Aqueous dispersion of polyurethanes from H12MDI,PTAd/PPG,and DMPA: Particle size of dispersion and physical properties of emulsion cast films

Aqueous dispersions of ionic/nonionic polyurethane (PU) were prepared from hydrogenated diphenylemthane diisocyanate (H₁₂MDI), poly(tetramethylene adipate) glycol (PTAd), polypropylene glycol (PPG), monofunctional ethylene-propylene oxide ether, and dimethylol propionic acid (DMPA). The effects of DMPA, PTAd/PPG ratio, and the average molecular weight of PPG on the state of dispersion, mechanical, and viscoelastic properties of the emulsion cast films were determined using Authosizer, Instron, and Rheovibron.     

One-Step Synthesis of W/O and O/W Emulsifiers in the Presence of Surface Active Agents

The main goal of this study was to describe the method of the synthesis of the dodecyl-, tetradecyl-, hexadecyl- and octadecyl-propylene glycol emulsifiers in the presence of selected anionic and nonionic surfactants. Acyl propylene glycol emulsifiers were produced by esterification of propane–1,2-diol (propylene glycol, PG) with C_12:0–C_18:0 fatty acids in the presence of anionic sodium dodecyl sulfate (SDS) and nonionic-poly(ethylene glycol) monolaurate (PEGML). The presence of SDS and PEGML in the reaction system caused microemulsion formation. Depending on the structure and amount of the surfactant in the system reactions proceeded at different rates and with different efficiency levels. The esterification of propylene glycol carried out under applied conditions causes products with the desired contents of propylene glycol monoesters (MAPG) to be obtained in a one-step reaction. Knowledge of the reaction kinetics creates the possibility to program the composition and properties of the synthesized emulsifiers. The interaction of nonionic, lipophilic MAPG with anionic, hydrophilic SDS or nonionic, hydrophilic PEGML influences the hydrophile–lipophile balance (HLB) values of the products which may be used to stabilize water-in-oil (W/O) and oil-in-water (O/W) emulsions. Use of the synthesized compounds allows stable emulsions to be prepared which include the following vegetable fats in the oil phase: mango oil, palm oil, shorea butter and hydrogenated soybean oil.     

α-sulfonated fatty acid esters: II. Solution behavior of α-sulfonated fatty acid polyethylene glycol esters

Sodium α-sulfonated, fatty acid polyethylene glycol monoesters [C _m H_2m+1CH(SO₃Na)COO(C₂H₄O) _n H] and diesters [C _m H_2m+1CH(SO₃Na)COO(C₂H₄O) _n COCH(SO₃Na)C _m H_2m+1], wherem=10–16 andn=1–35, were prepared by esterification of α-sulfonated, fatty acids with polyethylene glycols, followed by neutralization with NaOH. Crude products were purified by reversed-phase column chromatography on an octadecyl-modified silica gel. Characteristic solution behavior of these α-sulfonated fatty acid esters was, examined, and the following features were observed. All monoesters prepared in this work had Krafft points below 0°C and also possessed good calcium stabilities. Critical micelle concentrations of the monoesters increased monotonously, as a rule, with an increase in the number of oxyethylene units. These results suggest that the polyethylene glycol residue of the monoester behaves as a hydrophile. On the other hand, diesters possessed high water solubility, low foamability, and critical micelle concentrations that were lower by a factor of ten compared to those of the monoesters.     

Structure of ultrahigh molecular weight polyethylene–air counterflow flame

The combustion of ultrahigh molecular weight polyethylene (UHMWPE) in airflow perpendicular to the polyethylene surface (counterflow flame) was studied in detail. The burning rate of pressed samples of UHMWPE was measured. The structure of the UHMWPE–air counterflow flame was first determined by mass spectrometric sampling taking into account heavy products. The composition of the main pyrolysis products was investigated by mass spectrometry, and the composition of heavy hydrocarbons (C₇—C₂₅) in products sampled from the flame at a distance of 0.8 mm from the UHMWPE surface was analyzed by gas-liquid chromatography mass-spectrometry. The temperature and concentration profiles of eight species (N₂, O₂, CO₂, CO, H₂O, C₃H₆, C₄H₆, and C₆H₆) and a hypothetical species with an average molecular weight of 258.7 g/mol, which simulates more than 50 C₇—C₂₅ hydrocarbons were measured. The structure of the diffusion flame of the model mixture of decomposition products of UHMWPE in air counterflow was simulated using the OPPDIF code from the CHEMKIN II software package. The simulation results are in good agreement with experimental data on combustion of UHMWPE.     

Property evaluation and structure analysis of polyurethane/epoxy graft interpenetrating polymer networks

Polyurethanes obtained from 4,4′‐diphenylmethane diisocyanate (MDI) and polydiols with different molecular weights (polyethylene glycol and polyoxypropylene diols) were used as modifiers for diglycidyl ether of bisphenol A. Impact strength (IS), critical stress intensity factor (K_C), flexural strength and flexural strain at break were measured as a function of polyurethane (PUR) type and content. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and infrared spectroscopy (FTIR) were employed for the structure and morphology analysis. It was found that the addition of polyurethane with an excess of isocyanate groups to epoxy resin resulted in the formation of a grafted interpenetrating polymer network structure. The mechanical properties of epoxy resin were improved with 5 and 10% PUR. Moreover, it was observed that composites containing PUR based on higher molecular weight (PUR 1002 and PUR 2002) with long flexible segments exhibited higher impact strength while PUR prepared from polyethylene glycol had a higher flexural energy to break and a higher flexural modulus. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of series of pure polyethylene glycol ethers based onn-tridecanol,7-tridecanol,and oxo-process tridecyl alcohol

Puren-tridecyl, 7-tridecyl andoxo-tridecyl polyethylene glycol monoethers, C₁₃H₂₇O (C₂H₄O)_nH, were made by the Williamson reaction with n=4,6,8,10 and 12. Related crystalline diethers derived fromn-tridecanol were made in the range of 4–16 oxyethylene units. The compounds were extensively purified by crystallization (where applicable) or by chromatography and distillation. The final products are new compounds important for comparative studies of surface properties. Characterizing constants and physical properties including those of a large number of pure intermediates are reported. All but the lowest member of then-tridecyl monoether series are crystalline, melting between 26 and 40C. The related diethers melting between 37 and 50C have a minimum melting point when they contain between 6 and 8 oxyethylene units. Theoxo-tridecyl and 7-tridecyl monoethers are liquids.     

Organometallics in ethylene polymerization with a catalyst system TiCl4/Al(C2H5)2Cl/Mg(C6H5)2: 2. Polymerization process in pseudo-solution

A study has been made of ethylene polymerization in pseudo-solution with a catalyst system TiCl₄/Al(C₂H₅)₂Cl/Mg(C₆H₅)₂ in the presence of hydrogen as a regulator of polyethylene molecular weight. The polymerization process in pseudo-solution by adjustment of hydrogen makes it possible to produce polyethylene having a wide range of molecular weights. For this purpose melt indices between 0°–50°C/min are desirable and these values are not reached with a suspension type of ethylene polymerization with a catalyst system TiCl₄/Al(C₂H₅)₂Cl/Mg(C₆H₅)₂. The effect of the molar ratio cocatalyst/catalyst (Al/Ti and Mg/Ti) on the catalyst activity and on the polyethylene molecular weight was studied, together with the content of hydrogen as a regulator of the molecular weight. The catalyst productivity increased to some limiting molar ratio Mg/Ti and Al/Ti and further increase of organometallics in the catalyst system did not influence the polymer molecular weight. In the case of ethylene polymerization with this catalyst combination in the presence of hydrogen, some activation of the catalyst was observed. Two mechanisms, which may account for the activation effect of the hydrogen are discussed.     

Synthesis and the effect of hydrophobic dodecyl end groups on pH-responsive micellization of poly(acrylic acid) and poly(ethylene glycol) triblock copolymer in aqueous solution

A pH-responsive triblock copolymer of poly(acrylic acid)-b-poly(ethylene glycol)-b-poly(acrylic acid) containing hydrophobic dodecyl end groups (C₁₂H₂₅-PAA-b-PEG-b-PAA-C₁₂H₂₅) with narrow molecular weight distribution (M _w/M _n?=?1.30) was synthesized via reversible addition-fragmentation chain transfer polymerization of acrylic acid (AA). Poly(ethylene glycol) (PEG) capped with S-1-dodecyl-S??-(??,????-dimethyl-????-acetic acid) trithiocarbonate (DDATC) end groups was used as the macro chain transfer agent (PEG macro-CTA) and 2,2??-azobisisobutyronitrile (AIBN) as initiator for monomer acrylic acid. The effect of the hydrophobic dodecyl end groups on pH-sensitive self-association of C₁₂H₂₅-PAA-b-PEG-b-PAA-C₁₂H₂₅ in aqueous solution was investigated by fluorescence spectroscopy, dynamic light scattering and atomic force microscope. At pH ??5.5, the solution behavior of C₁₂H₂₅-PAA-b-PEG-b-PAA-C₁₂H₂₅ is like polyelectrolyte in aqueous solution, and the effect of dodecyl end groups is negligible. At pH <5.0, the hydrophobic dodecyl end groups contribute dominantly to the pH-sensitive micellization and result in the formation of micelles with stronger hydrophobicity and larger size at low concentration (critical micelle concentration is 0.062?g/L). In the range of pH 2.5?C3.5, the steady (R _h????35.0?nm) and narrow size distributed micelles (polydispersity index, PDI?<?0.2) can be obtained. The micelles formed by C₁₂H₂₅-PAA-b-PEG-b-PAA-C₁₂H₂₅ triblock copolymer in acidic solution are expected to have a core?Cshell?Ccorona structure, where the hydrophobic dodecyl groups form the core, and weak hydrophobic PAA/PEG hydrogen-bonded complexes form the shell and the uncomplexed PAA, and PEG chain segments form the corona.     

Cocatalytic activities of methylaluminoxane prepared by direct water addition method in ethylene polymerization over Cp2ZrCl2

The characterization of ethylene polymerization behaviors catalyzed over Cp₂ZrCl₂/MAO homogeneous system using methylaluminoxanes prepared by the direct hydrolysis of AlMe₃ (Me=methy1) were reported. The MAO was prepared at the ratio of [H₂O]/[A1]=1 and 0.5 and at three different temperatures, i.e., −40, −60 and −80 °C. The polymerization rate was not decreased with polymerization time when the MAO prepared at the ratio of [H₂O]/[AlMe₃]=l at −60 °C was used as a cocatalyst regardless of the ratio of Al/Zr and the polymerization temperature. The polymerization rate drastically decreased with polymerization time above 60 °C in case of using MAO prepared at the ratio of [H₂O]/[AlMe₃]=l at −80 °C. However, in case of the MAO prepared at the ratio of [H₂O]/ [AlMe₃]=0.5 at −80 °C, the rate continuously increased with polymerization time at the polymerization temperature of 70 °C and 80 °C. The amount of MAO needed to activate Cp₂ZrC1₂ was larger than that of MAO prepared at the ratio of [H₂O]/[A1]=1. The viscosity molecular weight of polyethylene (PE) cocatalyzed with MAO prepared at the ratio of [H₂O]/[Al]=0.5 was lower than that of polyethylene obtained with MAO prepared at the ratio of [H₂O]/[A1]=1.     

Amphiphilic diblock and ABC triblock methacrylate copolymers: synthesis and aqueous solution characterization

Three isomeric, linear, equimolar, amphiphilic ABC triblock copolymers comprising methyl methacrylate (MMA, nonionic hydrophobic), 2-(dimethylamino)ethyl methacrylate, (DMAEMA, ionizable hydrophilic) and hexa(ethylene glycol) methacrylate (HEGMA, nonionic hydrophilic) units (10 units in each block) were synthesized by group transfer polymerization (GTP). These were the three block sequence isomers, ABC, ACB and BAC. The corresponding random terpolymer was also prepared. The molecular weights and compositions of all the polymers were characterized by GPC and ¹H NMR. Measurements of the hydrodynamic diameters and cloud points of the copolymers in aqueous solution suggest that the various distributions of monomer units in the four terpolymers (the three triblocks and the random) result in different supramolecular structures with different colloidal stabilities.     

Living cationic polymerization of vinyl ethers with a functional group

Summary Vinyl ethers having oxyethylene units [CH₂=CHO-(CH₂CH₂O)-_nC₂H₅, n=1–4] were cleanly polymerized by the HI/I₂ initiator in a nonpolar solvent (toluene) at low temperatures (–15 and –40°C) to yield living-like polymers with a very narrow molecular weight distribution (Mw/Mn 1.2); the oxyethylene units in the monomers hardly disturbed the polymerization. The number-average molecular weight of the polymers increased proportionally to monomer conversion and the monomer-to-HI feed ratio. The polymerization rates of the (poly)ether-containing vinyl ethers were much greater than those of alkyl vinyl ethers under similar conditions, and it is presumed that the pendant ether oxygens intramolecularly activate the growing end. The polymers were soluble in methanol (with n1) and in water (with n2), depending on the number of oxyethylene units in the pendant.     

Synthesis, characterization and evaluation of amphiphilic diblock copolymer emulsifiers based on methoxy hexa(ethylene glycol) methacrylate and benzyl methacrylate

Linear, amphiphilic diblock copolymers based on the nonionic, hydrophilic monomer methoxy hexa(ethylene glycol) methacrylate (HEGMA) and the hydrophobic monomer benzyl methacrylate (BzMA) of different molecular weights and compositions were synthesized by group transfer polymerization. The molecular weights and comonomer compositions of these copolymers were characterized by gel permeation chromatography and proton nuclear magnetic resonance (¹H NMR) spectroscopy, respectively. Dynamic light scattering on aqueous solutions of the diblock copolymers indicated that all the copolymers formed aggregates whose size increased with the % w/w BzMA composition and with the overall molecular weight of the linear chains. Turbidimetry on 1% w/w aqueous copolymer solutions was used to determine the cloud points, which were found to increase with the composition in hydrophilic units and the linear chain molecular weight. After polymer characterization, xylene/water and diazinon (pesticide)/water emulsions were prepared using the above polymers as stabilizers at 1% w/w polymer concentration and at different overall organic phase/water ratios. At an organic phase/water mass ratio of 4/1, the lower molecular weight (2500 and 5000 g mol⁻¹) diblock copolymers provided stable single-phase o/w emulsions, matching the behavior of commercially available hydrophilic Pluronics.     

Crosslinking of addition copolymers from tricyclononenes bearing (CH3)3Si‐ and (C2H5O)3Si‐groups as a modification of membrane gas separation materials

Here, we report the synthesis and the study of gas‐transport properties of crosslinked highly permeable copolymers from Si‐containing norbornene derivatives. The initial high‐molecular‐weight copolymers were prepared via addition copolymerization of 3‐trimethylsilyltricyclo[4.2.1.0^2,5]non‐7‐ene (TCNSi1) with 3‐triethoxysilyltricyclo[4.2.1.0^2,5]non‐7‐ene (TCNSiOEt) in good or high yields using a Pd‐catalyst. The obtained copolymers included up to 10 mol% of TCNSiOEt units bearing reactive Si–O–C‐containing substituents. The crosslinking was readily realized by using simple sol–gel chemistry in the presence of Sn‐catalyst. The formed crosslinked copolymers were insoluble in common organic solvents. Permeability coefficients of various gases (He, H₂, O₂, N₂, CO₂, CH₄, C₂H₆, C₃H₈, n‐C₄H₁₀) in these copolymers before and after crosslinking were determined and the influence of the incorporated TCNSiOEt units as well as the crosslinking on gas transport properties were established. As a result, it was found that only a small reduction of gas‐permeability was observed when TNCSiOEt units were incorporated into the main chains, and the copolymers were crosslinked. At the same time, the selectivity for C₄H₁₀/CH₄ pair was increased. The suggested approach has allowed obtaining crosslinked polymers from Si‐containing monomers without a loss of the main membrane characteristics. POLYM. ENG. SCI., 59:2502–2507, 2019. © 2019 Society of Plastics Engineers     

Adsorption and desorption dynamics of associative polymers onto particulates of titanium dioxide,alumina and quartz

The authors have been investigating the adsorption and desorption dynamics of nonionic water soluble polymers on inorganic particles. The influence of the nature of polymers with and without associating hydrophobic end groups, the nature of adsorbents [TiO₂, Al₂O₃ (neutral, acid and basic), and SiO₂], polymer concentrations, linear velocity of fluids, and mutual diffusion of polymer molecules on the patterns of adsorption and desorption distribution of polymer concentrations are shown. The model polymer is a nonionic polyurethane polymer based on ethylene oxide. The polymer's structure is R-O-(DI-PEO)₆-DI-O-R (R is C₁₆H₃₃, DI is isophorone diisocyanate, and PEO is CARBOWAX^TM with a molecular weight of 8200). The phenomenological models of association and dissociation kinetics of associative polymers are suggested. The half-lives of clusters into adsorption and desorption layers are estimated. It is shown that heats of desorption of associative polymers are dependent essentially on heats of dissociation of clusters.     

Preparation of a topologically linked branch polymer containing cyclodextrin

Macromolecules containing topological linkages made of α‐cyclodextrin (αCD) and poly(ethylene glycol) (PEG) were prepared by condensation of mono‐6‐O‐deoxy‐mono‐6‐amino‐α‐cyclodextrin (NH₂‐αCD) with PEG dicarboxylic acid (PEG‐diCOOH) having one carboxyl group at both chain ends. The analysis of ¹H NMR and ¹³C NMR spectra of the condensation products showed completion of the condensation reaction between NH₂ and COOH groups, and the absence of ester linkages, thus indicating that all of the PEG chains carried one αCD molecule at both chain ends through amide linkages. Gel permeation chromatography analysis of these condensation products showed that NH₂‐αCD formed inclusion complexes with PEG‐diCOOH prior to condensation, resulting in macromolecules having topological linkages. In addition, the amount of the topological linkages increased with the increase of molecular weight of PEG‐diCOOH. This result shows that the complexation equilibrium of NH₂‐αCD with PEG‐diCOOH depends on the concentration of ethylene glycol units. Copyright © 2007 Society of Chemical Industry     

Molecular structure,crystallization behavior,and morphology of fractions obtained from an extrusion grade high-density polyethylene

An extrusion-grade of high density polyethylene (HOPE) (3 ethyl groups per 1000 carbons) has been divided into 16 fractions by preparative GPC and selective p-xylene extraction. The fractions, with molecular weights ranging from 900 to 1,000,000, have been studied by IR spectros-copy, DSC, WAXS, polarized microscopy, and small-angle light scattering (SALS), The average degree of chain branching (percent C₂H₅) is 0.5 percent for the part of the sample having a molecular weight lower than 10,000 and it decreases monotonically with increasing molecular weight, finally approaching 0.1 percent C2H5. A crystallinity depression with respect to linear PE equivalent to 20 percent/(percent C₂H₅) is recorded for all samples except for the very low molecular weight samples for which the crystallinity depression is much larger (30 to 35 percent/ (percent C₂H₅)). The unit cell volume increases with increasing percent C₂H₅, presumably due to the inclusion of ethyl groups in the crystals as interstitlals at 2gl kinks. The concentration of ethyl groups in the crystals (?_c) unanimously follows the relationship: ?_c(percent) = 0.32 + 0.25 log(percent C₂H₅) except for the low molecular weight fractions which have significantly lower values for ?_c. Our admittedly speculative explanation for this major discrepancy between high and low molecular weight samples is based on the idea that segments with ethyl groups close to chain ends have a greater difficulty in crystallizing than segments containing ethyl groups located at positions far from the chain ends. The fractions obtained from the extrusion-grade HDPE show a solidification temperature depression with respect to linear PE which can only be explained by the presence of chain branches in these samples. The depression is particularly pronounced for the low molecular weight samples as is expected from the data on molecular structure. Well-developed non-banded spherulites are observed in rapidly cooled (crystallized at about 35 K supercooling), low molecular weight samples (6,000 < M_w < 8,000)from the extrusion-grade HDPE in contrast to the axialites observed in linear PE of the same molecular weight and thermal treatment. This discrepancy in morphology has been related to the presence of ethyl groups in the extrusion grade HDPE fractions. Higher molecular weight samples (20,000 < M_w < 1,000,000)from the extrusion-grade HDPE and linear PE both display well-developed banded spherulites of similar nature as is expected due to the similarity in molecular structure of the two sets of sample.     

Characterization of the polymer of a dipyrrolyl monomer by pyrolysis mass spectrometry

In this work, characterization of a homopolymer of succinic acid bis(4‐pyrrol‐1‐ylphenyl) ester prepared by galvonastatic polymerization was carried out by direct pyrolysis mass spectrometry. Although decomposition of the monomer yielding mainly butadionic acid and pyrrole occurred under the galvonastatic polymerization conditions, growth of the polymer through the pyrrole moieties was also achieved, yielding a ladder‐type polymer film. The polypyrrole chains contained both quinoid and aromatic units as in the case of polypyrrole, yet the extent of network structure was significantly diminished. A three‐step mechanism is proposed for the thermal decomposition process. The first step involves the cleavage of C₄H₄NC₆H₄O end groups. In the second step, decomposition of phenyl ester units and polypyrrole chains having quinoid structure takes place. The final stage of thermal degradation was attributed to decomposition of polypyrrole chains having aromatic structure. Copyright © 2004 Society of Chemical Industry     

Selective detection of propanol vapour at low operating temperature utilizing ZnO nanostructures

We report on the propanol vapour (C₃H₈O) gas sensing characteristics of ZnO nanostructures prepared via hydrothermal assisted method. The ZnO-4h sensor showed a high response (i.e. resistance ratio), sensitivity and selectivity toward C₃H₈O gas at low operating temperature of 125 °C. A response and recovery times of approximately 190 and 200 s were recorded. The response of ZnO-4h based sensor to 40 ppm C₃H₈O was approximately 2 times higher than that of other sensing materials in dry air, while in the presence of 40% RH the response was 5 times higher. The exceptional C₃H₈O-sensing performance of ZnO-4h is related to more C₃H₈O adsorption sites provided by V_O. The ZnO-04h based sensor showed a clear repeatability towards 40 ppm C₃H₈O for four successive cycles in the presence of various RH of 40 and 60% at 125 °C. The sensor response improved in the presence of RH humidity showing that the water vapour was not competing with the C₃H₈O for the pre-adsorbed oxygen ions, thus its interfering effect in the C₃H₈O sensing was considerably minimized. The ZnO-4h based sensor was further tested for long-term stability and the sensor was very stable after 45 days. The fundamental sensing mechanism towards C₃H₈O vapour is also discussed.     

The pyrolysis of cellulose derivatives

The thermal degradation in vacuo of ethyl cellulose and cellulose acetate in the form of very thin films or bulk material between 230° and 320°C has been studied. With the ethyl cellulose films, volatilization (as measured by weight loss) was a first-order process up to about 50% reaction, with an activation energy of 208 kJ/mole. This is about the same as that associated with the initial drop in intrinsic viscosity of the solid during bulk pyrolysis, in which very high molecular weight material, probably crosslinked, was formed at a later stage. The volatile products from ethyl cellulose included H₂O, CO, CO₂, C₂H₄, C₂H₆, C₂H₅OH, CH₃CHO, unsaturated aliphatic compounds, and furan derivatives. Acetic acid and acetyl derivatives of D -glucose were produced from cellulose acetate. It is suggested that the polymers degrade by radical chain mechanisms, and a number of possible elementary steps are proposed.     

N-lauroyl-ethylenediamine chelates: Preparation and evaluation of surface tension and dispersant properties

A chelate surfactant was synthesized having a hydrophobic alkyl group and hydrophilic metal ion bonded to the former in the chelate configuration, and its properties were investigated. N-lauroyl-ethylenediamine (LEDA) was used as the hydrophobic chelating agent and salts of some transitional metals (e.g. iron, cobalt, nickel, copper and chromium) were reacted therewith. The reaction of LEDA with ferric sulfate on 1:1 equivalent reaction ratio afforded [Fe(LEDA) (H₂O)₄]3/2SO₄. In other reactions pure chelates were not obtained, but the products showed good surface activity.