Series Of Polyols Research Articles

Development of polyols analogous to neopentyl glycol and trimethylolpropane for the production of oleic acid-based biolubricants

Vegetable oils and animal fats have been known and used as lubricants and fuels since ancient times. However, the chain structure of the triacylglycerols (TAGs) generate limitations that discourage the use of these raw materials as lubricants. As an alternative to improve the physicochemical and thermo-oxidative characteristics of natural oils, the use of polyols without the β-hydrogens in the triacylglycerols structure is an efficient solution for the production of biolubricants. In this context, a series of polyols, analogous to trimethylolpropane (TMP) and neopentyl glycol (NPG) was synthesised and applied in the synthesis of polyol esters based on oleic acid. These esters were prepared by homogeneous catalysis using p-toluenesulfonic acid (p-TSA) and are intended for use as biolubricants. The synthesised polyols were characterized by one and two-dimensional NMR. The derived polyol esters were purified and had their structure confirmed by 1H and 13C NMR, infrared spectroscopy, and mass spectrometry. The polyol esters showed high viscosity index (189 – 222), thermo-oxidative stability (Tonset between 258 and 285 °C), and low melting points (between –19.4 and –47.6 °C). Furthermore, polyol esters showed reduced friction coefficients (0.021 – 0.041) and scar wear diameter on the metallic surface (0.274 – 0.448 mm). In addition to the satisfactory results of thermal stability and lubricity, which suggest the potential of these molecules as lubricants, all molecules were considered environmentally safe when evaluated through the Zebrafish toxicity model.

Kinetics Study of Acid-Catalyzed Sulfate Esterification Reactions for Atmospherically Relevant Polyols

Extensive laboratory and field studies have identified organosulfates as important constituents of secondary organic aerosol (SOA). However, the mechanisms by which these organosulfates form in the atmosphere remain uncertain. The rate constants for the acid-catalyzed sulfate esterification reactions of a series of polyols were measured via bulk kinetics experiments using nuclear magnetic resonance (NMR) spectroscopy. The NMR data indicated that while reactions that occurred at a terminal hydroxyl site were somewhat faster than reactions at internal hydroxyl sites, there were no other significant structure–reactivity trends among the series of polyols. These results suggest that neighboring hydroxyl groups do not significantly modify the sulfate esterification rates from those previously determined for monoalcohols. Extrapolation of the kinetics data to typical atmospheric SOA acidities suggests that sulfate esterification reactions of polyols are unlikely to be a significant source of organosulfates. This conclusion is consistent with a previous study of monoalcohols which made similar conclusions about the kinetic infeasibility of this reaction type.

Segmented shape memory polyurethane: Influence of soft segment types and length

Shape-memory polyurethanes (SMPUs) with heat induced characteristic can be altered to a programmed shape and return to its original shape upon thermal stimuli. SMPU has prompted a lot of interest for various applications such as biomedical appliances, fabrics, coatings, and sensors. In this study, a series of polyols (polycaprolactone (PCL), polyethylene glycol (PEG), polypropylene glycol (PPG)) with different molecular weight were used to synthesize SMPU together with 4,4-methylenebis(cyclohexyl isocyanate) (HMDI) as diisocyanate, and 1,4-butanediol (BD) as chain-extender via two-step bulk polymerization technique. Palm kernel oil-based polyol (PKO-p) was introduced as part of the soft segment. The SMPUs were analyzed using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), shape memory and tensile tests. The results showed that SMPU with lower molecular weight (PU-PCL2) achieved higher tensile strength (7.58 MPa) compared to higher molecular weight of PCL (1.55 MPa) apparently due to the low crystallinity. Moreover, PEG based SMPU (PU-PEG3) exhibited good shape memory property with 82% of shape fixity and shape recovery of more than 80%. It was revealed that the variation in molecular weight of the soft segments provides significant effects on the tensile and shape memory properties of SMPU.

Differential effect of polyol and sugar osmolytes on the refolding of homologous alpha amylases: A comparative study

Polyol and sugar osmolytes are known to enhance the stability of proteins, however, their role in assisting protein folding is not well understood. We asked whether these osmolytes have the same effect during refolding of a pair of thermophilic and mesophilic proteins. Herein, we have chosen α-amylases from Bacillus licheniformis (BLA) and Bacillus amyloliquefaciens (BAA) as thermophilic like and mesophilic counterparts respectively, having similar structures but differing thermostability. The effect of a series of polyols with varying number of -OH groups from 2 to 6 (Ethylene glycol, glycerol, erythritol, xylitol and sorbitol) and sugars (trehalose and sucrose) has been studied on the refolding of BLA and BAA. Our study demonstrates that glycerol, sorbitol and trehalose are the efficient cosolvents for BAA refolding, while comparatively less effective for BLA. Urea induced destabilization of BLA and BAA is differently compensated by polyol and sugar osmolytes during refolding. This suggests that the early species formed during BLA and BAA refolding are differently susceptible towards urea, indicating differential nature of their refolding pathways. Addition of trehalose at different times during refolding showed that the presence of trehalose is essential at the early stages of refolding. It is one of the first systematic study wherein the comparative effect of polyol and sugar assisted refolding of thermophilic and mesophilic protein has been carried out. The study highlights the differential effect of protein-osmolyte interactions during refolding of thermophilic and mesophilic proteins which may have implications in protein formulations, refolding and inhibition of aggregation.

Molecular mechanism underlying modulation of TRPV1 heat activation by polyols

Sensing noxiously high temperatures is crucial for living organisms to avoid heat-induced injury. The TRPV1 channel has long been known as a sensor for noxious heat. However, the mechanism of how this channel is activated by heat remains elusive. Here we found that a series of polyols including sucrose, sorbitol, and hyaluronan significantly elevate the heat activation threshold temperature of TRPV1. The modulatory effects of these polyols were only observed when they were perfused extracellularly. Interestingly, mutation of residues E601 and E649 in the outer pore region of TRPV1 largely abolished the effects of these polyols. We further observed that intraplantar injection of polyols into the hind paws of rats reduced their heat-induced pain response. Our observations not only suggest that the extracellular regions of TRPV1 are critical for the modulation of heat activation by polyols, but also indicate a potential role of polyols in reducing heat-induced pain sensation.

Attempts to Upcycle PET Wastes into Bio-based Long-lasting Insulating Materials

Following the green chemistry principles, three series of polyols with tailored chemical structures were obtained from PET wastes degradation via glycolysis and/or aminolysis and subsequent esterification-transesterification and/or amidation reactions, using an organic catalyst. As cleaving agents there were used various mixtures of renewable or potentially renewable reagents, selected from those that can be obtained from biomass by already applied or investigated and eventually patented biochemical and/or chemical processes. The polyols were characterized by physical-chemical methods, 1H-NMR, 13C-NMR and FT-IR Spectroscopy, and tested in the synthesis of rigid polyurethane foams, showing appropriate properties for spray foams formation and leading to materials with properties similar to conventional spray foams.

Effect of polyols on the structure and aggregation of recombinant human γ-Synuclein, an intrinsically disordered protein

Polyol osmolytes accumulated in cells under stress are known to promote stability in globular proteins with respect to their increasing hydroxyl groups but their effect on the structure, stability and aggregation of intrinsically disordered proteins (IDPs) is still elusive. The lack of a natively folded structure in intrinsically disordered proteins under physiological conditions results in their aggregation and fibrillation that gives rise to a number of diseases. We have investigated the effect of a series of polyols, ethylene glycol (EG), glycerol, erythritol, xylitol and sorbitol on the fibrillation pathway of recombinant human γ-Synuclein, used as a model, for an IDP known to form fibrils that play a role in neurodegeneration and cancer. With an increase in the number of –OH groups in polyols except EG, we observe a decrease in lag time for fibrillation at equimolar concentrations, suggesting stronger preferential exclusion of polyols that promotes γ-Syn self-association and oligomerization. The polyols act early during nucleation and their diverse effect on the rate of fibrillation suggests the role of favourable solvent-side chain interactions. With increasing –OH group, polyols stabilize the natively unfolded conformation of γ-Syn under non-fibrillating conditions and delay the structural transition to characteristic β-sheet structure by forming an α-helical intermediate during fibrillation. The results, overall suggest that the effect of osmolytes on IDPs is much more complex than their effect on globular protein stability and aggregation and a fine balance between the dominant unfavourable osmolyte-peptide backbone and favourable osmolyte-charged side chain interactions would govern their stability and aggregation properties.

Phase equilibria and the surface tension of polypropylene polyol series in water/methanol mixtures: A consideration of structural effects

The phase equilibria and surface tension of a polypropylene polyol (PPP) series was studied in aqueous solvent systems. The PPP series was composed of ethylene oxide (EO) and propylene oxide (PO) groups, exhibiting specific interactions with both water and alcohols. Binary and ternary liquid-liquid equilibria (LLE) of the PPP series were determined via thermo-optical analysis (TOA) methods, which represented closed-loop miscibility in water and Treybal Type 1 behavior in water and methanol (MeOH), respectively. The surface tension of the ternary PPP1/water/MeOH system was measured using a well-known plate method. The dendritic characteristics of the PPP series were reflected through modeling using lattice cluster theory (LCT) for complex structures of the polymer. The phase diagrams and surface tension of the PPP series were described from binary to ternary systems based on LCT incorporated with Guggenheim's treatment using predetermined parameters. The calculated results of both systems were in good agreement with the experimental data using the same interaction energy parameters.

Physicochemical Properties of Jatropha Oil-Based Polyol Produced by a Two Steps Method.

A low cost, abundant, and renewable vegetable oil source has been gaining increasing attention due to its potential to be chemically modified to polyol and thence to become an alternative replacement for the petroleum-based polyol in polyurethane production. In this study, jatropha oil-based polyol (JOL) was synthesised from non-edible jatropha oil by a two steps process, namely epoxidation and oxirane ring opening. In the first step, the effect of the reaction temperature, the molar ratio of the oil double bond to formic acid, and the reaction time on the oxirane oxygen content (OOC) of the epoxidised jatropha oil (EJO) were investigated. It was found that 4.3% OOC could be achieved with a molar ratio of 1:0.6, a reaction temperature of 60 °C, and 4 h of reaction. Consequently, a series of polyols with hydroxyl numbers in the range of 138–217 mgKOH/g were produced by oxirane ring opening of EJOs, and the physicochemical and rheological properties were studied. Both the EJOs and the JOLs are liquid and have a number average molecular weight (Mn) in the range of 834 to 1457 g/mol and 1349 to 2129 g/mol, respectively. The JOLs exhibited Newtonian behaviour, with a low viscosity of 430–970 mPas. Finally, the JOL with a hydroxyl number of 161 mgKOH/g was further used to synthesise aqueous polyurethane dispersion, and the urethane formation was successfully monitored by Fourier Transform Infrared (FTIR).

Synthesis and Deblocking Studies of Low Temperature Heat-Curable Blocked Polymeric Methylene Diphenyl Diisocyanates

One package heat curable polyurethane system typically requires blocked isocyanates with a relatively low deblocking temperature. In this study, a series of new aromatic secondary amines blocked polymeric methylene diphenyl diisocyanate (pMDI) was synthesized and characterized. Hot-stage FTIR, DSC and TGA spectroscopic methods were used to determine the deblocking temperatures of the blocked isocyanates. Cure reaction between the blocked isocyanates and a commercial polyl (PPG-2000) were carried out to establish structure and property relationship. Deblocking temperature and gel time of the blocked isocyanates based on N-methylaniline and N-methyl-o-toludine were lower than the blocked isocyanates with imidazole and methyl 4-methylaminobenzoate. Unexpected high deblocking temperature of imidazole and methyl 4-methylaminobenzoate was due to intra molecular hydrogen bonding. Solubility behavior of the blocked isocyanates was also studied using a series of polyols (PEG-400, Terathane-2000, PPG-2000, and castor oil).

Hydrogenolysis of Cellulose over Cu‐Based Catalysts—Analysis of the Reaction Network

A series of polyols, carbohydrates, and cellulose were tested in the aqueous, CuO/ZnO/Al2O3-catalyzed hydrogenolysis reaction at 245 °C and 50 bar H2. The compositions of liquid-phase products were analyzed; based on these results a unified reaction mechanism is proposed that accounts for the observed product distribution. Elementary transformations such as dehydration, dehydrogenation/hydrogenation, Lobry de Bruyn-van Ekenstein isomerization and retro-aldol cleavage were identified as most important for controlling the selectivity of simple polyols and carbohydrates. For cellulose the product distribution is considerably different than for glucose or sorbitol, indicating a change in the reaction pathway. Therefore, next to the traditional hydrolysis of the glycosidic bond, an additional depolymerization mechanism involving only the reducing ends of cellulose oligomers is proposed to account for this observation.

Assessing the hydration free energy of a homologous series of polyols with classical and quantum mechanical solvation models.

Molecular dynamics (MD) simulations associated with the thermodynamic integration (TI) scheme and the polarizable continuum model (PCM) in combination with the SMD solvation model were used to study the hydration free energy of the homologous series of polyols, C(n)H(n+2)(OH)n (1 ≤ n ≤ 7). Both solvation models predict a nonlinear behavior for the hydration free energy with the increase of the number of hydroxyl groups. This study also indicates that there is a sizable solute polarization in aqueous solution and that the inclusion of the polarization effect is important for a reliable description of the free energy differences considered here.

Durable Press Finishing of Cotton Fabrics with Citric Acid: Enhancement of Whiteness and Wrinkle Recovery by Polyol Extenders

A durable press finisher formula based on citric acid (CA), featuring polyol extenders, can be made to compare favorably to dimethylol dihydroxyethyleneurea (DMDHEU) or 1,2,3,4-butanetetracarboxylic acid (BTCA) in whiteness and wrinkle recovery performance. Durable press (DP) finishing of cotton fabrics with CA has long been implicated by inferior resilience enhancement and appreciable fabric yellowing, which hinder the industrialization of the technique despite the obvious merits of CA being cost-effective, nontoxic, and renewable. In this research, glycerol was used as the model compound for investigateing the mechanism of polyol’s whitening effect and for obtaining the optimized curing conditions. Then a series of polyols were investigated as extenders for the cross-linking of cotton with CA. Performance indicators such as the wrinkle recovery angle (WRA), CIE whiteness index (WI), tear strength (TS) retention, and DP rating of the treated fabrics were correlated with curing conditions and the structures of the extenders. It was found that the whitening power of the extenders is directly related to the number of primary hydroxyl groups. It was also found that polyols containing both primary and secondary hydroxyl groups are more effective at enhancing the resilience of treated fabrics. By using xylitol as the extender, DP ratings of 3.8–3.9 were imparted to both white and dyed cotton fabrics finished with CA without significant yellowing or discoloration. The addition of the extender was also favorable to the durability of the DP effects so that a DP rating of 3.5 was retained after 20 washing and tumble-drying cycles. It was shown that by using biobased extender xylitol two major drawbacks of DP finishing of cotton with CA could be eliminated, presenting an essentially green alternative to DMDHEU.

Synthesis and characterization of transparent and high impact resistance polyurethane coatings based on polyester polyols and isocyanate trimers

A series of polyester polyols were synthesized by polycondensation reaction using adipic acid (AA), 1,4-cyclohexanedicarboxylic acid (1,4-CHDA), and 1,6-hexanediol (HDO), 1,4-cyclohexanedimethanol (1,4-CHDM) and trimethylol propane (TMP), in which the molar ratio of the reactants AA/1,4-CHDA was varied. These series of polyols were reacted with isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), alone or in combination, to form polyurethane (PU) coatings.The physicochemical properties (chemical structure, hydroxyl value, acid value, and molecular weight) of the polyols so synthesized and the mechanical and optical properties (impact resistance, film flexibility, optical transmittance and phase separation) of the PU coatings so prepared were characterized with FTIR spectroscopy, wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and atomic force microscopy (AFM).The results of this study show that the AA/1,4-CHDA molar ratio, the isocyanate used, and the NCO/OH ratio all have a significant impact on the properties of the PU coatings. While AA/1,4-CHDA molar ratio does not seem to affect the film flexibility and optical transmittance of the PU coatings, it has a significant effect on the impact resistance of the coatings. Impact resistance of the PU coatings increases as the AA/1,4-CHDA molar ratio decreases (i.e. more 1,4-CHDA used). PU coatings based on IPDI and combination of IPDI and HDI exhibit higher impact resistance and optical transmittance than HDI-based coatings. While changing NCO/OH ratio has only a slight impact on the optical transmittance and little effect on film flexibility, impact resistance of the PU coatings first increase, then decline with an increase in NCO/OH ratio.

Effect of Hydrogen Bonds on pKa Values: Importance of Networking

The pK(a) of an acyclic aliphatic heptaol ((HOCH(2)CH(2)CH(OH)CH(2))(3)COH) was measured in DMSO, and its gas-phase acidity is reported as well. This tertiary alcohol was found to be 10(21) times more acidic than tert-butyl alcohol in DMSO and an order of magnitude more acidic than acetic acid (i.e., pK(a) = 11.4 vs 12.3). This can be attributed to a 21.9 kcal mol(-1) stabilization of the charged oxygen center in the conjugate base by three hydrogen bonds and another 6.3 kcal mol(-1) stabilization resulting from an additional three hydrogen bonds between the uncharged primary and secondary hydroxyl groups. Charge delocalization by both the first and second solvation shells may be used to facilitate enzymatic reactions. Acidity constants of a series of polyols were also computed, and the combination of hydrogen-bonding and electron-withdrawing substituents was found to afford acids that are predicted to be extremely acidic in DMSO (i.e., pK(a) < 0). These hydrogen bond enhanced acids represent an attractive class of Brønsted acid catalysts.

New Waterborne Polyurethane Dispersions from the Soybean-Oil-Based Polyols by Ring Opening of ESO with Glycol

A series of polyols (GSOLs) with a range of hydroxyl numbers based on epoxidized soybean oil (ESO) were prepared by ring opening with glycol. These Polyols of hydroxyl (OH) numbers ranging from 111 to 162 mg KOH/g were obtained. The environmentally friendly soybean-oil-based waterborne polyurethane dispersions (SPU) with very promising properties have been successfully synthesized from a series of soybean-oil-based polyols (GSOLs) with different hydroxyl numbers by a polyaddition reaction with toluene 2,4-diisocyanate (2,4-TDI). The structure and thermophysical properties of the resulting SPU films have been studied by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and hardness testing. The experimental results showed that the functionality of the GSOLs and the hard segment content play a key role in controlling the structure and the thermophysical properties of the SPU films.

Molecular basis for optical clearing of collagenous tissues

Molecular interactions of optical clearing agents were investigated using a combination of molecular dynamics (MD) simulations and optical spectroscopy. For a series of sugar alcohols with low to high optical clearing potential, Raman spectroscopy and integrating sphere measurements were used to quantitatively characterize tissue water loss and reduction in light scattering following agent exposures. The rate of tissue water loss was found to correlate with agent optical clearing potential, but equivalent tissue optical clearing was measured in native and fixed tissue in vitro, given long-enough exposure times to the polyol series. MD simulations showed that the rate of tissue optical clearing correlated with the preferential formation of hydrogen bond bridges between agent and collagen. Hydrogen bond bridge formation disrupts the collagen hydration layer and facilitates replacement by a chemical agent to homogenize tissue refractive index. However, the reduction in tissue light scattering did not correlate with the agent index of refraction. Our results suggest that a necessary property of optical clearing agents is hyperosmolarity to tissue, but that the most effective agents with the highest rates of optical clearing are a subset with the highest collagen solubilities.

Single-Centered Hydrogen-Bonded Enhanced Acidity (SHEA) Acids: A New Class of Brønsted Acids

Hydrogen bonds are the dominant motif for organizing the three-dimensional structures of biomolecules such as carbohydrates, nucleic acids, and proteins, and serve as templates for proton transfer reactions. Computations, gas-phase acidity measurements, and pK(a) determinations in dimethyl sulfoxide on a series of polyols indicate that multiple hydrogen bonds to a single charged center lead to greatly enhanced acidities. A new class of Brønsted acids, consequently, is proposed.

Polyurethane networks from different soy‐based polyols by the ring opening of epoxidized soybean oil with methanol, glycol, and 1,2‐propanediol

AbstractA series of polyols with a range of hydroxyl (OH) numbers based on soybean oil and epoxidized soybean oil were prepared by oxirane ring opening with methanol, glycol, and 1,2‐propanediol. The polyols, with average functionalities varying from 2.6 to 4.9, were characterized. Novel cast polyurethane resins were synthesized from these polyols and 2,4‐toluene diisocyanate. The sol fraction of the network decreased as the OH number of the polyol from which it was synthesized increased. None of the samples were completely soluble. The crosslinking density of the polyurethanes correlated directly with the functionality of the polyols. The thermal and mechanical properties of the cast resins were characterized with differential scanning calorimetry and thermogravimetry. The glass‐transition temperature increased with the OH number increasing, and the thermal stability of the resins was slightly decreased with the OH number increasing. The tensile strength at break increased with the OH number increasing. Polyurethanes prepared from polyols with OH numbers higher than 170 mg of KOH/g were glassy, whereas those with OH numbers below that value were rubbery. Glassy polyurethanes displayed decent mechanical strength, whereas rubbery samples showed relatively poor elastic properties and were characterized by lower strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Determinación de la densidad de entrecruzamiento de poliuretanos obtenidos a partir de aceite de ricino modificado por transesterificación

Se obtuvo una gama de polioles a partir del aceite de ricino modificado por transesterificación con pentaeritriol y glicerina. Los productos resultantes fueron caracterizados físico-químicamente. Se sintetizaron elastómeros de poliuretano a partir de los polioles derivados del aceite de ricino modificado. La densidad de entrecruzamiento se determinó por ensayos de hinchamiento a partir de la ecuación de Flory-Rehner apoyada en la espectroscopia MALDI TOF MS para determinar la estructura química de la unidad repetitiva promedio del poliuretano. Se estudió la variación de la densidad de entrecruzamiento de los poliuretanos con base en el índice de hidroxilo del poliol utilizado en la síntesis. Los resultados muestran que los PU obtenidos a través de la modificación del aceite con pentaeritriol tienen una mayor densidad de entrecruzamiento que los PU obtenidos a partir del aceite original y de los polioles derivados de la reacción de transesterificación del aceite con glicerina, debido a que estos polioles poseen una mayor funcionalidad hidroxílica.