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The polyethylene oxide‐polypropylene oxide (PEO‐PPO) based triblock copolymers are notable amphiphilic copolymers with a diverse range of applications. The presence of homo‐, and/or diblock impurities in copolymers with PEO‐PPO‐PEO triblock has been demonstrated. This finding suggests that the samples are blends rather than pure triblock copolymers. Furthermore, copolymers with triblock copolymer content of 0 or less than 20% by molar percentage have been identified. The hydrophilic‐lipophilic balance (HLB) is also calculated based on the exact composition of the blends. The effect of HLB values and compositional data on the initial foam height (in casein solution), the surface tension, and the contact angle are investigated. The correlation coefficients for the PPO‐PEO‐PPO copolymers versus HLB values are found to be high, while those obtained for the PEO‐PPO‐PEO copolymers versus values of HLB are significantly lower. The lower correlation coefficients for the PEO‐PPO‐PEO samples can be attributed to the presence of homo‐ and diblock (co)polymer contaminants. In addition, a linear regression model has been constructed to find a mathematical relationship between the percentage of ethylene oxide, the average number of propylene oxide units, and the properties of the copolymer. [ABSTRACT FROM AUTHOR]

Background: Orthodontics is a speciality of dentistry that uses a plethora of devices made from myriad materials to manage various malocclusions. Prolonged contact of orthodontic appliances with oral tissues can lead to cellular damage, highlighting the need for biocompatible materials to mitigate health risks. Objectives: To analyze the genotoxicity and cytotoxicity produced by metal brackets and coated metallic brackets with polymeric and nanoparticle coatings in oral mucosal cells. Materials & methods: The current study compares the toxicity of 3 different types of orthodontic brackets with control groups of oral mucosal cells. Each of the three treatment groups consisted of 10 samples of orthodontic brackets: stainless steel brackets(Group 1), nanoparticle-coated brackets(Group 2), and polymeric-coated brackets(Group 3) exposed to corrosion eluates employing an oral biomimicry model. Two types of oral mucosal cells- Human Gingival Fibroblasts and Buccal Epithelial Cells were used to study the cytotoxic and/or genotoxic effects of the elutes. Intergroup comparisons were conducted using one-way analysis of variance, while scanning electron microscopy evaluated surface characteristic. Results: The interaction between metal ions and oral mucosal cells showed no statistically significant difference for toxicity assays between the three groups(p > 0.005). However, polymeric and nanoparticle-coated groups showed reduced cellular differentiation when compared with conventional stainless-steel brackets. Conclusion: This in-vitro study shows that polymeric or nanoparticle coating of conventional metal brackets aids in enhancing corrosion-resistant characteristics of orthodontic appliances and reduces the toxic oral environment created by metal release in the oral cavity. [ABSTRACT FROM AUTHOR]

Introduction: Oligomeric alpha-synuclein in red blood cells (RBC-o-α-Syn) has been shown to be increased in patients with Parkinson's disease (PD). However, factors that affect RBC-o-α-Syn levels remain to be elucidated. The aim of this study is to analyze the correlations between RBC-o-α-Syn levels and the age, sex and different clinical variables of patients with PD. Methods: 167 patients with PD and 119 healthy controls (HC) were enrolled in this study. The patients with PD were diagnosed based on the MDS clinical diagnostic criteria for PD. All participants were evaluated for their clinical characteristics. Western blot analysis was used to examine the molecular sizes of RBC-o-α-Syn. A newly established chemiluminescent immunoassay was used to measure RBC-o-α-Syn levels. Results: Higher RBC-o-α-Syn levels were detected in PD patients than in HC subjects. The receiver operating characteristic (ROC) curve indicated that a cut off value of 55.29 ng/mg discriminated well between PD patients and HC subjects, with a sensitivity of 67.66% (95% CI: 60.24-74.29%), a specificity of 88.24% (95% CI: 81.22-92.86%), and an area under the curve (AUC) of 0.857. The levels of RBC-o-α-Syn were higher in female than male patients (p = 0.033). For different subtypes, the levels of RBC-o-α-Syn were higher in the MIX subtype than the tremor-dominant (TD) PD. In addition, the levels of RBC-o-α-Syn were higher in patients with than without cognitive impairment (p = 0.016), and negatively correlated with Mini-Mental State Examination (MMSE) scores (r = -0.156, p = 0.044). Conclusion: Our study demonstrates that RBC-o-α-Syn levels in patients with PD are higher than those in HC subjects and affected by the sex and the severity of cognitive impairment. [ABSTRACT FROM AUTHOR]

Background: The accuracy of a diagnostic test depends on its intrinsic characteristics and the disease incidence. This study aims to depict post-test probability of Pneumocystis pneumonia (PJP), according to results of PCR and Beta-D-Glucan (BDG) tests in patients with acute respiratory failure (ARF). Materials and methods: Diagnostic performance of PCR and BDG was extracted from literature. Incidence of Pneumocystis pneumonia was assessed in a dataset of 2243 non-HIV immunocompromised patients with ARF. Incidence of Pneumocystis pneumonia was simulated assuming a normal distribution in 5000 random incidence samples. Post-test probability was assessed using Bayes theorem. Results: Incidence of PJP in non-HIV ARF patients was 4.1% (95%CI 3.3-5). Supervised classification identified 4 subgroups of interest with incidence ranging from 2.0% (No ground glass opacities; 95%CI 1.4–2.8) to 20.2% (hematopoietic cell transplantation, ground glass opacities and no PJP prophylaxis; 95%CI 14.1–27.7). In the overall population, positive post-test probability was 32.9% (95%CI 31.1–34.8) and 22.8% (95%CI 21.5–24.3) for PCR and BDG, respectively. Negative post-test probability of being infected was 0.10% (95%CI 0.09–0.11) and 0.23% (95%CI 0.21–0.25) for PCR and BDG, respectively. In the highest risk subgroup, positive predictive value was 74.5% (95%CI 72.0-76.7) and 63.8% (95%CI 60.8–65.8) for PCR and BDG, respectively. Conclusion: Although both tests yield a high intrinsic performance, the low incidence of PJP in this cohort resulted in a low positive post-test probability. We propose a method to illustrate pre and post-test probability relationship that may improve clinician perception of diagnostic test performance according to disease incidence in predefined clinical settings. [ABSTRACT FROM AUTHOR]

Purpose. The purpose of the work is to analyze the properties of polymer dispersions with different chemical composition to determine the possibility of their further use as part of polymer coatings for the functionalization of fibrous materials. Methodology. Different types of polymer materials have used in the work: Plextol UltraFine PR 3500K (Synthomer, Germany), Vinavil Eva 1612 (Vinavil, Italy), Crilat 4815 (Vinavil, Italy), Impranil DLP-R (Covestro, Germany). The quality of water-emulsion film-forming systems and the possibility of their use in the process of functionalization of the surface for fibrous bases have determined by the content of dry residue and viscosity, pH, film-forming ability and resistance to the action of electrolytes. Findings. A comparative assessment of water-dispersible acrylic, vinyl and urethane polymers have made in order to determine the possibility of their further application for the functionalization of the surface of fibrous bases. It was determined that all polymer dispersions show resistance to the action of ammonium hydroxide. In addition, all polymer dispersions (with the exception of the aqueous dispersion of acrylic copolymer Plextol UltraFine PR 3500K) are resistant to sodium chloride, ammonium sulfate, and acetic acid. Given the close pH value, almost all polymer dispersions can be mixed without the risk of coagulation. In the future, it is of interest to determine the possibility of combining Crilat 4815 and Impranil DLP-R polymer dispersions when creating a hybrid acrylic-urethane coating for fibrous bases, given their similar resistance to electrolytes. Originality. Finely dispersed emulsions of film-forming acrylic-urethane polymers of the new generation are able to modify the surface of the fibrous material through interaction with its functional groups, which makes it possible to create competitive fabrics with improved stable properties, in particular for technical applications. Practical value. New types of water-dispersion systems on acrylic and urethane polymers are proposed for modifying the surface of fabrics in order to give fabrics new functional properties. It is expected that in these hybrid dispersions, the acrylic component will provide resistance to the action of alkalis and to external influences, while the polyurethane will increase the strength, flexibility and homogeneity of the formed film. [ABSTRACT FROM AUTHOR]

Several series of new polymers were synthesized in this study: binary copolyesters of vanillic (VA) and 4′-hydroxybiphenyl-4-carboxylic (HBCA) acids, as well as ternary copolyesters additionally containing 4-hydroxybenzoic acid (HBA) and obtained via three different ways (in solution, in melt, and in solid state). The high values of logarithmic intrinsic viscosities and the insolubility of several samples proved their high molecular weights. It was found that the use of vanillic acid leads to the production of copolyesters with a relatively high glass transition temperature (~130 °C). Thermogravimetric analysis revealed that the onset of weight loss temperatures of ternary copolyesters occurred at 330–350 °C, and the temperature of 5% mass loss was in the range of 390–410 °C. Two-stage thermal destruction was observed for all aromatic copolyesters of vanillic acid: decomposition began with VA units at 420–480 °C, and then the decomposition of more heat-resistant units took place above 520 °C. The copolyesters were thermotropic and exhibited a typical nematic type of liquid crystalline order. The mechanical characteristics of the copolyesters were similar to those of semi-aromatic copolyesters, but they were much lower than the typical values for fully aromatic thermotropic polymers. Thus, vanillic acid is a mesogenic monomer suitable for the synthesis of thermotropic fully aromatic and semi-aromatic copolyesters, but the processing temperature must not exceed 280 °C. [ABSTRACT FROM AUTHOR]

Polymer materials are typical insulators that are easily charged by contact electrification. Static charge generated by contact electrification on their surfaces can lead to lots of undesirable consequences, including a reduction in efficiency of manufacturing processes, damage to equipment, and even explosions. Thus, it is important to develop effective strategies to prevent the generation of static charge when surfaces of polymer materials come into contact. Here, we coated polymer materials with rhamnolipids (RLs) to create non‐charging surfaces. This innovative technique, based on glycosylated coatings using RLs, offers a universal solution that can be easily applied to a wide range of polymeric materials conferring resistance to surface charging via contact electrification. The amount of static charges generated was found to reduce dramatically in both low (~15%) and high (~60%) humidity situations. The reduction of charge is due to either or both of the following two mechanisms: by increasing surface conductivity driven by the hydrophilic groups of the RLs molecules, and or by their radical‐scavenging properties. Predictably, this new effective strategy is ideal for producing antistatic dipping and spray solution for various practical applications. [ABSTRACT FROM AUTHOR]

Due to their outstanding chemical and physical properties, polyimides are widely used in industrial applications. The degree of imidization of polyimides significantly influences their properties, making it an important factor in tailoring the material for specific applications. Imidization refers to the process of converting a precursor poly(amic acid) by removing water, and it is essential to analyze this process in detail to tune the final structure and properties of the material. Conventional techniques for this task include Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), or differential scanning calorimetry (DSC), but they lack the possibility of spatially and/or depth-resolved analysis or do not enable in-line monitoring capabilities. To overcome these limitations, we propose laser-induced breakdown spectroscopy (LIBS) as a powerful tool for the monitoring of the imidization reaction. To establish a measurement method, a total of 130 in-house prepared, self-synthesized samples were thermally cured to exhibit varying imidization degrees. IR spectroscopy served as a reference technique during method development, and a novel formula for calculating the degree of imidization, based on the C2 and H signal trends, was introduced. The calculated imidization degrees of model thin films based on LIBS were in good accordance with the IR reference method although minor differences between the two methods were expected due to varying information depth and the size of the sampled area. Additionally, the robustness of the procedure was demonstrated by depth profiling of a stacked model polymer, spiking with commercially available additives and, ultimately, by analyzing industry-relevant polymer samples. [ABSTRACT FROM AUTHOR]

Background: To assess the micro tensile bond strength (µTBS) of two resin matrix ceramic (RMC) blocks bonded to composite resin by using different repair protocols with and without chewing simulation (CS). Materials and methods: Two resin matrix ceramic blocks (Vita Enamic and Lava Ultimate) were divided into 4 groups according to the surface treatments: Bur grinding (control), Bur grinding + silane, 9.5% HF acid etching, and 9.5% HF acid etching + silane. The single bond universal adhesive was applied on all specimens after the surface treatments according to the manufacturer's instructions, it was administered actively on the treated surface for 20 s and then light cured for 10 s, followed by incremental packing of composite resin to the treated surface. Each group was further divided into 2 subgroups (with/without chewing simulation for 500,000 cycles). A micro tensile bond strength test was performed for each group (n = 15). The effect of surface treatments on the materials was examined by using a scanning electron microscope (SEM). The micro tensile bond strength (MPa) data were analyzed with a three-way ANOVA, the independent t-test, and one-way ANOVA followed by the Tukey post-hoc test. Results: µTBS results were significantly higher for Lava Ultimate than Vita Enamic for all the surface treatment protocols with (p < 0.01). The chewing simulation significantly negatively affected the micro-tensile bond strength (p < 0.001). Bur grinding + saline exhibited the highest bond strength values for Lava Ultimate, both with and without chewing simulation. For Vita Enamic, bur grinding + saline and HF acid + saline showed significantly higher bond strength values compared to other surface treatments, both with and without chewing simulation (p ≤ 0.05). Conclusion: Bur grinding + silane could be recommended as a durable repair protocol for indirect resin matrix ceramics blocks with composite resin material. [ABSTRACT FROM AUTHOR]

This article explores a new mode of chromatographic separation named BIST™ (Bridge Ion Separation Technique) that is designed specifically for the retention and separation of charged molecules. The proposed mechanism is supported by multiple examples. The separation technique is especially useful for analysis of low molecular weight charged polymers, the class of molecules where ion-exchange, ion-exclusion and size exclusion modes of separation do not work effectively. Among low molecular weight polymers, many compounds are of high importance for biological, medicinal, agricultural, and consumer applications. Some examples include heparin, poly amino acids, insulin, polyethyleneimine, as well as other peptides. The wide variety of applications of many charged polymers necessitates a high-quality analytical technique for testing and research of these compounds. [ABSTRACT FROM AUTHOR]

Several series of new polymers were synthesized in this study: binary copolyesters of vanillic (VA) and 4′-hydroxybiphenyl-4-carboxylic (HBCA) acids, as well as ternary copolyesters additionally containing 4-hydroxybenzoic acid (HBA) and obtained via three different ways (in solution, in melt, and in solid state). The high values of logarithmic intrinsic viscosities and the insolubility of several samples proved their high molecular weights. It was found that the use of vanillic acid leads to the production of copolyesters with a relatively high glass transition temperature (~130 °C). Thermogravimetric analysis revealed that the onset of weight loss temperatures of ternary copolyesters occurred at 330–350 °C, and the temperature of 5% mass loss was in the range of 390–410 °C. Two-stage thermal destruction was observed for all aromatic copolyesters of vanillic acid: decomposition began with VA units at 420–480 °C, and then the decomposition of more heat-resistant units took place above 520 °C. The copolyesters were thermotropic and exhibited a typical nematic type of liquid crystalline order. The mechanical characteristics of the copolyesters were similar to those of semi-aromatic copolyesters, but they were much lower than the typical values for fully aromatic thermotropic polymers. Thus, vanillic acid is a mesogenic monomer suitable for the synthesis of thermotropic fully aromatic and semi-aromatic copolyesters, but the processing temperature must not exceed 280 °C.

Photoresponsiveness is a promising characteristic of stimulus-responsive materials. Photoresponsiveness can be achieved by incorporating photoresponsive molecules into polymeric materials. In addition, multiple-stimuli-responsive materials have attracted scientists' interest. Among the numerous multiple-stimuli-responsive materials, moisture- and photoresponsive materials are the focus of this report. These stimuli-responsive materials responded to the stimuli synergistically or orthogonally. Unlike most stimulus-responsive materials utilizing moisture and light as stimuli, the materials studied herein switch their photoresponsiveness in the presence of moisture. Appropriate copolymers consisting of hydrophilic acrylamide-based monomers for the main chain and hydrophobic azobenzene moieties switched their bending behaviors at 6–9 wt% water contents. At water contents lower than 6 wt%, the polymeric materials bent away from the light source, while they bent toward the light source at water contents higher than 10 wt%. At a low water content, the bending behaviors can be described on the molecular scale. At a high water content, the bending behavior requires consideration of the phase scale, not only the molecular scale. By controlling the balance between hydrophilicity and hydrophobicity, the switching behavior was achieved. This switching behavior may inspire additional strategies for the application of polymeric material as actuators. [ABSTRACT FROM AUTHOR]

Background: The surface treatment to improve the repair bond strength may vary because CAD/CAM provisional restoration polymers exhibit a variety of microstructures. This study was conducted to evaluate the effect of surface treatments on the repairability of three different CAD/CAM polymers for long-term provisional restorations. Methods: Thirty specimens from each provisional restorative materials (CAD-Temp, Everest C-Temp, and PEEK) were divided into three groups: C: surfaces received no treatment; SB: surfaces were airborne particle abraded with 50 μm aluminum oxide; SB-T: surfaces received the same conditions as group SB in addition to thermocycling before and after treatment. Primer and nanohybrid repair resin composite were applied to the prepared CAD /CAM surfaces. The shear bond strength and the mode of failure were assessed. ANOVA and Tukey's significant difference tests were used to evaluate the data. Results: The SB group had significantly higher repair SBS values (p <.001) compared to the other groups (C and SB-T). Everest C-Temp significantly recorded the highest repair SBS (17.84 ± 0.19 MPa) in group SB, while the lowest repair SBS values (5.51 ± 1.14 MPa) for CAD-Temp were recorded in group C. PEEK significantly recorded the second highest repair SBS (15.96 ± 0.18) in the SB group. Conclusions: Everest C-Temp had the highest repair SBS after an airborne abrasion particle. Thermocycling had no significant effect on the repair SBS for PEEK. Everest C-Temp and PEEK are recommended as long-term durable provisional materials for clinical use. [ABSTRACT FROM AUTHOR]

An approach using pyrolysis with comprehensive two-dimensional gas chromatography with flame ionization detection is introduced for identifying common isolated plastic polymers. A quadrupole mass spectrometer is employed as a parallel detector to aid method development and improve polymer identification in complex matrices. Common plastic polymers including polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide, poly(methyl methacrylate), styrene-butadiene rubber, and polyethylene terephthalate are accurately identified within a total analysis time of 45 min. A strategy to enhance compatibility of high-resolution capillary gas chromatography using a 150-µm internal diameter column technology and a larger internal volume microfurnace–based pyrolyzer is discussed. This strategy resulted in minimizing the band broadening effect caused by the pyrolyzer's internal volume and overcoming the slow pressure buildup when the sample is inserted into the furnace. Prolonged pressure buildup to reach a final pressure setting can cause a safety shutdown to the pneumatic control system. The developed approach is complementary to spectroscopic techniques by offering mass based, chemical composition analysis of plastics. [ABSTRACT FROM AUTHOR]

A series of new wholly aromatic (co)polyesters based on m-substituted bifunctional comonomers—4′-hydroxybiphenyl-3-carboxylic (3HBCA) and 3-hydroxybenzoic (3HBA) acids with molar ratios of 3HBCA:3HBA from 0:100 to 60:40, respectively—was synthesized. NMR and FTIR spectroscopy methods proved the full compliance of the copolymer composition with the target ratio of comonomers, as well as high compositional homogeneity (absence of block sequences). The resulting copolyesters have a sufficiently high molecular weight and their intrinsic viscosity values are in the range of 0.6–0.8 dL/g. Thermal analysis showed that all 3HBCA-3HBA copolyesters are amorphous, and with an increase in the content of biphenyl units (3HBCA), the glass transition temperature increases significantly (up to 190 °C). The onset of the intense thermal decomposition of the synthesized polyesters occurs above 450 °C. Thus, this indicates a sufficiently high thermal stability of these polyesters. Rheological measurements have shown that melts of copolyesters with a high content of 3HBCA units exhibit anisotropic properties. At the same time, the method of polarization optical microscopy did not confirm the transition to the liquid crystal state for these polyesters. These results confirm that it is possible to obtain high-performance polyesters based on 3HBCA, but not a mesogenic comonomer. Thus, 3HBCA is a promising comonomer for the synthesis of new thermotropic copolyesters with controlled anisotropic properties. [ABSTRACT FROM AUTHOR]

The present paper deals with the determination of thermodynamic quantities of thermoplastic polymers by using an optical fiber interrogator. Typically, laboratory methods such as differential scanning calorimetry (DSC) or thermomechanical analysis (TMA) are a reliable state-of-the-art option for thermal polymer analysis. The related laboratory commodities for such methods are of high cost and are impractical for field applications. In this work, an edge-filter-based optical fiber interrogator, which was originally developed to detect the reflection spectrum of fiber Bragg grating sensors, is utilized for the detection of the boundary reflection intensities of the cleaved end of a standard telecommunication optical fiber (SMF28e). By means of the Fresnel equations, the temperature-dependent refractive index of thermoplastic polymer materials is measured. Demonstrated with the amorphous thermoplastic polymers polyetherimide (PEI) and polyethersulfone (PES), an alternative to DSC and TMA is presented as the glass transition temperatures and coefficients of thermal expansion are derived. A DSC alternative in the semi-crystalline polymer analysis with the absence of a crystal structure is shown as the melting temperature and cooling-rate-dependent crystallization temperatures of polyether ether ketone (PEEK) are detected. The proposed method shows that thermal thermoplastic analysis can be performed with a flexible, low-cost and multipurpose device. [ABSTRACT FROM AUTHOR]

The abundance of microplastics in the environment poses a constant threat to all parts of the ecosystem, and the scientific community is called upon to help solve the problem. Numerous studies have been published for microplastic analysis, especially in the last decade, with vibrational spectroscopy being the preferred method. According to recent literature, portable spectrometers operating in the near-infrared (NIR) range are being used for the analysis of different types of polymers, and this technique has recently found its way into the analysis of microplastics as a good alternative to expensive and complicated benchtop instruments, such as Fourier-transform infrared (FTIR) spectrometers. The aim of this study is to investigate and evaluate research trends, leading publications, authors, countries, and limitations of the use of NIR spectroscopy in microplastics research, with a comparison to the established FTIR technique. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to characterize and compare the behavior of human osteoblasts and human gingival fibroblasts in contact with polyetheretherketone (PEEK), zirconia, and titanium implant surface materials. Materials and Methods: PEEK, yttria-stabilized zirconia (YTZP), and titanium disks were produced under appropriate and similar conditions to achieve controlled surface features. Human osteoblasts and human gingival fibroblasts were cultured on disks for 14 days. Cell viability and proliferation were evaluated using a resazurin-based method. Morphology and cellular adhesion were observed using field emission gun-scanning electron microscopy (FEG-SEM). Alkaline phosphatase (ALP) activity and bone cell mineralization was evaluated on osteoblasts. Confocal laser scanning microscopy (CLSM) images of fluorescent-stained fibroblasts were obtained at 7 and 14 days of the culture. Results were presented as mean and standard deviation (SD). Group comparisons were tested using analysis of variance (ANOVA) (Tukey's post hoc) with appropriate statistical software, and significance was set at P < .05. Results: Cell viability and proliferation were higher in PEEK and YTZP groups compared with titanium on osteoblast cells (P < .05, all time points) and on fibroblasts (P < .05, 7 and 14 days). All groups showed an increase in ALP activity over time, which was not significant. Mineralization patterns demonstrated an increase in mineral content over time, which was more apparent in the YTZP group. Cell spreading was more evident on PEEK and YTZP specimens. Conclusion: The results suggest increased adhesion, viability, and proliferation of osteoblasts and gingival fibroblasts on zirconia and PEEK surfaces compared with titanium. These results are correlated with the increased wettability of these materials. [ABSTRACT FROM AUTHOR]

Marine microplastics (MPs) are recognized as a growing severe environmental concern. The vertical distribution pattern of MPs in the ocean is still elusive. Meanwhile, different sampling methods have been deployed in previous studies, resulting in difficulties in compiling data. In this study, for the first time, we explored ocean interior MP pollution in the Western Pacific Warm Pool simultaneously using both a CTD (Conductivity-temperature-depth) sampler and a large-volume in-situ filtration system. At the same sampling station, the average abundance of microplastics in the water column obtained by the two sampling methods was 0.37 ± 0.44 n/m3 (in-situ filtration) and 115.12 ± 64.13 n/m3 (CTD), respectively, which showed significant differences. Both methods found that the main chemical composition and shape of MPs were PET and fiber. Ocean current was identified as the dominant factor that impacted the horizontal distribution of MPs in the study area. The abundance of MPs in the surface layer was 5.4–703.8 times higher than that of the water column. The similar physical and chemical properties of MPs in the surface water and water column indicated that MPs in the water column originate from the sustained release from the surface layer. [Display omitted] ● This study investigated microplastic abundance in the Western Pacific water column. ● Differences of water-column microplastics collected by different methods. ● The large-volume in-situ filtration method better reflects realistic MP abundance. ● Increasing the sampling volume improves the reliability of CTD results. ● Fiber and PET were the dominant compositions of MPs. [ABSTRACT FROM AUTHOR]

We study theoretically the physical properties of Rouse polymers when a subset of monomers along the backbone is subjected to an additional driving force of exponentially correlated fluctuating noise. In other words, the polymers are made up of two kinds of particle, one of which has an additional coupling to an active bath that subjects those particles to extra forces. We analyze properties of these active polymers, such as the end to end distance and the local structure induced by active kicks. We then proceed to quantify how the dynamics of such polymers depend on the proportion of monomers which are being actively driven, and show how the dynamics transitions from the normal Rouse like behavior to substantially faster dynamics. Finally we analyze some of the non-equilibrium properties induced in these systems, such as the irreversibility. [ABSTRACT FROM AUTHOR]

The segmental dynamics of polymers is known to be closely related to the glass transition where the glass transition is the single most important parameter in its application. In this study, we designed an efficient and reliable experimental method to study the ensemble segmental dynamics of polymers by probing rotation of fluorescent molecules in the polymer matrix using a home-built microscope setup. The rotational dynamics of fluorescent molecules was analyzed using a fluorescence correlation method that extracts information through orthogonally polarized fluorescence images. From fluorescence intensities, autocorrelation functions (ACFs) were obtained in many areas simultaneously and by averaging several ACFs, well-defined ACF and precise experimental values were obtained from a single measurement movie. The robustness of the method and optimal experimental conditions were investigated by performing experiments with various probe concentrations, frame rates, and measurement lengths. By employing a home-built vacuum chamber, a wide temperature range was achieved, and we demonstrate the versatility and efficiency of imaging rotational FCM (fluorescence correlation microscopy) by probing segmental dynamics of different polymeric systems with glass transition temperature that differ by ≈100 K and with fragility ranging from 49 to 131. The imaging rotational FCM covers dynamics up to 4 orders of magnitude near the glass transition, and it was found that the rapidity of the stretching exponent β variation with temperature correlates with the fragility of polymers. [ABSTRACT FROM AUTHOR]

The effects of added salt on a planar dipolar polymer brush immersed in a polar solvent are studied using a field theoretic approach. The field theory developed in this work provides a unified framework for capturing effects of the inhomogeneous dielectric function, translational entropy of ions, crowding due to finite sized ions, ionic size asymmetry, and ion solvation. In this paper, we use the theory to study the effects of ion sizes, their concentration, and ion-solvation on the polymer segment density profiles of a dipolar brush immersed in a solution containing symmetric salt ions. The interplay of crowding effects, translational entropy, and ion solvation is shown to exhibit either an increase or decrease in the brush height. Translational entropy and crowding effects due to finite sizes of the ions tend to cause expansion of the brush as well as uniform distribution of the ions. By contrast, ion-solvation effects, which tend to be stronger for smaller ions, are shown to cause shrinkage of the brush and inhomogeneous distribution of the ions. [ABSTRACT FROM AUTHOR]

Polymeric complex coacervation occurs when two oppositely charged polyelectrolytes undergo an associative phase separation in aqueous salt solution, resulting in a polymer-dense coacervate phase and a polymer-dilute supernatant phase. This phase separation process represents a powerful way to tune polymer solutions using electrostatic attraction and is sensitive to environmental conditions such as salt concentration and valency. One area of particular research interest is using this to create nanoscale polymer assemblies, via (for example) block copolymers with coacervate-forming blocks. The key to understanding coacervate-driven assembly is the formation of the interface between the coacervate and supernatant phases and its corresponding thermodynamics. In this work, we use recent advances in coacervate simulation and theory to probe the nature of the coacervate-supernatant interface. First, we show that self-consistent field theory informed by either Monte-Carlo simulations or transfer matrix theories is capable of reproducing interfacial features present in large-scale molecular dynamics simulations. The quantitative agreement between all three methods gives us a way to efficiently explore interfacial thermodynamics. We show how salt affects the interface, and we find qualitative agreement with literature measurements of interfacial tension. We also explore the influence of neutral polymers, which we predict to drastically influence the phase behavior of coacervates. These neutral polymers can significantly alter the interfacial tension in coacervates; this has a profound effect on the design and understanding of coacervate-driven self-assembly, where the equilibrium structure is tied to interfacial properties. [ABSTRACT FROM AUTHOR]

Interplay between counterion-mediated interaction and stiffness inherent to polymer chain can bring substantial complexity to the morphology and dynamics of polyelectrolyte brush condensates. Trivalent counterions induce collapse of flexible polyelectrolyte brushes, over a certain range of grafting density, into octopus-like surface micelles; however, if individual chains are rigid enough, the ion-mediated local nematic ordering assembles the brush chains into fractal-like dendritic condensates whose relaxation dynamics is significantly slower than that in the surface micelles. Notably, the trivalent ions condensed in the dendritic condensates are highly mobile displaying quasi-one-dimensional diffusion in parallel along the dendritic branches. Our findings in this study are potentially of great significance to understanding the response of cellular organization such as chromosomes and charged polysaccharides on membranes to the change in ionic environment. [ABSTRACT FROM AUTHOR]

We conducted laboratory experiments to investigate a suspected effect of tetrahydrofuran (THF) on quantifying crystalline silica in samples collected from working with engineered stone when THF is used to process samples prior to the X-ray diffraction (XRD) analysis. Two groups of samples from grinding either engineered stone or granite were simultaneously taken from a laboratory testing system, with one group of samples using THF for processing and another group using muffle furnace for ashing. For each stone type, we also tested four levels of respirable dust loading on the samples by varying the grinding time from 1 to 8 min. Statistical analysis of the experimental results on crystalline silica contents of the two groups of samples showed that the difference between the two methods was not significant (P ≥ 0.05) for the granite at all four levels of respirable dust loading and for the engineered stone at the two levels of respirable dust loading greater than 0.5 mg. However, the crystalline silica content from using THF processing was significantly lower (P = 0.001) than that from using muffle furnace ashing for engineered stone when the respirable dust loading levels were less than 0.5 mg. For the engineered stone dust samples with grinding times of 1 and 2 min, the average respirable dust loading was about 0.19 and 0.34 mg, respectively; while the crystalline silica content from using THF processing was 30.9 and 21.5% lower than that from using muffle furnace ashing, respectively. Since most full-shift samples from field assessments in this industry are expected to have respirable dust loading less than 0.5 mg, muffle furnace or radio frequency plasma ashing should be specified as the preferred sample processing method instead of the THF processing method for quantification of crystalline silica when engineered stone is expected to present to avoid artificially reduced silica content values, which are likely caused by the reactions between THF and the resins in engineered stone. [ABSTRACT FROM AUTHOR]

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In liquid chromatography, several types of separation modes are known. Here, we are going to describe a new mode of retention and consecutively, a separation mechanism that to our knowledge was not identified as such before. We named this mode: Bridge Ion Separation Technique. This separation mode is possible when a double‐charged ionic modifier of the mobile phase forms a dynamic bridge between an identically charged stationary phase and analyte. This phenomenon was observed in the water‐reduced mobile phase and it is universal for both anions and cations as long as the column has the same charge as the analytes. This retention mechanism is observed with any number of charged functional groups in the analyte molecule but is more profound when the number of charges in the analyte molecule is increased. [ABSTRACT FROM AUTHOR]

Objective: Color and optical properties are particularly crucial to mimic natural tooth. This scoping review aimed to present an overview of the literature published on color and optical properties of 3D printing restorative polymer‐based materials. The literature search was performed in MED‐LINE/Pubmed, Scopus and Web of Science. Materials and methods: The literature search was conducted in the three databases based on the question: "Are the optical properties and color adequately reported on polymer‐based 3D printing dental restorative materials studies?" with no restriction on year of publication. Data were reported and synthesized following PRISMA‐ScR statement. Results: Nine studies fit the inclusion criteria. Five studies focused on evaluating only color stability; three articles assessed the color stability along with mechanical and morphological properties and only one study compared color parameters of 3D printed to conventional polymers. Two studies evaluated translucency parameter and no study was found evaluating scattering, absorption, and transmittance. Conclusions: Color and optical properties of 3D printed polymers that can be used in restorative dentistry are not adequately evaluated and characterized. Future studies on the influence of experimental printing conditions should include these physical properties to assist on improving esthetics. Clinical significance: This review shows the scarce literature existing on color and optical properties of 3D printing restorative polymer‐based materials. These properties and their study are of outmost importance to create materials that mimic natural tooth to allow clinicians to obtain esthetically pleasant restorations. [ABSTRACT FROM AUTHOR]

The aim of the work was to evaluate the antimicrobial activity of polymeric materials with immobilized N-Chlorosulfonamide groups against multidrug-resistant hospital strains of common microorganisms and to determine the resistance to microbial penetration of these materials. Materials and methods: the studied samples were copolymers of styrene with divinylbenzene in the form of staple fi bre and non-woven fabric with immobilized N-Chlorosulfonamide groups of various structures. Hospital strains of microorganisms have been isolated from clinical material; their antibiotic sensitivity has been determined by the Kirby-Bauer method. The agar diff usion method determines the antimicrobial activity of the polymers. Resistance to microbial penetration of samples of non-woven fabric has been determined by the membrane fi ltration method. Results: polymer samples have been synthesized with immobilized N-Chlorosulfonamide groups in the Na- and H-forms, and with the N, N-dichlorosulfonamide group, with chlorine concentration range 3.7–12.5 %. All samples demonstrated pronounced antimicrobial activity against both standard and hospital strains. Due to the higher specifi c surface area, staple fi bre is generally more effi cient. An increase in the zone of inhibition of the growth of microorganisms was observed with an increase in the concentration of immobilized chlorine. All the studied fabric samples are impermeable to S. aureus. The control samples containing the free sulfonamide group did not show antimicrobial properties. Conclusions: synthesized chlorine-active polymers have a pronounced antimicrobial activity against multidrug-resistant microorganisms, demonstrate high resistance to microbial penetration and therefore are promising for creating a wide range of medical products on their basis: dressings, protective masks, antimicrobial fi lters, etc. [ABSTRACT FROM AUTHOR]

Many petroleum-derived plastic materials are highly recalcitrant and persistent in the environment, posing significant threats to human and ecological receptors due to their accumulation in ecosystems. In recent years, research efforts have focused on advancing biological methods for polymer degradation. Enzymatic depolymerization has emerged as particularly relevant for biobased plastic recycling, potentially scalable for industrial use. Biodegradation involves adsorption to the plastic solid surface, followed by an interfacial reaction, resulting in cleavage of bonds of polymer chains exposed on the surface. Here, widely varying substrate-specific kinetics are observed, with the polymer's properties possessing a significant impact on the rate of this interfacial catalysis. Thus, there is a critical need for sensitive and accurate characterization of the material surface during and after interfacial depolymerization to fully understand the reaction mechanisms. Here, we provide a critical review of a range of techniques used in the analysis of material surfaces to characterize the chemical, topological, and morphological features relevant to the study of enzymatic biocatalysis, including microscopy techniques, spectroscopic techniques (e.g., X-ray diffraction analysis, Fourier transform infrared attenuated total reflectance spectroscopy, and mass spectrometry detection of analytes associated with degradation). Techniques for evaluation of surface energy and topology in their relevancy for sensitive detection of biological surface modifications are also discussed. In addition, this paper provides an overview of the strengths of these techniques and compares their performance in both sensitivity and throughput, including emerging techniques, which can be useful, particularly for the rapid analysis of the surface properties of polymeric materials in high-throughput screening of candidate biocatalysts. This research serves as a starting point in selecting and applying appropriate methodologies that provide direct evidence to the ongoing biotic degradation of polymeric materials., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests., (Copyright © 2024. Published by Elsevier B.V.)

A series of new wholly aromatic (co)polyesters based on m-substituted bifunctional comonomers—4′-hydroxybiphenyl-3-carboxylic (3HBCA) and 3-hydroxybenzoic (3HBA) acids with molar ratios of 3HBCA:3HBA from 0:100 to 60:40, respectively—was synthesized. NMR and FTIR spectroscopy methods proved the full compliance of the copolymer composition with the target ratio of comonomers, as well as high compositional homogeneity (absence of block sequences). The resulting copolyesters have a sufficiently high molecular weight and their intrinsic viscosity values are in the range of 0.6–0.8 dL/g. Thermal analysis showed that all 3HBCA-3HBA copolyesters are amorphous, and with an increase in the content of biphenyl units (3HBCA), the glass transition temperature increases significantly (up to 190 °C). The onset of the intense thermal decomposition of the synthesized polyesters occurs above 450 °C. Thus, this indicates a sufficiently high thermal stability of these polyesters. Rheological measurements have shown that melts of copolyesters with a high content of 3HBCA units exhibit anisotropic properties. At the same time, the method of polarization optical microscopy did not confirm the transition to the liquid crystal state for these polyesters. These results confirm that it is possible to obtain high-performance polyesters based on 3HBCA, but not a mesogenic comonomer. Thus, 3HBCA is a promising comonomer for the synthesis of new thermotropic copolyesters with controlled anisotropic properties.

The present paper deals with the determination of thermodynamic quantities of thermoplastic polymers by using an optical fiber interrogator. Typically, laboratory methods such as differential scanning calorimetry (DSC) or thermomechanical analysis (TMA) are a reliable state-of-the-art option for thermal polymer analysis. The related laboratory commodities for such methods are of high cost and are impractical for field applications. In this work, an edge-filter-based optical fiber interrogator, which was originally developed to detect the reflection spectrum of fiber Bragg grating sensors, is utilized for the detection of the boundary reflection intensities of the cleaved end of a standard telecommunication optical fiber (SMF28e). By means of the Fresnel equations, the temperature-dependent refractive index of thermoplastic polymer materials is measured. Demonstrated with the amorphous thermoplastic polymers polyetherimide (PEI) and polyethersulfone (PES), an alternative to DSC and TMA is presented as the glass transition temperatures and coefficients of thermal expansion are derived. A DSC alternative in the semi-crystalline polymer analysis with the absence of a crystal structure is shown as the melting temperature and cooling-rate-dependent crystallization temperatures of polyether ether ketone (PEEK) are detected. The proposed method shows that thermal thermoplastic analysis can be performed with a flexible, low-cost and multipurpose device.

Background: Rhei Radix et Rhizoma (rhubarb), as one of the typical representatives of multi-effect traditional Chinese medicines (TCMs), has been utilized in the treatment of various diseases due to its multicomponent nature. However, there are few systematic investigations for the corresponding effect of individual components in rhubarb. Hence, we aimed to develop a novel strategy to fuzzily identify bioactive components for different efficacies of rhubarb by the back propagation (BP) neural network association analysis of ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry for every data (UPLC-Q-TOF/MSE) and integrated effects. Methods: Through applying the fuzzy chemical identification, most components of rhubarb were classified into different chemical groups. Meanwhile the integration effect values of different efficacies can be determined by animal experiment evaluation and multi-attribute comprehensive indexes. Then the BP neural network was employed for association analysis of components and different efficacies by correlating the component contents determined from UPLC-Q-TOF/MSE profiling and the integration effect values. Finally, the effect contribution of one type of components may be totaled to demonstrate the universal and individual characters for different efficacies of rhubarb. Results: It suggested that combined anthraquinones, flavanols and their polymers may be the universal character to the multi-functional properties of rhubarb. Other components contributed to the individuality of rhubarb efficacies, including stilbene glycosides, anthranones and their dimers, free anthraquinones, chromones, gallic acid and gallotannins, butyrylbenzenes and their glycosides. Conclusions: Our findings demonstrated that the bioactive components for different efficacies of rhubarb were not exactly the same and can be systematically differentiated by the network-oriented strategy. These efforts will advance our knowledge and understanding of the bioactive components in rhubarb and provide scientific evidence to support the expansion of its use in clinical applications and the further development of some products based on this medicinal herb. [ABSTRACT FROM AUTHOR]

Reducing the concentration of carbon dioxide in the atmosphere is a major challenge for humanity as well as for living species on Earth. Not least because of the adverse effects of climate warming caused by the anthropological emissions of the CO2. We are interested in a complementary approach to capturing and storing CO2, which is to use CO2 as a raw material for chemical reactions. Specifically, it is a question of using the CO2 for the synthesis of certain types of biocompatible polymers. For the time being, these remain restricted to polycarbonates for economic reasons. The use of CO2 is also motivated by its abundance as a potentially unlimited source of carbon. The challenge of this chemical process is to use appropriate catalysts to synthesize polycarbonates in sufficient quantities and with interesting physical properties. There is also talk of producing biodegradable and biocompatible polycarbonates to ensure a relatively green footprint compared to conventional polycarbonate production processes. [ABSTRACT FROM AUTHOR]

In this work, a reliable and time-saving protocol for the measurement of polymers using photothermal-induced resonance (AFM-IR) at the nanoscale was developed and applied to 4 industrially relevant polymers: a polypropylene-based reactor thermoplastic polyolefin (rTPO), linear low density polyethylene (LLDPE) for molding and two recycled post-consumer polypropylene/polyethylene blends. In addition to the morphology obtained through AFM, we were able to identify and image the major components of each polymer, including the mineral fillers (talc and calcium carbonate) present in each blend using nanoscale spatial resolution infrared imaging. The protocol developed allows the quick analysis and identification at the nanoscale of the major components of a blend without having previous knowledge of the sample composition, a major advantage when compared to other traditionally used imaging techniques such as TEM and SEM.

We investigate how the electrical conductance of microfibers (made of polymers and conductive nanofillers) decreases upon uniaxial deformation by performing both experiments and simulations. Even though various elastic conductors have been developed due to promising applications for deformable electronic devices, the mechanism at a molecular level for electrical conductance change has remained elusive. Previous studies proposed that the decrease in electrical conductance would result from changes in either distances or contact numbers between conductive fillers. In this work, we prepare microfibers of single walled carbon nanotubes (SWCNTs)/polyvinyl alcohol composites and investigate the electrical conductance and the orientation of SWCNTs upon uniaxial deformation. We also perform extensive Monte Carlo simulations, which reproduce experimental results for the relative decrease in conductance and the SWCNTs orientation. We investigate the electrical networks of SWCNTs in microfibers and find that the decrease in the electrical conductance upon uniaxial deformation should be attributed to a subtle change in the topological structure of the electrical network. [ABSTRACT FROM AUTHOR]

We explore flexoelectro-optic effect in polymer stabilized cholesteric liquid crystals (CLC) with uniform lying helix texture. A method to enlarge the flexoelectric response of the CLC mixture is demonstrated by mixing two nematic liquid crystal host materials with large and small effective flexoelastic coefficients. By a choice of material composition of CLC mixture, a large angle of flexoelectrically driven in-plane rotation of helical axis with a submillisecond response time is obtained. Our findings will be useful for material design of future CLC mixtures for applications in flexoelectro-optic displays. [ABSTRACT FROM AUTHOR]

This paper presents a characterization of PA6 and the blend PA6+EPDM (60/40) by tensile tests in order to evaluate several mechanical properties for impact resistance applications. Results were found to be dependend on test rate (10 mm/min, 250 mm/min and 1000 mm/mm). SEM investigation point out a homogenous structure. The blend has better value of energy at break, for the higher test speed: for v=250 mm/min this characteristic has the value of energy at break 29.7 J and the blend has 76.3 J. At 1000 mm/min, PA6 has this charcateristic of 20 J, but for the blend, it is almost insensitive for the two higher test speeds (76.3 J at 250 mm/min and 72.4 J at 1000 mm/min, respectively) as compared to the neat polymer that decreases this feature when thr test spee increases. At the lowest teste speed, the values of energy at break for the materials in this study are close (90.2 J for PA6 and 87.7 J for the blend). The results from tensile tests pointed out that the formulated blend is recommended for impact resistance applications. [ABSTRACT FROM AUTHOR]

This paper describes the mechanism and trend of High gloss polymer compounds replacing of paintable plastic parts in automobile industry, and gives some solution overcoming the appearance defects that Painting free parts form easily flow marks and Weld lines in injection molding. [ABSTRACT FROM AUTHOR]

We investigate surface phonon propagation in a triangular-lattice phononic crystal of microscopic holes in a gold-coated polymer by time-resolved two-dimensional imaging and by finite-element simulations at sub-gigahertz frequencies. The simulations allow the effects of exciting different points in the crystal lattice to be studied in real space, and also in k-space by spatiotemporal Fourier analysis. The acoustic field in a sub-surface plane below the reach of the holes is also revealed in real-and k-spaces. In addition, we demonstrate pitfalls in the analysis of k-space data when searching for the presence of band gaps. Applications include surface-acoustic wave filter quality control. [ABSTRACT FROM AUTHOR]

We present a simple multiscale model for polymer chains in which it is possible to selectively remove degrees of freedom. The model integrates all-atom and coarse-grained potentials in a simple and systematic way and allows a fast sampling of the complex conformational energy surface typical of polymers whilst maintaining a realistic description of selected atomistic interactions. In particular, we show that it is possible to simultaneously reproduce the structure of highly directional non-bonded interactions such as hydrogen bonds and efficiently explore the large number of conformations accessible to the polymer chain. We apply the method to a melt of polyamide removing from the model only the degrees of freedom associated to the aliphatic segments and keeping at atomistic resolution the amide groups involved in the formation of the hydrogen bonds. The results show that the multiscale model produces structural properties that are comparable with the fully atomistic model despite being five times faster to simulate. [ABSTRACT FROM AUTHOR]

Mesoscale behavior of polymers is frequently described by universal laws. This physical property motivates us to propose a new modeling concept, grouping polymers into classes with a common long-wavelength representation. In the same class, samples of different materials can be generated from this representation, encoded in a single library system. We focus on homopolymer melts, grouped according to the invariant degree of polymerization. They are described with a bead-spring model, varying chain stiffness and density to mimic chemical diversity. In a renormalization group-like fashion, library samples provide a universal blob-based description, hierarchically backmapped to create configurations of other class-members. Thus, large systems with experimentally relevant invariant degree of polymerizations (so far accessible only on very coarse-grained level) can be microscopically described. Equilibration is verified comparing conformations and melt structure with smaller scale conventional simulations. [ABSTRACT FROM AUTHOR]

The rate of escape of an ideal bead-spring polymer in a symmetric double-well potential is calculated using transition state theory (TST) and the results compared with direct dynamical simulations. The minimum energy path of the transitions becomes flat and the dynamics diffusive for long polymers making the Kramers-Langer estimate poor. However, TST with dynamical corrections based on short time trajectories started at the transition state gives rate constant estimates that agree within a factor of two with the molecular dynamics simulations over a wide range of bead coupling constants and polymer lengths. The computational effort required by the TST approach does not depend on the escape rate and is much smaller than that required by molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

Grafting polymers to nanoparticles is one approach used to control and enhance the structure and properties of nanomaterials. However, predicting the aggregation behavior of tethered nanoparticles (TNPs) is a somewhat trial and error process as a result of the large number of possible polymer tethers, nanoparticles, and solvent species that can be studied. With the main goal of understanding how to control the dispersion and aggregation of TNP systems, molecular simulations and the hetero-statistical associating fluid theory for potentials of variable range have been used to calculate the fluid phase equilibrium of TNPs in both vacuum and in simple solvents under a wide range of conditions. The role of graft length, graft density, and solvent interactions is examined and trends established. Additionally, the fluid distribution ratio (k value) is used to study the solubility of TNPs in industrially relevant solvents including carbon dioxide, nitrogen, propane, and ethylene. [ABSTRACT FROM AUTHOR]

While a wide range of non-trivial predictions of the generalized entropy theory (GET) of glassformation in polymer melts agree with a large number of observed universal and non-universal properties of these glass-formers and even for the dependence of these properties on monomer molecular structure, the huge mathematical complexity of the theory precludes its extension to describe, for instance, the perplexing, complex behavior observed for technologically important polymer films with thickness below ~100 nm and for which a fundamental molecular theory is lacking for the structural relaxation. The present communication describes a hugely simplified version of the theory, called the simplified generalized entropy theory (SGET) that provides one component necessary for devising a theory for the structural relaxation of thin polymer films and thereby supplements the first required ingredient, the recently developed Flory-Huggins level theory for the thermodynamic properties of thin polymer films, before the concluding third step of combining all the components into the SGET for thin polymer films. Comparisons between the predictions of the SGET and the full GET for the four characteristic temperatures of glass-formation provide good agreement for a highly non-trivial model system of polymer melts with chains of the structure of poly(n-α olefins) systems where the GET has produced good agreement with experiment. The comparisons consider values of the relative backbone and side group stiffnesses such that the glass transition temperature decreases as the amount of excess free volume diminishes, contrary to general expectations but in accord with observations for poly(n-alkyl methacrylates). Moreover, the SGET is sufficiently concise to enable its discussion in a standard course on statistical mechanics or polymer physics. [ABSTRACT FROM AUTHOR]

A scheme originally proposed by G. Wei [Physica A 222, 152 (1995); Physica A 222, 155 (1995)] is redesigned to produce numerical shape parameters of arbitrary tree-branched polymers based on the Kirchhoff matrix eigenvalue spectrum. This method and two different Monte Carlo techniques (pivot and growth) are employed to investigate the asphericity of three and four junction comb polymers in both the ideal and excluded volume regimes. It is found that the extrapolated g-ratio and asphericity values obtained by all of these methods are in excellent agreement with each other and the available theory in the ideal regime and that polymers with a complete set of interior branches display a more sphere-like shape. [ABSTRACT FROM AUTHOR]