Synthesis and Aqueous Solution Viscosity of Hydrophobically Modified Xanthan Gum

Two xanthan gum derivatives hydrophobically modified by 4 or 8 tetradecyl chains per 100 xanthan gum structure units were synthesized. The derivatives were studied by scanning electron microscope and pyrene fluorescence spectrometry. And the aqueous solution apparent viscosity of the derivatives was investi- gated. The results indicate that the network of the derivatives with more hydrophobic groups is closer and tighter. With increasing of alkyl chain substitution degree, the hydrophobically associating interactions enhance in aqueous solution. Aqueous solution apparent viscosity of the derivatives increases with increasing of polymer concentration and alkyl substitution degree, and decreases with the increase of temperature. In the brine solution, the strong viscosity enhancement phenomenon appears. The interaction between the derivatives and surfactant sodium dodecylbenzene sulfonate is strong.

Aggregation Behavior and Structure of Associated Polyacrylamide Hydrophobically Modified with 2-Phenoxylethylacrylate

The aggregation behavior and structure of hydrophobically modified block copolymers of acrylamide and 2-phenoxylethylacrylate were investigated by viscometry, 1H NMR relaxation, 2D NOESY, fluorescence and dynamic light scattering. It Was found that the aggregation behavior was strongly dependent on the concentration of polymer solution and the hydrophobe contents. With varying concentration from 2.0, 6.0, 8.0 to 12.0 g/L, there were different aggregate morphologies distributed in aqueous solutions, such as monopolymer chain, micelle-like aggregate, multi-micelle aggregate and cross-linked network. According to the model of aggregation, it can give a reasonable explanation on the large magnitude enhancement of viscosity with the increasing of polymer concentration. Additional data of 2D NOESY and fluorescence show that the copolymer with higher hydrophobe content（molar fraction≥ 1%） is likely to form intra-molecular association.

The Effects of Fe2+ on the Aggregation Behavior of Residual Hydrophobic Modified Polyacryamide

The influences of Fe2+ on the aggregation behavior of residual hydrophobic modified polyacryamide (HMPAM) in treated oily wastewater were studied by fluorescence spectrum and DLS. The result of I1/I3 showed that the polarity of hydrophobic domain increased and the size of hydrophobic domain may be decreased with the increasing of Fe2+ in produced water. Fe2+ was helpful for the increase of hydrophobic domain, therefore due to the aggregation degree for HMPAM.

Hydrophobic aerogel-modified hemostatic gauze with thermal management performance

Current hemostatic agents or dressings are not efficient under extremely hot and cold environments due to deterioration of active ingredients,water evaporation and ice crystal growth.To address these challenges,we engineered a biocompatible hemostatic system with thermoregulatory properties for harsh conditions by combining the asymmetric wetting nano-silica aerogel coated-gauze(AWNSA@G)with a layer-by-layer(LBL)structure.Our AWNSA@G was a dressing with a tunable wettability prepared by spraying the hydrophobic nano-silica aerogel onto the gauze from different distances.The hemostatic time and blood loss of the AWNSA@G were 5.1 and 6.9 times lower than normal gauze in rat’s injured femoral artery model.Moreover,the modified gauze was torn off after hemostasis without rebleeding,approximately 23.8 times of peak peeling force lower than normal gauze.For the LBL structure,consisting of the nano-silica aerogel layer and a n-octadecane phase change material layer,in both hot(70℃)and cold(-27℃)environments,exhibited dual-functional thermal management and maintained a stable internal temperature.We further verified our composite presented superior blood coagulation effect in extreme environments due to the LBL structure,the pro-coagulant properties of nano-silica aerogel and unidirectional fluid pumping of AWNSA@G.Our work,therefore,shows great hemostasis potential under normal and extreme temperature environments.

Factors influencing the aggregation behavior of residual associative polymer in produced oily fluids

The influence of emulsified oil, suspended solids, Fe3＋, Fe2＋, cationic water clarifier and sulfate-reducing （SR） bacteria on the aggregation behavior of residual hydrophobic modified polyacrylamide in treated oily wastewater from polymer flooding was studied by fluorescence spectroscopy and dynamic light scattering. The result of I1/I3 showed that the polarity of hydrophobic microdomains increased, whereas the size of the hydrophobic microdomains may be decreased, where the value of I1/I3 represents the ratio of the intensity of peak 11 （374.0 nm） to that of peak/3 （385.0 nm） of the vibration fine structure of pyrene monomer emission in residual polymer solution. The results of the ratio of I1 at 48 h to I1 at 0 h （I1,48h/I1,0h） indicated that oil and cationic water clarifier could inhibit the aggregation to some extent, while Fe2＋ and suspended solids were helpful for aggregation, and Fe3＋ and SR bacteria had no significant influence on the aggregation of polymer.

Hydrophobically modified polyelectrolytes I. Dilute solution properties of fluorocarbon-containing poly (acrylic acid)

Dilute solution viscosity of fluorocarbon-containing hydrophobically modified poly (acrylic add) was measured in aqueous solutions of various NaCl concentrations. The intrinsic viscosity ([η]) and Huggins coefficient (kH) were evaluated using Huggins equations. It is found that, at low Nacl concentration, the modified polymers exhibit values of intrinsic viscosity ([η]) and Huggins coefficient (kH) similar to those of unmodified polymers. For both of the modified and unmodified polymers, the intrinsic viscosity decreases with increase of NaCl concentration, while the Huggins coefficient increases upon addition of NaCl. But the variation of [η] and kH is more significant for the modified polymers, which reflects the enhanced intra- and intermolecular hydrophobic association at higher Nacl concentration.

High-strength porous alumina ceramics prepared from stable wet foams

Porous ceramics have been widely used in heat insulation,filtration,and as a catalyst carrier.Ceramics with high porosity and high strength are desired;however,this high porosity commonly results in low strength materials.In this study,porous alumina with high porosity and high strength was prepared by a popular direct foaming method based on particle-stabilized wet foam that used ammonium polyacrylate(PAA)and dodecyl trimethyl ammonium chloride(DTAC)as the dispersant and hydrophobic modifier,respectively.The effects of the dispersant and surfactant contents on the rheological properties of alumina slurries,stability of wet foams,and microstructure and mechanical properties of sintered ceramics were investigated.The microstructure of porous ceramics was regulated using wet foams to achieve high strength.For a given PAA content,the wet foams exhibited increasing stability with increasing DTAC content.The most stable wet foam was successfully obtained with 0.40 wt%PAA and 0.02 wt%DTAC.The corresponding porous alumina ceramics had a porosity of 82%,an average grain size of 0.7μm,and a compressive strength of 39 MPa.However,for a given DTAC content,the wet foams had decreasing stability with increasing PAA content.A possible mechanism to explain these results is analyzed.

Specific Thermoresponsive Behaviours Exhibited by Optically Active and Inactive Phenylalanine Modified Hyperbranched Polyethylenimines in Water

Optically active and inactive hyperbranched polymers with specific thermoresponsive behaviours in water were reported.Through two steps hyperbranched polyethylenimine（HPEI） polymers terminated with different amount of D-phenylalanine（D-Phe）,L-phenylalanine（L-Phe） or DL-phenylalanine（DL-Phe） were prepared and characterized.The analyses on the solution properties by turbidimetry,dynamic light scattering,fluorescence probe and 1H-NMR demonstrated that all the polymers exhibited specific thermoresponsive behaviours in water,including：（1） In the dilute polymer concentration region,increasing the polymer concentration led to the increase of phase transition temperature;（2） The optically inactive thermoresponsive hyperbranched polymers showed a higher cloud-point temperature（Tcp） than their corresponding optically active ones in a relatively higher polymer concentration;（3） At the same polymer concentration the hydrophobic groups of the optically inactive HPEI-DL-Phe formed more perfect hydrophobic domain than those of the optically active HPEI-L-Phe and HPEI-D-Phe.