Dye aggregation and interaction of dyes with a water‐soluble polymer in ink‐jet ink for textiles

Detailed understanding of the interaction between dyes and additives and the aggregation behaviour of the dye molecules in aqueous solutions is required to develop ink‐jet ink for textiles. In the present study, the aggregation behaviour of three acid dyes (CI Acid Red 88, CI Acid Red 13 and CI Acid Red 27) containing different number of sulphonate groups in aqueous solutions was investigated by means of visible absorption spectroscopy. As a result, the higher the solubility of the dyes in water (the larger the number of sulphonate groups in the dyes), the lower are the aggregation constants of the dyes. For all the dyes, the aggregation constants decreased with increasing temperature, indicating the exothermic process of the dye aggregation. The thermodynamic process for CI Acid Red 88 with one sulphonate group is less enthalpic and more entropic than that for CI Acid Red 13, which contains two sulphonate groups. CI Acid Red 27, which includes three sulphonate groups, hardly forms any aggregates. To elucidate the effects of the polymer additive, the binding constants of the dyes with the water‐soluble polymer, poly(vinylpyrrolidone) and the aggregation constants of the dyes in aqueous polymer solutions were also estimated. In addition, the binding constants were influenced by the number of sulphonate groups in the acid dyes: the larger number of sulphonate groups diminished the binding constants. The aggregation constants in the presence of poly(vinylpyrrolidone) were smaller than those in its absence at every temperature for all dyes. This suggests that poly(vinylpyrrolidone) has disaggregation effects. Furthermore, poly(vinylpyrrolidone) makes the aggregation process less enthalpic with a greater entropic change. Thus, the aggregation process of the dyes in the polymer solutions is thermodynamically different from that in water, reflecting the interactions between the dyes and the polymer.     

Dispersing Carbon Nanotubes in Aqueous Solutions of Trisiloxane‐Based Surfactants Modified by Ethoxy and Propoxy Groups

Silicone surfactants favor spreading at interfaces and siloxane has strong interaction with carbon nanotubes (CNT), thus silicone surfactant may be a good dispersant of CNT. Here, four silicone surfactants (named S1E19, S2E38, S2E16 and S1E16P8) were used to disperse CNT in aqueous solutions. The effects of surfactant structure and concentration on the ability at dispersing CNT were considered. All of the four silicone surfactants can disperse CNT in aqueous solution and the sample with 1,000 mg L^?1 S1E16P8 was the best one. The hydrophilic group polyoxyethylene (PEO) and the hydrophobic groups siloxane and polypropylene (PPO) are crucial factors in the ability of dispersing CNT. S2E38 with more ethylene oxide (EO) groups has a stronger ability to disperse CNT than S2E16. The dispersion system provided by S1E19 which contains fewer siloxane and EO groups is relatively unstable and disperses less CNT. These experimental results are explained by molecular dynamics simulation. S2E38 compared with S1E19 and S2E16 has stronger interactions with CNT. The interaction energy of CNT with S1E16P8 which has a PPO moiety but fewer siloxane groups is close to that of S2E16. Furthermore, it can be concluded that these four surfactants are adsorbed on CNT mainly by van der Waals forces and the Si–O–Si chain of silicon surfactant was flexible due to the long Si–C bond and it could easily wrap onto the surface of CNT through hydrophobic and other intermolecular interactions. The hydrophilic part of PEO helped the CNT dispersed in the aqueous solution and prevented CNT from aggregating in water through steric stabilization.     

Extensional flow induced miscibility in a polymer blend

Summary Extensional flows can induce miscibility in a polymer blend of polystyrene with poly(vinyl methyl ether). Miscibility is observed as a change from turbidity to optical clarity when a phase separated blend flows isothermally in planar extension. In a start-up experiment at temperatures above the LCST, optical clarity does not appear instantaneously but after a time which depends on the rate of extension and the temperature, and it appears first near the region of highest extension. This effect is opposite to the observation for polymer solutions which exhibit shear-induced demixing. We attribute this to the fact that enthalpic effects largely determine blend miscibility, while the phase behavior of solutions is essentially controlled by entropic contributions. Since a deformation field decreases the configurational degrees of freedom of a polymer molecule, demixing is favored in solutions. However, the alteration of specific interactions rather than this entropic effect appears to be much more important in blends.     

Effect of crosslinking concentration on mechanical and thermodynamic properties in acrylic acid–co–methyl methacrylate hydrogels

The mechanical and thermodynamic properties of poly(acrylic acid‐co‐methyl methacrylate) hydrogels with varying crosslinker N,N′‐methylenebisacrylamide (NMBA) content are reported. A higher NMBA content generally led to a stronger and harder gel with lower water content. Swelling capacity decreased as the NMBA concentration increased between 0.5% and 2%, remaining constant beyond this range. The temperature changes of the partial molar Gibbs free energy of dilution and enthalpic and entropic contributions were examined. The thermodynamic parameters showed that swelling was an unfavorable and endothermic process. The freezing and nonfreezing water in the hydrogel was determined by differential scanning calorimetry (DSC). Freezing water content decreased with increasing crosslinker (NMBA) content, whereas the ratio of nonfreezing water to total water content increased with NMBA content because of the promoting of hydrophobic interactions in the hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4016–4022, 2006     

Probing the structure of polymer blends by vibrational spectroscopy: the case of poly(ethylene oxide) and poly(methyl methacrylate) blends

The blends of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) are prepared in the form of thin films from solution casting. The Fourier transform infrared spectra of the blends are recorded in the spectral range 400–4000 cm^?1. The spectra are analysed using various recent techniques of vibrational spectroscopy. It is concluded that upon blending PEO takes preferentially a planar zig-zag structure. Furthermore the intermolecular interactions between the molecules of PEO and PMMA in blends are very weak and their compatibility as blends is more ‘physical’ than ‘chemical’. Further, on the basis of the atomic charges transferred from model molecules it is seen that the blending is preferred with isotactic PMMA when compared to syndiotactic PMMA.     

Environment-induced nanostructural dynamical-change based on supramolecular self-assembly of cyclodextrin and star-shaped poly(ethylene oxide) with polyhedral oligomeric silsesquioxane core

The star-shaped amphiphilic inorganic–organic hybrid polymer POSS-(PEO)₈ prepared via click chemistry can self-assemble into spherical aggregates by directly dissolving the hybrid polymer in water. The regular spherical aggregates were gradually transformed to deformed spherical aggregates, cylinders and sheets through adding different amount of α-CD molecules into the POSS-(PEO)₈ spherical aggregates solution due to the host-guest inclusion complexation between POSS-(PEO)₈ aggregates and α-CD. Adding different amount of phenol which captured α-CD from PEO chains or increasing the environmental temperature of the self-assemblies solutions which also led to the slipping of α-CD out of PEO can reversibly and dynamically change the sheets to cylinders, deformed spherical aggregates or regular spherical aggregates, showing that the reversibly nanostructural dynamical-change can be induced by altering the environmental conditions of the solutions.     

Microscopic details of the sensing ability of 15-crown-5-ether functionalized poly(bithiophene)

Host-guest interactions between alkali ions (Li⁺, Na⁺ and K⁺) and a functionalized poly(bithiophene) with a 15-crown-5-ether covalently linked to two adjacent thiophene rings have been analyzed using theoretical methods. Results indicate that the considerable conformational flexibility of the polymer backbone is reduced when the cation accommodates in the cavity of the macrocycle. The enthalphic and entropic contributions to the binding have been estimated using quantum mechanical calculations and molecular dynamics trajectories, respectively. The enthalpic term becomes more favorable when the size of the cation decreases, while the entropy calculated for the “free state → bound state” process decreases when the size of the cation increases. On the other hand, calculated atomic-centered charges reflect that the π-conjugated system of the conducting polymer undergoes a partial oxidation upon the binding process. Moreover, the accommodation of the alkali cation in the macrocycle produces an increase of both the ionization potential and the lowest π-π^∗ transition energy of the polymer.     

Miscibility of blends of poly(methyl methacrylate) and oligodiols based on a bisphenol A nucleus and ethylene oxide or propylene oxide branches

Cloud-point curves of blends of poly(methyl methacrylate) (PMMA) with a series of oligodiols based on a bisphenol A nucleus and short branches of poly(ethylene oxide) or poly(propylene oxide) (BPA-EO or BPA-PO), and with PEO and PPO oligomers, were obtained using a light transmission device. Experimental results were fitted with the Flory-Huggins model using an interaction parameter depending on both temperature and composition. For PMMA/PEO and PMMA/PPO blends, the miscibility increased when increasing the size of the diol, due to the significant decrease in the entropic and enthalpic terms contributing to the interaction parameter. This reflected the decrease in the self-association of solvent molecules and in the contribution of terminal OH groups to the mismatching of solubility parameters. For PMMA/BPA-EO blends, a decrease of the entropic contribution to the interaction parameter when increasing the size of the oligodiol was also found. However, the effect was counterbalanced by the opposite contribution of combinatorial terms leading to cloud-point curves located in approximately the same temperature range. For PMMA/BPA-PO blends, the interaction parameter exhibited a very low value. In this case, the effect of solvent size was much more important on combinatorial terms than on the interaction parameter, leading to an increase in miscibility when decreasing the oligodiol size. For short BPA-PO oligodiols no phase separation was observed. The entropic contribution of the interaction parameter exhibited an inverse relationship with the size of the oligodiols, independent of the nature of the chains bearing the hydroxyls and the type of OH groups (primary or secondary). This indicates that the degree of self-association of solvent molecules through their OH terminal groups, was mainly determined by their relative sizes.     

Effect of ethanol addition on the elongational flow behavior of aqueous solutions of poly(ethylene oxide)

Summary In this work, we explore the effect of ethanol addition on the extension thickening behavior of aqueous solutions of poly(ethylene oxide) (PEO) in porous media and opposed-jets flow. The main aspect analyzed is the formation of transient entanglements of polymer molecules, which are responsible for the sudden increase in pressure drops and apparent extensional viscosities with strain rates observed in elongational flows of PEO solutions. The results show that changing the solvent by adding ethanol modifies the solution behavior because of two effects. First, the increase in the solvent viscosity increases the disentanglement time of the transient entanglements so that the onset of extension thickening occurs at lower strain rates in the presence of ethanol. Second, ethanol solutions are poorer solvents than water for PEO. This promotes intermolecular interactions between PEO coils when the solutions are semi-dilute. The net result is a lowering of the onset strain rate for extension thickening to values that are much smaller than those expected for the same PEO chains dissolved in a higher viscosity and poorer solvent. The results also show that coil-coil interactions in solution can be detected at lower concentrations in porous media flow than in opposed jets flow. Received: 24 August 2001/ Revised version: 29 October 2001/ Accepted: 6 November 2001     

Supramolecular selectivity of poly(ethylene oxide) in semi‐crystalline polymer nanocomposites

Semi‐crystalline polymer nanocomposites were prepared using successive meltings and recrystallizations techniques by intercalation of small guest molecules such as 4‐chlorotoluene (PCT), 4‐bromotoluene (PBT) and 1,4‐dibromobenzene (PDBB) into poly(ethylene oxide) (PEO) crystals. Differential scanning calorimetry, Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction experimental results show that supramolecular selectivity exists for the PEO–PDBB/PBT ternary system, while there is no supramolecular selectivity for PEO–PCT/PBT ternary nanocomposites. The interactions between PEO chains and small guest molecules have an important influence on the polymer conformation, which results in the dramatic difference in intercalation behavior. Copyright © 2007 Society of Chemical Industry     

Thermodynamic characterization of variants of mesophilic cytochrome c and its thermophilic counterpart

Thermal stability was measured for variants of cytochrome c-551(PA c-551) from a mesophile, Pseudomonas aeruginosa, and a thermophiliccounterpart, Hydrogenobacter thermophilus cytochrome c-552 (HTc-552), by differential scanning calorimetry (DSC) at pH 3.6.The mutated residues in PA c-551, selected with reference tothe corresponding residues in HT c-552, were located in threespatially separated regions: region I, Phe7 to Ala/Val13 toMet; region II, Glu34 to Tyr/Phe43 to Tyr; and region III, Val78to Ile. The thermodynamic parameters determined indicated thatthe mutations in regions I and III caused enhanced stabilitythrough not only enthalpic but also entropic contributions,which reflected improved packing of the side chains. Meanwhile,the mutated region II made enthalpic contributions to the stabilitythrough electrostatic interactions. The obtained differencesin the Gibbs free energy changes of unfolding [     

Electrospinning of aqueous lignin/poly(ethylene oxide) complexes

Microfibers of kraft lignin blended with poly(ethylene oxide) (PEO) were produced by electrospinning of the solution of lignin and high molecular weight poly(ethylene oxide) (PEO) in alkaline water. Interactions between lignin and PEO in alkaline aqueous solutions create association complexes, which increases the viscosity of the solution. The effect of polymer concentration, PEO molecular weight, and storage time of solution before spinning on the morphology of the fibers was studied. It showed that after one day the viscosity dropped and fiber diameter decreased. Results from the solutions in alkaline water and N,N‐dimethylformamide (DMF) with different polymer concentrations were compared. The 7 wt % of (Lignin/PEO: 95/5 wt/wt) in alkaline aqueous solution was successfully spun and the ratio of PEO in lignin/PEO mixture could be further reduced. In comparison, higher concentrations were needed to prepare a spinning solution in DMF and fiber diameters were in a much smaller range. The final target of spinning lignin is to produce carbonized fibers. Fibers spun from aqueous solutions had lower PEO content, which is a big advantage for the carbonization process as it reduces the challenges regarding melting of the fibers or void creation during carbonization. Furthermore, the larger diameter of these fibers inhibits disintegration of the carbonized fibers, which happens due to the mass loss during the process. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41260.     

Flow of mixtures of poly(ethylene oxide) and hydrolyzed polyacrylamide solutions through porous media

In this work, the porous media flow of polymer solutions of poly(ethylene oxide) (PEO), hydrolyzed polyacrylamide (HPAA), and their blends is investigated. Aqueous solutions of PEO exhibit critical extension thickening when flowing through porous media. HPAA solutions also exhibit critical extension thickening in excess salt environments, but their behavior changes to a more gradual extension thickening when dissolved in deionized water. The mixtures of solutions of HPAA and PEO therefore vary its porous media flow behavior, depending on the ionic environment. In deionized water, a critical extension thickening similar to that obtained with PEO is still observed when HPAA is mixed in at concentrations low enough so that its apparent viscosity does not mask the influence of PEO. In the presence of salt, only a critical extension thickening is observed, which is attributed to transient network formation of both PEO and HPAA molecules. The mixtures generally exhibit a less critical behavior and display a lower than expected sensitivity of the onset Reynolds number for extension thickening with concentration. The results presented herein indicate that interspecies molecular interactions through transient network formation and the associated flow modification play a major role in determining the complex non‐Newtonian flow behavior of these polymer solutions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 783–795, 1999     

Entropic effects in carbon nanotubes-templated crystallization of Poly(3-alkyl thiophenes,P3HT,P3OT)

A significant increase in polymer crystallinity is reported in composites of carbon-nanotubes (CNT) and Poly(3-octylthiophene-2,5-diyl), P3HT and Poly(3-octylthiophene-2,5-diyl), P3OT; Differential scanning calorimetry (DSC) reveal an increase from about 40% crystallinity of the native P3HT to ∼62% in composites containing 25 wt% MWNT. A similar behavior is observed in P3OT with ∼68% crystallinity, a double crystallization peak and higher melting temperature than the native polymers. The effect is unique to CNT and is not induced by fullerenes or graphene layers. High-resolution transmission electron microscopy, (HRTEM) of CNT-polymer dispersions reveal chains stacked upon the CNT in an elongated, stretched conformation. Following a detailed molecular study by Bernardi et al. and the HRTEM observations the DSC results are attributed to a CNT-mediated entropic effect: due to their intrinsic, 1D cylindrical shape the CNT impose an increased conjugation length on chains adsorbed and stacked upon dispersed CNT. Crystallization thus commences from a heterogeneous mixture of native chains and chains with a longer persistence length (higher effective rigidity) and consequentially a lower effective height of the entropic barrier for crystallization. The findings offer a new insight into the origins of CNT-induced polymer nucleation.     

Effects of chain conformation on miscibility, morphology, and mechanical properties of solution blended substituted polyphenylene and polyphenylsulfone

The effects of polymer conformation and degree of substitution on miscibility, morphology and mechanical properties of solution blended systems containing polyphenylsulfone and copolymers of phenylketone substituted p-phenylene with m-phenylene were studied. Static and dynamic light scattering studies were performed to obtain the z-average root mean square radius of gyration, second virial coefficient, weight average molecular weight and hydrodynamic radius. Solution blends of polyphenylsulfone with phenylene copolymers yielded free standing films. Blend miscibility was assessed by glass transition behavior, morphology was analyzed using atomic force microscopy and mechanical properties were measured using nanoindentation. Copolymer composition determined miscibility. Miscible blends exhibited homogeneous morphologies while immiscible blends displayed unique, heterogeneous morphologies. Polymer conformation in solution, rather than enthalpic contributions, was the primary determinant of miscibility. Successful reinforcement was achieved in blended systems.     

Analysis of polymer membrane formation through spinodal decomposition. II: Effect of Flory-Huggins enthalpic and entropic contributions

The phenomenological analysis of the thermal inversion membrane formation through spinodal decomposition was further developed to include enthalpic and entropic contributions to the Flory-Huggins interaction parameter. We found that material and processing conditions can be lumped into two parameters. One is the Deborah Number, De, which takes into account the thermal quenching relative to the phase separation induction time. The other one, designated as an ε-parameter, takes into account the quenching temperature relative to the spinodal temperature and the ratio of the enthalpic to the entropic contributions to the Flory-Huggins interaction parameter. From the model system, we found that the dimensionless interdomain distance, δ, as a function of 1/De (which is proportional to the cooling rate) falls in a relatively narrow banded region for all practical values of ε. As 1/De approaches infinity, δ is asymptotic up to maximum value of 3.5. This means that membranes made under applicable conditions will have a ratio of pore sizes of no more than 3.5. Other assumptions of the model are: (1) the mobility is temperature-independent; (2) the mutual diffusivity is a linear function of temperature; and (3) the thermal history (Temperature vs. Time), can be represented as two successive linear functions.     

Controlled drug release carriers based on PCL/PEO/PCL block copolymers

In order to create a new drug delivery system, the ibuprofen-loaded triblock copolymer PCL/PEO/PCL (PCEC) microspheres with a low PEO content (<2?wt%) were prepared by oil in water (o/w) solvent evaporation technique. The influence of PEO content, molecular weight of a polymer matrix and drug loading on the ibuprofen release profiles were evaluated. The interactions between polymer matrix and ibuprofen were detected by FTIR analysis. The presence of hydrophilic PEO segment in PCL chains caused the decrease in particle size, which further had a great impact on the drug release kinetics, i.e., initially faster release and significantly higher quantity of released drug compared to neat PCL. Ibuprofen release behavior from polymer matrix was governed by a diffusion process. In vitro cytotoxicity tests revealed that empty PCL and PCEC microspheres were not toxic at low concentrations, while ibuprofen-loaded microspheres exhibited cytotoxicity correlated with amounts of incorporated drug.     

The effect of carbon nanotube agglomeration on the thermal and mechanical properties of polyethylene oxide

The effects of agglomerated versus deagglomerated multiwalled carbon nanotubes on the thermal and mechanical characteristics of polyethylene oxide were studied. The specimens were prepared via solution‐sonication method, using two procedures. In the first procedure, CNT‐PEO solutions were prepared with as‐received MWCNTs, before sonication using an ultrasonic bath; in the second procedure, aggregated MWCNTs were first deagglomerated using high‐intensity ultrasonic processor, before mixing with the PEO. The two solution preparation procedures did result in significant thermal property differences such as increased transition temperature and crystallinity, but only one mechanical property can be conclusively associated with the sample preparation method—the breaking strain which was marginally higher for nanocomposites containing deagglomerated CNTs, although in all cases the breaking strains were much lower for nanocomposites than for unfilled polymer. However, the overall results confirm the effectiveness of CNTs both as nucleation agents for semicrystalline polymers, and as fillers for enhancement of mechanical properties of the matrix polymer. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

消防用PEO/OTAC/NaSal减阻体系的介观分子动力学分析

在全球能源紧张的背景下,“过程节能”手段的探索具有重要意义。消防工作在国民经济和社会发展中占据重要地位,将添加剂湍流减阻技术引进到消防系统,能提高消防水的射出速度和射程,在提高灭火效率的同时节省水泵功耗。根据消防水流特点,初步选定聚氧化乙烯/十八烷基三甲基氯化铵的聚合物/表面活性剂复配体系作为研究对象,借助介观分子动力学模拟手段,计算了此体系的抗剪切能力及表面张力。发现此体系的抗剪切能力较聚合物、表面活性剂单一体系有明显提升,且体系的表面张力较纯表面活性剂溶液有所提高,初步证明此体系适用于消防减阻。同时从分子动力学角度深入分析了复配体系内聚合物、表面活性剂分子之间的作用机制,可为进一步寻找适用于消防减阻的聚合物/表面活性剂复配添加剂体系提供理论指导。     

Graphene‐based composite with microwave absorption property prepared by in situ reduction

Binary composite of graphene/poly(ethylene oxide) (PEO) with microwave absorption property is prepared by in situ reduction process. Graphite oxide (GO) is prepared from flake graphite by modified Hummers' method and further dispersed in distilled water to get GO solution. Then, PEO powder is slowly added into GO solution to get GO/PEO solution, and graphene/PEO composites is prepared via a facile and quick reduction process in GO/PEO solution. PEO and graphene/PEO composites are characterized by scanning electron microscopy, atomic force microscopy, thermo gravimetric analysis, and vector network analyzer. The results show that graphene is uniformly dispersed in PEO matrix because GO and PEO can be uniformly dispersed at molecular level due to their water‐solubility and the agglomeration of graphene can be prevented by PEO macromolecular chains during in situ reduction process. Graphene/PEO composite has better thermal stability than PEO, which can be explained by the graphene restoration of sp² bonded carbon structure. Meanwhile, graphene/PEO composite shows excellent microwave absorption property at low grapheme content. The minimum reflection loss of graphene/PEO composite is up to −20.0 dB when the content of graphene is only 1 wt%. POLYM. COMPOS., 35:461–467, 2014. © 2013 Society of Plastics Engineers