Alternative approach to the design of thermosensitive polymers: The addition of hydrophobic groups to the ends of hydrophilic polyether

We synthesized thermosensitive polymers by adding hydrophobic groups to the ends of a hydrophilic polyether, poly(ethylene oxide‐co‐propylene oxide). The cloud points of the polymers were controlled by the molecular weight of the polyether and the kind of hydrophobic end group. The polymers showed relatively sharp phase transitions, as observed by turbidimetry. The order of the cloud points of the polymers with various end groups did not follow that of the critical micelle concentrations of the polymers determined with fluorescence measurements with pyrene as a probe. The cloud points of the polymers linearly decreased with increasing concentrations of salts (Na₂SO₄ and Na₃PO₄). The slopes of the linear lines were almost constant, regardless of the kind of hydrophobic group and the molecular weight of the polyether. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1007–1013, 2005     

Fabrication of Ti/black TiO2-PbO2 micro/nanostructures with tunable hydrophobic/hydrophilic characteristics and their photoelectrocatalytic performance

Journal of Solid State Electrochemistry - Herein, a novel Ti/black TiO2-PbO2 micro/nanostructured photoanode with tunable hydrophobic/hydrophilic characteristics was fabricated via the facile...     

Preparation of hydrophilic/hydrophobic porous materials

A novel porous material was designed and prepared in this work. A hydrophobic open-celled porous polystyrene (PS) was first synthesized via a concentrated emulsion polymerization of water in styrene. Subsequently the porous polystyrene was saturated with an aqueous solution of acrylamide (AM) and an initiator, which was subjected to another polymerization and the resulted polyacrylamide (PAM) penetrated in the cells and intercellular pores of the PS matrix. The PAM would change its volume according to the environmental humidity and thus adjusted the permeation of the material. The morphology, pore size distributions, water absorption, and vapor permeation of the materials were investigated.     

DNA sequencing with hydrophilic and hydrophobic polymers at elevated column temperatures

Read length in DNA sequencing by capillary electrophoresis at elevated temperatures is shown to be greatly affected by the extent of hydrophobicity of the polymer separation matrix. At column temperatures of up to 80 degrees C, hydrophilic linear polyacrylamide (LPA) provides superior read length and separation speed compared to poly(N,N-dimethylacrylamide) (PDMA) and a 70:30 copolymer of N,N-dimethylacrylamide and N,N-diethylacrylamide (PDEA30). DNA-polymer and polymer intramolecular interactions are presumed to be a major cause of band broadening and the subsequent loss of separation efficiency with the more hydrophobic polymers at higher column temperatures. With LPA, these interactions were reduced, and a read length of 1000 bases at an optimum temperature of 70 degrees -75 degrees C was achieved in less than 59 min. By comparison, PDMA produced a read length of roughly 800 bases at 50 degrees C, which was close to the read length attained in LPA at the same temperature; however, the migration time was approximately 20% longer, mainly because of the higher polymer concentration required. At 60 degrees C, the maximum read length was 850 bases for PDMA, while at higher temperatures, read lengths for this polymer were substantially lower. With the copolymer DEA30, read length was 650 bases at the optimum temperature of 50 degrees C. Molecular masses of these polymers were determined by tandem gel permeation chromatography-multiangle laser light scattering method (GPC-MALLS). The results indicate that for long read, rapid DNA sequencing and analysis, hydrophilic polymers such as LPA provide the best overall performance.     

A mild photoactivated hydrophilic/hydrophobic switch

Surface modification using light is one of the most powerful methods for controlling the physical and chemical properties offunctionalized surfaces. In this paper, we report on systems where soft UV irradiation (lambda = 365 nm) converts a "low" activity fluorocarbon to a "high" activity amine-functionalized surface. An amine-functionalized SAM (self-assembled monolayer) is first masked using a tertiary amine catalyzed reaction with an N-hydroxysuccinimidyl carbonyl reagent. This mild, room-temperature reaction introduces a hydrophobic photocleavable nitrobenzyl "protecting group" terminated with a fluorocarbon end-chain. UV irradiation (lambda = 365 nm) of this hydrophobic/fluorocarbon surface cleaves the nitrobenzyl residue, returning the surface to the original hydrophilic/amine-functionalized state. This provides a mild, generic method of producing surfaces with hydrophilic/hydrophobic patterns or patterned with amine functional residues. Two different protecting groups, one terminated with a single and the other with three fluorocarbon end chains, are compared. In the case of the more bulky protecting group, only a small proportion of the amine residues react, but the surface is equally hydrophobic and the amine residues equally well shielded from further reaction. Surfaces are characterized by X-ray photoelectron spectroscopy, ellipsometry, surface potential, and contact angle measurements. Images of the photopatterned SAMs were obtained using scanning electron microscopy.     

Preparation of stable aqueous suspension of a hydrophobic drug with polymers

Pharmaceutical preparation of a hydrophobic aldose reductase inhibitor 5-(3-ethoxy-4-pentyloxyphenyl)-2,4-thiazolidinedione (CT112) was investigated. CT112 dissolved in a basic solution with different kinds of polymers was neutralized by acid to obtain a suspension preparation. In particular, the addition of a polymer, hydroxypropyl methyl cellulose (HPMC) provided a stable CT112 suspension with a homogeneous particle size, and there seemed to be an optimal concentration of HPMC for the stable suspension. The addition of polysorbate 80 brought higher CT112 solubility in water, but did not provide a stable suspension. X-ray diffraction, IR spectrum, and thermal analysis revealed that the particles in the suspension with HPMC had lower degree of crystallinity, less hydrophobic particle surface, and lower melting point and decreased fusion enthalpy than the suspension without HPMC. These results suggested that the highly stable CT112 suspension could be attained by the adsorption of the polymer.     

Probing the transition from hydrophilic to hydrophobic solvation with atomic scale resolution

Picosecond and femtosecond X-ray absorption spectroscopy is used to probe the changes of the solvent shell structure upon electron abstraction of aqueous iodide using an ultrashort laser pulse. The transient L(1,3) edge EXAFS at 50 ps time delay points to the formation of an expanded water cavity around the iodine atom, in good agreement with classical and quantum mechanical/molecular mechanics (QM/MM) molecular dynamics (MD) simulations. These also show that while the hydrogen atoms pointed toward iodide, they predominantly point toward the bulk solvent in the case of iodine, suggesting a hydrophobic behavior. This is further confirmed by quantum chemical (QC) calculations of I(-)/I(0)(H(2)O)(n=1-4) clusters. The L(1) edge sub-picosecond spectra point to the existence of a transient species that is not present at 50 ps. The QC calculations and the QM/MM MD simulations identify this transient species as an I(0)(OH(2)) complex inside the cavity. The simulations show that upon electron abstraction most of the water molecules move away from iodine, while one comes closer to form the complex that lives for 3-4 ps. This time is governed by the reorganization of the main solvation shell, basically the time it takes for the water molecules to reform an H-bond network. Only then is the interaction with the solvation shell strong enough to pull the water molecule of the complex toward the bulk solvent. Overall, much of the behavior at early times is determined by the reorientational dynamics of water molecules and the formation of a complete network of hydrogen bonded molecules in the first solvation shell.     

Quantitative determination of surface energy using atomic force microscopy: the case of hydrophobic/hydrophobic contact and hydrophilic/hydrophilic contact

Atomic force microscopy (AFM) has been used to determine the surface energy of chemically modified surfaces at a local scale. In order to achieve this aim, it was necessary to graft both the AFM tip and the substrate with the same chemical functional groups. Two different organothiols terminated either by hydrophilic or hydrophobic chemical functionalities were used. Grafting process classically reported shows that after UV/ozone treatment for 30 min, the tip is coated by thermal deposition with 4‐5‐nm‐thick titanium layer followed by a 30‐nm‐thick gold layer. Finally, the tip is grafted by organothiols. The thickness of the layer deposited on the tip is of the same order of magnitude as the tip radius. To avoid the use of Ti and to decrease the thickness of the gold layer, we have developed a new way of grafting by using organic molecules like (3‐mercaptopropyl)triethoxysilane (MPS) as a linkage agent. Then this way of grafting was checked. Finally, AFM force‐distance curves, between grafted tips and chemically modified surface, were carried out in contact mode. Calibration of the various parts of the apparatus and especially of the cantilever (spring constant and tip radius) is of major importance to reach quantitative data. Finally, by applying a suitable theory of contact, we were able to determine the surface energy of our system. Copyright © 2005 John Wiley & Sons, Ltd.     

Unusual properties of water at hydrophilic/hydrophobic interfaces

The behaviour of water at mosaic hydrophilic/hydrophobic surfaces of different silicas and in biosystems (biomacromolecules, yeast cells, wheat seeds, bone and muscular tissues) was studied in different dispersion media over wide temperature range using 1H NMR spectroscopy with layer-by-layer freezing-out of bulk water (close to 273 K) and interfacial water (180 < T < 273 K), thermally stimulated depolarization current (TSDC) (90 < T < 270 K), infrared (IR) spectroscopy, and quantum chemical methods. Bulk water and water bound to hydrophilic/hydrophobic interfaces can be assigned to different structural types. There are (i) weakly associated interfacial water (1H NMR chemical shift delta(H) = 1.1-1.7 ppm) that can be assigned to high-density water (HDW) with collapsed structure (CS), representing individual molecules in hydrophobic pockets, small clusters and interstitial water with strongly distorted hydrogen bonds or without them, and (ii) strongly associated interfacial water (delta(H) = 4-5 ppm) with larger clusters, nano- and microdomains, and continuous interfacial layer with both HDW and low-density water (LDW). The molecular mobility of weakly associated bound water is higher (because hydrogen bonds are distorted and weakened and their number is smaller than that for strongly associated water) than that of strongly associated bound water (with strong hydrogen bonds but nevertheless weaker than that in ice Ih) that results in the difference in the temperature dependences of the 1H NMR spectra at T < 273 K. These different waters are also appear in changes in the IR and TSDC spectra.     

Stabilization of O/W emulsion with hydrophilic/hydrophobic clay particles

In this study, a stabilizing behavior of clay in a 40/60 w/w oil-in-water (O/W) emulsion is investigated by macro- and microscopic morphological observations, rheology, and X-ray diffraction measurements. Hydrophilic and hydrophobic clays (Montmorillonites) are tested for stabilization of emulsion. When hydrophilic clay showing interfacial localization is added to the emulsion, emulsion is not stable to phase separation (creaming). With hydrophobic clay, the emulsion shows phase inversion to water-in-oil (W/O) emulsion due to the increase in oil viscosity which results in phase separation of sedimentation. On the other hand, with the mixture of hydrophilic and hydrophobic clays, the emulsion shows a synergistic macroscopic and microscopic stabilization due to the formation of composite structure at the interface by hydrophilic and hydrophobic clays.     

2D-grid layered Pd-based cationic infinite coordination polymer/polyoxometalate crystal with hydrophilic sorption

The inorganic-organic hybrid compound composed of the novel infinite-chain Pd(II) complex and the polyoxometalate ({[(en)Pd(p-bpy)]2[alpha-SiW12O40].8DMSO.4DMF}infinity (1a:1 with 8DMSO.4DMF; monoclinic P2(1)/c (No. 14), a = 15.0188(3) A, b = 15.6962(3) A, c = 26.9793(6) A, beta = 106.3580(10) degrees , V = 6102.6(2) A(3)) has been successfully synthesized by the reaction of [(en)Pd(OH2)2]2[alpha-SiW12O40] (2) with 4,4'-bipyridine (p-bpy). The treatment in dry N(2) at 50 degrees C or evacuation at room temperature forms {[(en)Pd(p-bpy)](2)[alpha-SiW(12)O(40)].6.0DMSO}(infinity) (1b:1 with 6DMSO) with a drastic reduction of the interlayer spacing, which is characterized by the powder diffraction analysis and the single-crystal analysis of 1c (1 with 4.5DMSO.3.5DMF; monoclinic P2(1)/a (No. 14), a = 14.200(9) A, b = 22.8865(8) A, c = 14.8558(5) A, beta = 114.7990(10) degrees , V = 4383.0(2) A(3)). Compound 1b reversibly sorbs the hydrophilic molecules with the maintenance of the intrinsic structure, which is much different from hydrophobic guest-inclusion properties reported in the other Pd-based supramolecular systems.     

Displacement processes on hydrophilic/hydrophobic surfaces in methanol-water mixtures

The adsorption from methanol/water and the enthalpy of displacement of methanol by water were studied on K-60 silica gel, on graphitized PRINTEX-80, and onn-alkylammonium vermiculites. The adsorption between the hydrophobized silicate layers was followed by x-ray measurements. The excess isotherms of alkylammonium vermiculites in methanol/water exhibit two maxima corresponding to the two steps of the individual isotherm. The equilibrium constant of the exchange of water by methanol is calculated. For calculating the adsorption capacities and molar adsorption potentials, a new equation is proposed which combines the adsorption excess quantities with free energy and enthalpy functions.     

UV/TiO2降解丽华实军蓝制衣染料的研究

<正>印染废水是目前主要的难处理的有害工业废水之一[1]。近十几年发展起来的TiO2光催化氧化水处理技术,以其具有光催化活性高、降解彻底、非选择性、无二次污染、常温常压操作、能耗及材料消耗低且TiO2耐酸碱和耐光化学腐蚀、无毒等优点为解决这一难题提供了一种有效的方法,在印染废水处理中受到了广泛关注[2～6]。     

Thermal degradation of polyethylene containing antioxidant and hydrophilic/hydrophobic silica

High-density polyethylene, its composites with hydrophilic/hydrophobic silica and the antioxidant BHT (butylated hydroxytoluene) were studied using the thermogravimetric analysis. It has been shown that filling with silica as well as introducing BHT into the unfilled polymer increases the thermal-oxidative stability of the polymer. Immobilized BHT is inactive and it suppresses the stabilizing effect of hydrophobic silica surface in the processes of thermal oxidation at the initial stage. However, being gradually released from the surface antioxidant prolongs the resistance of the polymer against oxidation.     

Polymer nanoparticles with a sensitive CO2‐responsive hydrophilic/hydrophobic surface

Poly(methyl methacrylate) (PMMA) nanoparticles with a sensitive CO₂‐responsive hydrophilic/hydrophobic surface that confers controlled dispersion and aggregation in water were prepared by emulsion polymerization at 50 °C under CO₂ bubbling using amphiphilic diblock copolymers of 2‐dimethylaminoethyl methacrylate (DMAEMA) and N‐isopropyl acrylamide (NIPAAm) as an emulsifier. The amphiphilicity of the hydrophobic–hydrophilic diblock copolymer at 50 °C was triggered by CO₂ bubbling in water and enabled the copolymer to serve as an emulsifier. The resulting PMMA nanoparticles were spherical, approximately 100 nm in diameter and exhibited sensitive CO₂/N₂‐responsive dispersion/aggregation in water. Using copolymers with a longer PNIPAAm block length as an emulsifier resulted in smaller particles. A higher concentration of copolymer emulsifier led to particles with a stickier surface. Given its simple preparation and reversible CO₂‐triggered amphiphilic behavior, this newly developed block copolymer emulsifier offers a highly efficient route toward the fabrication of sensitive CO₂‐stimuli responsive polymeric nanoparticle dispersions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2149–2156     

由亲水和疏水硅胶制备的Co/Ru/SiO2催化剂的表征及催化性能研究

以亲水硅胶Degussa A300和疏水硅胶Degussa R106作为催化剂载体,采用等体积浸渍法制备了一系列钴基催化剂。利用MS、XRD、BET、FT-IR、TPR等手段考察了载体热稳定性,催化剂表面物相结构和还原性能等物化性能。结果表明,载体表面有机基团对催化剂中Co3O4尺寸大小有影响,有机基团对载体表面羟基的取代使得金属钴与载体的作用力减弱,有利于金属团聚为较大的颗粒。费-托反应结果表明,亲水硅胶性制得的催化剂通过后处理引入甲基后,造成催化剂活性下降,C18+的选择性下降,但使烃分布集中在C5～C18,这是由于表面甲基的空间位阻作用不利于反应中的吸附过程和链增长过程。由疏水载体制备的催化剂虽然钴颗粒较大,但是由于催化剂制备过程中部分有机基团的烧结,对催化剂活性产生了较大的负面影响,使催化活性降低,重质烃选择性明显降低。     

Displacement processes on hydrophilic/hydrophobic surfaces in 1-propanol-water mixtures

Selective adsorption of 1-propanol-water mixtures was investigated on adsorbents of various surface character. The enthalpy of displacement of 1-propanol by water was studied on graphitized PRINTEX-80, K-60 silicagel, and n-alkylammonium vermiculites. The free enthalpy and entropy isotherms of displacement were derived. The adsorption between the silicate layers of hydrophobic vermiculites was followed by x-ray measurements, and thermodynamic functions were calculated for the structural changes in the adsorption layers. Formation of alcohol-water clusters on the surfaces plays an important role.     

Controlled hydrophobic/hydrophilic chitosan: colloidal phenomena and nanosphere formation

N-Phthaloylchitosan-grafted poly(ethylene glycol) methyl ether (mPEG) gives a milky solution when dispersed in water and a series of solvents. The appearance of turbidity depends on the types of solvents, i.e., protic and aprotic solvents. N-Phthaloylchitosan-grafted mPEG shows an aggregation of sphere-like particles as observed by scanning electron microscopy. Transmission electron microscopy indicates that the spheres are at the nano level. When the chain length of mPEG is as high as 5×10³ Da the sphere size becomes as small as 80–100 nm on average as observed by transmission electron microscopy. By simply adjusting the hydrophobicity/hydrophilicity of the chitosan chain, a stable nanosphere can be obtained directly.     

Photocatalytic water treatment with different TiO2 nanoparticles and hydrophilic/hydrophobic layer silicate adsorbents

The degradation of 2-chlorophenol (2-CP) was investigated by a combination of TiO₂-based photocatalysis and adsorption. Three combined systems were compared: (i) TiO₂ was intercalated into the interlamellar space of a hydrophilic montmorillonite by means of a heterocoagulation process (TiO₂ pillared montmorillonite, TPM); (ii) TiO₂ was hydrothermally crystallized on hexadecylpyridinium chloride-treated montmorillonite (HDPM-T); (iii) hexadecylpyridinium chloride-treated montmorillonite (HDPM) was used as adsorbent and Degussa P25 TiO₂ as photocatalyst (HDPM/TiO₂).

The process of mineralization of the organic substrate was characterized by measuring the total organic carbon (TOC) and total inorganic chloride contents, while the degradation of 2-CP and the formation of intermediates were followed by HPLC. The adsorbent-photocatalyst systems were characterized by X-ray diffraction measurements. In all the investigated systems, the degradation of 2-CP was accompanied by a continuous decrease in TOC content. The most advantageous situation was found with HDPM/TiO₂, for which the highest rate of oxidation of 2-CP was observed. In this case the photocatalytically recovered adsorbent may be re-used without further regeneration. A significantly lower 2-CP degradation rate was observed when TiO₂ was fixed on layer silicates. When TPM was applied, only a rather low decrease in TOC content was observed during 10 h of irradiation, i.e. only slight mineralization of the organic pollutant occurred, which is probably due to the low crystallinity and small size of the TiO₂ particles. In the case of HDPM-T, the observed quite high reduction in TOC content shows that the hydrothermally processed TiO₂ sample may compete with the Degussa P25, but the degradation of the organic pollutant is accompanied by a continuous destruction of the adsorbent.     

Enzymatic bioactivity investigation of glucose oxidase modified with hydrophilic or hydrophobic polymers via in situ RAFT polymerization

Biomacromolecules, such as enzymes are widely used for biocatalysis, both at academic and industrial level, due to their high specificity and wide applications in different reaction media. Herein, taking GOx as a representative enzyme, in‐situ RAFT polymerization of four different monomers including acrylic acid (AA), methyl acrylate (MA), poly (ethylene glycol) acrylate (PEG‐A) and tert‐butyl acrylate (TBA) were polymerized directly on the surface of GOx to afford GOx‐poly (PEG‐A)(GOx‐PPEG‐A), GOx‐poly(MA)(GOx‐PMA), GOx‐poly(AA)(GOx‐PAA), and GOx‐poly(TBA)(GOx‐PTBA) conjugates, respectively. Thereinto, PAA and PPEG‐A represent the hydrophilic polymers, while PMA and PTBA stand for the hydrophobic ones. Effects of different polymer on the properties of GOx were investigated by measuring the bioactivity and stability of the as‐prepared and different GOx‐polymer conjugates. Higher bioactivity was obtained for GOx modified with hydrophilic polymers compared with that modified with hydrophobic ones. All the tested polymers can enhance the stability of the GOx, while the hydrophobic GOx‐polymers conjugates exhibited much better stability than the hydrophilic ones. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1289–1293