Polymer Molecular Weight Research Articles

Digital Strategies to Improve Product Quality and Production Efficiency of Fluorinated Polymers: 1. Development of Kinetic Model and Experimental Verification for Fluorinated Ethylene Propylene Copolymerization

Digitalization of industrial polymerization processes represents an effective and efficient approach for product-grade upgrading and for production efficiency improvement. A mechanistic model based on the first principles of elementary reactions and mass balances provides a powerful tool in the practice of process digitalization. In this work, we developed a comprehensive kinetic model for the batch process of bulk copolymerization of tetrafluoroethylene with hexafluoropropylene. A series of experimental runs were carried out under various conditions. The fluorinated ethylene propylene copolymer samples were collected, with the monomer conversions, copolymer compositions, and polymer molecular weights, as well as the melting and crystallization properties, fully analyzed. The model was then correlated with the data for estimation of the model parameters. The reactivity ratios were found to be r1 = 65.5 and r2 = 2.6 × 10–3. With a whole set of estimated parameters, the model was used to simulate results under different polymerization conditions close to industrial production processes, which were further verified with additional experimental data. The agreement between simulated and experimental results was good. The experimentally verified model provides a powerful tool for industrial process optimization aiming at improvement of product quality and production efficiency.

A new-fangled horizon in leather process to sidestep toxic chrome and formaldehyde using hyperbranched polymer

A novel chrome-free tanning and formaldehyde-free post tanning process with PEG-melamine base hyperbranched polymer by complexing aluminum (Al3+) present in aluminum sulfate for eco-friendly tanning applications. The hyperbranched polymers PEGM-400-C-Al and PEGM-600-C-Al were synthesized and characterized by FT-IR, NMR, UV, and XRD. The molecular weight of polymers was assessed by GPC and subjected to the leather process. The processed crust leathers were analyzed for physical characteristics by tensile strength, tear strength, elongation, and quality assessments by hand evaluation by experts. FE-SEM analyzed collagen fibers and fiber splitting of goat skin, and COD, BOD, and total solid in spent liquor were analyzed and compared. The highlighting feature of hyperbranched polymers is (a) Improved shrinkage temperature (Ts) (85±1°C), (b) Improved physical-mechanical properties (c) Better BOD, COD, and total solids over the aluminum sulfate tanning process. This study confirmed that hyperbranched polymer is effective for tanning and post-tanning leather, which obviates the need to use toxic chromium and formaldehyde for tanning leathers.

Erratum to: “The effect of polymer molecular weights on the electrical, rheological, and vapor sensing behavior of polycarbonate/multi‐walled carbon nanotube nanocomposites” [Polymer Composites. 2022, 43(8), 5095

Erratum to: “The effect of polymer molecular weights on the electrical, rheological, and vapor sensing behavior of polycarbonate/multi‐walled carbon nanotube nanocomposites” [Polymer Composites. 2022, 43(8), 5095

Additive Manufacturing of Anatomical Poly(d,l-lactide) Scaffolds

Poly(lactide) (PLA) is one of the most investigated semicrystalline polymers for material extrusion (MEX) additive manufacturing (AM) techniques based on polymer melt processing. Research on its application for the development of customized devices tailored to specific anatomical parts of the human body can provide new personalized medicine strategies. This research activity was aimed at testing a new multifunctional AM system for the design and fabrication by MEX of anatomical and dog-bone-shaped PLA samples with different infill densities and deposition angles. In particular, a commercial PLA filament was employed to validate the computer-aided design (CAD) and manufacturing (CAM) process for the development of scaffold prototypes modeled on a human bone defect. Physical-chemical characterization of the obtained samples by 1H-NMR spectroscopy, size exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) demonstrated a small reduction of polymer molecular weight (~5%) due to thermal processing, as well as that the commercial polymer employed was a semicrystalline poly(d,l-lactide). Mechanical characterization highlighted the possibility of tuning elastic modulus and strength, as well as the elongation at break up to a 60% value by varying infill parameters.

Dynamics of Polymer Chains in Poly(ethylene oxide)/Silica Nanocomposites via a Combined Computational and Experimental Approach.

The dynamics of polymer chains in poly(ethylene oxide)/silica (PEO/SiO2) nanoparticle nanohybrids have been investigated via a combined computational and experimental approach involving atomistic molecular dynamics simulations and dielectric relaxation spectroscopy (DRS) measurements. The complementarity of the approaches allows us to study systems with different polymer molecular weights, nanoparticle radii, and compositions across a broad range of temperatures. We study the effects of spatial confinement, which is induced by the nanoparticles, and chain adsorption on the polymer's structure and dynamics. The investigation of the static properties of the nanocomposites via detailed atomistic simulations revealed a heterogeneous polymer density layer at the vicinity of the PEO/SiO2 interface that exhibited an intense maximum close to the inorganic surface, whereas the bulk density was reached for distances ∼1-1.2 nm away from the nanoparticle. For small volume fractions of nanoparticles, the polymer dynamics, probed by the atomistic simulations of low-molecular-weight chains at high temperatures, are consistent with the presence of a thin adsorbed layer that exhibits slow dynamics, with the dynamics far away from the nanoparticle being similar to those in the bulk. However, for high volume fractions of nanoparticles (strong confinement), the dynamics of all polymer chains were predicted slower than that in the bulk. On the other hand, similar dynamics were found experimentally for both the local β-process and the segmental dynamics for high-molecular-weight systems measured at temperatures below the melting temperature of the polymer, which were probed by DRS. These differences can be attributed to various parameters, including systems of different molecular weights and nanoparticle states of dispersion, the different temperature range studied by the different methods, the potential presence of a reduced-mobility PEO/SiO2 interfacial layer that does not contribute to the dielectric spectrum, and the presence of amorphous-crystalline interfaces in the experimental samples that may lead to a different dynamical behaviors of the PEO chains.

Impact of polymer molecular weight on the efficiency of temperature swing solvent extraction for desalination of concentrated brines

Thermally-responsive non-ionic polymers can be used for temperature swing solvent extraction to desalinate concentrated brines. We determined how polypropylene glycols [PPG] with number average molecular weights (Mn) of 425, 725 or 1000 g/mol affected the quantity and quality of the extracted water, and overall process energy requirements using model 10 wt% NaCl (~100 g/L TDS) and field derived (82.1 g/L TDS) concentrated brines. The amount of water recovered and its salinity was highest for PPG425 (lowest Mn) and lowest for PPG1000 (highest Mn). PPG725 (intermediate Mn) provided the best balance between water recovery and salt rejection. PPG725 produced a water with low salinity (<1.6 wt% NaCl) from a field derived brine using a 20:1 Solvent:Feed ratio, with an overall energy consumption of 49 ± 13 kWh/m3treatedwater. This is comparable with mechanical vapor compression crystallizers (>50 kWh/m3treatedwater). The influent feed salinity at 20:1 S:F did not affect the water extraction efficiency, and NaCl(s) forms in the raffinate, suggesting the potential for near zero liquid discharge desalination in this process. Overall, PPG725 is a promising polymer for desalination of highly concentrated brines. Improving the efficiency of the water-polymer separation during thermal regeneration would further improve the attractiveness of this approach.

Ethylene homo and copolymerization by phosphorus‐benzoquinone based homogeneous and heterogeneous nickel catalysts

AbstractThe low cost and high abundancy of nickel makes it highly attractive for both industrial and academic researchers in the field of polyolefin. However, the development of high performance nickel catalysts for ethylene homo and copolymerization is highly challenging. In this contribution, two novel cationic nickel catalysts with quinone backbone and sterically hindered aryl substituents on phosphine have been synthesized and supported on solid supports to prepare heterogeneous catalysts. The homogeneous catalysts showed high activity and high thermal stability in ethylene polymerization. After heterogenization of these catalysts, all the polymerization parameters (polymerization activity, thermal stability, and polymer molecular weight) were significantly improved. The heterogeneous catalyst can achieve activity of up to 3.26 × 106 g mol−1 h−1, along with polyethylene molecular weight of up to 81.8 × 104 g mol−1. More importantly, these homogeneous and heterogeneous catalysts can realize copolymerization of ethylene with a series of polar comonomers such as methyl 10‐undecenoate, 10‐undecenol, and 6‐chloro‐1‐hexene.

Mechanistic Influence of Polymer Species, Molecular Weight, and Functionalization on Mucin–Polymer Binding Interactions

Improving both systemic and localized delivery of pharmaceuticals by optimizing the delivery vehicle properties is a major area of ongoing research. One such engineered property is mucoadhesion, wherein polymers are tailored to optimize polymer–mucin interactions to increase drug residence times and uptake efficiency. There are many examples of mucoadhesion as a drug delivery modality in the literature, yet the underlying mechanisms remain poorly understood, and its clinical translation is limited. Within this mechanistic lens, we found that nuclear magnetic resonance (NMR) is a powerful tool for uncovering polymer–mucin interactions. We investigated the influence of several polymer design parameters including molecular weight and repeating unit functionalization on mucoadhesion and uncovered several key findings in terms of the influence of these design parameters on polymer–protein intermacromolecular interactions. First, we probed individual polymer species including hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC), and carboxymethyl cellulose (CMC) and identified that molecular-weight-driven changes in the polymer–mucin interaction fingerprint result from perturbations in the polymer-specific binding complex. Specifically, we found that CMC and HPC complexes spatially reorient with increasing molecular weight, whereas HPMC complexes do not. We expanded this comparison to include functional group changes to the polymer repeating unit, where we showed that the addition of methyl groups to cellulose derivatives induces a unique binding fingerprint. Next, we expanded the mucoadhesive polymer series to include CMC, HPC, HPMC, poly(acrylic acid) (PAA), and poly((2-dimethylamino)ethyl methacrylate) (PDMAEMA) and observed a negative correlation between molecular weight and mucoadhesive interaction intimacy, highlighting the differences across polymer species. Finally, we explored polymers that lack mucin interactions to illustrate the limitations of polymer composition and molecular weight as predictors of mucoadhesive fate. Altogether, these experiments were used to report on mucoadhesive interactions at the atomic level and revealed that polymer design is dependent on both the availability and accessibility of mucoadhesive functional groups.

Microplastics in sewage sludge: Distribution, toxicity, identification methods, and engineered technologies

Microplastic pollution is becoming a global challenge due to its long-term accumulation in the environment, causing adverse effects on human health and the ecosystem. Sludge discharged from wastewater treatment plants (WWTPs) plays a critical role as a carrier and primary source of environmental microplastic contamination. A significantly average microplastic variation between 1000 and 301,400 particles kg−1 has been reported in the sludge samples. In recent years, advanced technologies have been successfully applied to address this issue, including adsorption, advanced oxidation processes (AOPs), and membrane bioreactors (MBRs). Adsorption technologies are essential to utilizing novel adsorbents (e.g., biochar, graphene, zeolites) for effectively removing MPs. Especially, the removal efficiency of polymer microspheres from an aqueous solution by Mg/Zn modified magnetic biochars (Mg/Zn-MBC) was obtained at more than 95%. Also, advanced oxidation processes (AOPs) are widely applied to degrade microplastic contaminants, in which photocatalytic by semiconductors (e.g., TiO2 and ZnO) is a highly suitable approach to promote the degradation reactions owing to strongly hydroxyl radicals (OH*). Biological degradation-aided microorganisms (e.g., bacterial and fungal strains) have been reported to be suitable for removing microplastics. Yet, it was affected by biotic and abiotic factors of the environmental conditions (e.g., pH, light, temperature, moisture, bio-surfactants, microorganisms, enzymes) as well as their polymer characteristics, i.e., molecular weight, functional groups, and crystallinity. Notably, membrane bioreactors (MBRs) showed the highest efficiency in removing up to 99% microplastic particles and minimizing their contamination in sewage sludge. Further, MBRs illustrate the suitability for treating high-strength compounds, e.g., polymer debris and microplastic fibers from complex industrial wastewater. Finally, this study provided a comprehensive understanding of potential adverse risks, transportation pathways, and removal mechanisms of microplastic, which full-filled the knowledge gaps in this field.

Cobalt Catalysts Bearing ortho‐(4,4′‐Dichlorobenzhydryl) Substituents and Their Use in Generating Narrowly Dispersed Polyethylene of High Linearity

AbstractSix well‐defined examples of ortho‐(4,4′‐dichlorobenzhydryl)‐substituted 2,6‐diaryliminopyridine‐cobalt dichloride complex, Co1−Co6, have been prepared in reasonable yield by treatment of the corresponding free ligand (L1−L6) with cobalt(II) chloride hexahydrate. The molecular structures of Co2 and Co3 highlight their pseudo‐square pyramidal geometry, the nonsymmetrical properties of the N,N,N′‐chelating ligand and the steric shielding conferred by the ortho‐(4,4′‐dichlorobenzhydryl) groups. On treatment with the aluminoxanes, MAO or MMAO, all cobalt complexes exhibited good to high productivities for ethylene polymerization (up to 8.96×106 g (PE) mol−1 (Co) h−1 at 60 °C) affording linear polyethylene with molecular weights in the range 28.8–250.2 kg mol−1. The steric properties of the ortho‐substituents were found to exhibit significant effects on the activity and molecular weight of the resulting polymers. For example, Co1/MAO proved the most active and thermally stable, while the more sterically encumbered Co3 in combination with either MAO or MMAO afforded the highest molecular weight polymer. All polymerizations were well‐controlled as is evidenced by the narrow dispersities displayed by the polymers, a feature that is characteristic of single‐site behavior. By comparison with their ortho‐benzhydryl‐substituted cobalt counterparts, the effect of the para‐chloride substitution was to increase thermal stability, raise activity and depress polymer molecular weight.

Dynamic behavior of nanofibrous bioscaffolds

Given that the mechanical forces acted on bioscaffolds affect the adhesion, proliferation, and migration of the cells within them, the study of their mechanical properties is considered as important. Mechanical forces on cell depend on the properties of bioscaffolds, which the characteristics are a function of their microstructure. The present study assesses the correlation between the microstructure and dynamic behavior of the nanofibrous mats produced at different electrospinning voltage and polymer molecular weight. Additionally, fiber diameter, cell size, and cell number of mats are estimated based on their density and BET adsorption data. The dynamic behavior of bioscaffolds was evaluated through employing dynamic mechanical analysis in temperature and frequency sweep modes. The results revealed that a reduction in fiber diameter elevated their number, and consequently enhanced cell count and decreased cell size. Further, a raise in molecular weight resulted in increasing the storage and loss modulus of scaffolds, and electrospinning voltage influenced the mechanical properties. Finally, the dynamic and mechanical properties of scaffold can be controlled by modifying its microstructure.

Tuning the thermodynamic, optical, and rheological properties of thermoresponsive polymer solutions via silica nanoparticle shape and concentration

HypothesisThe shape and quantity of hydrophilic silica nanoparticles (NPs) can be used to tune the microstructure, rheology, and stability of phase-separating polymer solutions. In thermoresponsive polymer systems, silica nanospheres are well-studied whereas anisotropic NPs have little literature precedent. Here, we hypothesize that NP shape and concentration lower the onset of rheological and turbidimetric transitions of aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions. ExperimentsDifferential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), turbidimetry, and oscillatory rheology are utilized to examine interactions between NPs, PNIPAM, and water and to track changes in phase separation and rheological properties due to NP concentration and shape. FindingsNP addition reduces phase separation enthalpy due to PNIPAM-NP hydrogen bonding interactions, the degree to which depends on polymer content. While NP addition minorly impacts thermodynamic and optical properties, rheological transitions and associated rheological properties are dramatically altered with increasing temperature, and depend on NP quantity, shape, and polymer molecular weight. Thus NP content and shape can be used to finely tune transition temperatures and mechanical properties for applications in stimuli-responsive materials.

One-Dimensional Assemblies of Co3O4 Nanoparticles Formed from Cobalt Hydroxide Carbonate Prepared by Bio-Inspired Precipitation within Confined Space

Nanostructured spinel-type cobalt(II,III) oxide (Co3O4) finds applications in a wide range of technological fields including clean energy conversion systems and electrochemical devices. Low-dimensional morphologies have been identified as particularly promising for the optimization of transport characteristics and the design of anisometric building blocks for the controlled assembly into higher order superstructures. We here introduce a facile bio-inspired room-temperature approach to direct precipitation of one-dimensional basic cobalt carbonate as a precursor to Co3O4 by combining confined submicrometer reaction environments with a carboxylated structure-directing polyelectrolyte. Variation of the polymer concentration and molecular weight then affords control over the mode of infiltration into cylindrical track-etch membrane pores. While a high concentration of the polyelectrolyte additive induces the formation of high aspect ratio smooth fibers with a length resembling the entire pore volume, shorter porous rods with a needle-like substructure are deposited at low polymer concentrations or higher molecular weights. The generality of the infiltration mechanism is demonstrated by gradual substitution of Co2+ ions by Mn2+. Calcination pseudomorphically transforms the resulting intramembrane basic cobalt and manganese carbonate rods and fibers into hierarchical one-dimensional oxides with a porous nanoparticle-based mesostructure.

Effect of Mono- and Multichlorinated Organic Compounds-Chlorocyclohexane and Hexachloro-p-xylene-On the Catalytic Properties of Titanium-Magnesium Catalysts in the Homo- and Copolymerization of Ethylene with 1-Hexene.

Ethylene polymerization and ethylene/1-hexene copolymerization over the titanium–magnesium catalytic system in the presence of chlorocyclohexane (CHC) and hexachloro-p-xylene (HCPX) has been studied. Modification of TMC with chlorocyclohexane and hexachloro-p-xylene increased catalyst activity severalfold for both ethylene polymerization and ethylene/1-hexene copolymerization. The key kinetic regularities of ethylene homopolymerization and ethylene/1-hexene copolymerization in the presence of CHC and HCPX were determined, and the copolymerization constants were measured. Molecular characteristics and the copolymer composition were determined for the synthesized samples of ethylene homopolymers and ethylene/hexene copolymers. Modification of the titanium–magnesium catalyst with chlorinated organic compounds reduced 1-hexene content in the copolymer; polymerization was sensitive to 1-hexene as a regulator of polymer molecular weight. The potential mode of action of chlorinated organic modifiers on catalytic properties of titanium–magnesium catalyst is discussed.

Characterization and optimization of polymer-polymer aqueous two-phase systems for the isolation and purification of CaCo2 cell-derived exosomes.

Exosomes are cell-derived vesicles that present attractive characteristics such as nano size and unique structure for their use as drug delivery systems for drug therapy, biomarkers for prognostic, diagnostic and personalized treatments. So far, one of the major challenges for therapeutic applications of exosomes is the development of optimized isolation methods. In this context, aqueous two-phase systems (ATPS) have been used as an alternative method to isolate biological molecules and particles with promising expectations for exosomes. In this work, fractionation of exosomes obtained from CaCo2 cell line and culture media contaminants were individually performed in 20 polymer-polymer ATPS. The effect of design parameters such as polymer composition, molecular weight, and tie-line length (TLL) on polyethylene glycol (PEG)-Dextran, Dextran-Ficoll and PEG-Ficoll systems was studied. After partition analysis, 4 of the 20 systems presented the best exosome fractionation from contaminants under initial conditions, which were optimized via salt addition (NaCl) to a final concentration of 25 mM, to improve collection efficiency. The PEG 10,000 gmol-1 –Dextran 10,000 gmol-1 system at TLL 25% w/w with NaCl, showed the best potential isolation efficiency. Following this proposed strategy, an exosome purification factor of 2 in the top PEG-rich phase can be expected furtherly demonstrating that ATPS have the potential for the selective recovery of these promising nanovesicles.

Modeling the Impact of Polychloramide Solution Properties on Bacterial Disinfection Kinetics.

Anionic water-soluble polychloramide biocides are of interest because, compared to conventional cationic antimicrobial polymers, anionic biocides are less likely to be sequestered or deactivated by contact with non-microbial soil. Although electrostatics can prevent anionic polymers from adsorbing on microbes, water-soluble polychloramides appear to transfer oxidative chlorine during transient contacts between polymer chains and microbe surfaces. The Chick-Watson model of disinfection kinetics has been modified to account for the contributions of polychloramide molecular weight (MW) and the polychloramide configuration in solution estimated from the overlap concentration, C*, below which dilute polymer chains exist as discrete objects in solution. The key assumption in the modeling was that the transfer rate of oxidative chlorine from polychloramide chains to microbe surfaces impacts the disinfection kinetics. Because both C* and MW are measurable, the polymer-modified Chick-Watson (PCW) model has one less unknown parameter than the two-parameter Chick-Watson equation. The PCW model predicts that lower MW polymers are more effective biocides compared with high MW counterparts. Additionally, polymers with more compressed configurations in solution are more effective biocides. Experimental evidence supports these conclusions. Based on the estimated time scale of bacteria/polymer collisions compared with disinfection kinetics, arguments are made that bacteria surfaces must be contracted many times by polychloramide chains to achieve sufficient Cl transfer to deactivate bacteria.

Nanostructured Electrospun Polycaprolactone-Propolis Mats Composed of Different Morphologies for Potential Use in Wound Healing.

This study aimed to investigate different types of morphologies obtained using the electrospinning process to produce a material that enables wound healing while performing a controlled release. Using benign solvents, the authors prepared and characterised electrospun polycaprolactone mats loaded with propolis, a popular extract in traditional medicine with potential for skin repair. Different morphologies were obtained from distinct storage periods of the solution before electrospinning to investigate the effect of PCL hydrolysis (average diameters of fibres and beads: 159.2–280.5 nm and 1.9–5.6 μm, respectively). Phytochemical and FTIR analyses of the extract confirmed propolis composition. GPC and viscosity analyses showed a decrease in polymer molecular weight over the storage period (about a 70% reduction over 14 days) and confirmed that it was responsible for the nanostructure diversity. Moreover, propolis acted as a lubricant agent, affecting the spun solutions’ viscosity and the thermal properties and hydrophilicity of the mats. All samples were within the value range of the water vapour transpiration rate of the commercial products (1263.08 to 2179.84 g/m2·day). Even though the presence of beads did not affect the propolis release pattern, an in vitro wound-healing assay showed that propolis-loaded mats composed of beaded fibres increased the cell migration process. Thus, these films could present the potential for use in wound dressing applications.

Considerations in the Development of Physically Stable High Drug Load API- Polymer Amorphous Solid Dispersions in the Glassy State

In this Commentary, the authors expand on their earlier studies of the solid-state long-term isothermal crystallization of amorphous API from the glassy state in amorphous solid dispersions, and focus on the effects of polymer concentration, and its implications for producing high load API doses with minimum polymer concentration. After presenting an overview of the various mechanistic factors which influence the ability of polymers to inhibit API crystallization, including the chemical structure of the polymer relative to the API, the nature and strength of API-polymer noncovalent interactions, polymer molecular weight, impact on primary diffusive molecular mobility, as well as on secondary motions in the bulk and surface phases of the glass, we consider in more detail, the effects of polymer concentration. Here, we examine the factors that appear to allow relatively low polymer concentrations, i.e., less than 10%w/w polymer, to greatly reduce crystallization, including a focus on the heterogeneous structure of the glassy state, and the possible spatial distribution and concentration of polymer in certain key regions of the glass. This is followed by a review and analysis of examples in the recent literature focused on determining the minimum polymer concentration in an amorphous solid dispersion, capable of producing optimally stable high drug load amorphous dispersions.

Preparation of size-tunable sub-200 nm PLGA-based nanoparticles with a wide size range using a microfluidic platform.

The realization of poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) from laboratory to clinical applications remains slow, partly because of the lack of precise control of each condition in the preparation process and the rich selectivity of nanoparticles with diverse characteristics. Employing PLGA NPs to establish a large range of size-controlled drug delivery systems and achieve size-selective drug delivery targeting remains a challenge for therapeutic development for different diseases. In this study, we employed a microfluidic device to control the size of PLGA NPs. PLGA, poly (ethylene glycol)-methyl ether block poly (lactic-co-glycolide) (PEG-PLGA), and blend (PLGA + PEG-PLGA) NPs were engineered with defined sizes. Blend NPs exhibit the widest size range (40–114 nm) by simply changing the flow rate conditions without changing the precursor (polymer molecular weight, concentration, and chain segment composition). A model hydrophobic drug, paclitaxel (PTX), was encapsulated in the NPs, and the PTX-loaded NPs maintained a large range of controllable NP sizes. Furthermore, size-controlled NPs were used to investigate the effect of particle size of sub-200 nm NPs on tumor cell growth. The 52 nm NPs showed higher cell growth inhibition than 109 nm NPs. Our method allows the preparation of biodegradable NPs with a large size range without changing polymer precursors as well as the nondemanding fluid conditions. In addition, our model can be applied to elucidate the role of particle sizes of sub-200 nm particles in various biomedical applications, which may help develop suitable drugs for different diseases.

Impact of Conjugated Polymer Characteristics on the Enrichment of Single-Chirality Single-Walled Carbon Nanotubes

Polymer characteristics influence the chiral selectivity and yield in the enrichment of (7,6) from Signis SG76 in toluene by various fluorene homopolymers and copolymers. Fluorene homopolymers such as poly(9,9-di-n-dodecylfluorene) (PFDD) and copolymers with anthracene such as poly[(9,9-dihexylfluorenyl-2,7-diyl)-co-(9,10-anthracene)] (PFH-A) result in high (7,6) selectivities of up to 67 and 72%, respectively. The selectivity is calculated by optical absorption using a known extinction coefficient and also evaluated by Raman scattering and photoluminescence excitation. In contrast, poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-(9,10-anthracene)] (PFO=A), with a double-bond spacer, results in (9,5) dominant extractions with the purity of (9,5) up to 80% after ultracentrifugation, which is believed to be the first report on the successful enrichment of (9,5) by conjugated polymers. The chiral selectivity is also greatly impacted by the length of alkyl side chain of fluorene homopolymers: hexyl group has low selectivity, while octyl, dodecyl, and tetradecyl (PFTD) groups show high selectivity toward (7,6), and the octadecyl group is prone to include bigger tubes. Interestingly, a chiral selection transition from (7,6) to (8,6) occurred using PFTD after a few enrichment cycles. The chiral purity of (8,6) was greatly improved from 50 to 86% after slow filtration. Polymer molecular weight (MW, here PFDD) also plays a role in the selectivity and yield. Low MW leads to a low yield, and high MW leads to a low selectivity, with the optimal range (Mn) being ca. 20–35 kDa when the polydisperse index is ca. 2–3. Molecular dynamics simulation confirms that different lengths of side chain of polyfluorene have different wrapping stabilities toward specific chirality, where PFTD shows greater stability toward (8,6) than (7,6).