Hydroxypropyl Groups Research Articles

Taguchi design-based synthesis and structural analysis of Cassia galactomannan hydroxypropyl derivative

Hydroxypropylation is a significant industrial process for diverse applications of polysaccharides. In the present study hydroxypropylation of Cassia gum derived from ruderal Cassia tora species was investigated using Taguchi's L'16 orthogonal array design of experiments. The optimized reaction conditions comprised: reaction temperature 50 °C, time 240 min, sodium hydroxide (0.015 mol), propylene oxide (0.0755 mol) and 60% aq. propane-2-ol. The maximum hydroxypropyl content, 8.43 and 7.71% were achieved using chromic acid titration and 1H NMR spectroscopic analysis respectively in the optimized product. The chemical shift values of substituted hydroxypropyl groups for methyl, methine and methylene protons at 0.98, 3.87 & 3.41 ppm along with respective carbons at δ 18.23, 69.41 & 79.13, and other assignments, 1H and 13C signals, were confirmed by COSY and HSQC correlation spectral analysis. The substituted hydroxypropyl groups, C 6 of the β-D-1, 4-linked-Manp unit, were established at 66.18 ppm.

Monitoring Polymorphic Phase Transitions in Flufenamic Acid Amorphous Solid Dispersions Using Hyphenated X-ray Diffraction-Differential Scanning Calorimetry.

Flufenamic acid (FFA) is a highly polymorphic drug molecule with nine crystal structures reported in the Cambridge Structural Database. This study explores the use of synchrotron X-ray powder diffraction combined with differential scanning calorimetry to study crystallization and polymorphic phase transitions upon heating FFA–polymer amorphous solid dispersions (ASDs). Ethyl cellulose (EC, 4 cp) and hydroxypropylmethylcellulose (HPMC) grades with different viscosities and substitution patterns were used to prepare dispersions with FFA at 5:1, 2:1, 1:1, and 1:5 w/w drug/polymer ratios by quench cooling. We employed a 6 cp HPMC 2910 material and two HPMC 2208 samples at 4000 and 100 000 cp. Hyphenated X-ray diffraction (XRD)–differential scanning calorimetry (DSC) studies show that the 6 and 100 000 cp HPMCs and 4 cp EC polymers can stabilize FFA form IV by inhibiting the transition to form I during heating. It appears that the polymers stabilize FFA in both amorphous and metastable forms via a combination of intermolecular interactions and viscosity effects. Increasing the polymer content of the ASD also inhibits polymorphic transitions, with drug/polymer ratios of 1:5 w/w resulting in FFA remaining amorphous during heating. The comparison of FFA ASDs prepared with different samples of HPMCs and ECs suggests that the chemical substitution of the polymer (HPMC 2208 has 19–24% methoxy groups and 4–12% hydroxypropyl groups, while HPMC 2910 has 28–30% methoxy groups and 7–12% hydroxypropyl groups) plays a more significant role in directing polymorphic transitions than the viscosity. A previously unreported polymorph of FFA was also noted during heating but its structure could not be determined.

Effect of β-cyclodextrins on the physical properties and anti-staling mechanisms of corn starch gels during storage

The aim of this study was to investigate the effects of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) on the physical and anti-staling properties of corn starch (CS). It was found that the addition of β-CDs significantly decreased the storage and loss modulus of CS gel. Moreover, it reduced CS gel setback viscosity and hardness, in which HP-β-CD primarily exhibited a more pronounced effect. The long and short-range ordered structure showed that the relative crystallinity of CS gel was delayed with the β-CDs incorporation. Meanwhile, the β-CDs promoted the inhibition of water migration. In addition, the microstructure observation showed that β-CDs can better maintain the stability of CS gel structure during storage. Consequently, the addition of β-CDs could delay the retrogradation of CS gel, and the introduction of hydroxypropyl groups was more effective, which provided a theoretical basis and new insights for the production of starch-based food industrial products.

Preparation and intrinsic kinetics study of the scale-up production of hydroxypropyl agar by heterogeneous hydroxypropylation reaction

Hydroxypropylation is effective in modifying the structure and properties of agar. So far, the industrial scale-up production of hydroxypropylated agar has not been evaluated. Therefore, the large-scale production of the hydroxypropylation of agar using a heterogeneous reaction system was evaluated in the present this study. The structures and properties of the hydroxypropyl agar (HPA) product were measured and the intrinsic kinetics of the heterogeneous reaction were determined and analyzed. The results showed that the large-scale HPA had good thermal stability, and lower viscosity, gelling temperature and melting temperature compared with those of agar. The SEM indicated that the improvement of solubility of HPA was not only due to the hydrophilic effect of hydroxypropyl group, but also due to the formation of cluster structure and grid structure. The characteristic of heterogeneous hydroxypropylation reaction were determined by preliminary kinetic experiments, which demonstrated that the reaction order of propylene oxide was 2, while that for agar was approximately 0. The reaction activation energy of heterogeneous hydroxypropylation reaction was calculated to be 83.50 kJ/mol using the Arrhenius formula. Taken together, the results would provide guidances for the industrialization of hydroxypropyl agar.

Effect of Hydroxypropyl methylcellulose from oil palm empty fruit bunch on oil uptake and physical properties of French fries

Oil palm empty fruit bunches (OPEFB) can be used as raw material for Hydroxypropyl Methylcellulose (HPMC). HPMC can be used as a French fries coating to reduce oil uptake. This research aims to study the utilization of HPMC OPEFB as a French fries coating. This research consists of two stages. The first stage is cellulose extraction and HPMC synthesis. HPMC synthesis through alkalization, methylation, propylation, and neutralization. The second stage is the use of HPMC as a French fries coating with different concentrations (0, 1, 2, and 3%). Potatoes that have been peeled and washed, cut lengthwise with a thickness of about 0.5 cm. Further dipped in HPMC solution with different concentrations for 10 seconds, then carried out a frying pan. The HPMC from OPEFB is characterized by methyl and hydroxypropyl groups found at a wavenumber of 2891.30 cm-1, a ring of pyranose at 995.79 cm-1 and hydroxyls (OH) groups at 3371.10 cm-1. The coating of French fries with 3% HPMC OPEFB can reduce oil absorption by 16.09%. The higher the concentration of HPMC, will reduce the fat content but increase the moisture and the texture of French fries become softer. The preferred type of coating was HPMC 1%.

Plasticized hydroxypropyl cassava starch blended PBAT for improved clarity blown films: Morphology and properties

Plasticized hydroxypropyl cassava thermoplastic starch (TPS) with glycerol was blended with polybutylene adipate terephthalate (PBAT) via blown-film extrusion. Effects of PBAT/TPS ratios (60/40 and 50/50) and degrees of substitution (DS) for hydroxypropyl groups in TPS on film properties were investigated. All PBAT/TPS blend films were determined for morphology, thermal stability, thermomechanical, mechanical and barrier properties. Higher DS increased film clarity and glossy surface, improved compatibility between PBAT and TPS, reduced crystallinity and enhanced exposure of hydroxyl groups and hydrogen-bonding of the films. Blending caused phase separation with dispersed starch granules in continuous PBAT matrices, giving high surface roughness. Increased TPS and DS facilitated formation of co-continuous structures and miscibility, improving elongation by approximately 210%. Different DS modified microstructure and hydrophilicity of PBAT/TPS films which consequently reduced water vapor permeability by 34%. Modified DS in hydroxypropyl starch efficiently improved clarity, mechanical and barrier properties of bioplastic packaging.

Liposomal Fe(III) Macrocyclic Complexes with Hydroxypropyl Pendants as MRI Probes.

Paramagnetic liposomes containing Fe(III) complexes were prepared by incorporation of mononuclear (Fe(L1) or Fe(L3)) or dinuclear (Fe2(L2)) coordination complexes of 1,4,7-triazacyclononane macrocycles containing 2-hydroxypropyl pendant groups. Two different types of paramagnetic liposomes were prepared. The first type, LipoA, has the mononuclear Fe(L1) complex loaded into the internal aqueous core. The second type, LipoB, has the amphiphilic Fe(L3) complex inserted into the liposomal bilayer and the internal aqueous core loaded with either Fe(L1) (LipoB1) or Fe2(L2) (LipoB2). LipoA enhances both T1 and T2 water proton relaxation rates. Treatment of LipoA with osmotic gradients to produce a nonspherical liposome produces a liposome with a chemical exchange saturation transfer effect as shown by an asymmetry analysis but only at high osmolarity. LipoB1, which contains an amphiphilic complex in the liposomal bilayer, produced a broadened Z-spectrum upon treatment of the liposome with osmotic gradients. The r1 relaxivity of LipoB1 and LipoB2 were higher than the r1 relaxivity of LipoA on a per Fe basis, suggesting an important contribution from the amphiphilic Fe(III) center. The r1 relaxivities of paramagnetic liposomes are relatively constant over a range of magnetic field strengths (1.4-9.4 T), with the ratio of r2/r1 substantially increasing at high field strengths. MRI studies of LipoB1 in mice showed prolonged contrast enhancement in blood compared to the clinically employed Gd(DOTA), which was injected at a 2-fold higher dose per metal than the Fe(III)-loaded liposomes.

Dinuclear Fe(III) Hydroxypropyl-Appended Macrocyclic Complexes as MRI Probes.

Four high-spin Fe(III) macrocyclic complexes, including three dinuclear and one mononuclear complex, were prepared toward the development of more effective iron-based magnetic resonance imaging (MRI) contrast agents. All four complexes contain a 1,4,7-triazacyclononane macrocyclic backbone with two hydroxypropyl pendant groups, an ancillary aryl or biphenyl group, and a coordination site for a water ligand. The pH potentiometric titrations support one or two deprotonations of the complexes, most likely deprotonation of hydroxypropyl groups at near-neutral pH. Variable-temperature 17O NMR studies suggest that the inner-sphere water ligand is slow to exchange with bulk water on the NMR time scale. Water proton T1 relaxation times measured for solutions of the Fe(III) complexes at pH 7.2 showed that the dinuclear complexes have a 2- to 3-fold increase in r1 relaxivity in comparison to the mononuclear complex per molecule at field strengths ranging from 1.4 T to 9.4 T. The most effective agent, a dinuclear complex with macrocycles linked through para-substitution of an aryl group (Fe2(PARA)), has an r1 of 6.7 mM-1 s-1 at 37 °C and 4.7 T or 3.3 mM-1 s-1 per iron center in the presence of serum albumin and shows enhanced blood pool and kidney contrast in mice MRI studies.

Effects of varying levels of succinylation and hydroxypropylation on functional, thermal and textural characteristics of white sorghum starch

AbstractBackground and objectivesStarch is a versatile storage biopolymer with exceptional physicochemical properties. However, sometimes it owes certain functional inabilities in the native form which could be effectively overcome by chemical modifications to meet specific requirements. The present study was conducted to improve the functional properties of native sorghum starch chemically modifying via succinylation and hydroxypropylation. Native sorghum starch was modified with different concentrations of succinic anhydride and propylene oxide and was subsequently analyzed for physicochemical, thermal, and textural properties.FindingsThe swelling power and water retention capacity tend to improve upon substitution with succinyl and hydroxypropyl groups while succinylation did not have any pronounced effect on solubility of sorghum starch. All modified starches resulted in more clear starch paste than native starch but hydroxypropylated starch pastes were the most transparent to light. Succinylation did not bring about any change in pasting temperature; however, peak viscosity, hot paste viscosity, and cold paste viscosity increased significantly. Hydroxypropylated starches exhibited lower pasting temperature, higher peak viscosity for only starch substituted with 30% propylene oxide. Thermal gelatinization temperatures and enthalpy of gelatinization were significantly reduced after hydroxypropylation of sorghum starch. Percent retrogradation (%R) was significantly reduced for starches treated with 3% and 4% succinic anhydride and for all hydroxypropylated starches.ConclusionsWe concluded that hydroxypropylated starch substituted with 30% reagent exhibited the most desirable physicochemical properties and the lowest retrogradation.Significance and noveltyThis study highlighted the benefits of using different concentrations of succinic anhydride and propylene oxide to improve the functional properties of sorghum starch.

Combined effects of hydroxypropylation and alcoholic alkaline treatment on structural, functional and rheological characteristics of sorghum and corn starches

This study describes the effects of hydroxypropylation (HP) on sorghum and corn cold water soluble (CWS) starches prepared via alcoholic alkaline treatment (AAT). Propylene oxide (5% and 12% on starch weight basis) was used to modify both sorghum and corn starches. SEM analysis revealed that HP modification prior to AAT altered the granular morphology of native CWS starches. The characteristic peaks at 2980.28 cm−1 and 2979.87 cm−1 indicated the presence of hydroxypropyl groups and the complete loss of the granular order for HS12-CWS (hydroxypropylated sorghum CWS starch treated with 12% propylene oxide based on dry starch weight) and HC12-CWS (hydroxypropylated corn CWS starch treated with 12% propylene oxide based on dry starch weight) starches. Increase in swelling power and water binding capacity of HP modified CWS starches was observed. However, Percent transmittance was significantly reduced due to fragmented water-soluble granules. HP-modified CWS starch gels exhibited a more rigid gel network. Broader linear viscoelastic range suggesting greater stability and well dispersed behavior of HP-CWS starches. High G′ values of HP-CWS starches were due to the ordered and elastic gel network that resisted deformation. Furthermore, all HP-CWS starches exhibited higher shear and thermal resistance compared to unmodified CWS starches.

The apparent formation constants of asiatic acid and its derivatives existing in Centella asiatica with cyclodextrins by HPLC

The retention of triterpenoids in the C18 column and apparent formation constants of triterpenoids with cyclodextrins (CDs) were studied using HPLC. As the effective mobile phase additives, CDs can improve the separation of triterpenoid glycosides (asiaticoside B, madecassoside and asiaticoside) and reduce the retention of triterpenoids, and it is attributed to that triterpenoids forms a 1:1 inclusion complexes with CDs. The apparent formation constants of these complexes depend on the structure of triterpenoids, as well as on the substituent group and the hydrophobic cavity size of CDs. Triterpenoid glycosides had less apparent formation constants with HP-β-CD and Glu-β-CD, which might be related that hydroxypropyl group and glucose group in the structure of HP-β-CD and Glu-β-CD were unfaver to formation of the inclusion complexes. Asiaticoside B had larger apparent formation constants with CDs than madecassoside and asiaticoside. Larger apparent association constants of triterpenoid acids (madecassic acid and asiatic acid) were obtained with γ-CD than β-CD and its derivatives, which are related that triterpenoid acids fit well into the γ-CD cavity, and form relatively stable inclusion complexes. The ∆G (25 °C), ∆H and ∆S reveal that the inclusion processes between triterpenoids and CDs were not spontaneous, exothermic, and enthalpically driven. In addition, the usefulness of CDs for simultaneous analysis of five triterpenoids in HPLC and drug delivery vehicles was described.

A facile method to control the phase behavior of hydroxypropyl cellulose

We report a facile chemical method to convert the hydroxyl groups of hydroxypropyl cellulose (HPC) into carbamates. It was achieved by the reaction of HPC with N-methyl carbamoylimidazole, which is a safe and easy to handle replacement for the particularly hazardous reagent methyl isocyanate. Using a series of HPC with a range of molar substitution of hydroxypropyl groups, we synthesized HPC methylcarbamates showing lower critical solution temperature (LCST) in the range between 94 and 15 °C. A linear dependence of LCST versus methylcarbamate degree of substitution is observed. The lower the initial hydroxypropyl content of HPC, the greater the effect of methylcarbamate on the LCST. Surface tension study showed that methylcarbamate modification has an insignificant effect on the hydrophilic-hydrophobic balance of the macromolecules below LCST unless the molecular substitution of hydroxypropyl groups is so low (0.8) that the native cellulose OH groups can react with N-methyl carbamoylimidazole.

Effect of hypergravity on the modification of xanthan gum

To improve the properties of xanthan gum (XG), 3-chloro-2-hydroxypropyltrimethylammonium chloride and propylene oxide were used as modifiers to etherify XG and to obtain cationic hydroxypropyl xanthan gum (HCXG), and cationic hydroxypropyl xanthan gum (CHCXG), further optimized by super-gravity reaction. The structure of the product was characterized by infrared spectroscopy and nuclear magnetic resonance. The rheological properties of XG, HCXG, and CHCXG solutions and their performance as fracturing fluids were studied. Infrared and nuclear magnetic test results showed that the cationic etherification agent and hydroxypropyl group were successfully connected to XG, and the degree of substitution of CHCXG was higher. The rheological properties of the CHCXG solution and the performance of the fracturing fluid base fluid were superior to those of the XG and HCXG solutions. The viscosity of the solution after the super-gravity modification was further increased, and the apparent viscosity of the 0.4% CHCXG solution was 28.96% higher than that of the HCXG solution. After XG modification, the solution strength, yield stress, viscoelasticity, temperature resistance, and shear resistance were all significantly improved. The rheological properties of the HCXG solution and the performance of the fracturing fluid base fluid are good and can be used for fracturing fluid thickener.

CoII Complexes as Liposomal CEST Agents.

Three paramagnetic CoII macrocyclic complexes containing 2-hydroxypropyl pendant groups, 1,1',1'',1'''-(1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetrayl)tetrakis- (propan-2-ol) ([Co(L1)]2+ , 1,1'-(4,11-dibenzyl-1,4,8,11-tetraazacyclotetradecane-1,8-diyl)bis(propan-2-ol) ([Co(L2)]2+ ), and 1,1'-(4,11-dibenzyl-1,4,8,11-tetraazacyclotetradecane-1,8-diyl)bis(octadecan-2-ol) ([Co(L3)]2+ ) were synthesized to prepare transition metal liposomal chemical exchange saturation transfer (lipoCEST) agents. In solution, ([Co(L1)]2+ ) forms two isomers as shown by 1 H NMR spectroscopy. X-ray crystallographic studies show one isomer with 1,8-pendants in cis-configuration and a second isomer with 1,4-pendants in trans-configuration. The [Co(L2)]2+ complex has 1,8-pendants in a cis-configuration. Remarkably, the paramagnetic-induced shift of water 1 H NMR resonances in the presence of the [Co(L1)]2+ complex is as large as that observed for one of the most effective LnIII water proton shift agents. Incorporation of [Co(L1)]2+ into the liposome aqueous core, followed by dialysis against a solution of 300 mOsm L-1 produces a CEST peak at 3.5 ppm. Incorporation of the amphiphilic [Co(L3)]2+ complex into the liposome bilayer produces a more highly shifted CEST peak at -13 ppm. Taken together, these data demonstrate the feasibility of preparing CoII lipoCEST agents.

Hydrolysis of Hydroxypropyl Methylcellulose by Trifluoromethanesulfonic Acid and Subsequent Determination of Chemical Structure by 13C NMR Spectroscopy

The hydrolysis of three hydroxypropyl methylcellulose samples with varying degrees of polymerization by aqueous solutions of trifluoromethanesulfonic acid with a concentration of 1, 2, 3, and 4% at a temperature of 80, 90, 100, and 110°C in a microwave reactor is studied. The completeness of hydrolysis is estimated by 13C NMR spectroscopy of the disappearance of the signal the acetal carbon atom. It is shown that the concentration of acid has the greatest influence on the hydrolysis rate, the effect of temperature increase is not so strong, and the effect of reaction time is even smaller. Using 13C NMR spectroscopy, substitution parameters at the second, third, and sixth positions (DSC-2, DSC-3, and DSC-6) are determined, the amount of methyl (DSMe) and hydroxypropyl groups (DSHP) is estimated, and the total degree of substitution (DStotal) is calculated.

Aggregation and antimicrobial properties of gemini surfactants with mono- and di-(2-hydroxypropyl)ammonium head-groups: Effect of the spacer length and computational studies

Cationic gemini surfactants, alkanediyl-α,ω-bis[(2-hydroxypropyl)dodecylammonium] dibromide (abbreviated as C12-s-C12[iso-Pr(OH)] and C12-s-C12[iso-Pr(OH)]2, with s = 2, 3, 4 and 5) have been synthesized, and their aggregation properties in aqueous solution have been studied by surface tension, electrical conductivity and dynamic light scattering methods. On the basis of the results of studying aqueous solutions of the synthesized gemini surfactants by tensiometric and conductometric methods, their principal surfactivity parameters, such as the degree of counterion binding (β), critical micelle concentration (CMC), effectiveness of surface tension reduction (πCMC), surface excess concentration (Γmax), area per molecule at the interface (Amin), changes of Gibbs free energies of adsorption (ΔGad) and micellization (ΔGmic) have been calculated. For both classes of these gemini surfactants, a character of the surfactivity parameters change with an elongation of the spacer chain was defined and comparative analysis with other ammonium-type gemini surfactants having different head-groups was performed. Using dynamic light scattering method, regularities of variation of the aggregates sizes were studied depending on the number of 2-hydroxypropyl groups and the spacer chain length was investigated. Meanwhile, it was revealed that the mentioned gemini surfactants possess antimicrobial properties. The mechanism of the epoxide ring opening and salt formation reactions were calculated by using Kohn–Sham DFT with the B3LYP functional. The epoxide ring opening via primary (dodecylamine) and secondary (INT2) amines was determined as exergonic (13.4 and 4.4 kcal/mol) reactions as observed experimentally.

Исследование процесса влагопереноса в сырцовых пряниках с фруктовой начинкой, изготовленных с использованием различных видов модифицированного крахмала

Мучные кондитерские изделия со сроком годности 1 месяц и более являются самым востребованным видом сладкого у потребителя. Пряники являются вторым по популярности видом в этой группе изделий – 16% в структуре потребления по данным Росстата РФ. Срок годности сырцовых пряников с начинкой зависит от скорости их микробиологической порчи, обусловленной интенсивностью и направлением процессов влагопереноса. При высокой скорости миграции влаги пряники быстро черствеют, а низкая скорость процессов влагопереноса повышает риск плесневения. Провели исследования динамики изменения массовой доли влаги и активности воды в различных частях сырцовых пряников с начинкой – в выпеченном полуфабрикате и в начинке в процессе хранения в течение 3,5 месяцев. Оценили влияние модифицированных крахмалов трех видов: этерифицированные фосфатными группами (Е 1412), ацетильными группами (Е 1422) и с комбинацией фосфатных и гидроксипропильных групп (E 1442) на влагоудерживающие свойства в начинках. Потери влаги в начинке, изготовленной с крахмалом, этерифицированном комбинацией фосфатных и гидроксипропильных групп значительно меньше – в 2–2,5 раза, чем при использовании крахмалов, этерифицированных фосфатными или ацетильными группами. Рассчитали скорость процесса влагопереноса для изделий, изготовленных с использованием различных видов крахмала, по коэффициенту диффузии. Выявлено, что скорость влагопереноса минимальна для крахмала E 1442, о чем свидетельствует наименьший коэффициент диффузии – 1,097. Предложена схема прогнозирования сохранности сырцовых пряников с фруктовой начинкой на основе результатов исследования процессов влагопереноса и характеристик влагоудерживающих добавок (модифицированный крахмал). Схема процесса представлена в виде совокупности подсистем с указанием параметров и факторов, оказывающих влияние на скорость влагопереноса. Полученные результаты позволяют прогнозировать риски плесневения сырцовых пряников с фруктовой начинкой в процессе их хранения.

Kinetics, thermodynamics and mechanisms of phosphate sorption onto bottle gourd biomass modified by (3-chloro-2-hydroxypropyl) trimethylammonium chloride

The sorption kinetics and thermodynamic parameters of phosphate removal from aqueous solution using quaternary ammonium–modified bottle gourd biomass as a sorbent were studied in a batch reactor. The cationic sorbent, containing trimethylammonium and hydroxypropyl groups, was obtained through the chemical reactions of the lignocellulosic Lagenaria vulgaris shell with (3-chloro-2-hydroxypropyl)trimethylammonium chloride. Experimental data of phosphate sorption from aqueous solutions of different initial concentrations (5–140 mg P L−1) have been analysed by reaction kinetics and diffusion models. The characteristic rate constants calculated by linear and non-linear regression analyses of the experimental results are presented. The phosphate sorption reaches equilibrium in 20–30 min, depending on the initial phosphate concentration. The maximum sorption capacity of quaternary ammonium–modified bottle gourd (QABG) sorbent was 18 mg P g−1at 20 oC. The sorption system is best described by a non-linear equation of the pseudo first-order model ( R2 > 0.996). The Weber–Morris model indicated that the sorption process took place in three steps, whereby the intra-particle diffusion is not the only rate-controlling step. In addition, the effect of temperature (20 oC–50 oC) on sorption kinetics was also investigated. The various thermodynamic parameters suggest that phosphate sorption is favoured and is an exothermic process. The activation energy and the sticking probability confirmed that anion exchange is the dominant mechanism. These results provide valuable information for the potential use of agricultural residues in the treatment of wastewaters.

Surface properties and premicellar aggregation behavior of cationic gemini surfactants with mono- and di-(2-hydroxypropyl)ammonium head groups

Novel cationic gemini surfactants - pentanediyl-1,5-bis[mono(2-hydroxypropyl) alkylammonium] dibromide and pentanediyl-1,5-bis[di(2-hydroxypropyl) alkylammonium] dibromide {in the abbreviation form - CnC5Cn[iso-Pr(OH)] and CnC5Cn[iso-Pr(OH)]2; alkyl - CnH2n+1 with n = 8, 9, 12 and 16} were synthesized. Surface tension, electroconductivity and dynamic light scattering methods were applied to study aggregation properties of these surfactants in aqueous medium. By tensiometric method it was established that, at two studied concentrations in water, the synthesized gemini surfactants form aggregates. This occurs well below the critical micelle concentrations (CMC) of these surfactants. The influence of the length of the surfactants alkyl chain and the number of the 2-hydroxypropyl fragments in the head group on the surface activity parameters and binding degree of the counterion has been studied. By dynamic light scattering method, the impact of the number of the 2-hydroxypropyl groups in the gemini surfactants with C12–chain on the micelles sizes at the concentrations higher than CMC has been investigated. It was revealed that the synthesized surfactants possess an antimicrobial property.

Drastic Change of Mechanical Properties of Polyrotaxane Bulk: ABA–BAB Sequence Change Depending on Ring Position

Polyrotaxane (PR), consisting of many ring molecules and an axis polymer, is a typical supramolecular structure with unique topological characteristics. In this study, we demonstrated the drastic change of the macroscopic mechanical properties depending on the ring position of PR in bulk. Poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer was employed as an axis polymer to control the position of β-cyclodextrin (β-CD). To transfer the β-CD positions, hydroxypropyl groups (HPPR) and hydrophobic trimethyl silyl groups (TMS-HPPR), which have hydrophilic and hydrophobic β-CD, respectively, were synthesized. β-CDs in HPPR were localized on a central PPO segment and formed crystal domains. The axis polymer of HPPR could not bridge β-CD crystal domains, resulting in a melt state at high temperature. On the other hand, β-CDs in TMS-HPPR were transferred to both PEO segments and formed crystal domains. The axis polymer in TMS-HPPR could bridge the β-CD crystal domains, resulting in an elastic state even at high temperature. We succeeded in demonstrating the potential ability of PR: the macroscopic mechanical properties of PR can be changed from a melt state to an elastic one by manipulating the ring positions.