Polyol Molecules Research Articles

Ladderphanes: A New Type of Duplex Polymers

A polymeric ladderphane is a step-like structure comprising multiple layers of linkers covalently connected to two or more polymeric backbones. The linkers can be planar aromatic, macrocyclic metal complexes, or three-dimensional organic or organometallic moieties. Structurally, a DNA molecule is a special kind of ladderphane, where the cofacially aligned base-pair pendants are linked through hydrogen bonding. A greater understanding of this class of molecules could help researchers develop new synthetic molecules capable of a similar transfer of chemical information. In this Account, we summarize our studies of the strategy, design, synthesis, characterization, replications, chemical and photophysical properties, and assembly of a range of double-stranded ladderphanes with many fascinating structures. We employed two norbornene moieties fused with N-arylpyrrolidine to connect covalently with a range of relatively rigid linkers. Ring opening metathesis polymerizations (ROMP) of these bis-norbornenes using the first-generation Grubbs ruthenium-benzylidene catalyst produced the corresponding symmetrical double-stranded ladderphanes. The N-arylpyrrolidene moiety in the linker controls the isotactic selectivity and the trans configuration for all double bonds in both single- and double-stranded polynorbornenes. The π-π interactions between these aryl pendants may contribute to the high stereoselectivity in the ROMP of these substrates. We synthesized chiral helical ladderphanes by incorporating asymmetric center(s) in the linkers. Replication protocols and sequential polymerization of a monomer that includes two different polymerizable groups offer methods for producing unsymmetical ladderphanes. These routes furnish template synthesis of daughter polymers with well-controlled chain lengths and polydispersities. The linkers in these ladderphanes are well aligned in the center along the longitudinal axis of the polymer. Fluorescence quenching, excimer formation, or Soret band splitting experiments suggest that strong interactions take place between the linkers. The antiferromagnetism of the oxidized ferrocene-based ladderphanes further indicates strong coupling between linkers in these ladderphanes. These polynorbornene-based ladderphanes can easily aggregate to form a two-dimensional, highly ordered array on the graphite surface with areas that can reach the submicrometer range. These morphological patterns result from interactions between vinyl and styryl end groups via π-π stacking along the longitudinal axis of the polymer and van der Waals interaction between backbones of polymers. Such assembly orients planar arene moieties cofacially, and polynorbornene backbones insulate each linear array of arenes from the adjacent arrays. Dihydroxylation converts the double bonds in polynorbornene backbones of ladderphanes into more hydrophilic polyols. Hydrogen bonding between these polyol molecules leads to self-assembly and produces structures with longitudinally staggered morphologies on the graphite surface.

Performance of nanosilica in acrylic polyol 2K polyurethane coatings

PurposeThe purpose of this paper is to formulate two component polyurethane coatings based on acrylic polyol, to study the effects of variable nanosilica loadings in these coatings on different morphological, optical, mechanical, corrosion resistance and weather resistance properties and to study the intercalation of acrylic polyol molecules into nanosilica crystals by XRD technique.Design/methodology/approachTwo component polyurethane coatings were synthesised using acrylic polyol and isocyanate HDI. The nanosilica was incorporated in polyurethane formulation at the weight ratios of 1%, 3% and 5% based on total weight of polyol and isocyanate. The performance of nanocoatings was compared for variable loads of nanosilica for different properties such as morphological, optical, mechanical, corrosion resistance, weather resistance and were studied for intercalation of acrylic polyol into nanosilica crystals by XRD technique.FindingsImprovement in the properties of polyurethane coatings is achieved with the incorporation of nanosilica. The improvement is the result of inherently high properties of inorganic nanosilica. Tensile strength, scratch hardness, abrasion resistance, corrosion and weathering resistance show significant improvement in performance with the incorporation of nanosilica. Properties are found to deteriorate beyond a certain loading of nanosilica; hence it is important to optimise loading level. The optimal range for high performance was found to be in the range of 1% to 3%. The improvement was a result of synergistic behaviour and good interfacial interaction between polyurethane and nanosilica at optimal levels.Research limitations/implicationsThe method used for incorporation of nanosilica into polyurethane was direct incorporation method. The other method of incorporation, i.e. in situ addition and its effect on properties can also be studied.Practical implicationsWith the addition of optimal loading level of nanosilica to polyurethane coatings, properties can be enhanced up to the mark. The addition is relatively easy and cost effective.Originality/valueThe paper proves the significance of incorporation of nanosilica on original properties of polyurethane coatings and widens the area of applications of two component polyurethane coatings from acrylic polyol by strengthening them in their properties. The coatings can be applicable in high performance topcoats especially for automotive topcoats.

LINKED UNSATURATED POLYESTER BLENDED WITH POLYOL (HTPBO)

This study was carried out to improve resistance to weathering Conditions especially ultra energy rays through physical blending with polyol monomer of 10%,20%,and30% ratios.The molding casting method was used to manufacture the samples which were exposed to high tempreture (110c) for (85)hours. The morphological study showed the nature of the distribution of polyol molecules and their miscibility with unsaturated polyester, as well as, the polymer mixtures surface..Also The photo graphs after radiation revealed that the surface showed aclear difference according to mixing ratios and the extent of degradation factors. The samples were continuosly exposed to uv-rays after radiation for 300 hours wavelength 245 nm, the photographs showed clear difference in the synthesized sample surface due to photodegradation which observed by uv-spectra. The percentages 20% and 30% showed a great sensitivity towards light . These samples gave swelling as a result of disohants indicating their degradation was faster than other samples.( if compared with the results of the virgin sample). It was proved that polyol with flexible properties can give improvement to the properties of unsaturated polyester of Hard properties via blending by 10% and lower ratios that give stabilization to the studied samples .

Theoretical Studies on the Unimolecular Decomposition of Propanediols and Glycerol

Polyols, a typical type of alcohol containing multiple hydroxyl groups, are being regarded as a new generation of a green energy platform. In this paper, the decomposition mechanisms for three polyol molecules, i.e., 1,2-propanediol, 1,3-propanediol, and glycerol, have been investigated by quantum chemistry calculations. The potential energy surfaces of propanediols and glycerol have been built by the QCISD(T) and CBS-QB3 methods, respectively. For the three molecules studied, the H(2)O-elimination and C-C bond dissociation reactions show great importance among all of the unimolecular decomposition channels. Rate constant calculations further demonstrate that the H(2)O-elimination reactions are predominant at low temperature and pressure, whereas the direct C-C bond dissociation reactions prevail at high temperature and pressure. The temperature and pressure dependence of calculated rate constants was demonstrated by the fitted Arrhenius equations. This work aims to better understand the thermal decomposition process of polyols and provide useful thermochemical and kinetic data for kinetic modeling of polyols-derived fuel combustion.

Photocatalytic reforming of C3-polyols for H2 production: Part (I). Role of their OH groups

TiO2 photocatalyst was prepared by sol–gel method, and then loaded with 1.0wt.% Pt by impregnation-chemical reduction method (denoted as PT). Photocatalytic reforming (PR) of C3-polyols (glycerol, propyleneglycol, and isopropanol) which have similar carbohydrate structure but possess different number of OH groups for H2 production over PT was performed to study the role of their OH groups in the reforming reaction. The results indicated that the H2 evolution rate and the mineralization efficiency of polyols (oxidized to CO2) are highly correlated with the number of OH groups they contain. The more OH group it has, the higher H2 evolution rate can be obtained, as well as the generation of CO2. The roles of the OH group were discussed in terms of providing an anchor for the chemical adsorption of polyols to the PT and serving as an effective holes scavenger to trigger the reforming reaction. For a polyol molecule, only OH directly connected segment can be effectively converted to H2 and CO2 via the PR process.

Essential Structural Factors of Bis-1,2-diol in Polyol Molecules for Capturing Boron

The binding mechanism between boron and polyol molecules was investigated by using Nuclear Magnetic Resonance (11B-NMR), Electrospray Ionization Time-of-Flight Mass Spectrometry (ESI-TOF-MS) and computational chemistry. The results of 11B-NMR and ESI-TOF-MS showed that N-methyl-D-glucamine (NMG) and boron mainly forms the 2:1 complex. On the other hand, the 3-amino-1,2-propanediol (APD) - boron complex was not observed under the condition when the equivalent amount of APD was added to the boron solution. The peak of the APD-boron complex in the 11B-NMR measurement was observed under the concentration condition of excess APD to boron. We investigated the structural features of polyol-boron complexes by using computational chemistry, and it was found that the distortion of the dihedral angles of the bis-1,2-diol in the polyol molecules significantly affected the ability to capture boron.

Morphology-conserved transformation: synthesis of hierarchical mesoporous nanostructures of Mn2O3 and the nanostructural effects on Li-ion insertion/deinsertion properties

By means of morphology-conserved transformation, we have synthesized hierarchically structured Mn2O3 nanomaterials with different morphologies and pore structures. The key step of this method consists of the formation of a precursor containing the target materials interlaced with the judiciously chosen polyol-based organic molecules, which are subsequently knocked out to generate the final nanomaterials. In the present work, two kinds of precursor morphologies, oval-shaped and straw-sheaf-shaped, have been selectively prepared by hydrothermal treatment of different functional polyol molecules (oval-shape with fructose and straw-sheaf-shape with β-cyclodextrin) and potassium permanganate. Thermal decomposition of the precursors resulted in the formation of mesoporous Mn2O3 maintaining the original morphologies, as revealed by extensive characterization. These novel hierarchical nanostructures with different pore sizes/structures prompted us to examine their potential as anode materials for lithium ion batteries (LIBs). The electrochemical results with reference to LIBs show that both of our mesoporous Mn2O3 nanomaterials deliver high reversible capacities and excellent cycling stabilities at a current density of 200 mA g−1 compared to the commercial Mn2O3 nanoparticles. Moreover, the straw-sheaf-shaped Mn2O3 exhibits a higher specific capacity and a better cycling performance than the oval-shaped one, due to the relatively higher surface area and the peculiar nanostrip structure resulting in the reduced length for lithium ion diffusion. Morphology-conserved transformation yields two kinds of hierarchical mesoporous Mn2O3 nanomaterials with high capacities and cycling stabilities for lithium ion batteries.

Molecular basis for polyol-induced protein stability revealed by molecular dynamics simulations

Molecular dynamics simulations of chymotrypsin inhibitor 2 in different polyols (glycerol, xylitol, sorbitol, trehalose, and sucrose) at 363 K were performed to probe the molecular basis of the stabilizing effect, and the data in water, ethanol, and glycol were compared. It is found that protein protection by polyols is positively correlated with both the molecular volume and the fractional polar surface area, and the former contributes more significantly to the protein's stability. Polyol molecules have only a few direct hydrogen bonds with the protein, and the number of hydrogen bonds between a polyol and the protein is similar for different polyols. Thus, it is concluded that the direct interactions contribute little to the stabilizing effect. It is clarified that the preferential exclusion of the polyols is the origin of their protective effects, and it increases with increasing polyol size. Namely, there is preferential hydration on the protein surface (2 A), and polyol molecules cluster around the protein at a distance of about 4 A. The preferential exclusion of polyols leads to indirect interactions that prevent the protein from thermal unfolding. The water structure becomes more ordered with increasing the polyol size. So, the entropy of water in the first hydration shell decreases, and a larger extent of decrease is observed with increasing polyol size, leading to larger transfer free energy. The findings suggest that polyols protect the protein from thermal unfolding via indirect interactions. The work has thus elucidated the molecular mechanism of structural stability of the protein in polyol solutions.

The Impact of Polyols on Water Structure in Solution: A Computational Study

Using molecular dynamics simulations, we study the effect of polyalcohols on water structuring in concentrated solutions, comparing six different polyols that vary in the number of hydroxyl groups and internal structure. For all polyols, we find that the hydrogen bond network order, as assessed by changes in the tetrahedral order parameter, is distorted in the binary solutions as compared with that of pure water and depends on the number of hydroxyl groups and the polyol conformation. While the total number of hydrogen bonds is only slightly reduced relative to that found in pure water, we find that hydrogen bonds that form with polyols tend to be less linear than hydrogen bonds formed between water molecules. We suggest that this reflects the competition between water and polyol molecules for hydrogen bonding with surrounding waters and offer a link between this competition and the resulting disorder that follows polyol solvation. The conclusions of this study should help shed light on the action that polyols can have as stabilizers to other macromolecules such as proteins in solution.

Densities and apparent molar volumes of myo-inositol in aqueous solutions of alkaline earth metal salts at different temperatures

Apparent molar volumes ( V φ ) of myo-inositol in water and in aqueous solutions of alkaline earth metal salt MCl 2 (M = Mg, Ca, Sr, Ba) under various concentrations and temperatures ranging from 293.15 K to 318.15 K have been measured by a precise vibrating-tube digital densimeter. The calculated partial molar volumes ( V φ 0 ) have been used to obtain the corresponding transfer partial molar volumes ( Δ trs V φ 0 ) of the polyol from water to various salt solutions. The experimental results show that V φ 0 of myo-inositol increases with enhancement of salt concentration and ascension of temperature. The interpretation is that these results arise from the dominant interaction of MCl 2 with the charged centers of myo-inositol. Δ trs V φ 0 of myo-inositol increases with enhancement of concentration of MCl 2 while decreases with the ascension of temperature. The change tendency of volume property of myo-inositol has been rationalized in the light of weak interactions between myo-inositol molecules, the polyol molecules and coexistent ions as well as the polyol molecules and solvent molecules with a cosphere overlap model applied.

Radiation-chemical synthesis of polymer polyols and related composites

The possibility of using ionizing radiation to initiate monomer grafting to polyol was studied. The results are indicative of the formation of a chemical bond between polyol and polystyrene molecules. The resulting polymer polyol has a lower viscosity compared to the initial compound, which is an advantage for the synthesis of polyurethane. Moreover, the possibility of producing metal-containing composites based on polymer polyol was shown.

Characterization of AgMaT2, a plasma membrane mannitol transporter from celery, expressed in phloem cells, including phloem parenchyma cells.

A second mannitol transporter, AgMaT2, was identified in celery (Apium graveolens L. var. dulce), a species that synthesizes and transports mannitol. This transporter was successfully expressed in two different heterologous expression systems: baker's yeast (Saccharomyces cerevisiae) cells and tobacco (Nicotiana tabacum) plants (a non-mannitol-producing species). Data indicated that AgMaT2 works as an H(+)/mannitol cotransporter with a weak selectivity toward other polyol molecules. When expressed in tobacco, AgMaT2 decreased the sensitivity to the mannitol-secreting pathogenic fungi Alternaria longipes, suggesting a role for polyol transporters in defense mechanisms. In celery, in situ hybridization showed that AgMaT2 was expressed in the phloem of leaflets, petioles from young and mature leaves, floral stems, and roots. In the phloem of petioles and leaflets, AgMaT2, as localized with specific antibodies, was present in the plasma membrane of three ontologically related cell types: sieve elements, companion cells, and phloem parenchyma cells. These new data are discussed in relation to the physiological role of AgMaT2 in regulating mannitol fluxes in celery petioles.

Formation of Lipid Emulsions and Clear Gels by Liquid Crystal Emulsification

Recently developed emulsion technologies for the formation of fine emulsions, lipid emulsions and clear gels by liquid crystal emulsification were reviewed. As a basic information on liquid crystal emulsification, the structures and characteristic behaviours of lyotropic liquid crystals were summarized. Formation of a liquid crystalline phase was often seen in emulsions and biological systems. The significance of liquid crystal formation during emulsification was analysed by comparing the states and stabilities of emulsions prepared by different processes. Then uses of liquid crystals for formation of the characteristic emulsions and gels were also discussed. In liquid crystal emulsification, an oil phase is dispersed directly into the lamellar liquid‐crystalline phase composed of surfactant, glycerol and water to prepare a gel‐like oil‐in‐liquid crystal emulsion. This is followed by dilution with the remaining water to produce an emulsion. From the phase behaviour during emulsification and analysis of the local motion of the liquid crystal membrane by fluorometry, it was confirmed that the interaction between surfactant and a polyol molecule such as glycerol promotes hydrogen bonding and enhances the strength of the lamellar liquid crystal membranes, which results in the formation of oil‐in‐liquid crystal emulsions. The interaction between the liquid crystal and oil was analysed from the changes in molecular motion of the membrane at the oil‐liquid crystal interface using the spin label technique of electron spin resonance (ESR). The fluidity of the liquid crystal membrane did not change when oil was added, and therefore oil‐in‐liquid crystal emulsions of various oils were prepared by the identical process. This lack of dependence of the liquid crystal membrane on oil results in the unique properties of liquid crystal emulsification, which can be used for oils of various polarity and different molecular constituents. When a self‐organizing artificial stratum corneum lipid containing pseudo‐ceramide was used as a principal component of the oil, a multilamellar emulsion of concentric lamellar structure was formed. The multilamellar emulsion supplements the physiological function of stratum corneum by the identical mechanism as natural intercellular lipids. High‐pressure treatment of the lipid emulsion produced a gel‐like emulsion crystal, in which the homogeneous nanoemulsion droplets were arranged in a hexagonal array.This review paper was presented at the Conference of the Asian Societies of Cosmetic Scientists 2005 in Bangkok.

Synthesis and Characterization of Titania-Sugar Alcohol Complex Nanoparticles

Complexes between TiO 2 and sugar alcohol molecules or polyol molecules were prepared by heating the mixture of titanium isopropoxide (TIP) and ethylene glycol, glycerin, meso-erythritol, or D-mannitol aqueous solution at 368 K for 24 h. The degree of crystallization of TiO 2 in the obtained TiO 2 -sugar alcohol or polyol complex depended on the concentration of the polyol and sugar alcohol aqueous solution. When the TiO 2 -sugar alcohol or polyol complex was prepared by using the same concentration of the sugar alcohol or polyol aqueous solution, the degree of crystallization of the TiO 2 in the complex decreased with increase in the number of OH groups per molecule. According to the results of the DTA measurements and the element analysis, the strength of the interaction between Ti 4+ ions and polyol or sugar alcohol molecules increased with increases in the number of OH groups in the molecules. The heat treatment of TiO 2 -D-mannitol complex in 0.5 mol/l HNO 3 aqueous solution at more than 318 K enabled to obtain TiO 2 -D-mannitol complex nanoparticles by breaking the bonds between the D-mannitol molecules and Ti 4+ ions. The obtained TiO 2 -D-mannitol complex nanoparticles had large surface area which was more than 300 m 2 /g and showed photocatalytic activity. Furthermore, the complex nanoparticles can be dispersed into the distilled water with high stability.

Effects of surface properties of colloidal silica particles on redispersibility and properties of acrylic-based polyurethane/silica composites

Nanosilica particles with different surface properties were designed and prepared using colloidal silica particles and four different qualitative silane coupling agents (SCA), namely methyltriethoxysilane (MTES), octyltriethoxysilane (OTES), vinyltriethoxysilane (VTES) and methacryloxypropyltrimethoxysilane (MATMS), and further applied in acrylic resins and corresponding polyurethane coats by in situ polymerization. It was found that different qualitative SCA molecules had very different impacts on the redispersibility of nanosilica particles, the adsorbed acrylic polyol molecules, the viscosities of acrylic polyol/silica hybrid resins, and the properties of acrylic-based polyurethane/silica composites.

Synthesis of rutile and anatase TiO2 nanoparticles from Ti-peroxy compound aqueous solution with polyols

Ti-peroxy compound was synthesized from Ti(O-iPr)4 and H2O2. Anatase and rutile TiO2 nanoparticles were prepared by heating the Ti-peroxy compound diluted with a polyol aqueous solution at 368 K for 24 h. In this research, ethylene glycol, glycerin, erythritol, and D-mannitol were used as polyols in the diluting solution. The ratio of anatase/rutile of the TiO2 obtained depended on the polyol concentration in the diluting solution. Furthermore, the polyol concentration at which single-phase anatase could be obtained was lowest when the number of OH groups in the polyol molecule was the highest. With increasing polyol concentration, the obtained TiO2 nanoparticles showed increasing specific surface area and decreasing particle size.

A novel thermostable xylanase from Thermomonospora sp.: influence of additives on thermostability

An alkalothermophilic Thermomonospora sp. producing high levels of xylanase was isolated from self-heating compost. The culture produced 125 IU/ml of xylanase when grown in shake flasks at pH 9 and 50°C for 96 h. The culture filtrate also contained cellulase (23 IU/ml), mannanase (1 IU/ml) and β-xylosidase (0.1 IU/ml) activities. The xylanase was active at a broad range of pH (5–9) and temperature (40–90°C). The optimum pH and temperature were 7 and 70°C, respectively. The enzyme was stable in the pH range 5–8 and was thermostable with half-lives of 8 and 4 h at 60°C and 70°C, respectively, but only 9 min at 80°C. The effects of a variety of compounds to enhance the stability of xylanase at 80°C was studied. Addition of sorbitol, mannitol and glycerol increased the thermostability of xylanase in proportion to the number of hydroxyl groups per polyol molecule. Glycine also offered protection against thermoinactivation. Xylan, trehalose, gelatin and trehalose–gelatin mixture had marginal effect on the thermostability of xylanase at 80°C.

Water Activity in Polyol Systems

Water activities of binary and ternary mixtures containing polyols were measured using an electronic hygrometer with temperature ranging from (10 to 35) °C. The concentrations of the mixtures varied according to the solubility limit for each polyol (d-sorbitol, d-mannitol, xylitol, meso-erythritol, and glycerol). Results were compared with the group contribution-based models ASOG and UNIFAC. The predictions using parameters from the literature were poor, probably as a consequence of the strongly polar hydroxyl groups bounded to consecutive carbon atoms in the polyol molecule. Better agreement was obtained by readjusting some of the interaction parameters. The data bank used in this procedure included water activity data as well as polyol solubility data taken from the literature. The best results were achieved using the UNIFAC−Larsen model with an average relative deviation of 0.9% for water activity and solubility data.

Cubic-Phase-Based Concentrated Emulsions

The effect of different types of added oil on the formation of a discontinuous micellar-type cubic phase was investigated in water–polyoxyethylene dodecyl ether (C12EO25) systems by phase study and small-angle X-ray scattering. The thermal stability of the cubic phase increases upon addition of oil, especially short-chain hydrocarbons. However, in the heptane system, the maximum melting temperature of the cubic phase is lower than that for decane due to the formation of a different liquid crystal phase. The effect of polyols on C12EO25 cubic phases was also investigated. It was found that the thermal stability of the cubic phase decreases with polyol concentration. The destabilizing effect becomes large as the polyol molecule penetrates further into the surfactant palisade layer. Although the solubilization of oil in the cubic phase is very low, a large amount of excess oil can be incorporated and a transparent cubic-phase-based concentrated emulsion is formed. The transparency is attributed to the very small difference in the refractive indices between the cubic and excess-oil phases.

Titration calorimetric determination of the pairwise interaction parameters of glycerol, D-threitol, mannitol, and D-glucitol in dilute aqueous solutions

Enthalpic pairwise interaction parameters, hjj, were determined by titration calorimetry at 25°C for dilute solutions of glycerol, D-threitol, manitol, and D-glucitol in water. The parameters for these and other polyols conform to the expression hjj (J-kg−1)=145+135nOH−21.5n OH 2 −41.7 dl 2 -160.5ndlld, where nOH=nC is the number of hydroxyl groups (carbon atoms), ndl is the number of dl configuration of a vicinal pair of OH-groups, and ndlld is the number of such configurations in the polyol molecules. A rationalization of this expression is given.