Synthesis and Properties of Cationic Fluorinated Polyacrylate Soap-Free Latex

Cationic fluorinated polyacrylate soap-free latex (CFMBD) was synthesized by semi-continuous seeded emulsion polymerization of dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA), butyl acrylate (BA), and dimethylaminoethyl methacrylate (DM) with a novel cationic polymerizable emulsifier, maleic acid double ester-octadecyl poly(ethyleneoxy)₂₀ ether-ethylene trimethyl ammonium chloride (R303), and 2,2′- azobis (2 - methylpropionamidine) dihydrochloride (VA-50) was utilized as the initiator. Effects of some factors, such as VA-50 amount, R303 amount and DFMA amount, on stability and average particle size of the CFMBD were discussed in detail, and the optimal polymerization condition was obtained. In addition, the emulsion and its film were characterized by Fourier transform infrared (FTIR) spectrometry, thermogravimetry analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS), respectively. FTIR confirmed the structure of the CFMBD. With the increasing of DFMA amount, water absorption of the film decreased and water contact angle of the film increased. While the DFMA amount was more than 6 g in the recipe, the water contact angle (107.5°) and the water absorption (7.8 wt%) of the film showed no more changes. Meanwhile, thermal stability of the copolymer was greatly improved with the increasing of DFMA amount. XPS analysis indicated the fluoroalkyl groups had the tendency to enrich at the film-air interface.     

A novel approach to fluorinated polyurethane by macromonomer copolymerization

For the first time, through macromonomer radical copolymerization, a novel fluorinated polyurethane (FPU) was synthesized based on partly acrylate-endcapped polyurethane macromonomers with hexafluorobutyl acrylate (HFBA). Partly acrylate-endcapped polyurethane (PU) macromonomers were synthesized using isophronediisocyanate (IPDI), dimethylol propionic acid (DMPA), polyethylene adipate glycols (PEA) etc. The novel fluorinated polymer, which bore PU side chains and fluorinated side chains, was confirmed by F¹⁹ NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis, scanning electron spectroscopy (SEM) etc. Copolymerization of polyurethane macromonomers with hexafluorobutyl acrylate (HFBA) was briefly investigated. The surface tension of FPU solution was measured and showed sharply decrease compared to that of pure polyurethane. Results from SEM showed a uniform size distribution of phase micro-domains on the fracture surface of FPU.     

Synthesis, characterization and properties of a novel fluorinated polyurethane

A novel fluorinated polyurethane (FPU) was prepared by fluorinated polyether glycol (PTMG-g-HFP) as a soft segment, 1,6-hexamethylene diisocyanate (HDI) or toluene diisocyanate (TDI) as a hard segment and 1,4-butanodiol (BDO) as a chain extender. Fourier transform infrared spectroscopy (FTIR), ¹H NMR, ¹³C NMR and gel permeation chromatography (GPC) were used to characterize the structure of the fluorinated polyurethane. The thermal stabilities of the fluorinated polyurethane and the corresponding hydrogenated polyurethane were studied by thermogravimetric analysis (TGA). X-ray photoelectron spectroscopy (XPS) analysis at two different sampling depths for the fluorinated polyurethane was used to investigate the surface compositions of FPU. And the mechanical properties of the fluorinated polyurethane and the corresponding hydrogenated polyurethane were also measured. Chemical resistance of polyurethane films was estimated through spot tests with different solvents. The results showed that FPU had high thermal stability, strain-hardening property and good chemical resistance. The XPS measurements showed the fluorine enrichment on the surface of FPU.     

Synthesis of Fluorinated Polyurethane/Polyacrylate Hybrid Emulsion Initiated by 60Co γ-Ray and Properties of the Latex Film

Based on the solvent-free method, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared via emulsion polymerization without traditional emulsifier. For the purpose of increasing the grafting ratio of polyurethane and polyacrylate, ⁶⁰Co γ-ray radiation polymerization had been adopted to enhance the hardness of latex film. The chain structure and polymerization progress were confirmed by the analysis of Fourier transform infrared spectroscopy. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area. The effect of DFMA content on thermal stability, mechanical property and water resistance were investigated systematically by thermal weight loss analysis, tensile strength test, absorbed water ratio and water contact angle.     

Preparation and properties of Nafion/hollow silica spheres composite membranes

In present work, hollow silica spheres (HSS)/Nafion^® composite membranes were prepared by solution casting. The thermal properties, water retention, swelling behavior and proton conductivity of the composite membranes were explored. It was found that HSS dispersed well at micrometer scale in the obtained composite membranes by SEM and TEM observation. Thermal properties of composite membranes were improved than that of recast Nafion^® membrane. Compared with the recast Nafion^® membrane, the composite membranes showed higher water uptake and lower swelling degree at the temperature range from 40 to 100 °C. At the same HSS loading, the smaller the diameter of HSS in composite membranes, the more the water uptake, however, the swelling degree of composite membranes was increased. The proton conductivity of the composite membrane with 3–5 wt.% HSS (120 and 250 nm) increased distinctively at above 60 °C, reached the optimal value at 100 °C, and decreased slowly when the temperature exceeded 100 °C.     

Development of Bionic Polymers

Bionics, an artificial imitation of natural products, has always been a forever dream in the fairy tale or scientific fiction when we were childhood and children live now. However, the development of science in molecular scale makes this dream of childhood and manhood realize today.Bionics, a branch of science concerned with application the data about the functioning of biological system to the solution of engineering problems, become top-priority of science in the 21st century.However, few examples are given in molecular-level or nano-scale controlling lotus-like surface (a bionic surface for vast potential application). In the same time, such a typical bionic surface (as well known, so called "Lotus-effect") is a symbol or a totem that scientists can develop a novel approach to prepare desired surface and to control its microstructure or morphology at one's pleasure.In general, a film with a water contact angle (CA) higher than 150° can be defined as a superhydrophobic surface. The Langmuir-Blodgett film prepared by using CF3(CF2)10COOH possesses the lowest surface tension, which is 6 mJ/m2 (1). However, the water CA on a smooth surface with regularly aligned C20F42 with close-hexagonal packed -CF3 groups is only 119° (2).Obviously, only adjusting chemical composition is not enough to produce a superhydrophobic surface. Wenzel et al (3) suggested that the contact angle θ' of a liquid droplet on a rough solid surface should be written as:cosθ, =γcosθ = γ(γs-γsl)/γl, here γ is a roughness factor and γsl, γs and γl denote the interfacial tensions of the solid-liquid, the solid-gas, and the liquid-gas interfaces,respectively. This γ is always larger than 1 and a rough surface will be more water-repellent or more wettable to a liquid when intrinsic contact angle θ is bigger or smaller than 90°, respectively.Therefore, a general approach to obtain superhydrophobic surfaces is using a combination of depressing surface energy and enhancing surface roughness (4-17).Super-hydrophobic polymeric surface has been prepared in this case with a mixture of low-cost fluorine-end-capped polyurethane(FPU) and commonly available polymethyarylates(PMA) under ambient conditions. No obvious structures were observed by SEM for the pure FPU coated surface.The surface morphology is uniformly smooth at both low and high magnifications. The CA on the surface is about 95°, which indicates that FPU film has better hydrophobicity than pure polyurethane without fluorine-group, whose CA is about 65°. However, the hydrophobicity of polymer surface changes dramatically as the film is directly prepared through a one-step coating of a FPU/PMA solution between 10-30℃. The CA is up to 166 . The result shows that the SA can be dramatically decreased with small amount of FPU, and the SA reached a limiting value of 3.4 ± 2.0 ° when the FPU content in the FPU/PMA mixture is between 20 ～ 60 wt%. The water drop is unstable on these surfaces, and with a very small tilt-angle, the water drop will roll off the surface.It means that such a polymeric surface exhibits an excellent superhydrophobicity. In addition, the polymer surface possesses not only a better hydrophobicity than that of natural lotus leaf (CA measured is about 160°), but also a lypophobic property: the oil contact angle on the same surface is 140°, while the surface of lotus is lypophilic. Most interestingly, we have found that the coated film prepared by FPU/PMA mixture has a two-length scaled rough micro-nano-binary structure, that is, every micro-papilla (300-700nm) on the polymeric surface is also covered by nano-papillae ranging from 30-40nm. These MNBs is very much the same as the natural lotus-leaf surface in micro- and nano-scales. Compared with lotus surface structure, the NMBs structure on this bionic polymeric surface prepared is in less scale. The results clearly demonstrated that a bionic polymeric surface similar to the natural lotus-leaf surface can be obtained by a one-step coating process. The results showed also that such a bionic polymeric surface possess of some "self-repairing" properties similar to that of natural surfaces and the effects of preparation temperature and concentration as well as substrate made no obvious difference on the hydrophobicity of the bionic polymeric surfaces..In conclusion, we demonstrated that the MNBs of a bionic polymeric film has been one-step obtained with the use of the self-aggregation of PMA combining with a nano-scaled phase separation of amphiphilic copolymer during the drying process in ambient atmosphere. This remarkable result provides many potential possibilities, including coating, hygienic, medical,environmental, and industrial processing applications.     

Chitosan‐modified graphene oxide as a modifier for improving the structure and performance of forward osmosis membranes

Chitosan (CS) with good hydrophilicity and charged property was used to modify graphene oxide (GO), the obtained GO‐CS was used as a novel modifier to fabricate thin film composite forward osmosis (FO) membranes. The results revealed that the amino groups on CS reacted with carboxyl groups on GO, and the lamellar structure of the GO nanosheets was peeled off by CS, resulting in the reducing of their thicknesses. The GO‐CS improved the hydrophilicity of polyethersulfone (PES) substrate, and their contact angles decreased to 64° with the addition of GO‐CS in the substrate. GO‐CS also increased the porosity of the substrate and surface roughness of FO membrane, thereby optimizing the water flux and reverse salt flux of FO membrane. The average water flux of the FO membrane reached the optimal flux of 21.34 L/(m² h) when GO‐CS addition was 0.5 wt%, and further addition of GO‐CS to the substrate would decrease the water flux of FO membrane, and the reverse salt flux also decreased to the lowest value of 2.26 g/(m² h). However, the salt rejection of the membrane increased from 91.4% to 95.1% when GO‐CS addition increased from 0.5 to 1.0 wt% under FO mode using 1 mol/L sodium chloride (NaCl) solution as draw solution (DS). In addition, high osmotic pressure favored water permeation, and at the same concentration of DS, magnesium chloride (MgCl₂) exhibited better properties than NaCl. These results all suggested that GO‐CS was a good modifier to fabricate FO membrane, and MgCl₂ was a good DS candidate.     

Surface modification of PVDF porous membranes

A novel method for the surface modification of PVDF porous membranes was introduced. Styrene-(N-(4-hydroxyphenyl) maleimide) alternating copolymer SHMI-Br was blended with PVDF to fabricate SHMI-Br/PVDF membranes. The C-Br bond on the SHMI-Br/PVDF membrane was served as initial site of ATRP, and P(PEGMA) brush was grafted on the PVDF membrane. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR/FTIR) was used to prove the P(PEGMA) brushes were successfully grafted onto the SHMI-Br/PVDF membrane surface. Introduction of P(PEGMA) brushes on the PVDF membrane surface enhanced the hydrophilicity effectively. When the PEGMA degree of grafting was 16.7 wt%, the initial contact angle of PVDF membrane decreased from 98° to 42°. The anti-fouling ability of PVDF membrane was improved significantly after P(PEGMA) brush was grafted. Taking the PEGMA degree of grafting 16.7 wt% as an example, the flux of protein solution was about 151.21 L/(m² h) when the pH value of the BSA solution was 4.9. As the pH value was increased to 7.4, the flux was changed to 180.06 L/(m² h). However, the protein solution flux of membrane M3 (PEGMA: 0 wt%) was only 73.84 L/(m² h) and 113.52 L/(m² h) at pH 4.9 and 7.4, respectively.     

Study on superabsorbent composite—VII. Effects of organification of attapulgite on swelling behaviors of poly(acrylic acid‐co‐acrylamide)/sodium humate/organo‐attapulgite composite

A novel multifunctional superabsorbent composite from acrylic acid (AA), acrylamide (AM), sodium humate (SH) and organo‐attapulgite (organo‐APT), PAA‐AM/SH/organo‐APT, was synthesized by aqueous solution polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification of APT with hexadecyltrimethyl ammonium bromide (HDTMABr) was proved by FT‐IR. The effects of organo‐APT (HDTMA‐APT) content in the superabsorbent composite and organification degree of it on water absorbency of the superabsorbent composite were studied. The effects of incorporated HDTMA‐APT on swelling rate, water absorbency in various saline solutions and reswelling capability of the superabsorbent composite were also investigated. The results indicate that organification of APT had a remarkable influence on swelling behaviors of the superabsorbent composites. Comparing with the composite doped with APT, water absorbency for the composite incorporated with 10 wt% HDTMA‐APT was enhanced from 996 to 1282 g g^?1 in distilled water and from 63 to 68 g g^?1 in 0.9 wt% NaCl solution, respectively. The superabsorbent composite acquired its highest water absorbency when the organification degree of APT was 8.02 wt%. Water absorbency of the composites in various saline solutions decreased with the increasing concentration, especially for the multivalent cations. In addition, swelling rate and reswelling capability of the superabsorbent composite were also improved by introducing HDTMA‐APT into the composite compared with that of incorporating APT. Copyright © 2006 John Wiley & Sons, Ltd.     

Composition and solution properties of fluorinated block copolymers and their surface structures in the solid state

A series of diblock copolymers composed of methyl methacrylate and 2-perfluorooctylethyl methacrylate (PMMA₁₄₄-b-PFMA _n ) with various PFMA block lengths were prepared by atom transfer radical polymerization (ATRP). The surface structures and properties of these polymers in the solid state and in solution were investigated using contact angle measurement, X-ray photoelectron spectroscopy (XPS), sum frequency generation (SFG) vibrational spectroscopy, surface tension and dynamic laser light scattering (DLS). It was found that with increasing PFMA block length, water and oil repellency decreased, the ratio of F/C increased with increasing film depth, and the degree of ordered packing of the perfluoroalkyl side chains at the surface decreased. When the number of PFMA block units reached 10, PMMA segments were detected at the copolymer surface, which was attributed to the PFMA block length affecting molecular aggregation structure of the copolymer in the solution and the interfacial structure at the air/liquid interface, which in turn affects surface structure formation during solution solidification. The results suggest that copolymer solution properties play an important role in structure formation on the solid surface. Supported by the National Natural Science Foundation of China (Grant Nos. 50573069 and 20704038) and Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT 0654)     

Preparation of sulfonated poly(phthalazinone ether sulfone ketone) composite nanofiltration membrane

Thin film composite (TFC) membranes were prepared from sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) as a top layer coated onto poly(phthalazinone ether sulfone ketone) (PPESK) ultrafiltration (UF) support membranes. The effects of different preparation conditions such as the SPPESK concentration, organic additives, solvent, degree of substitution (DS) of SPPEK and curing treatment temperature and time on the membrane performance were studied. The SPPESK concentration in the coating solution was the dominant factor for the rejection and permeation flux. The TFC membranes prepared from glycerol as an organic additive show better performance then those prepared from other additives. The rejection increased and the flux decreased with increasing curing treatment temperatures. The salt rejections of the TFC nanofiltration (NF) membranes increased in the order MgCl₂ < MgSO₄ < NaCl < Na₂SO₄. TFC membranes showed high water flux at low pressure. SPPESK composite membranes rejections for a 1000 mg L⁻¹ Na₂SO₄ feed solution was 82%, and solution flux was 68 L m⁻² h⁻¹ at 0.25 MPa pressure.     

PVDF Hollow fiber Membrane with High Flux and High Rejection Ratio Prepared by Irradiation Induced Grafting of PAA

Summary: A modified poly (vinylidene fluoride) (PVDF) hollow fiber membrane with higher flux and flux recovery rate was prepared by γ-radiation induced grafting of acrylic acid (AA). The influence of radiation dose and monomer concentration on the grafting degree was investigated. The results indicated that the grafting degree increased in the lower monomer volume fraction until the monomer volume fraction exceeded 20%. The grafting degree increased with the increase of radiation dose. Structural and morphological of the original and grafted membrane surface were characterized by FT-IR, scanning electron microscopy (SEM). The results indicated that acrylic acid was grafted onto PVDF hollow fiber membrane and the grafted membrane was more hydrophilic than original PVDF. There was a slight increase of breaking strength and yield stress with the increase of the grafting degree of AA. The pure water flux increased initially but decreased subsequently with the raise of grafting degree. When the grafting degree was 4.4%, the maximum pure water flux reached 1496.3 L/m² × h, 1.79 times of original membrane. The pure water flux, flux recovery rate and rejection ratio for bovine serum albumin could improve simultaneously in a low grafting degree (<4.4%).     

Water soluble amino grafted silicon nanoparticles and their use in polymer solar cells

Stable aqueous amino-grafted silicon nanoparticles(SiNPs-NH2) were prepared via one-pot solution method. By grafting amino groups on the particle surface, the dispersion of SiNPs in water became very stable and clear aqueous solutions could be obtained. By incorporating SiNPs-NH2 into the hole transport layer of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid(PEDOT:PSS), the performance of polymer solar cells composed of poly[2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene](MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester(PCBM) as active layer can be improved. SiNPs-NH2 are dispersed uniformly in the PEDOT:PSS solution and help form morphologies with small-sized domains in the PEDOT:PSS film. SiNPs-NH2 serve as screens between conducting polymer PEDOT and ionomer PSS to improve the phase separation and charge transport of the hole transport layer. As a result, the sheet resistance of PEDOT:PSS thin films is decreased from(93 ± 5) × 105 to(13 ± 3) × 105 ?/□. The power conversion efficiency(PCE) of polymer solar cells was thus improved by 9.8% for devices fabricated with PEDOT:PSS containing 1 wt% of SiNPs-NH2, compared with the devices fabricated by original PEDOT:PSS.     

Polyethersulfone sulfonated by chlorosulfonic acid and its membrane characteristics

Sulfonated polyethersulfone (SPES) was prepared by homogeneous method with chlorosulfonic acid as sulfonating agent and concentrated sulfuric acid as solvent. The presence of sulfonic acid groups in SPES was confirmed by ¹H NMR and FTIR. Thermogravimetric analysis (TGA) studies were carried out to investigate the thermal stability of SPES. Membranes were cast from SPES solutions in N-methyl-2-pyrrolidone. Tensile strength of prepared membranes decreased with degree of sulfonation (DS) but water uptakes of SPES membranes increased with DS. Compared with unsulfonated polyethersulfone membrane, the hydrophilicity of SPES membranes was increased, as shown by a reduced contact angle with water. Amorphous structures for SPES membranes were detected by X-ray diffraction. Atomic force microscopy phase images of the membranes clearly showed the hydrophilic domains at higher DS.     

Aggregate formation and surface activity of partially deacetylated water-soluble chitin

Water-soluble chitin (WSC), partially acetylated, was prepared by using N-acetylation in mild conditions. The aggregation behavior of WSC in aqueous solution was investigated. the results showed that the surface tension decreased with increasing WSC concentration in the high dilute solution, the critical aggregation concentration was about 0.010 g/ml. The degree of deacetylation had an obvious effect on the surface tension. Introduction of acetyl favored aggregation formation. The possible aggregation mechanism of WSC in water was attributed to the molecules’ conformation transition, resulting in change of intra- and inter-molecular interactions such as hydrogen bonding and hydrophobic interaction.     

Poly (caprolactone)/poly (ethylene glycol) pervaporation blend membranes: Synthesis,characterization, and performance

Poly (caprolactone) membranes with addition of different poly (ethylene glycol) concentrations were prepared for separation of water/isopropanol azeotropic mixture by pervaporation process. Different characterization tests including Fourier transform infrared, scanning electron microscopy, water contact angle, and thermogravimetric analysis were carried out on the prepared membranes. In addition, the effect of poly (ethylene glycol) PEG content on the swelling degree and the performance of the prepared membranes in pervaporation process were investigated. According to the obtained results, all the membranes were water selective and the blend membrane containing 3 wt% PEG exhibited the best pervaporation performance with a water flux of 0.517 kg/m² hour and separation factor of 1642 at the ambient temperature. Hydrophilicity improvement of the blend membranes was confirmed by constant decrease in water contact angle of the membranes as PEG content increased in the casting solution. Scanning electron microscopy cross‐sectional images indicated that the blend membranes containing PEG had a closed cellular structure. Furthermore, mechanical and thermal properties of the membranes decreased by adding PEG.     

Preparation and performance of a novel polyimide foam

A new type of polyimide foam (PIF) was prepared and characterized based on a one‐pot process by the reaction of a first solution with different ratios of a second solution. The first solution was comprised of pyromellitic dianhydride (PMDA), N, N‐dimethyl formamide (DMF), methanol, water, surfactant, and catalysts, while the second solution contained polyaryl polymethylene isocyanate (PAPI). In the present study, the relationships among compositions, structures, and properties of PIFs were investigated. The results indicated that with the increase in the weight ratio of PAPI/(first solution), the foaming degrees of PIFs increased from 10.14 to 10.52 times and the apparent densities before postcure decreased from 15.96 to 14.51 kg/m³. The open cell contents, average sound absorption coefficients, and average cellular diameters of PIFs after postcure increased with increase in the weight ratio of PAPI/(first solution). The glass transition temperatures (T_g) of PIFs after postcure first increased from 287 to 299°C, then decreased to 292°C, and the 5% weight loss temperatures and 10% weight loss temperatures presented the same trend as well. The compressive and flatwise tensile properties scaled very well with the relative densities of the foams after postcure, with the highest compressive strength of 0.03 MPa and the highest flatwise tensile strength of 0.15 MPa. Copyright © 2011 John Wiley & Sons, Ltd.     

Solid-state Electrochemistry of Gadolinium Hexacyanoferrate Modified Electrode and Electrocatalytic Properties of Gadolinium Hexacyanoferrate

A new electroactive polynuclear inorganic compound of rare earth metal, gadolinium hexacyanoferrate (GdHCF), was prepared and characterized using the techniques of FTIR spectroscopy, thermogravimetric analysis (TG), UV-Vis spectrometry, X-ray photoelectron spectroscopy (XPS), ICP atomic emission spectroscopy, and EDX. The results of ICP atomic emission spectroscopy, EDX, and TGA indicated that the prepared GdHCF sample had a stoichiometry of NaGdFe(CN)₆·12H₂O (when GdHCF was prepared in NaCl solution). The FTIR spectrum of GdHCF showed that there were two types of water molecules in the structure of GdHCF: one was the interstitial water (5 H₂O), which resulted from the association of water due to H-bonding, and the other was water coordinated with Gd (7 H₂O). The results obtained using XPS showed that the oxidation state of Fe and Gd in the GdHCF sample was +2 and +3, respectively. GdHCF was immobilized on the surface of spectroscopically pure graphite (SG) electrode forming the GdHCF/SG electrode, and the solid-state electrochemistry of the resultant electrode was studied using cyclic voltammetry. The cyclic voltammetric results indicated that the GdHCF/SG electrode exhibited a pair of well-defined and stable redox peaks with the formal potential of E^0′=(197±3) mV. The effects of the concentration of the supporting electrolyte on the electrochemical characteristics of GdHCF were studied, and the results showed that the value of E^0′ increased linearly with the activity of the cationic ion of the supporting electrolyte (lga_Na⁺), with a slope of 54.1 mV, which may become a novel method for determining the activity of Na⁺ in solution. Further experimental results indicated that GdHCF had electrocatalytic activities toward the oxidation of dopamine (DA) and ascorbic acid (AA), and the electrocatalytic current increased linearly with the concentration of DA (or AA) in the range of 1.0–10.0 mmol·L^?1 (for DA) or 0.5–20.0 mmol·L^?1 (for AA).     

New superporous hydrogels composites based on aqueous Carbopol solution (SPHCcs): synthesis, characterization and in vitro bioadhesive force studies

In this investigation new superporous hydrogels composites based on aqueous Carbopol^® solution (SPHCcs) were prepared. SEM images indicated that the inner surface of SPHCcs contained a lot of pores connected each other and the outer surface of them was non-porous. The swelling ratio decreased with increasing the content of aqueous Carbopol^® solution, and the final swelling ratio was similar to that of the SPH although the initial swelling ratio was lower. The density measurement revealed that the porosity increased when aqueous Carbopol^® solution was incorporated. It was observed from in vitro bioadhesive force study that SPHCcs adhered to the intestinal mucosal more quickly and exhibited higher mucoadhesion as compared with SPH. It is evident that the hydrogels synthesized in this study could be a potential candidate for transmucosal drug delivery system.     

The adsorption of salicylic acid onto γ-alumina and kaolinite from solution in hexane studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT)

It was possible to determine the maximum loading of salicylic acid adsorbed onto γ-alumina and kaolinite clay after exposure to salicylic acid dissolved in hexane by examination using diffuse reflectance infrared Fourier transform infrared spectroscopy (DRIFTS). The maximum surface loading of salicylic acid (which resisted washing with fresh hexane) on γ-alumina was four times that observed using water as a solvent (approximately 3.0 compared with 0.7 molecules/nm²). Washing the sample with water removed the organic which was in excess to the maximum level observed for samples prepared with aqueous solution. The spectra of samples prepared with a loading up to the maximum observed with aqueous solution showed no significant differences to those of samples where the organic had been adsorbed from hexane (with the same surface loading). New peaks were observed for loadings greater than 1 molecules/nm², but the salicylic acid was still present as carboxylate (with no clear evidence for the carbonyl group). Salicylic acid adsorbed more readily to the surface of kaolinite from solution in hexane than from aqueous solution (up to maximum average loading of 2 molecules/nm²). Washing the samples with water removed the organic to a loading in the region of 0.2 molecules/nm², independent of the initial loading. Salicylic acid was adsorbed onto kaolinite as the carboxylate. The findings indicate that uptake is mediated by a surface water layer even in the absence of bulk water.