NMR Analyses and Statistical Modeling of Biobased Polymer Microstructures-A Selected Review

NMR analysis combined with statistical modeling offers a useful approach to investigate the microstructures of polymers. This article provides a selective review of the developments in both the NMR analysis of biobased polymers and the statistical models that can be used to characterize these materials. The information obtained from NMR and statistical models can provide insights into the microstructure and stereochemistry of appropriate biobased polymers and establish a systematic approach to their analysis. In suitable cases, the analysis can help optimize the synthetic procedures and facilitate the development of new or modified polymeric materials for various applications. Examples are given of the studies of poly(hydroxyalkanoates), poly(lactic acid), and selected polysaccharides, e.g., alginate, pectin, and chitosan. This article may serve as both a reference and a guide for future workers interested in the NMR sequence analysis of biobased materials.

Bilayer Films of Poly(lactic acid) and Cottonseed Protein for Packaging Applications

Poly(lactic acid) (PLA) is a common biobased film-former made from renewable biomass, such as polysaccharides from sugarcane, corn, or cassava. It has good physical properties but is relatively expensive when compared to the plastics used for food packaging. In this work, bilayer films were designed, incorporating a PLA layer and a layer of washed cottonseed meal (CSM), an inexpensive agro-based raw material from cotton manufacturing, where the main component is cottonseed protein. These bilayer films were made through the solvent casting method. The combined thickness of the PLA/CSM bilayer film was between 47 and 83 μm. The thickness of the PLA layer in this film was 10%, 30%, or 50% of the total bilayer film’s thickness. Mechanical properties of the films, opacity, water vapor permeation, and thermal properties were evaluated. Since PLA and CSM are both agro-based, sustainable, and biodegradable, the bilayer film may be used as an eco-friendlier food packaging material, which helps reduce the environmental problems of plastic waste and microplastics. Moreover, the utilization of cottonseed meal may add value to this cotton byproduct and provide a potential economic benefit to cotton farmers.

Methods of Microencapsulation of Vegetable Oils: Principles, Stability and Applications - A Minireview

In addition to being used in food, fuel and lubricants, vegetable oils are promising in many other applications such as food additives, nutritional supplements, cosmetics and biomedicine; however, their low oxidative stability can limit their use. Microencapsulation is a well-established method for the preservation of oil against degradation, controlled release of active ingredients, protection against external factors during storage, and enhanced durability. In this article, microencapsulation methods for vegetable oil are reviewed, including physical methods (spray-drying and freeze-drying), physicochemical methods (complex coacervation, ionic gelation and electrostatic layer-by-layer deposition), and chemical methods (interfacial/in situ polymerization). This article also provides information on the principles, parameters, advantages, disadvantages and applications of these methods.

Effect of Nanocellulose on the Properties of Cottonseed Protein Isolate as a Paper Strength Agent

Currently, there is an increasing interest in the use of biopolymers in industrial applications to replace petroleum-based additives, since they are abundantly available, renewable and sustainable. Cottonseed protein is a biopolymer that, when used as a modifier, has shown improved performance for wood adhesives and paper products. Thus, it would be useful to explore the feasibility of using cellulose nanomaterials to further improve the performance of cottonseed protein as a paper strength agent. This research characterized the performance of cottonseed protein isolate with/without cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs) to increase the dry strength of filter paper. An application of 10% protein solution with CNCs (10:1) or CNFs (50:1) improved the elongation at break, tensile strength and modulus of treated paper products compared to the improved performance of cottonseed protein alone. Further analysis using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) indicated that the cottonseed protein/nanocellulose composites interacted with the filter paper fibers, imparting an increased dry strength.

Surface and Thermal Characterization of Cotton Fibers of Phenotypes Differing in Fiber Length

Cotton is one of the most important and widely grown crops in the world. Understanding the synthesis mechanism of cotton fiber elongation can provide valuable tools to the cotton industry for improving cotton fiber yield and quality at the molecular level. In this work, the surface and thermal characteristics of cotton fiber samples collected from a wild type (WT) and three mutant lines (Li1, Li2-short, Li2-long, Li2-mix, and liy) were comparatively investigated. Microimaging revealed a general similarity trend of WT ≥ Li2-long ≈ Li2-mix > Li1 > Li2 short ≈ liy with Ca detected on the surface of the last two. Attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and thermogravimetric measurements also showed that Li2-short and liy were more similar to each other, and Li2-long and Li2-mix closer to WT while Li1 was quite independent. FT-IR results further demonstrated that wax and amorphous cellulose were co-present in fiber structures during the fiber formation processes. The correlation analysis found that the FT-IR-based maturity parameter was well correlated (p ≤ 0.05) to the onset decomposition temperature and all three weight-loss parameters at onset, peak, and end decomposition stages, suggesting that the maturity degree is a better parameter than crystallinity index (CI) and other FT-IR parameters that reflect the thermal stability of the cotton fiber. In summary, this work demonstrated that genetic mutation altered the surface and thermal characteristics in the same way for Li2-short and liy, but with different mechanisms for the other three mutant cotton fiber samples.

Synthesis and Characterization of Hydrophobically Modified Xylans

Xylan is a major type of hemicellulose that has attracted a lot of research and development activities. It is often derivatized in order to improve its properties. In the literature, hydrophobic modification of polymers is often used to produce surfactant-like materials and associative thickeners. In this work, we have derivatized xylan with alkyl ketene dimer (AKD) and two types of alkenyl succinic anhydrides (ASAs). The xylan-AKD derivatives have been made at 90 °C, using dimethyl sulfoxide as solvent and 4-dimethylaminopyridine as promoter. Samples with degrees of substitution (DS) up to 0.006 have been produced. The xylan-ASA derivatives have been synthesized at 120 °C in dimethyl sulfoxide with DS up to 0.105-0.135. The structures of these products have been confirmed with NMR and FT-IR. These xylan derivatives increase the structural diversity of xylan and provide additional options for people seeking to use hydrophobically modified polysaccharides in their applications.

Changing the Landscape: An Introduction to the Agricultural and Food Chemistry Technical Program at the 258th American Chemical Society National Meeting in San Diego

This special issue of the Journal of Agricultural and Food Chemistry (JAFC) is a highlight of the Agricultural and Food Chemistry Division (AGFD) technical program at the 258th National Meeting of the American Chemical Society (ACS) in San Diego, CA, U.S.A., on August 25-29, 2019. At the conference, AGFD had 44 oral sessions at 19 symposia and 100 poster presentations with more than 400 abstract submissions. The technical program covered a broad range of current research and development topics in agricultural and food chemistry, including bioactive food components, diet and human nutrition, utilization of agricultural materials in food systems, food packaging, nanotechnology, and food safety, as well as several special award symposia. This is the first JAFC special issue that highlights an ACS national meeting program with joint efforts from AGFD.

Pequi oil microencapsulation by complex coacervation using gelatin-cashew gum

New functional foods and beverages can be developed using bioactive compounds present in pequi oil. Complex coacervation is an encapsulation method used for preserving bioactive molecules, especially those that are hydrophobic or sensitive to high temperatures. The objective of this work was to produce and characterize pequi oil microparticles using cashew gum/gelatin matrix (CG/GE) through complex coacervation. Gum Arabic (GA) was also studied in comparison with CG. The coacervation process was performed withoutpequi oil to determine the ideal proportions of the matrix components, followed by the embedding of the oil inthe microparticles for evaluation. Satisfactory microparticles were produced at pH 4.5 in the weight ratios of CG/GE = 2:1 and GA/GE = 1:3. Pequi oil release was greater in acidic pH, especially at pH 2 for the CG/GE matrix. The encapsulation efficiency for CG/GE and GA/GE was 72.53% (±4.80) and 82.77% (±6.09), respectively. The results showed that the CG/GE combination seemed very promising as anencapsulation matrix, especially for food applications involving pH values higher than 3.

Preparation and characterization of carboxymethyl cashew gum grafted with immobilized antibody for potential biosensor application

This report details the design of carboxymethylated cashew gum (CG) as a platform for antibody (Ab) immobilization, which can then be used as a biosensor for bacteria detection. The CG was isolated and characterized, followed by conversion to carboxymethyl cashew gum (CMCG). The CMCG film was a viable support for antibody immobilization; it was electrodeposited on gold surface using the cyclic voltammetry technique, applying a potential sweep from -1.0 V to 1.3 V with a scan rate of 50 mV s^-1 and 10 scans. The COOH groups on the surface of the film were critical in promoting Ab bonding. The immobilization of the Ab was mediated by protein A (PrA) for recognition of the antigen. Voltammetry studies were used to monitor the antibody immobilization. Finally, the analytical response of the CMCG-PrA-Ab system was evaluated with the chronoamperometry technique and was found to detect Salmonella Typhimurium bacteria rapidly and efficiently.

Cellulose nanocrystal driven microphase separated nanocomposites: Enhanced mechanical performance and nanostructured morphology

The interest in the modification of cellulose nanocrystals (CNCs) lies in the potential to homogenously disperse CNCs in hydrophobic polymer matrices and to promote interfacial adhesion. In this work, poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PBA) were grafted onto CNCs, thereby imparting their hydrophobic traits. The successful grafting modification led to the increased thermal stability of modified CNCs (MCNCs), and the hydrophobic surface modification was integrated with crystalline structure and morphology of CNCs. The nanocomposites with 7 wt% MCNCs/PBA-co-PMMA had an increase in Young's modulus of >25-fold and in tensile strength at about 3 times compared to these of neat PBA-co-PMMA copolymer. In addition, a micro-phase separated morphology (PBA soft domains, and PMMA and CNC hard domains) of MCNCs/PBA-co-PMMA nanocomposites was observed. The large increase in the storage moduli (glass transition temperatures) and organized morphology of MCNCs/PBA-co-PMMA nanocomposites also elucidated the relationship between mechanical properties and micro-phase separated morphology. Therefore, the MCNCs are effective reinforcing agents for the PBA-co-PMMA thermoplastic elastomers, opening up opportunities for their wide-spread applications in polymer composites.

NMR Analysis of Poly(Lactic Acid) via Statistical Models

The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. In this work, we prepared several PLA samples with a tin catalyst at different L,L-lactide and D,D-lactide ratios. Upon analysis of the tetrad intensities with the pair-addition Bernoullian model, we found substantial deviations between observed and calculated intensities due to the presence of transesterification and racemization during the polymerization processes. We formulated a two-state (pair-addition Bernoullian and single-addition Bernoullian) model, and it gave a better fit to the observed data. The use of the two-state model provides a quantitative measure of the extent of transesterification and racemization, and potentially yields useful information on the polymerization mechanism.

Surface Characterization of Cottonseed Meal Products by SEM, SEM-EDS, XRD and XPS Analysis

The utilization of cottonseed meal products as valuable industrial materials needs to be exploited. We have recently produced water-washed cottonseed meal, total cottonseed protein, sequentially extracted water- and alkali-soluble proteins, and two residues after the total and sequential protein extractions at a pilot scale. In this work, the surface characteristics of the six cottonseed meal products were examined by scanning electron microscopy (SEM), scanning electron microscopy- energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that the surface properties of the six products differed from those of a commercial soy protein flour examined comparatively in this work. The compact morphology and relative-high N composition were observed in all three protein products, with greater similarity between the total protein and alkali-soluble protein. The surfaces of the two residue products were more porous with polysaccharide features. Washed cottonseed meal possessed the surface features similar to those of the residues. In the meantime, the N-associated functional groups were under-represented in the surfaces of all samples, compared to their bulk composition. Information derived from this work increased the understanding of the surface functional properties of cottonseed meal products, which would benefit their practical utilization.

Effects of Particle Size on the Morphology and Water- and Thermo-Resistance of Washed Cottonseed Meal-Based Wood Adhesives

Water washing of cottonseed meal is more cost-efficient and environmentally friendly than protein isolation by means of alkaline extraction and acidic precipitation. Thus, water-washed cottonseed meal (WCSM) is more promising as biobased wood adhesives. In this work, we examined the effects of the particle size on the morphology and adhesive performance of WCSM. Pilot-scale produced and dried WCSM was treated by three grinding methods: (1) ground by a hammer mill and passed through a 0.5-mm screen, (2) further ground by a cyclone mill and passed through a 0.5-mm screen, or (3) further ground by a ball mill and passed through a 0.18-mm screen. Micro-morphological examination revealed two types of particles. The filament-like particles were mainly fibrous materials from residual linters. Chunk-like particles were more like aggregates or accumulations of small particles, with proteins as the major component. Further grinding of the 0.5-mm Hammer product with the Cyclone and Ball mill led to more fine (smaller) particles in the WCSM products. The impact of further grinding on the dry and soaked adhesive strengths was minimal. However, the decrease of the hot and wet strengths of WCSM products by the additional grinding was significant (p ≤ 0.05). Data presented in this work is useful in developing the industrial standards of WCSM products used in wood bonding.

Modification of Cellulose with Succinic Anhydride in TBAA/DMSO Mixed Solvent under Catalyst-Free Conditions

Homogeneous modification of cellulose with succinic anhydride was performed using tetrabutylammonium acetate (TBAA)/dimethyl sulfoxide (DMSO) mixed solvent. The molar ratio of succinic anhydride (SA) to free hydroxyl groups in the anhydroglucose units (AGU), TBAA dosage, reaction temperature, and reaction time were investigated. The highest degree of substitution (DS) value of 1.191 was obtained in a 10 wt% TBAA/DMSO mixed solvent at 60 °C for 60 min, and the molar ratio of SA/AGU was 6/1. The molar ratio of SA/AGU and the TBAA dosage showed a significant influence on the reaction. The succinoylated cellulose was characterized by ATR-FTIR, TGA, XRD, solid state CP/MAS ¹³C NMR spectroscopy (CP/MAS ¹³C NMR), and SEM. Moreover, the modified cellulose was applied for the adsorption of Cu²⁺ and Cd²⁺, and both the DS values of modified cellulose and pH of the heavy metal ion solutions affected the adsorption capacity of succinylated cellulose. The highest capacity for Cu²⁺ and Cd²⁺ adsorption was 42.05 mg/g and 49.0 mg/g, respectively.

Preparation of acetonides from soybean oil, methyl soyate, and fatty esters

This paper describes the preparation of a new type of branched vegetable oil and its methyl ester that involves the formation of acetonides. A facile and environmentally friendly synthesis has been found to produce acetonides that entails the use of ferric chloride as a catalyst and is conducted at room temperature. The products have been fully characterized with the help of model compounds, including elemental analysis, infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), and gas chromatography-mass spectrometry (GC-MS).

Synthesis of an amine-oleate derivative using an ionic liquid catalyst

A facile (and environmentally friendly) reaction between epoxidized methyl oleate and aniline to produce an oleate-aniline adduct, without the formation of fatty amide, was discovered. This reaction was carried out neat, with a catalytic amount of an ionic liquid. No solvent was used, no byproducts were produced, and the ionic liquid could be recovered and recycled. The reaction products were fully characterized by NMR and GC-MS.

Azide derivatives of soybean oil and fatty esters

An environmentally friendly water-based pathway to form the azide derivatives of soybean oil and fatty esters is reported. This entails first the formation of epoxides and then the azidization of the epoxides. The azidization reaction is carried out at high yields in water with only a small amount of an ionic liquid as a catalyst. The distribution of azide and alcohol functionalities on the fatty acid moiety is approximately random. This reaction has been applied to methyl oleate, methyl linoleate, soybean oil, and methyl soyate. The resulting structures have been studied by NMR.

In situ preparation of beta-D-1-O-hydroxylamino carbohydrate polymers mediated by galactose oxidase

[reaction: see text] Galactose oxidase produced a C-6 aldehyde in various terminal-containing galactose hydroxylamines for the simultaneous in situ generation of an A-B type condensation for the construction of unique oxime polymers. Molecular weights of the corresponding polymers were determined to be in the range of 4200-8900 g/mol, respectively. This indicates that approximately 20-25 sugar units were incorporated in these unique polymers.

Enzymatic modification of hydroxyethylcellulose by transgalactosylation with beta-galactosidases

beta-galactosidases from A. oryzae and a thermophilic CLONEZYME glycosidase library were used to catalyze the transfer of the beta-D-galactopyranosyl moiety from lactose to the hydroxyl groups of hydroxyethylcellulose (HEC) in sodium acetate buffer. The degree of substitution was quantified by using galactose oxidase enzymatic assays. Depolymerization was also observed in the course of the transglycosylation reactions.