Hydrophilic surface formation on polymers by ion-assisted reaction

The wettability and adhesion of various polymers were improved using ion-assisted reaction (IAR) method, in which the polymer surfaces were irradiated by energetic ions in a reactive gas environment. The addition of new polar groups on polymer surfaces and permanent wettable polymer surfaces (water contact angle below 30° and surface free energy 60–70 mJ/m²) have been accomplished by IAR treatment. The changes in wettability and surface free energy were critically dependent on the ion dose, the ion beam energy and the flow rate of the reactive gas. Improvements in wettability and surface free energy are primarily attributed to the increase of polar components due to the formation of polar groups such as –(C=O)–, –(C=O)–O–, –(C–O)–, etc. The characteristics of the IAR treatment have been reviewed, with outstanding results regarding the wettability and adhesion of various polymers from polyolefin to fluoropolymers.     

Tensile and impact strengths of steel fiber reinforced polymer impregnated concrete

Ordinary concrete was reinforced by (i) steel fiber, (ii) polymer impregnation, and (iii) by both steel fiber and polymer impregnation. The tensile strength of concrete was increased 2.62 times by steel fiber reinforcement, 5.56 times by polymer impregnation, and 7.52 times by the combined technique. The increase in impact strength for these three cases were 2–3, 7–15, and 9–15 times respectively, over the plain concrete. Polymer loading was increased from 7% to 9.5% by pressure impregnation at 15 atm. Then the tensile strength of the steel fiber reinforced and polymer impregnated concrete was increased by 8.5 times and the impact strength by 12–28 times.     

Preparation of transparent silica–PMMA nanocomposite hard coatings

The preparation of silica–PMMA nanocomposite was reported. The surface modified-silica nanoparticles can be well dispersed in organic solvent and incorporated into the polymer resin. The nanocomposite showed improved mechanical property and can be applied on different acrylic functional materials. DSC analysis showed that the glass transition temperature of the hybrids was increased with increasing content of silica. Good transparency (>90%) and hardness grade (>5H) is observed in nanocomposite with 10 wt% silica content.     

Stimuli sensitive copolymer poly(N-tert-butylacrylamide-ran-acrylamide): processing into thin films and their transitional behaviour

Temperature sensitive polymer hydrogels are being extensively studied because of their potential applications in biomedical, robotics, and chemical industry. However, major hurdles in their development have been their slow response, low efficiency, and poor mechanical properties. One of the main reasons for these shortcomings is the difficulty of processing them into mechanically fine structures in polymer gel form. In this work, a novel approach has been developed to process temperature sensitive copolymers based on acrylamide into mechanically stable thin films. A series of temperature sensitive random linear copolymers of N-tert-butylacrylamide (NTBA) and acrylamide (Am) were synthesized by solution polymerization method, using regulated dosing of comonomer Am having a higher reactivity ratio (r_Am=1.5) than NTBA (r_NTBA=0.5). Copolymers with varying feed ratios of NTBA and Am (80:20 to 20:80 mol%) were synthesized and characterized. The actual incorporation of less reactive comonomer NTBA was found to be lower than the feed and was found to vary between 75 mol% with feed of 80 and 11 mol% for a feed of 20%. Linear copolymer with 40:60 feed ratio of NTBA and Am monomers, with actual incorporation of NTBA to the extent of 27 mol%, was selected for processing. The copolymer films of thickness in the range of 10–200 microns could be obtained from aqueous solution in the presence of citric acid or 1,2,3,4-butane tetracarboxylic acid as crosslinkers and sodium hypophosphite as catalyst. Subsequently, the films were crosslinked at 150–160 °C to obtain mechanically strong insoluble films. The crosslinks were formed between reactive amide side groups of the acrylamide moiety of the polymer and the carboxylic acid group of the crosslinker. The transition temperatures of the crosslinked films were found to shift towards the lower temperature from 37 °C (in linear copolymer) to 22–25 °C. High surface to volume ratio of the prepared films lead to significant increase in swelling percentage from 490 to 2980% and faster response time from 1280 min (in the first cycle) to 5 min compared to polymerized-gel samples (2 mm disc) of the same composition.     

An FTIR/ATR in situ study of sorption and transport in corrosion protective organic coatings: Paper 2. The effects of temperature and isotopic dilution

A detailed temperature variation (18–50 °C) FTIR/ATR study of sorption and desorption of water into a series of cured epoxy resins has been reported. For higher temperatures (35–50 °C) the data were modelled with a single Fickian diffusion equation, giving an increased D as the temperature increased and an activation energy (E_A) in the 55–60 kJ mol⁻¹ region. At lower temperatures (18–35 °C)—well-below the T_g—a two-stage sorption equation was needed and the apparent E_A was negative. This is probably associated with changes in water clustering among the distributed ‘voids’ in the glassy polymer associated with chain relaxation at extended times. The use of D₂O as a penetrant allowed diffusion coefficient measurements for highly dense epoxy matrices, where FTIR/ATR cannot detect the ν(OH) band of water over and above the residual polymer–OH groups (in the dry state). The data for the D₂O studies were notably influenced by isotopic exchange; which was found to be a diffusion controlled process, even in a polymer matrix.     

Inorganic/organic hybrid coatings for aircraft aluminum alloy substrates

A series of water-based stable sol–gel systems have been developed. Various functional groups including amino, epoxy, vinyl, and allyl groups can be incorporated into the sol–gel network to interact with organic polymer resins. The solid content of these sol–gel-based coating formulations varies from 2.5 to 45%. The sol–gel coating of alumina–silica networks derived from low solid content solutions (2.5%) has been developed and evaluated to replace the current conversion coating pretreatment process. Sol–gel coatings derived from the high solid content solutions (17–45%) have shown excellent mechanic strength, good adhesion, and provide corrosion protection of the aluminum substrate when cured at elevated temperatures. Sol–gel/epoxy resin hybrid coatings have been formulated and studied. The hybrid coating showed enhanced mechanical strength such as hardness and abrasion resistance. When cured at elevated temperatures (80°C), all of the hybrid coatings studied passed wet adhesion testing. Some of the hybrid coatings pass wet adhesion testing when cured at room temperature. However, water-sensitivity remains for most of the room temperature cured hybrid coatings.     

Direct esterification of a hydroxyl functional polyester resin with p-hydroxybenzoic acid: Part A: investigation of the direct esterification reaction scheme and characterisation of products

Direct esterification of a hydroxyl functional polyester resin with p-hydroxybenzoic acid (PHBA) was carried out at 200–230°C in the presence of p-toluene sulphonic acid and xylene. Acid value, molecular weight distribution, differential scanning calorimetry and both ¹H and ¹³C NMR analysis were used to monitor the reaction. The optical texture of the final products were examined using a polarising optical microscope. The products from the reaction were the polyester with approximately 1 PHBA molecule per polymer chain end and unreacted PHBA. The dominant reaction in the system appears to be transesterification, resulting in a decrease of the molecular weight during the reaction. A liquid crystalline phase was not formed as multiple grafts of PHBA were not formed.     

Graft polymerization of vinyl monomers from initiating groups introduced onto polymethylsiloxane-coated titanium dioxide modified with alcoholic hydroxyl groups

The grafting of vinyl polymers onto the surface of polymethylsiloxane-coated titanium dioxide modified with alcoholic hydroxyl groups (Ti/Si–R–OH) were investigated. The introduction of azo and trichloroacetyl groups onto the surface of Ti/Si–R–OH was achieved by the reaction of the surface alcoholic hydroxyl groups with 4,4′-azobis(4-cyanopentanoic acid) and trichloroacetyl isocyanate, respectively. The radical polymerizations of vinyl monomers were successfully initiated by the azo groups introduced onto the surface and by the system consisting of Mo(CO)₆ and Ti/Si–R–COCCl₃. During the polymerization, the corresponding polymers were effectively grafted onto the titanium dioxide surface through propagation from surface radicals formed by the decomposition of azo groups and by the reaction of Mo(CO)₆ with trichloroacetyl groups on the surface. The percentage of grafting and grafting efficiency in the graft polymerization initiated by the system consisting of Ti/Si–R–COCCl₃ and Mo(CO)₆ were much larger than those initiated by azo groups. The polymer-grafted titanium dioxide was found to produce a stable colloidal dispersion in good solvents for the grafted polymer. The dispersibility of poly(N,N-diethylacrylamide)-grafted titanium dioxide in water was controlled by temperature. In addition, the wettability of the surface of titanium dioxide to water was readily controlled by grafting of hydrophilic or hydrophobic polymers.     

Reduction mechanism of tioglycolic acid on keratin fibers using microspectrophotometry and FT-Raman spectroscopy

In order to investigate the reduction mechanism of thioglycolic acid (TG) on the keratin fibers, cross-sectional samples of white human hair treated with TG were prepared. The heterogeneous reaction between TG and keratin fibers involving the diffusion of TG into human hair was analyzed at the molecular level using microspectrophotometry and FT-Raman spectroscopy. The diffusion of TG into human hair clearly increased by increasing the treatment time and by raising pH. The TG relative concentration and the disconnected relative concentration of disulfide (–SS–) groups at various depths of the hair samples with pH 9.0 were in good agreement, indicating that the reaction rate (the disconnection of –SS– groups) was faster than the diffusion rate of TG into human hair. From these experiments, we demonstrated that TG diffuses gradually beyond the cuticle region, and toward the inside of the cortex region along with the disconnection of –SS– groups.     

An FTIR/ATR in situ study of sorption and transport in corrosion protective organic coatings: 1. Water sorption and the role of inhibitor anions

Both sorption and desorption transport coefficients of water and the inhibitor (HPO₄²⁻) in a series of epoxy resins (model paints) of different cross-linking density have been reported. Water diffusion is unaffected by low electrolyte concentrations (0.1 μm) but is retarded at 0.6 M chloride ion levels, presumably due to water–polymer–polymer interaction shielding. Swelling is small, but may be significant for polymer chain relaxation. The FTIR data have been used to add a molecular level interpretation of the four different pseudo-Fickian processes observed at room temperature. These data are consistent with rapid sorption onto polymer active (OH, NH), sites followed by slower incorporation of water into polymer microvoids where cluster sizes are smaller. The reverse process (on desorption) is also evident from the water, ν(OH), spectral distribution. No evidence of significant accumulation of ‘bulk’ water at the polymer–substrate interface was found.     

以葡萄糖为碳源不同碳化方式固体酸催化剂的制备与性能评价

以葡萄糖为碳源,发烟硫酸为磺酸化试剂,分别采用水热碳化法和热解碳化法制备碳基固体酸催化剂。使用扫描电镜、热重分析、X射线衍射和傅里叶变换红外光谱等对催化剂进行表征,并评价催化剂在纤维素水解反应中的性能。结果表明,两种碳化方式制备的碳基固体酸催化剂在形貌上具有很大差异,但结构上均含有—OH、—COOH和—SO_3H官能团,对于纤维素的水解反应,在150℃反应3 h,纤维素水解率超过60%。     

Poly(styrene-alt-maleic anhydride)-4-aminophenol conjugate: synthesis and antibacterial activity

Poly(styrene-alt-maleic anhydride) (SMA) may be conveniently used as an intermediate in preparing functional polymers since active agents containing amino or hydroxy groups can be linked to it via ring-opening reaction. In this study, SMA was reacted with 4-aminophenol (AP) to obtain SMA–AP conjugate. The glass transition temperature (218 °C) of the polymer was higher than that of SMA (202 °C) due to intermolecular hydrogen bonding. The polymer underwent thermal degradation in two steps where the initial weight loss began to occur at about 230 °C due to the formation of acid anhydride bonds with loss of water. SMA-AP exhibited bactericidal activity against E. coli and S. aureus, but it did not show any inhibition zone against the bacteria cells. No free AP was detected from the polymer incubated under similar conditions. Therefore, it was concluded that SMA–AP may be a bactericidal material by itself and its bactericidal activity may last for a fairly long period of time under neutral conditions.     

Synthesis of fluorine-containing polyphosphates: low-temperature solution polycondensation of bisphenol AF and aryl phosphorodichloridates

This paper describes the synthesis of aromatic polyphosphates from the reaction of various aryl phosphorodichloridates with bisphenol AF in a chlorinated hydrocarbon solvent under low-temperature conditions. The polyphosphates obtained were characterized by IR,¹³3C- and ³¹P-NMR spectra, elemental analysis, inherent viscosity, TGA, DSC, X-ray diffraction, LOI, contact angle and molar mass measurement. All the polyphosphates obtained had high yields and the inherent viscosities were in the range 0.25–0.31 dl g⁻¹. The weight average molar masses ( ) were in the range 0.96 × 10⁴−1.33 × 10⁴ with relatively narrow molar mass distributions ( ). All the polymers, except polymer C, are stable up to 250°C, exhibited 10% loss of mass at 417–463°C, and had 20–30% residual mass at 700°C in nitrogen. The X-ray diffraction patterns revealed that all the polyphosphates are semicrystalline and polymer E, containing a flexible ether linkage, has a relatively large degree of crystallinity. The fluorine-containing polyphosphates have glass-transition temperatures between 81–108°C and polymer C, having a NO₂ group in the side chain phenyl ring, has the highest T_g value. The polyphosphates obtained from bisphenol AF showed better thermal stabilities and higher LOI values than those obtained from bisphenol A. The polyphosphates have good flame retardancy, as indicated by high limiting oxygen index values in the range of 47–60. The water contact angles (θ_w) of all polyphosphates are in the range of 76–109°. The contact angles of polymers A and B are larger than other polyphosphates which contain more oxygen content or bromine atoms (polymers C, D and E).     

Effect of functional group of ferrocene redox substance on the transport properties of newly designed ion exchange membrane prepared from polymer gel

A different newly designed cationic exchange polymer membrane and anionic exchange polymer membrane were introduced, and also the transport properties of these polymeric membranes were investigated in this study. The transport properties of these polymer membranes in contact with ferrocene redox derivatives were estimated by using electrochemical techniques such as cyclicvoltammetry, chronopotentiometry, and chronoamperometry techniques, respectively. The used ferrocene redox substances, which have different functional groups, were (Ferrocenylmethyl) trimethylamonium iodide, FcMA, Ferrocenedimethanol, FcDM, and Ferrocene carboxylic acid, FcCA. It indicated that the performance of a membrane depended on the content of polymer gel, anionic exchange polymer site (20 wt % and 50 wt %) or cationic polymer exchange site (20 wt % and 50 wt %), and the efficiency of the functional groups of cationic and anionic exchange polymer site as well. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The molecular origin of enhanced toughness in double-network hydrogels: A neutron scattering study

Double-network hydrogels (DN-gels) are a new class of crosslinked polymer networks with extraordinary mechanical properties while containing 80–90 vol.% water. Small-angle neutron scattering (SANS) was applied to investigate the molecular origin of the mechanical properties observed in DN-gels. We present SANS results in both deformed and undeformed conditions for a tough DN-gel made of poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) and polyacrylamide (PAAm). The SANS measurements indicate that deformation of DN-gels results in periodic and mesoscale (1.5 μm) compositional fluctuations in both PAMPS and PAAm. In addition, SANS measurements also indicate that the DN-gel constituents interact favorably with each other while in water. This favorable interaction between PAMPS and PAAm is consistent with the rheological results on solution mixtures of these two polymers. The implications of the above observations to toughening mechanisms are discussed.     

Fracture toughness of interfaces between glassy polymers in a trilayer geometry

We studied the fracture behavior of trilayer A/B/A assemblies based on polystyrene (PS) and poly(methylmethacrylate) (PMMA) where the central layer of the A polymer was confined (0.5–200 μm) between two thick plates of the B polymer (1– 3 mm). Diblock and random P(S-MMA) copolymers were used to provide a good stress transfer across the interfaces. Fracture experiments were performed with the double-cantilever beam method and the fracture mechanisms were observed by optical microscopy on microtomed slices of the damaged zone. The measured _c of the A/B interface fractured during the test was dependent on the molecular structure at the interface (random copolymer, diblock copolymer or no copolymer), on the crazing stress of the bulk materials and on the interfacial shear stresses. When the phase angle of the loading was even slightly positive, oblique crazes were observed in the PS increasing greatly _c. If PS was the central layer, this resulted in a very marked dependence of _c on the thickness of the central layer for a thickness range 10–200 μm which was not observed when the PMMA was the central layer. Thermal treatments modifying the interfacial shear stresses were also found to have a very strong effect on _c.     

Activated carbons prepared from rice hull by one-step phosphoric acid activation

Activated carbons were prepared from rice hull by one-step phosphoric acid activation in this work. The evolution of pore structure and surface chemistry in the activation temperature range of 170–450 °C was investigated through various characterization techniques. The results showed that the development of porosity (extent of activation) was negligible at activation temperature below 300 °C, and rapid evolution occurred in 300–400 °C. Porous activated carbon with bimodel pore structure (pore < 1 nm and pore > 1 nm) and BET surface area as high as 1295 m²/g was obtained at 450 °C. The ash contents of samples prepared in this study were in the range of 5–21%. The ash contents of carbons prepared in this study initially decreased from 21.03% to 4.89% with the change of temperature from 170 to 300 °C, then increased to 8.72% at 450 °C. Boehm titration results suggested that low activation temperature (300 °C) benefits the formation of acidic surface groups. With the increase of activation temperature from 300 to 350 °C, the concentrations of strong, intermediate and weak acidic surface groups decreased from 2.23, 1.87, and 2.73 to 1.66, 1.32, and 2.16 mmol H⁺/g, respectively. Over 350 °C, the change of these groups were insignificant. FTIR results revealed the existence of carbonyl-containing, phosphorus-containing groups, and groups containing Si–O bond. The relative concentration of carbonyl-containing groups decreases with an increase in activation temperature, while that of phosphorus-containing groups follows the reverse trend. The content of Si–O decreased first, then slowly increased with the increase of activation temperature. Boehm titration and FTIR (Fourier transform infrared spectroscopy) results indicated that the surfaces of these carbons contain both temperature-sensitive and temperature-insensitive groups. The temperature-sensitive part consists mainly of carbonyl-containing groups, such as carboxylic groups, while the temperature-insensitive part is primarily phosphorus-containing groups and groups containing Si–O bond. This study demonstrated that carbon products with relative low ash content and high activation degree can be prepared from rice hull by H₃PO₄ activation at suitable temperature.     

A new curing system for automotive topcoat

In response to the need for an acid rain resistant topcoat, a curing system was prepared using two kinds of acrylic polymers; one contains a half-ester of acid anhydride and the other both a hydroxyl and glycidyl group as the functional groups. The half-ester group polymer does not react with a hydroxyl group at room temperature, but releases alcohol and reproduces an acid anhydride at elevated temperatures, and subsequently rapid polymer–polymer reaction through acid anhydride and hydroxyl group occurs. Carboxyl group produced during this crosslinking reaction reacts with glycidyl group. This reaction made it possible to design a one component curing system with a higher crosslink density. Upon adapting the curing system for automotive clearcoat, a function of mar resistance was also necessary, which was achieved by using hydroxyl monomer containing longer alkylene group.     

Photodynamic inactivation of bacterial spores on the surface of a photoactive polymer

Novel photoactive polymers were prepared by covalently binding an anthraquinone (AQ) derivative through its 2-position to acid groups of a commercially available ethylene–acrylic acid copolymer, and the photodynamic action of films prepared using these polymers was evaluated. Inoculation of Bacillus cereus spores onto the surface of photoactive polymer films having an AQ content of 35% w/w, followed by exposure to low-power UV-A light, was found to significantly enhance the inactivation of the spores compared with their survival on the surface of inert polymer substrates. It was shown that this effect most likely originates from the photo-induced production of singlet oxygen by the photoactive polymer. These results provide compelling evidence that singlet oxygen produced exogenously by a polymeric substrate can successfully inactivate microbes located on the substrate’s surface.     

Formation of active state in vanadium–titanium oxide system regarding to reaction of oxidation of β-picoline to nicotinic acid

Binary vanadia–titania catalysts comprising 5–75 wt.% of V₂O₅ and 95–25 wt.% of TiO₂, pretreated at the temperature ranging between 300 and 700°C, were studied as heterogeneous catalysts for oxidation of β-picoline at 250°C, and inlet concentrations of the following components (vol.%): 1% of 3-picoline, 20% of oxygen, 30% of steam. Nicotinic acid, 3-pyridinecarbaldehyde and CO₂ were the reaction products. The most active state for oxidation of 3-picoline into nicotinic acid was shown to result from formation of coherent interface between V₂O₅ and TiO₂ (anatase) crystallites. This state was generated at the temperature particular for each composition and persists below the temperature of the anatase to rutile transition.