Polymer Size Research Articles

The determination of the lower critical concentration temperature and intrinsic viscosity: The syneresis reaction of polymeric gels

This work studies (by rheological method) the temperature dependence of coil-to-coil contact critical concentration (C* in g/L) and the intrinsic viscosity ([η] in L/g) as the capacity of a single-coil to bind the solvent molecules and increase the solution viscosity accordingly. The C* and [η] were measured and fitted by a model to characterize the thermodynamic stability of the kappa-carrageenan (kC) polysaccharide in solution. The weakest C* and greatest [η] of the kC was found to be ≈ 0.44 g/L and ≈1.23 L/g, respectively. The temperature where the C* was weakest was found at ≈ 30 °C and is referred to as the lower critical concentration temperature (LCCT). The expansion of the polysaccharide was greater at the LCCT, but its capacity to bind the solvent molecules was found greater at ≈ 20 °C according to the model. The hydrodynamic permeability resistance was defined as C*[η] and was shown to decrease smoothly by a slope of 2.6 × 10−3/°C with the increase in temperature from 0 °C to 45 °C, then strongly by a slope of 22.5 × 10−3/°C after 60 °C. Therefore, if a polymer solution at LCCT is gelled at lower or higher temperature, the polymer sizes will decrease (syneresis reaction), but the [η] and gel elasticity will interfere with the kinetics of the reaction to determine thereafter the serum holding capacity of the gels.

Biophysical properties of tense quaternary state polymerized human hemoglobins bracketed between 500kDa and 0.2μm in size.

Polymerized hemoglobin (Hb)-based oxygen carriers (HBOCs) are a scalable and cost-effective red blood cell (RBC) substitute. However, previous generations of commercial polymerized HBOCs elicited oxidative tissue injury in vivo due to the presence of low molecular weight polymeric Hb species (<500 kDa) and cell-free Hb (64 kDa). Polymerized human Hb (PolyhHb) locked in the tense quaternary state (T-state) exhibits great promise to meet clinical needs where past polymerized HBOCs failed. This work shows that separation of T-state PolyhHb via a two-stage tangential flow filtration (TFF) purification train such that the Hb polymers are bracketed between 500 kDa and 0.2μm creates a uniform polymer size and largely eliminates the Hb species which elicit deleterious side effects in vivo. Biophysical characterization of these materials demonstrates their potential effectiveness as an RBC substitute and verifies the low percentage of low molecular weight Hb polymers and cell-free Hb. Size exclusion chromatography confirms that T-state PolyhHb can be consistently produced in a size range between 500 kDa and 0.2μm. Furthermore, the average molecular weight of all PolyhHb species produced is one or two orders of magnitude larger than that of the commercial polymerized HBOCs Hemolink and Oxyglobin, respectively. Haptoglobin binding kinetics confirms that two-stage TFF processing of PolyhHb reliably removes cell-free Hb and low molecular weight polymeric Hb species. T-state PolyhHbs demonstrate lower auto-oxidation rates compared to unmodified Hb and prior generations of commercial polymerized HBOCs. These results demonstrate T-state PolyhHb's feasibility as a next-generation polymerized HBOC for potential use in transfusion medicine.

Progress on the photo aging mechanism of microplastics and related impact factors in water environment

As an emerging pollutant, microplastics (MPs, plastic particles with size 5 mm) pollution in water has acquired extensive attention in recent years due to their small particle size and stable properties, which can act as a carrier for pollutants in water environment and have toxic hazards to aquatic organisms. After entering into water environment, MPs are readily undergone varied types of weathering processes (i.e., hydrolysis, photo oxidation, mechanical abrasion, and biodegradation), leading to shifted surface morphology (i.e., surface roughness, specific surface area, and size) and physicochemical properties (i.e., melting temperature, surface charge, molecular weight, crystallinity, and hydrophobicity). Among different weathering processes of MPs in water, sunlight induced photo aging process has been considered as primary contributor, which will further impact the MPs behaviors, such as aggregation and deposition in water column, adsorption to organic and inorganic pollutants, leaching of additives, as well as toxicity to organisms in water. From the perspective of MPs aging mechanism, photo aging process of MPs in water environment is a free radical associated chain reaction process and readily to be affected by polymer types, plastic additives, halogen ions, and natural organic matters. These components are generally photochemical activated and prone to involved in the direct or free radical associated indirect photo aging process processed. However, limited information has referred the impact of plastic additives and water constitutes on the long term weathering process for MPs in water, which will pose a great difference between laboratory-accelerated weathering and long-term natural weathering. Studying the photo aging mechanism of MPs in water environment is of great significance for evaluating their formation process and potential ecological risks. Based on the above considerations, we systematically reviewed the photo aging and fragmentation processes of MPs in water environment. The content of this work contains: (1) Photo aging mechanism and changes of MPs physicochemical properties during aging process in water. Research results revealed that photo aging process could affect the molecular arrangement and mechanical properties of MPs, and further fragment into smaller size secondary MPs even in nano-scale particles, which is important to explain the formation of MPs in current water environment. (2) Critical effect of plastic properties, such as polymer type, size, and plastic additives on the aging of MPs in water; for the impact of plastic additives on the aging process of MPs, results in this work suggested that photo aging mechanism of MPs could be modified due to the presence of plastic additive (i.e., antioxidant and colorant). (3) Role of water constitutes (i.e., Cl−, Br, and NOM) on the photo aging process of MPs in water. The results emphasized the multiple impacts of water constitutes (halogen ions and natural organic matter) in the photo aging process of MPs in the water environment, illustrating that MPs may have different aging time and mechanisms in different water matrices. Moreover, impact of microorganism induced biodegradation for MPs in water is also proposed. In further study, more concentration should be concerned on the combined effects of plastic additives and water quality conditions on the aging process of MPs, which is helpful to shorten the distance between laboratory accelerated weathering and long-term aging process of MPs in natural waters. Besides, results of this paper can also provide theoretical support for comprehensively and systematically assessing the environmental behavior, toxicological effects and ecological risks of aged MPs in natural water environment.

Thermal- vs Light-Induced On-Surface Polymerization.

On-surface polymerization is a powerful bottom-up approach that allows for the growth of covalent architectures with defined properties using the two-dimensional confinement of a highly defined single-crystal surface. Thermal heating is the preferred approach to initiate the reaction, often via cleavage of halogen substituents from the molecular building blocks. Light represents an alternative stimulus but has, thus far, only rarely been used. Here, we present a direct comparison of on-surface polymerization of dibromo-anthracene molecules, induced either thermally or by light, and study the differences between the two approaches. Insight is obtained by a combination of scanning tunneling microscopy, locally studying the polymer shape and size, and X-ray photoelectron spectroscopy, which identifies bond formation by averaging over large surface areas. While the polymer length increases slowly with the sample heating temperature, illumination promotes only the formation of short covalent structures, independent of the duration of light exposure. Moreover, irradiation with UV light at different sample temperatures highlights the important role of molecular diffusion across the surface.

Adaptable Multivalent Hairy Inorganic Nanoparticles.

We report a polymer brush-based approach for fabricating multivalent patchy nanoparticles (NPs) with the number of nanodomains (valency) from 6 to 10, potentially from 1 to 10, by exploiting the lateral microphase separation of binary mixed homopolymer brushes grafted on NPs with a radius comparable to the polymer sizes. Well-defined mixed brushes were grown on 20.4 nm silica NPs by two-step surface-initiated reversible deactivation radical polymerizations and microphase separated laterally upon casting from a good solvent, producing multivalent NPs on 2D surfaces. A linear relationship between valency and average core size for the corresponding valency was observed. The mixed brush NPs exhibited abilities to form "bonds" through the overlap of nanodomains and to change the valency when interacting with adjacent NPs. This method could open up a new avenue for studying patchy NPs.

Near-infrared hyperspectral imaging for polymer particle size estimation

This study examines the potential of near-infrared hyperspectral imaging for assessing the size of polymer particles in model fractions based on the scattering phenomena. Different fractions of ground polymers, either polymethyl methacrylate or polypropylene, were characterized by near-infrared spectra collected between 900 and 1700 nm. The possibility to estimate the size of polymer particles using hyperspectral images was confronted with a basic single spot near-infrared measurement. Hyperspectral imaging, in addition to the standard spectral data dimension, provides information about the spatial distribution of sample components and reveals changes in physical properties. Therefore, one can gain a better insight into the scattering phenomena and study the physical inhomogeneity of a sample in terms of particle size distribution. The partial least-squares models constructed to estimate particle size of polymers that were characterized by hyperspectral images (a pixel-based approach) outperforms models built for mean spectra regardless of the considered powdered polymer.

Diffusion of Short Semiflexible DNA Polymer Chains in Strong and Moderate Confinement.

In many technological applications, DNA is confined within nanoenvironments that are smaller than the size of the unconfined polymer in solution. However, the dependence of the diffusion coefficient on molecular weight and characteristic confinement dimension remains poorly understood in this regime. Here, convex lens-induced confinement (CLiC) was leveraged to examine how the diffusion of short DNA fragments varied as a function of slit height by using single-molecule fluorescence tracking microscopy. The diffusion coefficient followed approximate power law behavior versus confinement height, with exponents of 0.27 ± 0.01, 0.32 ± 0.02, and 0.42 ± 0.06 for 692, 1343, and 2686 base pair chains, respectively. The weak dependence on slit height suggests that shorter semiflexible chains may adopt increasingly rodlike conformations and therefore experience weaker excluded-volume interactions as the confinement dimension is reduced. The diffusion coefficient versus molecular weight also exhibited apparent power law behavior, with exponents that varied slightly (from -0.89 to -0.85) with slit height, consistent with hydrodynamic interactions intermediate between Rouse and Zimm model predictions.

Dedicate to commemorate of Prof. Lina Zhang

Dedicate to commemorate of Prof. Lina Zhang

Detection of Exposure to Microplastics in Humans: A Systematic Review

BACKGROUND: Microplastics are able to enter the human body through food chains, personal care products, contact (skin) from the soil, water or inhalation of microplastics in the air. AIM: This article aims to identify the presence of microplastics that are exposed to humans. METHODS: Systematic review using four bibliographic databases (Google Scholar, Wiley Online Library, PubMed, and Science Direct). Literature search from 2016 to 2021, in the search found as many as 10983 papers extracted using PRISMA guidelines, a total of five papers were selected for review. RESULTS: In this review article, the presence of oral, dermal, and inhalation exposed microplastics is found in feces, colon, placenta, scalp hair, hand skin, facial skin, and saliva. Several methods are used to identify microplastics according to polymer types, shape, and sizes microplastics in humans. The polymer type often found in the article is polypropylene. In addition, fibers, fragments and films are detectable shape of microplastic, while the size of microplastics &gt;5 mm. CONCLUSION: This literature study provides evidence that microplastics of various types of polymers, shapes and sizes are ubiquitous in humans. Hence, the possibility of health risks resulting from microplastic exposure in the human body should not be ignored.

Multiple length scale structure-property relationships of wheat starch oxidized by sodium hypochlorite or hydrogen peroxide

Wheat is a potential source of oxidized starch, but there is no systematic study reporting the effects of oxidation conditions on the structural changes and subsequent physical properties. We report the properties of oxidized wheat starch granules treated with 2, 5, and 10% hydrogen peroxide (at pH 4 and 10) or sodium hypochlorite (at pH 4, 7, and 10). Increasing concentrations favored the formation of carbonyl groups by H2O2 and carboxyl groups by NaOCl. Granule morphology and molecular order were little affected, but increasing oxidant concentration reduced polymer size. Both oxidants influenced temperatures of gelatinization and caused major reductions in pasting viscosities. Principal component analysis (PCA) suggested that both functional group content and depolymerization contributed to the variations in gelatinization, pasting, and solubility properties. Controlled oxidation of wheat starch by H2O2 or NaOCl can produce oxidized starches of different functional properties useful in diverse potential applications.

Fluorescent Tagging of Polymer Particles with PBN for the Detection of Microplastics in Personal Care Goods

Objectives : Plastic pollution has been aggravated due to the massive use of disposable products and single-use face masks since the coronavirus disease (COVID-19) pandemic. There is growing interest regarding detection and identification of plastic pollution in daily life. The aim of this study is (1) to investigate suitability of a fluorescent labelling method for the detection of polymers, (2) to detect microplastics in personal care goods, and (3) to identify the detected plastic particles.Methods : In order to detect plastic particles in real samples, a 1-pyrenebutyric acid N-hydroxysuccinimidyl ester (PBN) fluorophore was used as a dye for staining plastic particles. First, the capability of PBN was evaluated by staining a model polymer of polyethylene (PE) particles, and its desorption and photobleaching was also investigated. Using the optimum staining condition, microplastics were detected in a laboratory-controlled sample and commercially available products, specifically in cleansers, scrubs, and toothpastes. Finally, the detected microplastics were identified using an attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR) analysis.Results and Discussion : The PE particles fluoresced blue light after being stained with PBN at a concentration of 100 μg/mL for 3-5 min without post treatments (e.g., fixation and drying), but the particles should be detected within 24 h due to the photobleaching of PBN. The desorption of PBN fluorophore occurred when the stained PE particles were washed with 25% acetone rather than rinse-off with deionized (DI) water. All of the tested personal care goods contained plastic particles and various sizes and shapes (e.g., spherical, rounded, and irregular shapes) of particles were found in different types and brands of products. The detected particles were identified as PE, polypropylene (PP), polycarbonate (PC), ethylene vinyl acetate (EVA), polystyrene (PS), and polyvinyl chloride (PVC) polymers.Conclusions : The PBN was shown to effectively stain polymer particles and it allowed visual identification of microplastics in personal care goods. Various types and sizes of polymers were included into the commercially available products as ingredients, indicating a primary source of plastic pollution in aquatic environment.

Thermoelectric Properties of ex-situ PTH/PEDOT Composites

A thermoelectric material can convert temperature difference into electrical potential difference. Today, intensive researches are being carried out in order to use flexible, non-toxic and inexpensive conductive polymers instead of hard, hard-to-shape, expensive and toxic semiconductor metals used as thermoelectric materials. Among the conductive polymers investigated for this purpose, poly(3,4-ethylenedioxythiophene) (PEDOT) is the most promising. However, its thermoelectric properties alone are not sufficient. Thermoelectric properties can be increased by incorporating nanoparticles in inorganic, organic or polymeric structures into conductive polymers. In this study firstly, PTh was synthesized with and without magnetic field by oxidative polymerization in aqueous media in the presence of poly(sulfonic acid diphenyl aniline). Secondly, PEDOT was synthesized with and without magnetic field in aqueous media by oxidative polymerization. Then, ex-situ PTH/PEDOT composites were obtained with different ratios of PTh/PEDOT. Particle sizes of polymers were measured and their FTIR and UV-vis. spectra were taken. Seebeck coefficient and electrical conductivity were measured from thin films of polymers. Power factor values were calculated. It was found that the Seebeck coefficients of PTh and ex-situ PTH/PEDOT composites increased with magnetic field. The highest Seebeck coefficient and power factor of PEDOTs were obtained from PEDOT synthesized without magnetic field as 1683.3 µV/K and 98.2 µW/mK2, respectively. The highest Seebeck coefficient and power factor of ex-situ PTh/PEDOT composites were obtained from (PTh/PEDOT3)m synthesized with magnetic field as 400 µV/K and 0.1 µW/mK2, respectively.

Unraveling the Role of Architecture in Polymer-Based Glues for Hydrogels.

We investigate polymers of different architectures as potential candidates for the development of glues for hydrogels. Using a combination of coarse-grained modeling and molecular dynamics simulations, we systematically characterize the link between experimentally tunable parameters and adhesion energy. We find that, for a broad set of parameters, adhesion is controlled almost exclusively by the total amount of glue at the interface and by the glue-hydrogel affinity. Instead, it is largely independent of changes in polymer architecture and size, a conclusion that shines new light on previously observed experimental trends. Additionally, we show that the scaling behavior of the properties we measure can be explained by modeling the glue as an ensemble of ideal, noninteracting, and linear polymer segments. We expect that the fundamental insights herein provided will aid the design of new polymer-based adhesives for hydrogels.

Surface characteristic and sinking behavior modifications of microplastics during potassium permanganate pre-oxidation

Microplastics (MPs) occur in the source water of worldwide drinking water treatment plants (DWTPs). Pre-oxidation treatments become the initial stage for MPs treatment in DWTPs. Investigating the modifications of MPs after pre-oxidations is important to understand their fate in DWTPs. In this study, potassium permanganate oxidation (PPO) was applied to treat four high abundant MPs in DWTPs, including polyethylene (PE), polyethylene terephthalate (PET), polyvinylchloride (PVC) and polystyrene (PS). Influences of polymer types, sizes and pH were considered. After 10 mg L−1 PPO, only slight corrosions were observed on all MPs. Whereas, the appearances of O-Mn spectrum and the observation of nano-scale particles indicated the generation of nascent state Mn-oxides (MnO2) on MPs surface. This adhesion of MnO2 contributed to increasing density and hydrophilicity. As a result, the sinking performance of MPs was enhanced, e.g. the sinking ratio of 6.5 µm MPs increased 30% (PET), 20% (PVC) and 30% (PS) compared with pristine ones upon pH 7 PPO. These results implied that the practical PPO can enhance the sinking behavior of MPs. Of note, PE seems to be persistent and requires special concern.

The influence of propane and n-butane on the structure and separation performance of cellulose acetate membranes

This work presents the impact of propane and n-butane on the CO2/CH4 separation performance of both cellulose diacetate (CDA) and cellulose triacetate (CTA) membranes by exposing both pristine membranes to either propane (400 kPa) or n-butane (200 kPa) at room temperature (22 ± 2 °C) for 4 weeks. The propane and n-butane sorption isotherms in both membranes were anomalous at 35 °C. X-ray diffraction (XRD) results indicated that the crystalline nature of both polymers was altered by this exposure, although dynamic scanning calorimetry (DSC) did not detect a significant change in the overall crystallinity. Positron Annihilation Lifetime Spectroscopy (PALS) revealed that the average pore size of the CTA polymer and the number of free volume elements of both membranes also increased, even though the sorption uptake was less than 2 wt%. CO2 and CH4 permeabilities at 35 °C were essentially unaffected by the propane or n-butane exposure, indicating that while the crystalline regions of the polymer were affected, plasticization of the glassy amorphous region did not occur. There was a slight decrease in CH4 permeability for the CDA membrane after n-butane exposure, consistent with a slight decline in the CH4 solubility at this feed pressure. The propane and n-butane permeabilities were 0.029 Barrer at 300 kPa and 0.019 Barrer at 125 kPa for the fresh CTA membrane, but these fell significantly after long term exposure to these gases, possibly due to penetrant clustering.

Post-translational cleavage of HMW-GS Dy10 allele improves the cookie-making quality in common wheat (Triticum aestivum).

The online version contains supplementary material available at 10.1007/s11032-021-01238-9.

Inducing pH control over the critical micelle concentration of zwitterionic surfactants via polyacids adsorption: Effect of chain length and structure

HypothesisThe critical concentration above which micelles form from zwitterionic surfactant solutions and their thermodynamic stability is affected by the interaction with weak Brønsted polyacid chains (An) via the formation of charged hydrogen bonds between the latter and anionic moieties. ExperimentsThe interaction between zwitterionic micelles and polyacids capable of forming hydrogen bonds, and its dependence on the environmental pH and polymer structure, has been studied with constant–pH simulations and a restricted primitive model for all electrolytes. FindingsAt low pH, the formation of polyacid/micelle complexes is witnessed independently of the polymer size or structure, so that the concentration above which micelles form is substantially decreased compared to polyacid–free cases. Upon rising pH, polymer desorption takes place within a narrow range of pH values, its location markedly depending on the size and structure of polyacids, and on the relative disposition between headgroup charged moieties. Thus, the desorption onset for long linear polyacids (A60) interacting with sulphobetainic headgroups is roughly two pH units higher than for six decameric chains (6A10) adsorbed onto micelles bearing phosphorylcholinic headgroups. This effect, together with the preferential desorption of chain ends at intermediate pH, may be exploited for drug delivery purposes or building advanced metamaterials.

Structure-function analysis of purified proanthocyanidins reveals a role for polymer size in suppressing inflammatory responses

Proanthocyanidins (PAC) are dietary compounds that have been extensively studied for beneficial health effects due to their anti-inflammatory properties. However, the structure-function relationships of PAC and their mode-of-action remain obscure. Here, we isolated a wide range of diverse PAC polymer mixtures of high purity from plant material. Polymer size was a key factor in determining the ability of PAC to regulate inflammatory cytokine responses in murine macrophages. PAC polymers with a medium (9.1) mean degree of polymerization (mDP) induced substantial transcriptomic changes, whereas PAC with either low (2.6) or high (12.3) mDP were significantly less active. Short-term oral treatment of mice with PAC modulated gene pathways connected to nutrient metabolism and inflammation in ileal tissue in a polymerization-dependent manner. Mechanistically, the bioactive PAC polymers modulated autophagic flux and inhibited lipopolysaccharide-induced autophagy in macrophages. Collectively, our results highlight the importance of defined structural features in the health-promoting effects of PAC-rich foods.

Evaluation of performance of hot mix asphalt contained various sizes of Reclaim asphalt pavement and polymer modified Bitumen

The present investigation intends to investigate the performance of Hot Mix Asphalt (HMA) included Reclaim Asphalt Pavement (RAP) and Polymer Modified Bitumen (PMB) binder prepared with Novolac (phenol–formaldehyde solid resin)polymer. In order to assess the mechanical properties and performance of HMA with various RAP contents, several laboratory tests such as Marshall tests, indirect tensile strength testing, moisture damage evaluation, creep compliance test, and wheel track test was performed. The substitution was conducted in two stages: the first stage includes replacing the coarse aggregate with RAP up to 40percent with an increment of 10percent and the second stage includes the substitution of fine aggregate with the same percentages. The PMB binder was prepared by testing several mixes with various percentages of Novolac and its cross-linking agent (Hexamine). The findings of experimental work showed that the use of PMB binder significantly improves the mechanical properties and performance of HMA. Also, it shows that the substitution of coarse aggregate with RAP produces a substantial improvement in mechanical properties and performance of HMA compared with the substitution of fine aggregate or with control mix.

Additive‐Free Energetic Film Based on Graphene Oxide and Nanoscale Energetic Coordination Polymer for Transient Microchip

AbstractTransient microchips have promising applications in data security and privacy protection. A simple fabrication process and short transient time are two crucial requirements for transient microchips. In this study, a facile drop‐casting method is used to develop a transient microchip based on an energetic film and a microheater on a substrate. It is found that the graphene oxide‐energetic coordination polymer composite based energetic film plays an important role in simplifying the fabrication process and achieving fast transient time due to its inherent film forming ability, strong binding to substrate, and highly energetic characteristics. The interlayer confinement effect of graphene oxide (GO) can significantly reduce the size of energetic coordination polymer (ECP) to nanometer scale. Van der Waals forces between GO layers and coordination bonds between GO and metal ions are responsible for the film formation ability. Furthermore, the reduction of ECP size and the compact stacking lay the foundation for the excellent combustion and pressure production performance of the energetic film. The strong adhesion of the energetic film and the substrate is confirmed by drop experiments. More importantly, the fabricated silicon based transient microchip can achieve self‐destruction within 1 second.