Molecular Chains Research Articles

High energy density of biaxially oriented polypropylene film in cryogenic environment for advanced capacitor

In this paper, a method of significantly increasing the energy density of biaxially oriented polypropylene (BOPP) film by cryogenic environment has been proposed. The notable enhancements in the dielectric and energy storage performance can be attributed to precise microstructure manipulation, aimed at controlling charge injection limitations and optimizing molecular chain dynamics. The experimental results show that the maximum discharged energy density of BOPP film with thicknesses of 3.4 μwm has reached 11.83 J cm−3 at −196 °C (2.9 times that at 25 °C) with a charge-discharge efficiency of 92.74%. The direct current breakdown strength as high as 1120.4 kV mm−1 is obtained at −196 °C, exhibiting a substantial 63.7% augmentation compared to the measurement at 25 °C. Furthermore, reductions in conductance loss and capacitance loss (post self-healing testing) are realized. Mechanistic insights into the observed enhancements are investigated through computational simulations. This research provides a pivotal advancement and valuable perspective towards the development of film capacitors boasting the excellent energy storage characteristics.

A phosphorus/fluorine‐containing block copolymer endows epoxy with multifunctionality

AbstractIn order to achieve flame retardant, hydrophobic, and toughened epoxy resins, phosphorus/fluorine‐containing block copolymer (FBCP) was synthesized by reversible addition‐fragmentation chain transfer polymerization, and then the as‐synthesized PMADOPO‐b‐PHFBA block copolymer was used as additive to modify the epoxy resin, accompanying with a random copolymer (FRCP) serving as control group. It showed that due to the regular arrangement of molecular chains, FBPC formed a fibrous‐like structure at the fracture interface of epoxy/PMADOPO‐b‐PHFBA (EP/FBCP) samples, effectively enhancing the toughness of epoxy composite materials. The fracture energy of EP90/FBCP‐10 was higher than that of EP90/FRCP‐10 and was about twice than that of pure EP. The addition of 3 wt% FBCP could enhance the limited oxygen index (LOI) of EP97/FBCP‐3 to 33.2% and reached a V‐1 UL‐94 rating. As the addition of FBCP increased, the LOI gradually increased. When the addition of FBCP was 10%, the LOI and UL‐94 of EP90/FBCP‐10 was 38.2% and V‐0 grade, respectively. Meanwhile, the presence of fluorine element effectively reduced the surface energy of the composite EP material. Compared with pure EP, the water contact angle of EP90/FBCP‐10 was about 101° with an increasing of 20.8%. Furthermore, the flame‐retardant mechanism of EP/FBCP epoxy composites was discussed.

Removal of proteins and lipids affects structure, in vitro digestion and physicochemical properties of rice flour modified by heat-moisture treatment.

The objective of this experiment was to investigate the role of endogenous proteins and lipids in the structural and physicochemical properties of starch in heat-moisture treatment (HMT) rice flour and to reveal their effect on starch digestibility under heat. The findings indicate that, in the absence of endogenous proteins and lipids acting as a physical barrier, especially proteins, the interaction between rice flour and endogenous proteins and lipids diminished. This reduction led to fewer starch-protein inclusion complexes and starch-lipid complexes, altering the granule aggregation structure of rice flour. It resulted in a decrease in particle size, an increase in agglomeration between starch granules, and more surface cracking on rice granules. Under HMT conditions with a moisture content of 30%, slight gelatinization of the starch granules occurred, contributing to an increased starch hydrolysis rate. In addition, the elevated thermal energy effect of HMT enhanced interactions between starch molecular chains. These resulted in a decrease in crystallinity, short-range ordering, and the content of double-helix structure within starch granules. These structural transformations led to higher pasting temperatures, improved hot and cold paste stability, and a decrease in peak viscosity, breakdown, setback, and enthalpy of pasting of the starch granules. The combined analysis of microstructure, physicochemical properties, and in vitro digestion characteristics has enabled us to further enhance our understanding of the interaction mechanisms between endogenous proteins, lipids, and starches during HMT. © 2024 Society of Chemical Industry.

Complex conductivity as a tool to investigate the electrical behavior between graphene oxide and reduced graphene in supercapacitors: Correlation between the electrical properties

The storage mechanisms of solid-solid supercapacitors based on graphene oxide (rGO/GO/rGO) were explored by Zhang Q et al. (Zhang et al., 2014) [1], using Density Functional Theory (DFT) and Impedance Spectroscopy (EIS) to elucidate the unusual capacitive behavior of GO sandwich films. Their study revealed alternating charged layers without diffusion zones. Analysis of complex impedance (Z*) data, ranging from 10−3 to 3.106 Hz, was conducted using an equivalent circuit, though this was limited to Nyquist plot data.To further investigate charge storage mechanisms, the current study delved deeper into complex impedance (Z*) and conductivity (σ*). A theoretical approach identified relaxation processes in the imaginary parts of (Z″) and (σ'') across frequencies. Extrapolation up to 3.10^9 Hz and deconvolution confirmed three distinct relaxation processes in Z* and σ*, similar to Cole-Cole relaxation, which describes Maxwell-Wagner-Sillars (MWS) relaxation. This reflects local electrical interactions between active sites on molecular chains and counterions, creating induced dipolar moments or diffusion processes.The identified relaxations at low, medium, and high frequencies correspond well with DFT results, attributed to specific regions: graphene oxide (GO), the (rGO/GO) interface, and reduced graphene (rGO). Key parameters extracted from each relaxation, such as relaxation time, ionic strength, and conductivity values at different frequencies, showed good correlation. This approach, based on deep conductivity (σ*) analysis, effectively highlighted the charge conduction and storage mechanisms in rGO/GO/rGO supercapacitor films.

Developing PEEK composites with exceptional thermal conductivity and electromagnetic shielding properties by constructing a dense dual-continuous filler network

Polyether ether ketone (PEEK) has regular and rigid molecular chain and is insoluble in most organic solvents. Therefore, it is challenging to use PEEK matrix composites for thermal conductivity (TC) and electromagnetic interference (EMI) shielding applications. Herein, PEEK composites with hybrid fillers were fabricated by solution blending and non-solvent-induced phase separation (NIPS) methods based on a chemical conversion reaction between soluble precursor PEEK-dithiolane and PEEK. Synergistic interaction between hybrid fillers (graphene nanosheets and multiwalled carbon nanotubes) improves the thermal and electrical conductivity of the composites. The effect of the hot-pressing pressure on the conductive/thermal network densification was investigated. The composites performed optimally at a hot pressure of 200 MPa and a filler content of 20.08 vol%. The maximum in-plane and out-of-plane TC reached 10.46 W·m–1·K–1 and 4.8 W·m–1·K–1, respectively, which were 4619 % and 2414 % higher than the corresponding TC of PEEK. Simultaneously, the optimised composite demonstrated significantly improved electrical conductivity (3517 S/m) and EMI shielding effectiveness (66.1 dB). These excellent characteristics are attributed to the solution blending–NIPS method, which improves the dispersion of hybrid fillers in the matrix and forms an internal and external dual-continuous thermal conductive network. The dual-continuous network creates effective channels for phonon and electron transport and enhances EM wave loss. This work provides inspiration for the preparation of PEEK composites as advanced EMI protection and thermal management materials.

Role of Annealing with Electric Field Toward Improvement of Ferroelectric and Electroactive Properties of PVDF Copolymer and Terpolymer Thin Films.

The present study elucidates the role of annealing with electric field on lamellar crystalline structure and molecular orientation of polymer chains in ferroelectric copolymer (P(VDF-TrFE)) and ferroelectric terpolymer (P(VDF-TrFE-CFE)) spin-coated thin films. The ferroelectric polymer thin films annealed under an electric field support the growth of nanostructure with an "edge-on" lamellar crystalline structure having in-plane molecular chain orientation. The poled P(VDF-TrFE) thin films have higher remnant polarization (Pr) ≈6.2µCcm-2 and saturation polarization (Ps) ≈8.2µCcm-2 at an applied electric field of 250 MV/m compared to unpoled thin films having Pr ≈4.7 and Ps ≈6.2µCcm-2. Also, poled P(VDF-TrFE) thin films show lower coercive field (Ec) ≈94 MV/m compared to an unpoled thin film having Ec ≈105 MV/m. Similarly, poled PVDF-TrFE-CFE thin film shows better ferroelectric properties having Pr ≈0.4 and Ps ≈5.7µCcm-2 at an applied electric field of 200 MVm-1 compared to unpoled thin films having Pr ≈0.4 and Ps ≈4.1µCcm-2. The storage energy efficiency of unpoled and poled P(VDF-TrFE-CFE) thin films is measured to be ≈75% and 80%. Annealing of ferroelectric P(VDF-TrFE) polymer thin films under an electric field demonstrates improved ferroelectric and electroactive properties.

Shearo-caloric effect enhances elastocaloric responses in polymer composites for solid-state cooling

Room-temperature elastocaloric cooling is considered as a zero-global-warming-potential alternative to conventional vapor-compression refrigeration technology. However, the limited entropy and large-deformation features of elastocaloric polymers hinder the creation of the breakthrough in their caloric responses and device development. Herein, we report that the addition of a small amount of inorganic nanofillers into the polymer induces the aggregate of the effective elastic chains via shearing the interlaminar molecular chains, which provides an additional contribution to the entropy in elastocaloric polymers. Consequently, the adiabatic temperature change of −18.0 K and the isothermal entropy change of 187.4 J kg−1 K−1 achieved in the polymer nanocomposites outperform those of current elastocaloric polymers. Moreover, a large-deformation cooling system with a work recovery efficiency of 56.3% is demonstrated. This work opens a new avenue for the development of high-performance elastocaloric polymers and prototypes for solid-state cooling applications.

The structural and digestive properties of indica rice starch-fatty acid complexes

The structural and digestive properties of indica rice starch-fatty acid complexes and the effects of lipoxygenase on the structural and digestive properties of the complexes were examined in this study. The complexes were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform-infrared spectroscopy and Raman spectroscopy. The results showed that indica rice starch had the highest molecular chain order and the highest crystallinity, and the crystallization disappeared after gelatinization, and the formation of indica rice starch-fatty acid complexes promoted the transformation of starch crystal structure from A-type to V-type. Lipoxygenase reduced the regularity of starch molecular crystal structure in the complexes, while enzyme protein improved the order of starch molecular structure in the complexes. The regularity of starch crystal structure in the complexes could improve with the increase of composite temperature and the increase of fatty acid unsaturation. In vitro digestibility and in vitro digestion kinetics showed that the formation of indica rice starch-fatty acid complexes reduced the digestibility of indica rice starch to a certain extent. The RDS content of indica rice starch was 66.42 ± 0.39 %, and lipoxygenase reduced the reduction of rapidly digested starch content during complexes digestion, while enzyme protein increased the content of resistant starch.

Highly Reversible and Dendrite-Free Zinc Anodes Enabled by PEDOT Nanowire Interfacial Layers for Aqueous Zinc-Ion Batteries.

The aqueous zinc-ion batteries (ZIBs) have gained increasing attention because of their high specific capacity, low cost, and good safety. However, side reactions, hydrogen evolution reaction, and uncontrolled zinc dendrites accompanying the Zn metal anodes have impeded the applications of ZIBs in grid-scale energy storage. Herein, the poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires as an interfacial layer on the Zn anode (Zn-PEDOT) are reported to address the above issues. Our experimental results and density functional theory simulation reveal that the interactions between the Zn2+ and S atoms in thiophene rings of PEDOT not only facilitate the desolvation of hydrated Zn2+ but also can regulate the diffusion of Zn2+ along the thiophene molecular chains and induce the dendrite-free deposition of Zn along the (002) surface. Consequently, the Zn||Cu-PEDOT half-cell exhibits highly reversible plating/stripping behavior with an average Coulombic efficiency of 99.7% over 2500 cycles at 1 mA cm-2 and a capacity of 0.5 mAh cm-2. A symmetric Zn-PEDOT cell can steadily operate over 1100 h at 1 mA cm-2 (1 mAh cm-2) and 470 h at 10 mA cm-2 (2 mAh cm-2), outperforming the counterpart bare Zn anodes. Besides, a Zn-PEDOT||V2O5 full cell could deliver a specific capacity of 280 mAh g-1 at 1 A g-1 and exhibits a decent cycling stability, which are much superior to the bare Zn||V2O5 cell. Our results demonstrate that PEDOT nanowires are one of the promising interfacial layers for dendrite-free aqueous ZIBs.

Enhancing the tribological performance of polyimide composite coatings with amino-functionalized MXene nanofillers

At the nanoscale, the surface properties of nanomaterials are of utmost importance. Amino-functionalized MXene (AMXene) was prepared by grafting 3-aminopropyltriethoxysilane (APTES) upon the top layer of Ti3C2Tx. AMXene is introduced into the polyimide (PI) matrix coatings. The findings indicate that the dispersion of AMXene in PI is further substantially enhanced based on the principle of “similar compatibility”, which is attributable to the creation of more hydrogen bonds between AMXene and highly polar PI matrix molecular chains. The addition of AMXene lowered the factor of friction by 34.1 % and the rate of abrasion by 84.8 % compared to unadulterated PI. In addition, the PI/AMXene composites exhibit significant reinforcement properties at different loads and speeds.

First principles study of electronic structure of x-form phthalocyanine crystals doped with one-dimensional iodine atomic chains

The x-form phthalocyanine (Pc) crystal is composed of a square-lattice arrangement of one-dimensional and double-period molecular chains with molecular planes normal to the stacking direction, and doped iodine (I) atomic chains between these molecular chains are known to induce the insulator-metal transition. Using the van der Waals density functional method, we investigate the electronic structure of a single x-form silicon Pc (x-SiPc) chain and the x-SiPc crystal undoped and doped with I atomic chains in a comparative manner. Although a SiPc molecule has a Si pz derived orbital just above the LUMO, the aligned Si atoms in x-crystals, each of which is at the center of the molecular plane, dimerize in the stacking direction, which prevents formation of a Si metallic band. In a single SiPc chain, two molecules in each primitive unit cell are stacked face-to-face with a staggering angle of 45°. However, when these molecular chains aggregate to create x-crystals, the staggering angle deviates from 45° to about 40° to form H–H bonding orbitals like H2 molecules between neighboring molecular planes in the lateral direction. Doping of the I atomic chains converts half-filling of the doubly degenerate bands to a lower band occupancy, which corresponds to the insulator-metal transition observed experimentally. The equally spaced I atomic chains create a metallic band due to pz-orbital overlapping with an effective-mass ratio of 0.15. Although the SiPc chains operate to create equally spaced I atomic chains, the effect of I atoms trying to trimerize is larger. This trimerization prevents pz orbitals of I atoms from making a metallic band.

Quantifying the conductivity of a single polyene chain by lifting with an STM tip

Conjugated polymers are promising candidates for molecular wires in nanoelectronics, with flexibility in mechanics, stability in chemistry and variety in electrical conductivity. Polyene, as a segment of polyacetylene, is a typical conjugated polymer with straightforward structure and wide-range adjustable conductance. To obtain atomic scale understanding of charge transfer in polyene, we have measured the conductance of a single polyene-based molecular chain via lifting it up with scanning tunneling microscopy tip. Different from semiconducting characters in pristine polyene (polyacetylene), high conductance and low decay constant are obtained, along with an electronic state around Fermi level and characteristic vibrational mode. These observed phenomena result from pinned molecular orbital owing to molecule-electrode coupling at the interface, and weakened bond length alternation due to electron-phonon coupling inside single molecular chain. Our findings emphasize the interfacial characteristics in molecular junctions and promising properties of polyene, with single molecular conductance as a vital tool for bringing insights into the design and construction of nanodevices.

Comparison of RT-PCR cycle threshold values between individual and pooled SARS-CoV-2 infected nasopharyngeal swab specimens.

The molecular reverse transcription-polymerase chain reaction (RT-PCR) testing of respiratory tract swabs has become mandatory to confirm the diagnosis of coronavirus disease 2019 (COVID-19). However, RT-PCR tests are expensive, require standardized equipment, and relatively long testing times, and the sample pooling method has been introduced to solve this issue. The aim of this study was to compare the cycle threshold (Ct) values of the individual sample and pooled sample methods to assess how accurate the pooling method was. Repeat RT-PCR examinations were initially performed to confirm the Ct values for each sample before running the pooled test procedure. Sample extraction and amplification were performed in both assays to detect ORF1ab, N, and E genes with a cut-off point value of Ct <38. Overall, there was no difference in Ct values between individual sample and pooled sample groups at all concentrations (p=0.259) and for all pooled sizes. Only pooled size of five could detect the Ct value in the pooled samples for all concentration samples, including low-concentration sample (Ct values 36 to 38). This study highlighted that pooled RT-PCR testing strategy did not reduce the quality of individually measured RT-PCR Ct values. A pool size of five could provide a practical technique to expand the screening capacity of RT-PCR.

Study of structural, surface energies, and tribomechanical properties of thermoplastics irradiated by electron beam

This study investigates the effects of electron irradiation on the structural, surface energy, and tribomechanical properties of two key thermoplastics: polyetheretherketone (PEEK) and polytetrafluoroethylene (PTFE). The experimental methods included electron beam irradiation using the ILU-10 pulsed linear accelerator, Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), microhardness testing, surface roughness assessment, tribology tests, and contact angle measurements.The FT-IR analysis revealed significant chemical changes on the surfaces of the polymers, including oxidation processes and the breaking of molecular bonds. XRD analysis showed an increase in the crystallinity of PTFE after irradiation, while the structure of PEEK remained stable. Microhardness testing indicated a notable increase in hardness for both polymers, particularly for PTFE, suggesting cross-linking of molecular chains. Surface roughness measurements demonstrated a decrease in roughness for both irradiated polymers. Tribology tests revealed that electron irradiation increased the coefficient of friction for PTFE and PEEK under various loads, which can be attributed to the alterations in their surface properties. Contact angle measurements indicated improved wettability of the irradiated surfaces, especially for PEEK, due to the formation of new functional groups. The total surface energy increased for both polymers post-irradiation, as determined using the Owens-Wendt-Rabel-Kaeble method. Electron irradiation leads to significant modifications in the surface and bulk properties of PEEK and PTFE, enhancing their tribomechanical and adhesive properties. These changes open new opportunities for the application of these materials in various engineering fields where specific performance characteristics are required.

Effect of DNA's Molecular Weight on their Solution Viscosity, Critical Concentrations, and Liquid Crystals Formation

AbstractThe study of the dynamics of nucleic acids in solution, their flow properties, and viscoelasticity is of great importance for understanding their biological functions. Many important properties of nucleic acids, such as DNA, depend on polymer concentration, CDNA, molecular weight (MW), rigidity, and external salt content, the latter parameter affecting electrostatic interactions. Furthermore, DNA molecular chains can organize, in vitro, into liquid crystalline phases at high CDNA. In this work, three DNA samples with different MW were studied in solution in a broad concentration range (CDNA from 0.025 to 200 mg mL−1, depending on DNA MW). Firstly, the intrinsic viscosities and MW for all DNA samples were determined through capillary and rheological measurements. Then, the overlap concentrations, C*, were estimated from the relation C* ≈ [η]−1. DNA chain characteristics were then analyzed in terms of the influence of DNA MW on the solution viscosities and on the overlap parameter, CDNA[η]. Flow birefringence appearance was identified by screening a wide CDNA range through visual observations with crossed polarizers. Finally, crossed‐light polarized microscopy was used to identify the appearance of liquid crystals at rest, confirming that higher CDNA are needed to obtain liquid crystals for low MW DNA samples.

A green extraction method for agar with improved thermal stability and water holding capacity

The conventional agar extraction method has drawbacks such as high energy consumption, low yield, poor quality, and possible residual harmful factors, which greatly limit its application in high-end fields such as biomedicine and high-end materials. This work explored a new freezing-thawing-high-temperature coupling technique for agar extraction. It increased the yield and the strength of agar by 10.6 % and 13.7 %, respectively, as compared to direct high-temperature extraction of agar (HA). The greater molecular weight and lower sulfate content of agar obtained from freeze-thaw cycles combined with high temperature extraction (FA) may be attributed to the desulfurization effect caused by freeze-thaw cycles and the preservation of the molecular chain structure. The reduction in sulfate content decreases the steric hindrance resistance of the polysaccharide chains, enhances their interactions, and promotes the regularity and density of the agar structure, while also improving its water retention and thermal stability. In conclusion, this research can offer a theoretical basis and guidance for the eco-friendly extraction of agar with improved agar characteristics and expended its applications.

Effect of alkaline protease content on the structure and properties of natural rubber

AbstractThe solidification technology of natural rubber exerts a significant impact on the properties of natural rubber. The solidification technology of alkaline protease has been highly valued by researchers at home and abroad because of its good solidification effect, excellent vulcanization performance, and low pollution. In this study, the effects of alkaline protease solidification technology and enzyme dosage on the structure and properties of natural rubber were investigated and compared with those of formic acid solidification technology. The solid‐state NMR results showed that increasing the enzyme dosage increased the molecular chain entanglements in the raw rubber. The gel content test results showed that the natural network structures (i.e. gels) increased after the addition of alkaline protease. The test results of the vulcanization characteristics showed that the addition of alkaline protease significantly shortened the positive vulcanization time. The Mw was the largest at an enzyme dosage of 0.07%. The test results for mechanical properties showed that the mechanical properties were best when the enzyme dosage was 0.07%. In addition, as the alkaline protease dosage increased, the Akron abrasion volume of natural rubber decreased, and the Akron abrasion volume was the lowest at an enzyme dosage of 0.07%.

Study of the dual role mechanism triggered by in-situ cross-linking in hollow fiber membrane matrix

In this paper, a novel polyvinylidene fluoride (PVDF) hollow fiber membrane with uniform pore size and hydrophilic cross-linked network in membrane matrix was developed by non‐solvent induced phase separation method. The dual role mechanism of in-situ cross-linking in regulating molecular chain arrangement during phase separation and preventing deterioration of membrane mechanical properties were analyzed. The results demonstrated that the cross-linked network formed by in-situ crosslinking entangled with PVDF molecular chains which improved the regularity of PVDF molecular chains, increasing the uniformity of the pore size distribution, the percentage of the most probable pore size of the modified membrane increased to 93.25 %. The cross-linked network was immobilized in the membrane which formed semi-interpenetrating structure, maintaining the mechanical properties of the membrane. The permeation flux of the modified membrane increased by 24.1 times to 477.7 L m−2 h−1 compared to the original PVDF membrane. The rejection of BSA was maintained at 98.5 %, with the tensile strength increased to 2.52 MPa. The modified membrane exhibited persistent hydrophilicity in 21 days washing experiment with improved antifouling performance.

Mechanism of sodium lauryl sulfate reducing froth stability of dodecylamine in hematite flotation: Experiments and molecular dynamics simulation

In this study, the influence of sodium lauryl sulfate (SLS) on the stability of dodecylamine (DDA) froth during the reverse flotation of hematite was investigated due to the frequent issue of excessively viscous foam leading to suboptimal reverse flotation outcomes. The research involved conducting flotation tests and two/three-phase froth stability assessments to explore how a specific molar ratio combination of DDA and SLS could enhance the flotation performance while simultaneously mitigating froth stability. The investigation into the mechanism by which SLS reduces the stability of DDA froth was aided by molecular dynamics simulations. The findings revealed that in the collector system comprising DDA and SLS, several key changes occurred at the molecular level. These included a decrease in the thickness of the electric double layer at the interface, a reduction in the thickness of the gas–liquid interface layer, weakening of the interaction strength between the head group and water molecules, a decrease in the coordination numbers of water molecules in the first hydration layer, and an enhanced migration ability of water molecules. Furthermore, there was an increased inclination angle between the head groups or molecular chains of the collector and the Z-axis, resulting in a diminished interaction depth between the head group and water and a closer positioning of the molecular tail chain to the gas–liquid interface with a more pronounced curvature. Consequently, these molecular adjustments led to a sparser arrangement of DDA molecules at the gas–liquid interface, lower coverage of the interface adsorption layer, and increased gas permeation, ultimately reducing DDA froth stability. The aforementioned conclusions provide a comprehensive molecular-level analysis of the principal mechanisms that can effectively reduce foam stability, including the attenuation of molecular head group-water interactions, reduction in gas–liquid interface layer thickness, decrease in gas–liquid interface orderliness, and enhancement of water molecule migration capability. The implications of this research extend to providing theoretical insights for addressing foam control challenges in DDA flotation processes.

Starch Characteristics and Amylopectin Unit and Internal Chain Profiles of Indonesian Rice (Oryza sativa).

Indonesia is arguably a major player in worldwide rice production. Though white rice is the most predominantly cultivated, red, brown, and red rice are also very common. These types of rice are known to have different cooking properties that may be related to differences in their starch properties. Investigating the starch properties, especially the fine structure of their amylopectin, can help understand these differences. This study aims to investigate the starch characteristics of some Indonesian rice varieties by evaluating the starch granule morphology and size, molecular characteristics, amylopectin unit and internal chain profiles, and thermal properties. Starches were extracted from white rice (long grain (IR-64) and short grain (IR-42)), brown rice, red rice, and black rice cultivated in Java Island, Indonesia. IR-42 had the highest amylose content of 39.34% whilst the black rice had the least of 1.73%. The enthalpy of gelatinization and onset temperature of the gelatinization of starch granules were between 3.2 and 16.2 J/g and 60.1 to 73.8 °C, respectively. There were significant differences between the relative molar amounts of the internal chains of the samples. The two white rice and black rice had a significantly higher amount of A-chains, but a lower amount of B-chains and fingerprint B-chains (Bfp) than the brown and red rice. The average chain length (CL), short chain length (SCL), and external chain length (ECL) were significantly longer for the red rice and the black rice in comparison to both the white rice amylopectins. The long chain length (LCL) and internal chain length (ICL) of the sample amylopectins were similar. Rice starches were significantly different in the internal structure but not as much in their amylopectin unit chain profile. These results suggest the differences in their amylopectin clusters and building blocks.