Starch is one of the most abundant biopolymers on Earth, accumulated in granules within cereals, tubers, roots, and seeds. Each granule is built from two polysaccharides: amylose, a predominantly linear alpha-(1–4) linked glucan that tends to retrograde and form strong films, and amylopectin, a highly branched molecule that produces softer gels and weaker films. The ratio of these two components, along with the degree of crystallinity imparted by amylopectin’s short branches, determines how a given starch behaves under heat, pressure, and hydration. Native starches, however, suffer from well-known limitations, including poor thermal stability, syneresis, and retrogradation, which restrict their usefulness in demanding applications such as pharmaceutical formulations.

To overcome these weaknesses, the research team turned to chemical modification, specifically esterification with malonic acid, a dicarboxylic acid that can bridge adjacent starch chains through ester bonds. The process was deliberately designed to be environmentally benign: the reaction was carried out in water at 90 degrees Celsius, avoiding the organic solvents that typify conventional starch modification routes. Formaldehyde was used as a co-crosslinking agent, a detail the authors themselves flag as a limitation, noting that future work should confirm its complete removal and explore aldehyde-free alternatives. Nevertheless, the predominantly aqueous approach represents a meaningful step toward greener excipient manufacturing.

The chemical evidence for successful modification was compelling. Attenuated total reflectance Fourier transform infrared spectroscopy revealed a new carbonyl stretching peak near 1720 wavenumbers, the signature of ester bonds linking malonate groups to the starch backbone. Titrimetric analysis established a degree of substitution of 0.081 plus or minus 0.009, meaning roughly one in twelve anhydroglucose units carried a malonate substituent. While modest compared with some other carboxylic-acid-modified starches, this substitution level proved sufficient to disrupt the native hydrogen-bonding network and limit chain mobility, with measurable downstream consequences for water uptake, matrix integrity, and drug release.

X-ray diffraction provided structural confirmation of this disruption. Native Gorakhnath-509 starch displayed the characteristic A-type diffraction pattern typical of cereal starches, with reflections at 15, 17, 18, and 23 degrees two-theta. After modification, the intensities of these peaks were visibly attenuated, indicating a qualitative loss of the native semicrystalline order. The authors are careful to note that because the starch was pregelatinized before chemical treatment, thermal processing itself may have contributed to the loss of crystallinity, and a gelatinized but chemically unmodified control was not included in the experimental design. This is an honest caveat that tempers, but does not eliminate, the structural interpretation.

The functional payoff emerged most clearly in the tablet formulations. Using diclofenac sodium as a model drug, the team compressed tablets containing 1, 3, and 5 percent by weight of either native or modified starch as the binder. At the lowest binder level, the modified starch delivered harder tablets, 16.5 plus or minus 0.46 newtons versus 15.66 plus or minus 0.57 newtons for native starch, a statistically significant difference confirmed by one-way ANOVA with Tukey’s post hoc test. Friability, the tendency of tablets to crumble during handling, fell to 0.15 percent for the modified formulation compared with 0.37 percent for its native counterpart, and all six formulations remained comfortably below the pharmacopoeial acceptance threshold of 1.0 percent.

Intriguingly, the hardness advantage did not persist at higher binder concentrations. At 3 and 5 percent binder levels, the modified starch formulations were actually softer than their native counterparts, a concentration-dependent reversal the authors attribute, tentatively, to differences in the deformation and compaction behavior of the esterified matrix at higher loadings. The underlying mechanism was not directly probed in this study, but the finding underscores a broader lesson in excipient science: chemical modification does not produce uniform improvement, and formulation scientists must map performance across the full range of use concentrations before drawing conclusions about superiority.

The dissolution results may prove to be the study’s most consequential contribution. At every binder concentration, tablets containing modified starch released diclofenac sodium faster and more completely than those bound with native starch. The most striking contrast appeared at the 3 percent binder level, where the modified formulation achieved approximately 96 percent cumulative release compared with 77 percent for the native starch version. Kinetic modeling with the DDSolver software showed that the Korsmeyer-Peppas model provided the best fit across all six formulations, with correlation coefficients between 0.9897 and 0.9997. Release exponents greater than 1.0 pointed to Super Case-II transport, a mechanism in which drug release is governed not by simple Fickian diffusion but by the coupled processes of polymer swelling, chain relaxation, and matrix erosion.

This transport mechanism fits neatly with the swelling observations. When tablets were placed on agar gel plates, the modified starch formulations swelled more dramatically than their native counterparts, consistent with the enhanced water uptake expected from a more amorphous, esterified matrix. The combination of high release exponents, pronounced swelling, and XRD evidence for a lightly crosslinked, less crystalline structure paints a coherent mechanistic picture: water penetrates the tablet, the modified starch matrix hydrates and relaxes, and the gel layer gradually erodes, releasing drug in a sustained and predictable fashion. For a biodegradable, rice-derived excipient, this is precisely the kind of controlled-release behavior that formulators seek.

The study is not without limitations, and the authors acknowledge them candidly. The absence of scanning electron microscopy leaves the morphological changes of the modified starch unvisualized, the thermal confound in the modification process complicates attribution, and formal life-cycle assessment would be needed before making sweeping environmental claims. Yet the core achievement stands: a high-amylose rice starch from a regional cultivar, transformed through a largely solvent-free reaction into a pharmaceutical binder that improves tablet integrity at low concentrations and enables sustained, Super Case-II drug release. As the industry searches for biocompatible, biodegradable excipients, this work suggests that the answer may be growing in the paddy fields of the eastern Himalayas, waiting only for the right chemistry to unlock its potential.

Subject of Research: Chemical modification of Gorakhnath-509 rice starch with malonic acid for use as a pharmaceutical tablet binder and controlled-release excipient

Article Title: Structural and functional evaluation of modified native rice starch for tablet formulations

Article References: Structural and functional evaluation of modified native rice starch for tablet formulations. (n.d.). https://doi.org/10.1007/s44371-026-00953-6

Image Credits: AI Generated

DOI: 10.1007/s44371-026-00953-6

Keywords: rice starch, malonic acid, crosslinking, tablet binder, diclofenac sodium, drug release, Korsmeyer-Peppas, green chemistry, pharmaceutical excipient, X-ray diffraction, degree of substitution, biodegradable polymer

The research team, led by Amanda S. Giroto, set out to build a controlled-release urea fertilizer from carboxymethyl cellulose, or CMC, a renewable, low-toxicity derivative of cellulose that is abundant, highly hydrophilic, and capable of forming films and hydrogels. CMC has long been viewed as a promising scaffold for agricultural delivery systems, but it carries a fundamental weakness: its affinity for water is so strong that, unless the polymer network is stabilized, it swells excessively or dissolves outright, releasing its payload by disintegration rather than by regulated diffusion. The Brazilian group tackled this problem with a dual strategy, crosslinking the polymer chains with citric acid, a cheap and food-safe polycarboxylic acid that forms ester bonds with cellulose hydroxyl groups, and dispersing bamboo-derived biochar throughout the matrix as a physical barrier and adsorptive phase.

The experimental design was deliberately systematic. A 2 percent aqueous CMC solution was prepared, urea was added at 50 percent of the polymer mass, and biochar was incorporated at a fixed 1 percent of total composite mass. Citric acid was then introduced at four levels, 0, 10, 20, and 30 percent by weight relative to CMC, and the mixtures were heated to 80 degrees Celsius for two hours to drive the crosslinking reaction before being cast into self-supporting films and dried. The resulting formulations, labeled CMC/U, CMC/U/BC/CA0, CA10, CA20, and CA30, were probed with X-ray diffraction, infrared spectroscopy, electron microscopy, and thermal analysis, then subjected to swelling tests, water-retention trials in sandy soil, aqueous urea-release experiments, and a 42-day soil incubation tracking ammonia volatilization and ammonium formation.

The structural characterization revealed formulation-dependent changes in the crystalline organization and thermal environment of urea within the matrices. Electron microscopy showed that the non-crosslinked material possessed a smooth surface with well-defined urea crystals, while biochar incorporation produced a rougher, more heterogeneous morphology dotted with porous features. The 10 percent citric acid formulation displayed a relatively cohesive structure, the 20 percent version was the most compact and homogeneous, and the 30 percent sample turned granular and fragmented. Thermal analysis showed that the decomposition temperature of the polymer backbone shifted progressively upward with increasing citric acid content, reaching roughly 284 degrees Celsius at the highest loading, evidence of a more thermally stabilized network. Differential scanning calorimetry, meanwhile, showed that the sharp melting endotherm of pure urea at about 136 degrees Celsius was broadened, reduced, or suppressed in the composites, indicating that urea molecules were dispersed and interacting within the polymeric network rather than sitting as free crystalline granules.

The swelling experiments delivered the study’s most striking numbers. Without citric acid, the composites rapidly lost their structural integrity in water, forming a viscous gelatinous mass that could not even be weighed reliably. In contrast, all crosslinked formulations remained intact throughout immersion, and the 10 percent citric acid composite swelled to approximately 7500 percent of its dry mass within an hour, compared with about 4800 percent at 20 percent crosslinker and 2800 percent at 30 percent. Counterintuitively, the highest swelling did not translate into the fastest nutrient release. In water, pristine urea dissolved almost instantaneously, releasing its entire payload within the first four hours, whereas the CA10 composite had surrendered only about 18 percent of its urea at that point and roughly 80 percent by the end of the eight-day test. The 20 and 30 percent formulations released faster, with the CA20 sample reaching up to 90 percent.

This non-linear relationship between crosslinker content and release behavior is one of the paper’s central insights. The authors argue that beyond an optimal point, additional citric acid restricts polymer-chain mobility, increasing matrix rigidity and morphological heterogeneity in ways that can open preferential diffusion pathways and accelerate transport rather than slow it. Kinetic modeling reinforced the complexity of the mechanism. All composites fitted the Higuchi diffusion model well, but the Peppas–Sahlin analysis showed that urea release involved simultaneous diffusional transport and polymer-chain relaxation, with the relaxational contribution growing from roughly a quarter to nearly 40 percent of the modeled release over the first eight hours. The researchers are careful to note that the data do not support describing the process as purely Fickian diffusion; instead, release emerges from the coupled interplay of hydration, structural reorganization, and solute transport.

Water retention, a critical co-benefit for drought-prone agriculture, also improved. In sandy soil amended with the composites and held at 40 degrees Celsius, the non-crosslinked biochar formulation retained about 59 percent of its initial water after 120 hours, compared with 47 percent for unamended sand, although this difference fell short of statistical significance. At 24 hours, significant differences among treatments were detected, and the biochar-containing matrices showed a consistent tendency toward better long-term moisture preservation, a property the authors attribute to the hydrogel’s water-holding capacity combined with biochar’s porosity.

Perhaps the most consequential results came from the soil incubation. Over 42 days under conditions deliberately chosen to accelerate urea hydrolysis and nitrogen loss, every composite reduced measured ammonia volatilization relative to pure urea. Pure urea lost the most nitrogen as ammonia, 3.74 milligrams, while the uncrosslinked CMC/urea composite lost the least, 2.29 milligrams, a statistically significant reduction. Ammonium dynamics shifted as well: in the first week, the composites sustained higher exchangeable ammonium pools than pristine urea, suggesting that the matrices kept nitrogen in a plant-available mineral form for longer rather than letting it escape as gas. A partial nitrogen recovery accounting, based on the two measured pools, ranged from 56.4 to 72.4 percent of the applied nitrogen, with the remainder classified conservatively as unaccounted because nitrate and matrix-associated nitrogen were not directly quantified.

The practical implications are considerable. Because CMC, citric acid, and biochar are all inexpensive, renewable, and biodegradable, the proposed system sidesteps the central criticism of commercial controlled-release fertilizers, many of which rely on non-biodegradable synthetic coatings that persist in soil. The fabrication route is equally appealing: a simple aqueous process, a single heating step at 80 degrees Celsius, and air drying, with no exotic reagents or energy-intensive procedures. The authors frame the work as demonstrating that one biodegradable polymer matrix, properly architected, can efficiently regulate nutrient release through a simple, scalable, and sustainable strategy for advanced nitrogen fertilizers.

The deeper lesson, however, is about optimization philosophy. Increasing crosslinker content did not monotonically improve performance, and the best formulation was the one that balanced swelling, structural integrity, and diffusion-pathway continuity rather than the most heavily crosslinked one. As agriculture confronts the twin pressures of feeding a growing population and cutting the nitrogen pollution that warms the climate and degrades waterways, studies like this one suggest that the smartest fertilizers of the coming decade may be built not from petrochemical shells but from engineered plant polysaccharides, kitchen-safe acids, and charcoal, tuned with precision at the molecular scale.

Subject of Research: Development of citric acid-crosslinked carboxymethyl cellulose and biochar composites for controlled-release urea fertilizer

Article Title: Controlled urea release from CMC-based composites: effects of citric acid crosslinking and biochar incorporation

Article References: Giroto, A. S., Prado, T. R., Yashima, A., Valle, S. F., Alves, B. L., & Gonçalves, M. (2026). Controlled urea release from CMC-based composites: effects of citric acid crosslinking and biochar incorporation. Polymer Bulletin, 83(11), Article 636. https://doi.org/10.1007/s00289-026-06685-y

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06685-y

Keywords: controlled-release fertilizer, carboxymethyl cellulose, urea, biochar, citric acid crosslinking, nitrogen use efficiency, ammonia volatilization, biodegradable polymer, hydrogel, soil water retention, release kinetics, sustainable agriculture

The separator is one of four core components of every lithium-ion battery, sitting between the graphite anode and the oxide cathode. Its job is deceptively simple: physically keep the electrodes apart so electrons cannot short the cell, while its pores must admit liquid electrolyte and let lithium ions shuttle back and forth during charge and discharge. Polypropylene has long dominated this role because of its mechanical strength, chemical resistance, low cost and easy processability. Yet it is entirely petroleum-derived and non-biodegradable, meaning that as the battery fleet swells, so will a stream of durable plastic waste. The research team, led by Sajad Rasouli of the Research Institute of Petroleum Industry in Tehran with colleagues from Islamic Azad University, the Institute for Color Science and Technology and the University of Garmsar, set out to answer a question that has been largely neglected: could a biodegradable polymer actually beat polypropylene at its own game?

The answer hinged on two chemical interventions. First, the team chain-extended the PBAT using maleic anhydride activated by a dicumyl peroxide initiator. In this reaction, the anhydride ring opens and couples with the hydroxyl end groups of PBAT chains, forging covalent bridges between individual molecules. The result is a higher molecular weight polymer with reduced chain mobility, which translates into improved thermal and mechanical stability. Second, because PBAT is slightly polar and polypropylene is completely nonpolar, the two polymers would normally refuse to mix. The researchers solved this by blending in polypropylene-grafted-maleic anhydride as a compatibilizer: its polypropylene backbone merges with the pure polypropylene phase while its anhydride groups interact with PBAT macromolecules, knitting the two immiscible materials into a coherent whole.

Manufacturing relied on a four-step gravure printing route rather than conventional film blowing or electrospinning. Chain-extended PBAT was compounded with a polypropylene–polypropylene-grafted-maleic anhydride mixture in a single-screw extruder, with 30 percent by weight of dioctyl phthalate oil fed in as a liquid porogen and plasticizer. The molten compound was deposited onto a rotating gravure cylinder, compressed between impression cylinders into a uniform film of roughly 100 micrometers, then uniaxially stretched at 65 degrees Celsius to a final thickness of just 20 to 30 micrometers. The critical chemistry came afterward: the film was soaked in ethanol for two days, leaching out the dioctyl phthalate and leaving behind an interconnected network of nanoscale cavities. The team confirmed by Fourier-transform infrared spectroscopy that extraction efficiency reached about 99.3 percent, with the characteristic fingerprint peaks of the plasticizer vanishing completely after treatment.

The resulting microstructure is remarkable. In the pure chain-extended PBAT membrane, the extraction produced spherical, uniformly distributed cavities averaging just 68 nanometers in diameter with a standard deviation of 45.64 nanometers, a number density of 16.7 holes per square micrometer and a porosity of 42.9 percent. By comparison, most polyolefin-based separators reported in the literature exhibit oval cavities on the micrometer scale. The researchers attribute this morphology to the affinity between the ester-rich, aromatic dioctyl phthalate and the similarly structured PBAT, which allows the plasticizer to disperse homogeneously before removal. When the PBAT content was cut in half to 50 weight percent, the average cavity size swelled 204 percent to 208 nanometers, while pore density fell by 86 percent and porosity dropped to 34.2 percent. Below that ratio, at 25 weight percent PBAT, the compatibilizer could no longer prevent phase separation, yielding a heterogeneous, irregular pore structure unsuitable for ion transport.

Wettability measurements told a complementary story. Water contact angles of roughly 80 to 82 degrees for the high-PBAT membranes sit comfortably in the hydrophilic regime, meaning the pores will readily draw in the polar carbonate electrolyte. Reducing PBAT to 50 weight percent left the surface wettability essentially unchanged, and because its larger pores encouraged capillary penetration over time, the contact angle actually fell from 81.3 to 78.6 degrees during measurement. Bulk wettability, quantified through electrolyte uptake, told a similar tale: pure PBAT absorbed 128.7 percent of its weight in electrolyte, while the 50 percent PBAT formulation still absorbed 94.3 percent. Increasing polypropylene further degraded both uptake and surface wettability, pushing the contact angle toward the hydrophobic zone that battery engineers consider disastrous for ion transport. Balancing microstructure, wettability and mechanical reinforcement from the polypropylene fraction, the team identified the 50 weight percent chain-extended PBAT formulation, labeled BP50, as the optimum.

Electrochemical testing put the claims to the test in a CR2032 coin cell built with a graphite anode and a lithium nickel-cobalt-manganese oxide cathode. Electrochemical impedance spectroscopy yielded resistances of 2.84 ohms for the electrolyte and 36.82 ohms against lithium-ion penetration, with an estimated solid electrolyte interface thickness of 81.27 micrometers. The computed ionic conductivity of 2.86 millisiemens per centimeter dwarfs the 0.34 millisiemens per centimeter reported for polypropylene separators under comparable conditions, and the authors’ radar-chart comparison shows BP50 outperforming separators made from ultra-high molecular weight polyethylene, poly(vinylidene fluoride) variants, cellulose nanocrystals, collagen-chitosan hybrids, zeolite-coated polypropylene and other published polymer membranes. Linear sweep voltammetry confirmed reversible lithiation and delithiation with negligible side reactions up to 1.8 volts, delivering capacities of 69.10 and 63.52 milliampere-hours per gram during delithiation and lithiation respectively.

The team argues that PBAT’s biodegradability does not compromise safety inside the cell. Practical lithium-ion batteries normally operate below 45 degrees Celsius, and even aggressive high-rate use rarely pushes well-controlled cells past 60 degrees, whereas thermal or hydrolytic degradation of PBAT requires substantially higher temperatures along with moisture, oxygen and biological activity. The non-aqueous electrolyte also does not chemically corrode the polyester, and the chain-extension step further stabilizes the polymer by raising molecular weight and curbing chain mobility. Compared with electrospun separators that often suffer from weak mechanical strength and thermal shrinkage despite high porosity, the gravure-printed membranes combine safety, mechanical integrity and electrochemical stability in a single roll-to-roll-compatible process.

The broader implications are significant. A separator that can be printed at industrial speeds, using a blend in which half the polymer decomposes in soil within two months thanks to PBAT’s biodegradation rate of 2.16 per day, offers the battery industry a credible route away from persistent fossil plastics without sacrificing performance. Because the gravure printing route is already a mature printing-industry technology, scaling the process may require less reinvention than entirely novel fabrication schemes. If the printed BP50 membrane can be validated at commercial scale and over long cycle life, the humble separator, often an afterthought in battery design, could become a showcase for how sustainable materials science turns one of electrification’s biggest waste liabilities into an environmental advantage.

Beyond the headline numbers, the study offers a useful lesson in polymer blend physics. Immiscible polymer pairs typically form coarse, disconnected phases because the thermodynamic penalty of mixing their segments is high, and the interfacial tension drives the minor component into large droplets. A graft compatibilizer lowers this penalty by anchoring at the interface, reducing surface tension between the phases and stabilizing a fine, dispersed morphology. In this system, that interfacial engineering is what allows a nano-porous structure to survive the stretching and extraction steps: without well-dispersed PBAT domains, the leached porogen would leave behind irregular, micron-scale voids rather than the uniform 68-nanometer cavities that govern ion transport.

The choice of gravure printing also deserves attention from a manufacturing standpoint. Gravure coating is a high-throughput, roll-to-roll technique already ubiquitous in packaging and printed electronics, capable of depositing controlled film thicknesses at speeds far exceeding batch methods. Demonstrating that a functional battery separator can be patterned this way suggests a pathway in which separator fabrication could be integrated into existing printing infrastructure, potentially lowering capital costs and enabling thickness control at the micrometer scale that is difficult to achieve with conventional dry or wet stretching of polyolefin films.

The work also highlights how formulation trade-offs shape separator design. Porosity, pore size, mechanical strength and electrolyte uptake are coupled variables: raising the biodegradable fraction improved wettability and conductivity but relied on the polypropylene fraction for fatigue resistance and dimensional stability. The authors’ systematic sweep of blend ratios, tracking cavity size, pore density and absorption capacity across compositions, illustrates the kind of compositional mapping needed before any new separator chemistry can be considered commercially credible.

Finally, the environmental argument rests on quantified biodegradation rather than vague green claims. PBAT’s reported soil decomposition within two months, and its biodegradation rate exceeding that of polylactic acid, give the blend a defined end-of-life pathway, though real-world battery recycling streams, separator recovery and lifecycle emissions would need assessment before the sustainability benefit can be fully claimed.

Subject of Research: Development of a biodegradable chain-extended PBAT/polypropylene lithium-ion battery separator fabricated by gravure printing

Article Title: Novel high-performance lithium-ion battery separator made of chain-extended-poly(Butylene Adipate-co-terephthalate)/modified-polypropylene using gravure printing

Article References: Rasouli, S., Arshadi, M., Ataeefard, M., Ghamarpoor, R., & Salehi, M. M. (2026). Novel high-performance lithium-ion battery separator made of chain-extended-poly(Butylene Adipate-co-terephthalate)/modified-polypropylene using gravure printing. Journal of Materials Science: Polymers, 1(1), Article 20. https://doi.org/10.1007/s44493-026-00016-3

Image Credits: AI Generated

DOI: 10.1007/s44493-026-00016-3

Keywords: lithium-ion battery, battery separator, PBAT, polypropylene, gravure printing, biodegradable polymer, ionic conductivity, maleic anhydride, chain extension, porosity, electrolyte wettability, energy storage