, resulting in unique clinical manifestations. Organ damage attributable to the paraprotein, not fulfilling criteria for a lymphoid or plasma cell malignancy has recently been termed monoclonal gammopathy of clinical significance (MGCS) and encompasses an important family of disorders for which diagnostic and treatment algorithms are evolving. IgM related MGCS include unique entities such as cold haemagglutinin disease, IgM related neuropathies, renal manifestations and Schnitzler’s syndrome. The diagnostic approach to, and management of these disorders differs significantly from other categories of MGCS. We describe a practical approach to the evaluation of these patients and our approach to their treatment. We will also elaborate on the key unmet needs in IgM MGCS and highlight potential areas for future research.

Preparation, characterization and application of maleic anhydride-modified polylactic acid macromonomer based on direct melt polymerization

A one-pot two-step method based on direct melt polymerization (DMP) for the synthesis of polylactic acid (PLA) macromonomer and its further functionalized application has been developed. The first stage of the reaction is a copolycondensation of lactic acid (LA) and maleic anhydride (MAH) to obtain the macromolecule poly(lactic acid-co-maleic anhydride) (PLAM) with reactive double bonds, and the second stage is a radical copolymerization of different acrylates with PLAM to afford the modified PLA functional materials. The influences of the acrylates have been investigated. The results show that the species with substituted methyl groups in acrylate can polymerize relatively stable. On the other hand, the more carbon atoms in the ester segment of acrylate, the higher intrinsic viscosity [η] and terminal decomposition temperature for the acrylate-modified PLAMs. Among six kinds of acrylates used as the third monomer, such as acrylic acid (AA), methyl acrylate (MA), butyl acrylate (BA), methacrylic acid (MAA), methyl methacrylate (MMA), and butyl methacrylate (BMA), the BMA-modified PLAM has the biggest [η] (0.7566 dL/g) and the terminal decomposition temperature (418 °C) for there are more carbon atoms in BMA. Due to excellent reactivity of the intermediate PLAM, the final modified product can have the anticipated properties for the PLA material by the controllable regulating as different purposes. Thus, this strategy as a green and simple method provides well application prospect for PLA materials in industrial plastics, biomedicine etc.

Ultrasonic treatment of Dendrobium officinale polysaccharide enhances antioxidant and anti-inflammatory activity in a mouse D-galactose-induced aging model.

Utilization of the biological macromolecule Dendrobium officinale polysaccharide (DOP) as a functional ingredient is limited by its high intrinsic viscosity and molecular weight. The goal of the present study was to improve rheological properties of DOP by ultrasonic treatment. Such a treatment resulted in the degradation of DOP and consequent reduction of rheological properties. Among DOP samples treated with ultrasonication at low (L), medium (M), and high (H) power intensities (25, 50, 75 w/cm2), M‐DOP displayed the highest reactive oxygen species (ROS) and reactive nitrogen species (RNS) radical scavenging activity in vitro. In a mouse D‐galactose (D‐Gal)‐induced aging model, M‐DOP significantly increased activities of antioxidant enzymes and reduced levels of pro‐inflammatory cytokines in liver. Real‐time polymerase chain reaction (RT‐PCR) analysis indicated that M‐DOP upregulated messenger RNA (mRNA) expression of anti‐inflammatory/antioxidant proteins such as Nrf2 (nuclear factor erythroid 2‐related factor), hemeoxygenase‐1 (HO‐1), and NAD(P)H:quinone oxidoreductase (NQO1) in liver. In summary, M‐DOP displayed a strong radical scavenging activity in vitro, and ameliorated liver injury in the mouse aging model through the promotion of Nrf2/HO‐1/NQO1 signaling pathway.

Renewable Furfural-Based Polyesters Bearing Sulfur-Bridged Difuran Moieties with High Oxygen Barrier Properties

With the goal of achieving high barrier with bio-based materials, for example, for packaging applications, a series of novel furfural-based polyesters bearing sulfide-bridged difuran dicarboxylic acid units with high oxygen barrier properties were synthesized and characterized. For the novel poly(alkylene sulfanediyldifuranoate)s, a 11.2–1.9× higher barrier improvement factor compared to amorphous poly(ethylene terephthalate) was observed which places the novel polyesters in the top class among previously reported 2,5-furandicarboxylic acid (FDCA) and 2,2′-bifuran-based polyesters. Titanium-catalyzed polycondensation reactions between the novel synthesized monomer, dimethyl 5,5′-sulfanediyldi(furan-2-carboxylate), and four different diols, ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, afforded difuran polyesters with high intrinsic viscosities (0.76–0.90 dL/g). These polyesters had good thermal stability, decomposing at 342–363 and 328–570 °C under nitrogen and air, respectively, which allowed processing them into free-standing films via melt-pressing. In tensile testing of the film specimens, tensile moduli in the range of 0.4–2.6 GPa were recorded, with higher values observed for the polyesters with shorter diol units. Interestingly, besides the low oxygen permeability, the renewable sulfide-bridged furan monomer also endowed the polyesters with slight UV shielding effect, with cutoff wavelengths of ca. 350 nm, in contrast to FDCA-based polyesters, which lack significant UV light absorption at over 300 nm.

Ethylene glycol-soluble Ti/Mg-citrate complex catalyst for synthesis of high intrinsic viscosity poly(ethylene terephthalate)

Antimony-free poly(ethylene terephthalate) (PET) has been synthesized through polycondensation of p-phthalic acid and ethylene glycol, and then subjected to a viscosity-increasing process by liquid-state polycondensation (LSP). For both of these processes, a novel environmentally benign ethylene glycol-soluble Ti/Mg bimetal (TM) catalyst has been used. The structure of the TM catalyst has been comprehensively characterized and its catalytic activity in the polycondensation reaction has been evaluated and compared with those of other titanium-based catalysts. The results reveal that the TM catalyst is a chelated complex with high catalytic activity for polycondensation to afford PET without significant side reactions. Indeed, the LSP process catalyzed by TM affords a PET product with high intrinsic viscosity suitable for industrial yarn production (1.08 dL/g) within 60 min, and that exhibits higher thermostability with increasing intrinsic viscosity. Finally, the kinetics of the TM-catalyzed polycondensation has been probed based on the variation of intrinsic viscosity with increasing polycondensation time.

Effect of Extraction Procedures with Ultrasound and Cellulolytic Enzymes on the Structural and Functional Properties of Citrus grandis Osbeck Seed Mucilage.

The structural and functional properties of Citrus grandis Osbeck (CGO) seed mucilage by different extraction practices, including conventional citrate buffer, ultrasonic-assisted (UAE), enzymatic-assisted extraction (EAE) with cellulase or Celluclast® 1.5 L and various ultrasonic-assisted enzymatic extraction (UAEE) procedures were investigated. It was found that CGO seed from agricultural and processing byproducts is an excellent new source of high methoxyl pectin with quite high intrinsic viscosity (about 108.64 dL/g) and molecular weight (about 1.9 × 106) as compared with other pectin sources. UAEE with Celluclast® 1.5 L enhanced the extraction yield most pronouncedly (about 2.3 times). Moreover, the monosaccharide composition of CGO seed mucilage is least affected by EAE with Celluclast® 1.5 L. In contrast, EAE with cellulase dramatically reduces the galacturonic acid (GalA) content to less than 60 molar%, and increases the glucose (Glc) content pronouncedly (to about 40 molar%), which may be considered as an adverse effect in terms of pectin purity. Though extraction procedures involved with ultrasound and cellulolytic enzymes generally show a decrease in GalA contents, weight average molar mass and intrinsic viscosity, EAE with Celluclast® 1.5 L is least affected, followed by UAE and UAEE with Celluclast® 1.5 L. These features can be leveraged in favor of diversified applications.

Effect of the chemical and structural characteristics of pulps of Eucalyptus and Pinus on the deconstruction of the cell wall during the production of cellulose nanofibrils

The species Eucalyptus globulus, Eucalyptus nitens and Pinus radiata, are important supplies for the production of cellulose pulp in the world market, which can be used for the production of cellulose nanofibrils (CNFs). Understanding how the characteristics of different raw materials affect the production and final properties of nanofibrillated celluloses is very useful, both for the pulp industry and for the end user. The aim of this research was to determine how the chemical and structural differences of the commercial Kraft pulps of E. globulus, E. nitens and P. radiata affect the production and the morphological and rheological characteristics of the CNFs produced through an enzymatic-mechanical process. On one hand, the results showed that pine fibers were easier to deconstruct than eucalyptus fibers, however, pine CNFs were found to have the largest fibril width and a lower aspect ratio (length /width). On the other hand, the pulp of E. globulus, was the one that obtained a better aspect ratio and higher intrinsic viscosity.