Average Molecular Weight Values Research Articles

Efficient one-pot strategy for fluorescent conjugated polymers derived from 8-amino-1-naphthalene-3,6-disulfonic acid: Synthesis, thermal and optical properties

Schiff base polymers, also known as poly(imines) or poly(azomethine)s, constitute a subset of conjugated polymers. The Schiff base compound was synthesized via the condensation reaction between 8-amino-1-naphthalene-3,6-disulfonic acid and 4-hydroxybenzaldehyde. Subsequently, both 8-amino-1-naphthalene-3,6-disulfonic acid and its Schiff base derivative were polymerized into a poly(naphthol) (PANAPDSA) and Schiff base polymer (PANAPDSASB) under alkaline condition using H2O2 (35 % aqueous solution) as oxidant via oxidative polycondensation (OP). The chemical structures of the synthesized compounds were approved using NMR, FT-IR, UV–Vis, element and LC-MS/MS spectroscopic techniques. The synthesized polymers exhibited lower optical and electrochemical band gaps compared to their respective monomers, suggesting their potential utility as semiconductor materials. The poly(naphthol) derivative exhibited high fluorescent emission intensity of 1000 a.u. when excited at 300 nm with a photoluminescence (PL) emission quantum yield of 13.6 % at 392 nm of emission wavelength in N,N-dimethylformamide (DMF) solution. Weight average molecular weight (Mw) values of PANAPDSA and PANAPDSASB ranged from 9500 Da to 11200 Da, with PDI values between 1.12 and 1.13. The synthesis of conjugated polymers could hold significant importance in technological advancements.

Aromatic (co)polycarbonates bearing pendant 2,3-dimethylmaleimido group based upon a new phthalimidine-containing “cardo” bisphenol

A new “cardo” bisphenol viz., 1-(2-(1,1-bis(4-hydroxyphenyl)-3-oxoisoindolin-2-yl)ethyl)-3,4-dimethyl-1H-pyrrole-2,5-dione (PPH-MA) was synthesized in a two-step reaction sequence starting from phenolphthalein. PPH-MA was utilized as a step-growth monomer for the synthesis of a homo- and fourco-polycarbonates bearing pendant 2,3-dimethylmaleimido groups (PC-MAs) via solution polycondensation of PPH-MA or various mol % compositions of PPH-MA and bisphenol-A, respectively, with triphosgene.1H NMR spectroscopy confirmed the chemical structure and composition of PC-MAs. Inherent viscosity and number average molecular weight values of PC-MAs were in the range 0.45–0.64 dL g−1 and 18,300 − 36,200 g mol−1, respectively, indicating the formation of polymers of medium to reasonably high molecular weights. Tough, transparent and flexible films of PC-MAs could be cast from chloroform solution. X-ray diffraction studies indicated the amorphous nature of PC-MAs. The 10% weight loss temperature (T10) values of PC-MAs were in the range 373–443 °C indicating their good thermal stability.

Amylose molecular weight affects the complexing state and digestibility of the resulting starch–lipid complexes

Previous RS5 (type 5 resistant starch) research has significantly broadened starch use and benefited society, yet the effects of the molecular weight of amylose on RS5 remain underexplored. In this study, amyloses with different molecular weights were complexed with caproic acid (C6), lauric acid (C12), and stearic acid (C18) to observe the effects of the molecular weight of amylose on the structure and in vitro digestive properties of RS5. Gel permeation chromatography revealed that the peak average molecular weight (Mp) values of high-amylose cornstarch NF-CGK (CGK), high-amylose cornstarch obtained via cornstarch via autoclave (high temperature and high pressure)-cooling combined pullulanase enzymatic hydrolysis (CTE), and high-amylose cornstarch NF-G370 (HCK) were 21,282, 171,537, and 188,084 before fatty acid complexation, respectively. Additionally, their weight average molecular weight (Mw) values of 32,429, 327,344, and 410,610 and hydrolysis rates of 58.12 %, 86.77 %, and 64.58 %, respectively. The hydrolysis rate of low-Mw amylose (GCK) complexes with fatty acids was lower than that of HCK and CTE starch–lipid complexes. However, HCK and CTE having similar molecular weights, there was no significant difference in the hydrolysis rate of starch–lipid complexes. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and complexing index analyses confirmed the formation of these complexes. This study proposed the mechanism of RS5 formation and provided guidance for its future development.

Highly crystalline, heat resistant and biodegradable copolyesters from fully bio-based bis(pyrrolidone) monomer

Improving the heat resistance of bio-based and biodegradable polyesters is of great significance to extend their applications. Herein, N,N’-trans-1,4-cyclohexane-bis(pyrrolidone-4-methyl carboxylate) (T-CBPMC) was prepared through efficient Michael-addition reaction between dimethyl itaconate and trans-1,4-cyclohexanediamine. The obtained T-CBPMC was copolymerized into aliphatic poly(butylene succinate) (PBS), and a series of PBSPs copolymers with T-CBPMC (BP) molar percentages between 41−80 mol % and weight average molecular weight (Mw) values ranging between 5.77*104 and 6.67*104 g/mol were prepared. BP units efficiently facilitated the melting temperature (203-251 °C) and isothermal-crystallization rate (t1/2 < 20 s) of PBSPs, endowing the highest heat resistance among commercial biodegradable polyesters, which helps maintain stable in pasteurization, high-temperature disinfection, and microwave environments. Moreover, these copolymers displayed remarkable mechanical, gas barrier properties and degradability. PBSP40-PBSP60 obtained high elastic modulus (335–872 MPa) and tensile strength (24.7–31.5 MPa), and good toughness simultaneously. Multiple-ring structures and large steric hindrance of BP units resulted in superior O2 barrier performance than that of non-degradable PET films. Importantly, the PBSP copolyesters showed obvious degradation in water environments and relatively better enzymatic degradation. It was interesting to find that even with 70 % of the BP units, the PBSP copolyesters still retained hydrolysis ability. The resulting PBSP copolyesters open the way for alternative candidates of biodegradable packaging materials with rapid crystallization, high heat-resistance and gas barrier.

Non-isothermal kinetics of the organocatalytic ring-opening polymerization of ε-caprolactone with metal-free α‑hydroxy acids: Eco-friendly and facile synthesis process

Metal-free and green α‑hydroxy acids (AHA) such as l-malic (MA), DL-mandelic acid (MDL), and citric acid (CA) were successfully and effectively utilized as an effective initiator for the solvent-free ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The performance of AHAs in the polymerization of ε-CL was completely and powerfully investigated via the non-isothermal differential scanning calorimetry (DSC). The proceed of ROP of ε-CL with AHAs could be real-time monitored by the obtained polymerization exotherms at different heating rates. The polymerization exotherms obtained from the ROP of ε-CL with CA occurred at a lower temperature range than MA, and MDA, respectively. From the kinetics study, the average activation energy (Ea) values for the ROP of ε-CL with CA (38.0 ± 1.8 kJ mol−1) were lower than MA (45.2 ± 3.6 kJ mol−1) and MDA (48.8 ± 6.2 kJ mol−1). Using the first-order model fitting, the values of pre-exponential factor (lnA0) for the ROP of ε-CL with CA, MA, and MDA were 7.0 ± 0.3, 8.5 ± 0.2, and 8.9 ± 0.3, respectively. The effectiveness of AHAs in the synthesis of PCL was clarified by conducting a larger-scale (4.0000 g) polymerization using conventional heating and microwave (MW) irradiation methods. From conventional heating, the green AHAs produced PCL with the number average molecular weight (Mn) and dispersity (Đ) values in the range of 5.18 × 103 - 1.43 × 104 g mol−1 and 1.14–2.02, respectively. The irradiation by MW could enhance the synthesis of PCL by reducing the synthesis time. By using the MW power of 450 W and irradiation time of 30 min, the PLC was obtained from the ROP of ε-CL with MA and MDA initiators, and the Mn of the obtained PCL from MW heating was 4.28 × 103 - 8.45 × 103 g mol−1. The mechanism for the ROP of ε-CL with all AHAs was proposed through the activated monomer mechanism.

High Molar Mass Polycarbonates as Closed-Loop Recyclable Thermoplastics.

Using carbon dioxide (CO2) to make recyclable thermoplastics could reduce greenhouse gas emissions associated with polymer manufacturing. CO2/cyclic epoxide ring-opening copolymerization (ROCOP) allows for >30 wt % of the polycarbonate to derive from CO2; so far, the field has largely focused on oligocarbonates. In contrast, efficient catalysts for high molar mass polycarbonates are underinvestigated, and the resulting thermoplastic structure-property relationships, processing, and recycling need to be elucidated. This work describes a new organometallic Mg(II)Co(II) catalyst that combines high productivity, low loading tolerance, and the highest polymerization control to yield polycarbonates with number average molecular weight (Mn) values from 4 to 130 kg mol-1, with narrow, monomodal distributions. It is used in the ROCOP of CO2 with bicyclic epoxides to produce a series of samples, each with Mn > 100 kg mol-1, of poly(cyclohexene carbonate) (PCHC), poly(vinyl-cyclohexene carbonate) (PvCHC), poly(ethyl-cyclohexene carbonate) (PeCHC, by hydrogenation of PvCHC), and poly(cyclopentene carbonate) (PCPC). All these materials are amorphous thermoplastics, with high glass transition temperatures (85 < Tg < 126 °C, by differential scanning calorimetry) and high thermal stability (Td > 260 °C). The cyclic ring substituents mediate the materials' chain entanglements, viscosity, and glass transition temperatures. Specifically, PCPC was found to have 10× lower entanglement molecular weight (Me)n and 100× lower zero-shear viscosity compared to those of PCHC, showing potential as a future thermoplastic. All these high molecular weight polymers are fully recyclable, either by reprocessing or by using the Mg(II)Co(II) catalyst for highly selective depolymerizations to epoxides and CO2. PCPC shows the fastest depolymerization rates, achieving an activity of 2500 h-1 and >99% selectivity for cyclopentene oxide and CO2.

Multi‐Technique Approach to Identify Potent Antimicrobial Agents from Calotropis procera: Insight into Pharmacophore Modeling, Molecular docking, MD simulation, and DFT Approaches

AbstractIn this research, natural compounds from Calotropisprocera were screened according to their antimicrobial activity against the pathogenic microbes selected as E. coli, S. aureus, Traypanosomabrucei, Moraxella catarrhalis, and Leishmaniaamazonensis. A 3D‐QSAR study was performed that evaluated the correlation of the structural parameters for the antimicrobial activity of the natural compounds which were selected based on their antimicrobial in‐vivo and in‐vitro studies previously. The screened active compounds were further studied by molecular docking to analyze the various interactions between the ligands and target proteins. Molecular docking was also performed with the three FDA‐approved antibiotics Cephalexin, Dicloxacillin, and Levofloxacin, having antimicrobial potential, and their results were compared with the docking results of the hit compounds. Results of ADME/T study of the compounds revealed that the two compounds stigmasterol and caryophyllene oxide are the hit compounds having no toxicity, best values of TPSA and average molecular weight. Validation of the docking results was also carried out by re‐docking as well as by molecular dynamic simulation. DFT study was also carried out to explore the stability and chemical properties of active compounds. Results showed that caryophyllene oxide is the hit compound because of the highest Moldock score with 3VOB protein, better than standard drugs and according to dynamic simulation analysis. Therefore, the derived results in these studies provide crucial information for designing antimicrobial drugs by using natural compounds that have better antimicrobial activity.

OPEFB pretreatment using the low-cost N,N,N-dimethylbutylammonium hydrogen sulfate ionic liquid under varying conditions

This study investigates the effects of temperature and period on the pretreatment of OPEFB using the low-cost N,N,N-dimethylbutylammonium hydrogen sulfate ionic liquid ([DMBA][HSO4] IL) with 20 wt% of water. The results demonstrate that higher pretreatment temperatures (120, 150, and 170 °C) and longer periods (0.5, 1, and 2 h) enhanced lignin recovery, resulting in increased purity of the recovered pulp and subsequently enhanced glucose released during enzymatic hydrolysis. However, at 170 °C, prolonging the period led to cellulose degradation and the formation of pseudo-lignin deposited on the pulps, resulting in a decreasing-trend in glucose released. Finally, the analysis of extracted lignin reveals that increasing pretreatment severity intensified lignin depolymerisation and condensation, leading to a decrease in number average molecular weight (Mn), weight average molecular weight (Mw) and polydispersity index (Đ) values.

Effect of Monomers of 3-Hydroxyhexanoate on Properties of Copolymers Poly(3-Hydroxybutyrate-co 3-Hydroxyhexanoate)

The properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx) copolymers with different ratios of monomers synthesized by the wild-type strain Cupriavidus necator B-10646 on sugars, and an industrial sample from Kaneka synthesized by the recombinant strain C. necator NSDG-ΔfadB1 on soybean oil, were studied in a comparative aspect and in relation to poly(3-hydroxybutyrate) P(3HB). The copolymer samples, regardless of the synthesis conditions or the ratio of monomers, had reduced values of crystallinity degree (50–60%) and weight average molecular weight (415–520 kDa), and increased values of polydispersity (2.8–4.3) compared to P(3HB) (70–76%, 720 kDa, and 2.2). The industrial sample had differences in its thermal behavior, including a lower glass transition temperature (−2.4 °C), two peaks in its crystallization and melting regions, a lower melting point (Tmelt) (112/141 °C), and a more pronounced gap between Tmelt and the temperature of thermal degradation (Tdegr). The process, shape, and size of the spherulites formed during the isothermal crystallization of P(3HB) and P(3HB-co-3ННx) were generally similar, but differed in the maximum growth rate of the spherulites during exothermic crystallization, which was 3.5–3.7 μm/min for P(3HB), and 0.06–1.25 for the P(3HB-co-3HHx) samples. The results from studying the thermal properties and the crystallization mechanism of P(3HB-co-3HHx) copolymers are important for improving the technologies for processing polymer products from melts.

Effect of mixing phenol/rice husk to the ability form phenolic resin

Rice is an essential plant that brings high economic value to Viet Nam. In addition to the main product, rice agriculture produces a significant amount of by-products each year. This waste is known as rice husk. The amount of rice husks discharged each year is estimated to be over 9 million tons. They are usually processed by burning. Another amount is released into the environment. These treatments are potentially harmful to the environment and bring low economic efficiency. Therefore, many ways of treatment were suggested and considered. In this study, rice husk was used to synthesize phenolic resin. The rice husk was ground to powder less than 500μm. The husk powder, phenol, and sulfuric acid were mixed with different ratios. The mixtures were heated to 150℃ and soaked for 180 minutes. The efficiency of the reaction was evaluated through the remaining amount of rice husk. The C13 Nuclear Magnetic Resonance Spectroscopy (C13 - NMR) and Fourier Transform Infrared Spectroscopy (FTIR) were used to determine the structure and functional groups of the resin. A number average molecular weight (Mn) and a weight average molecular weight (Mw) were defined by using Gel Permeation Chromatography (GPC). The results show that phenolic resin was synthesized successfully from rice husk. The optimal ratio between phenol and rice husk powder is 2:1 with a 5% sulfuric acid additive. The efficiency of the reaction is determined at 90.34%. The results of structure prediction by FTIR and C13 - NMR show that the molecular formula of the formed resin is (CH2 - C6H4 - OH)n. It has the weight average molecular weight value of 11709 and the number average molecular weight of 7782. The synthesized phenolic resin can be applied as a binder or as one kind of heat-resistant plastic.

Aminolysis of Poly-3-Hydroxybutyrate in N,N-Dimethylformamide and 1,4-Dioxane and Formation of Functionalized Oligomers.

The degradation pattern of bacterial poly-3-hydroxybutyrate (PHB) in dimethylformamide (DMF) and dioxane solutions at 100 °C assisted by ethylenediamine, 1,4-diaminobutane and monoaminoethanol was studied. When diamines were introduced into the PHB solution in DMF in the amount of 1 mol of the reagent to 5 or 10 mol of PHB monomers, a rapid decrease in the molecular weight of the polymer was observed. The initial value of the weight average molecular weight (Mw) 840 kDa had decreased by 20-30 times within the first 10-20 min of the experiment, followed by its gradual decrease to several thousand Da. When a similar molar quantity of aminoethanol was added, the molecular weight decreased slower. PHB had been degrading much slower in the dioxane solution than in DMF. By varying the number of reagents, it was possible to reach stabilization of the Mw at 1000-3000 Da when using diamines and 8000-20,000 Da using aminoethanol. 1H NMR analysis of the oligomers revealed of amino and amido groups forming in their structure. From the opposite end of the polymer chain, residues of 3-hydroxybutyric, crotonic and isocrotonic acids were formed during degradation. Differential scanning calorimetry indicated that after oligomerization there was a decrease in the melting point from 178 °C to 140-170 °C depending on the decrease in the molecular weight. The method proposed can be used for obtaining aminated PHB oligomers.

Core-Crosslinked Star Copolymers as Viscosity Index Improvers for Lubricants

Core cross-linked star (CCS) copolymers were prepared by reversible addition–fragmentation chain-transfer polymerization according to the arm-first technique and studied as viscosity index improvers for the application in hydraulic lubricants. A one-pot two-step synthetic procedure was optimized: starting from PMA arms with a precisely controlled structure and three different molecular weights and using different amounts of either divinylbenzene or ethylene glycol dimethacrylate as cross-linking agents, CCS copolymers with a high star yield (63 to 88%) were obtained. CCS copolymers present weight average molecular weight values ranging from 130,000 to 420,000 g mol–1 and a number of arms comprised between 4 and 13. All samples were employed, without any purification step, in the preparation of model lubricant formulations for hydraulic fluid applications. A good compromise between viscosity index improvement and capability to resist chain breaking reactions was obtained for CCS copolymers with target molecular weight for the PMA arms of 20,000 g mol–1. Improved performances with respect to a commercial additive were obtained.

The Molecular Composition of Humic Acids in Permafrost Peats in the European Arctic as Paleorecord of the Environmental Conditions of the Holocene

The purpose of our research is focused on examination of the transformation regularities of molecular composition of humic acids (HAs) in the hummocky frozen peatlands of the European Arctic as a marker of climatic changes in the Holocene, and assessment of the stabilization of soil organic matter under the conditions of modern climatic warming. Histosols located in the two subzones of the European Arctic served as the research subjects. This territory is actively used for reindeer breeding, which is a vital agricultural branch in the Far North of the Russian Federation. The data obtained reveal the main trends in the formation of HAs from Arctic peatlands under different environmental conditions. Modern peat sediments (top layers) in the middle and late Holocene period formed out of bryophyte residues and contained HAs with long-chain carbohydrate and paraffin structures in their composition. These structures enlarged the dynamic radii of HA molecules, and, thus, caused high average molecular weight values. The more favorable climatic conditions of the early Holocene (the Atlantic optimum) defined the botanical composition of peat, which was dominated by tree and sedge communities with high contents of lignin components and, as a consequence, a larger share of aromatic fragments, characterized by thermo-biodynamic resistance in HAs of horizons in the lower and central profile parts. The molecules of HAs are an archive of paleoclimatic records. The Subboreal and Subatlantic climatic conditions determined the specifics of vegetation precursors and, as a result, the molecular structure of HAs in seasonally thawed layers, with a predominance of long-chain aliphatic fragments. The conversion of HAs from Histosols led to an increase in the proportion of carbon in branched and short-chain paraffinic structures with their subsequent cyclization and aromatization. The results of this process are most clearly manifested in layers formed during the Holocene I and II climatic optima. Higher biologically active temperatures of the seasonally thawed layer of soils at bare spots (without vegetation) determined the accumulation of thermodynamically more stable HA molecules with a high content of aromatic fragments. This contributed to both the stabilization of the SOM and the conservation of peatlands in general.

Kraft Lignin with Improved Homogeneity Recovered Directly from Black Liquor and Its Application in Flexible Polyurethane Foams.

An effective method that can produce a large amount of Kraft lignin with improved homogeneity is strongly desired for Kraft lignin’s high-value applications and scientific advancements. Herein, a one-pot acid-catalyzed liquefaction method was developed to recover Kraft lignin directly from black liquor. The recovery rate and properties of the recovered lignin were affected by the reaction time, reaction temperature, moisture content (MC), pH, and acid categories. The highest lignin recovery rate of 75% was achieved when the concentrated black liquor (MC = 25%) reacted with methanol at pH = 7 and 160 °C for 10 min using acetic acid as the catalyst. Most of the recovered lignin from this method showed an average molecular weight (Mw) value less than 2000 Da and a polydispersity (PDI) value less than 2.0. Such a PDI value was lower than that of current acid precipitated lignin (around 2.2–5.4). The recovered lignin was directly used to replace 20% of the petroleum-based polyol in the formula of a flexible polyurethane (PU) foam, and it was found that the molecular weight characteristics of the lignin affected the physical and mechanical properties of the flexible PU foams. The recovered lignin with the Mw value of 1600 Da and the PDI value of 1.8 was able to maintain the major physical and mechanical properties of the flexible PU foams. This study provided a promising way to recover lignin with improved homogeneity from black liquor with the potential to customize lignin properties to meet the requirements of downstream processes.

Data-Driven Modelling of Polyethylene Recycling under High-Temperature Extrusion.

Two main problems are studied in this article. The first one is the use of the extrusion process for controlled thermo-mechanical degradation of polyethylene for recycling applications. The second is the data-based modelling of such reactive extrusion processes. Polyethylenes (high density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE)) were extruded in a corotating twin-screw extruder under high temperatures (350 °C < T < 420 °C) for various process conditions (flow rate and screw rotation speed). These process conditions involved a decrease in the molecular weight due to degradation reactions. A numerical method based on the Carreau-Yasuda model was developed to predict the rheological behaviour (variation of the viscosity versus shear rate) from the in-line measurement of the die pressure. The results were successfully compared to the viscosity measured from offline measurement assuming the Cox-Merz law. Weight average molecular weights were estimated from the resulting zero-shear rate viscosity. Furthermore, the linear viscoelastic behaviours (Frequency dependence of the complex shear modulus) were also used to predict the molecular weight distributions of final products by an inverse rheological method. Size exclusion chromatography (SEC) was performed on five samples, and the resulting molecular weight distributions were compared to the values obtained with the two aforementioned techniques. The values of weight average molecular weights were similar for the three techniques. The complete molecular weight distributions obtained by inverse rheology were similar to the SEC ones for extruded HDPE samples, but some inaccuracies were observed for extruded UHMWPE samples. The Ludovic® (SC-Consultants, Saint-Etienne, France) corotating twin-screw extrusion simulation software was used as a classical process simulation. However, as the rheo-kinetic laws of this process were unknown, the software could not predict all the flow characteristics successfully. Finally, machine learning techniques, able to operate in the low-data limit, were tested to build predicting models of the process outputs and material characteristics. Support Vector Machine Regression (SVR) and sparsed Proper Generalized Decomposition (sPGD) techniques were chosen to predict the process outputs successfully. These methods were also applied to material characteristics data, and both were found to be effective in predicting molecular weights. More precisely, the sPGD gave better results than the SVR for the zero-shear viscosity prediction. Stochastic methods were also tested on some of the data and showed promising results.

Molecular weight characteristics of polyetheretherketone (PEEK): analysis of determination conditions

Polyetheretherketone (PEEK), which is highly resistant to aggressive media and various types of radiation, is widely used in various industries. At the same time, the information on the molecular weight characteristics of PEEK, which is necessary for the creation of polymer materials with specifi ed properties, is quite limited. Determination of these characteristics is complicated by the almost complete insolubility of PEEK in organic solvents. The work is devoted to the analysis of the applicability of viscometry, determination of the melt fl ow index and gel permeation chromatography (GPC) for assessing the molecular weight characteristics of PEEK. The preliminary modifi cation of the polymer to transform it into a soluble state has been considered as an alternative approach. A GPC-method of the determination of molecular mass of sulfonated PEEK has been developed. The values of average molecular weights for samples produced by Petrov Institute of Plastics and a commercial sample Victrex 150G were determined. Good agreement of the GPC data with the results of determining the melt fl ow index of the polymer makes it possible to consider the latter as an express method for assessing the molecular weight of a polymer.

The Relationship between Molecular Size and Polarity of Atmospheric Organic Aerosol in Singapore and Its Implications for Volatility and Light Absorption Properties

Organic aerosol, which is a complex mixture, has been categorized by both chemical (e.g., degree of oxygenation and molecular weight (MW)) and physical (e.g., water solubility and optical) characteristics. However, the inter-relationships among these characteristics have not been well-established yet. This study developed a novel framework on the inter-relationship among volatility, water solubility, and MW. The framework suggests that water-soluble organic matter (WSOM) can have relatively small MW (<200) because highly polar species tend to have lower volatility. On the other hand, water-insoluble organic matter (WISOM) needs to have larger MW than the threshold, as less polar species tend to be highly volatile. The idea was tested by analyzing aerosol samples collected at Singapore. Both WSOM and WISOM were extracted from the samples. The WSOM fraction was further classified by polarity using the 1-octanol–water method. The samples were analyzed by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). APCI-MS is a soft-ionization technique that dominantly provides [M–H]− ions. The APCI-MS data validated the newly developed idea on the MW distributions for WSOM and WISOM. The positive matrix factorization (PMF) analysis was applied to the APCI-MS data. The analysis for WSOM also supported the inverse relationship between polarity and MW. The PMF outputs were combined with the ultraviolet–visible absorption data for obtaining absorption Ångstrom exponents (AAE) for each factor. The result suggests that highly polar WSOM factors have relatively small values of average MW (≤205) and higher values of AAE (>8.5), connecting polarity and optical properties of OM.

Facile Synthesis of Hydrophilic Homo-Polyacrylamides via Cu(0)-Mediated Reversible Deactivation Radical Polymerization.

In this work, copper-mediated reversible deactivation radical polymerization (RDRP) of homo-polyacrylamides was conducted in aqueous solutions at 0.0 °C. Various degrees of polymerization (DP = 20, 40, 60, and 80) of well-defined water-soluble homopolymers were targeted. In the absence of any significant undesirable side reactions, the dispersity of polydiethylacrylamide (PDEA) and polydimethylacrylamide (PDMA) was narrow under controlled polymerization conditions. To accelerate the polymerization rate, disproportionation of copper bromide in the presence of a suitable ligand was performed prior to polymerization. Full conversion of the monomer was confirmed by nuclear magnetic resonance (NMR) analysis. Additionally, the linear evolution of the polymeric chains was established by narrow molecular weight distributions (MWDs). The values of theoretical and experimental number average molecular weights (Mn) were calculated, revealing a good matching and robustness of the system. The effect of decreasing the reaction temperature on the rate of polymerization was also investigated. At temperatures lower than 0.0 °C, the controlled polymerization and the rate of the process were not affected.

Temperature- and pH-sensitive hydrogels of sequential Ti-containing interpenetrating polymer networks

Hydrogels of sequential Ti-containing interpenetrating polymer networks based on hydrophilic cross-linked polyurethanes with different molecular weight of polyethylene glycols and Ti-containing copolymer were synthesized based on 2-hydroxyethyl methacrylate and titanium isopropoxide. The composition of sequential interpenetrating polymer networks was determined by the degree of equilibrium swelling of the polyurethane networks in 2-hydroxyethyl methacrylate and Ti-containing comonomer. It was established that the content of the second component of the interpenetrating polymer networks increases with increasing the average molecular weight value of the polyurethane network. It was shown that the obtained highly sensitive hydrogels of Ti-containing interpenetrating polymer networks react to the changes in the temperature and pH. These factors significantly change the equilibrium water content in the hydrogels. Differential scanning calorimetry allowed determining the phase transitions that are characteristic of bound and free water, which is a part of the hydrogel of polyurethanes, interpenetrating polymer networks and Ti-containing interpenetrating polymer networks. The results showed that the content of bound water and the degree of its binding to the components of the interpenetrating polymer networks depend on the chemical structure of the network, the nature of a second polymer component (which is a part of the interpenetrating polymer networks), the polarity and hydrophilicity of macromolecules, and the size of hydrogel cells. Regardless of the nature of the second polymer component, there is a general trend for all interpenetrating polymer networks: the total water content increases with increasing the average molecular weight of the polyurethane matrix networks.

Predictive identification of co-formers in co-amorphous systems

This work aims to understand the properties of co-formers that form co-amorphous pharmaceutical materials and to predict co-amorphous system formation. A partial least square – discriminant analysis (PLS-DA) was performed using known co-amorphous systems described by 36 variables based on the properties of the co-former and the binding energy of the system. The PLS-DA investigated the propensity to form co-amorphous material of the active pharmaceutical ingredients: mebendazole, carvedilol, indomethacin, simvastatin, carbamazepine and furosemide in combination with 20 amino acid co-formers. The variables that were found to favour the propensity to form co-amorphous systems appear to be a relatively large value for average molecular weight and the sum of the difference between hydrogen bond donors and hydrogen bond acceptors for both components, and a relatively small or negative value for excess enthalpy of mixing, excess enthalpy of hydrogen bonding and the difference in the Hansen parameter for hydrogen bonding of the coformer and the active pharmaceutical ingredient (API). To test the predictive power of this model, 29 potential co-formers were used to form either co-amorphous or crystalline two-component materials with mebendazole. Of these 29 two-component systems, the co-amorphous nature of a total of 26 materials was correctly predicted by the model, giving a predictive hit rate of 90 %.