In this research, the porous polymer structures (IPN) were made from natural isoprene rubber (NR) and poly(methyl methacrylate) (PMMA). The effects of molecular weight and crosslink density of polyisoprene on the morphology and miscibility with PMMA were determined. Sequential semi-IPNs were prepared. Viscoelastic, thermal and mechanical properties of semi-IPN were studied. The results showed that the key factor influencing the miscibility in semi-IPN was the crosslinking density of the natural rubber. The degree of compatibility was increased by doubling the crosslinking level. The degree of miscibility at two different compositions was compared by simulations of the electron spin resonance spectra. Compatibility of semi-IPNs was found to be more efficient when the PMMA content was less than 40 wt.%. A nanometer-sized morphology was obtained for a NR/PMMA ratio of 50/50. Highly crosslinked elastic semi-IPN followed the storage modulus of PMMA after the glass transition as a result of certain degree of phase mixing and interlocked structure. It was shown that the morphology of the porous polymer network could be easily controlled by the proper choice of concentration and composition of crosslinking agent. A dual phase morphology resulted from the higher concentration and the lower crosslinking level. This was used for developing porous structures from the elastic semi-IPN. The mechanical performance was correlated with morphology, and the thermal stability was comparable with respect to pure NR. Investigated materials might be interesting for use as potential carriers of bioactive molecules aimed for innovative applications such as in food packaging.

The relaxations of natural rubber (NR)/poly(methyl methacrylate) (PMMA) interpenetrating polymer networks (IPNs) were studied using dynamic mechanical analysis, electron spin resonance (ESR) and solid state NMR spectroscopy. Samples with a lower concentration of PMMA in IPNs (25 wt%) showed only one relaxation, which corresponds to NR with a slight shift to higher temperature. IPNs with 35 wt% of PMMA showed very broad transitions arising from beta- and alpha-relaxations in PMMA, with the beta-relaxation slightly shifted to lower temperature. These compositions also showed a higher modulus at all temperatures. Highly phase separated IPNs showed a complete drop of modulus at 423 K. Higher crosslinking in the NR phase increases the miscibility and decreases the temperature difference between transitions, while in PMMA it increases the phase separation and does not affect the beta-relaxation of the PMMA chains. The ESR results showed that PMMA chains located in the PMMA-rich and NR-rich domains have different motional characteristics. The strong interaction between PMMA and NR chains was also observed by carbonyl relaxation in solid state NMR spectra. It was found that medium level crosslinking is needed for better interpenetration between phases. (C) 2013 Society of Chemical Industry

Morphology, mechanical properties, thermal stability and gas transport behaviour of interpenetrating polymer networks (IPNs) based on PI/PMMA have been investigated using various techniques. Crosslinking level of both phases and concentration of PMMA were found to have noticeable effects on the compatibility of immiscible components during IPN formation. Effect of crosslinking was studied by preparing IPNs with varying amount of crosslinker concentration in each phase. Crosslinking of both phases facilitated deeper interpenetrations between both networks, and certain degree of compatibility is attained during IPN formation. Nanometre-sized domains were observed for highly crosslinked IPN. Lower concentration of PMMA was found to favour phase mixing more effectively than others. DSC curve of 65/35 IPN showed a broad transition arising from the α and β-relaxations of PMMA due to the higher flexibility attained by mixing with the highly mobile PI chains. The mechanical properties of the IPNs were correlated to the morphology of the system and 50/50 composition showed maximum mechanical properties among the studied compositions. Mode of mechanical failure, thermal stability and gas transport behaviour were also analysed. IPNs having nanometre-sized domains showed least gas permeability among the studied samples.

Main chain and segmental dynamics of polyisoprene (PI) and poly(methyl methacrylate) (PMMA) chains in semi IPNs were systematically studied over a wide range of temperatures (above and below T-g of both polymers) as a function of composition, crosslink density, and molecular weight. The immiscible polymers retained most of its characteristic molecular motion; however, the semi IPN synthesis resulted in dramatic changes in the motional behavior of both polymers due to the molecular level interpenetration between two polymer chains. ESR spin probe method was found to be sensitive to the concentration changes of PMMA in semi IPNs. Low temperature spectra showed the characteristics of rigid limit spectra, and in the range of 293-373 K. complex spectra were obtained with the slow component mostly arising out of the PMMA rich regions and fast component from the PI phase. We found that the rigid PMMA chains closely interpenetrated into the highly mobile PI network imparts motional restriction in nearby PI chains, and the highly mobile PI chains induce some degree of flexibility in highly rigid PMMA chains. Molecular level interchain mixing was found to be more efficient at a PMMA concentration of 35 wt.%. Moreover, the strong interphase formed in the above mentioned semi IPN contributed to the large slow component in the ESR spectra at higher temperature. The shape of the spectra along with the data obtained from the simulations of spectra was correlated to the morphology of the semi IPNs. The correlation time measurement detected the motional region associated with the glass transition of PI and PMMA, and these regions were found to follow the same pattern of shifts in a-relaxation of PI and PMMA observed in DMA analysis. Activation energies associated with the T-g regions were also calculated. T-50G was found to correlate with the T-g of PMMA, and the volume of polymer segments undergoing glass transitional motion was calculated to be 1.7 nm(3).C-13 T-1 rho measurements of PMMA carbons indicate that the molecular level interactions were strong in semi IPN irrespective of the immiscible nature of polymers. The motional characteristics of H atoms attached to carbon atoms in both polymers were analyzed using 2D WISE NMR. Main relaxations of both components shifted inward, and both SEM and TEM analysis showed the development of a nanometer sized morphology in the case of highly crosslinked semi IPN. (C) 2010 Elsevier Ltd. All rights reserved.

The diffusion and transport of inhibitor-free methyl methacrylate monomer through crosslinked natural rubber (NR) have been studied at different temperatures. NR has been vulcanised by conventional, efficient and peroxide vulcanisation technique. ESR spin probe spectroscopy was used to study the flexibility of NR network chains at different temperatures. The dependence of diffusion coefficient on the nature of crosslinks and temperature has been studied. The intrinsic diffusion coefficient was found to increase with increase of temperature. The interaction parameter, permeability, sorption coefficient and molecular weight between crosslinks have been evaluated using diffusion data. The morphology of the swollen network and thermodynamic parameters has been determined using diffusion data. The efficient and peroxide system showed the least uptake and the conventional system showed the highest uptake. This study also proved that same extent of crosslinking can be achieved for different vulcanising systems by curing the samples to a common rheometric torque. The theoretical modelling shows Fickian mode of diffusion with a slight deviation.

Electron spin resonance (ESR) spectroscopy is a technique commonly used in studying polymer systems during last decades. This technique gives the information about molecular dynamics and matrix structure on the level of a chain segment. ESR spectroscopy is particularly successful in studying inhomogeneous polymer systems, like for example natural rubber. The large number of polymer materials does not possess stable paramagnetic centers and therefore, various nitroxide free radicals are usually used in order to investigate such materials by ESR. A nitroxide radical can be introduced in a polymer matrix by diffusion during the swelling of a polymer in a nitroxide solution. Such an application of nitroxides in ESR spectroscopy is known as spin probe method. In the present study, this method has been used to investigate the segmental dynamics and matrix structure of rubber nanocomposite materials and interpenetrating polymer networks. Natural rubber (NR) filled with the nanosilica particles having a diameter of 13 nm was crosslinked by sulphur. The sulphur content was constant and equal 2.5 phr in all samples. The amount of nanosilica was varied from 5 phr to 20 phr. ESR measurements were performed with the nitroxide radical 4-hydroxy-2, 2, 6, 6-tetramethylpiperidine-1-oxyl. The spin probe was incorporated in the material by swelling the samples in the toluene probe solution. Spectra were measured in a wide temperature range from -100 °C to 80 °C. ESR spectra observed in the vicinity of T5mT, the temperature related to the glass transition temperature, consist of the broad and narrow component characteristic for the slow and fast motion of the spin probe, respectively. The spectral shapes strongly depend on the nanosilica content. In fact, the higher amount of nanosilca results in higher amount of the broad spectral component. This suggests that an addition of nanosilica particles leads to the restriction in segmental motions. An influence of the coupling agent on the motional behavior of NR chain segments was also investigated. The narrow component, indicating fast segmental motions, which is neatly pronounced in the spectrum of the sample without coupling agent, almost disappears by an addition of 4 phr of the coupling agent. According to these ESR results, it can be concluded that the interaction of the nanoparticles with NR chain segments become more efficient when the coupling agent is present in the matrix. Additional ESR measurements were made with the interpenetrating polymer networks (IPNs) composed of natural rubber and poly(methyl methacrylate) (PMMA). The results have shown that the local motions of the NR chain segments strongly depend on the amount of PMMA component. The higher amount of PMMA leads to the restriction in dynamics of the polyisoprene chain segments.

Emulsions of vegetable oils were prepared using ionic and non-ionic surfactants for use as metal working fluids. The conditions for an enhanced mutual miscibility for soybean oil or modified soybean oil and water were investigated to prepare emulsions for vegetable oil-based components. Oil modification was achieved using ozonation and sulfurization reactions. The products were characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The viscosities of the modified oil were considerably higher than the starting oil. The emulsions were obtained with the aid of three different surface-active agents at room temperature. The stability and efficiency of these emulsions were evaluated. These emulsions also showed good stability and anticorrosion properties. The phase behavior was evaluated using phase diagrams. Cryo-scanning electron microscopy (cryo-SEM) was used in describing the oil–water interaction during the emulsion formation. It was found that the phase behavior was dependent on the nature and the concentration of surfactant used. Modified soybean oil required comparatively increased amounts of surfactant than the regular oil to obtain a stable emulsion.

Three different biodegradable polyesters, namely, polycaprolactone (PCL), polybutylene succinate (BIONOLLE), and a copolyester of adipic acid, terephthalic acid, and 1,4-butanediol (EASTAR) were melt-blended using a twin-screw extruder. The percentage composition of each of the aforementioned polymers was varied to obtain different blends, and the mechanical properties were evaluated. Selected blends showed significant improvement in tensile strength as compared with the individual polymers used to prepare the blend. The compatibility between the polymer phases was examined via Fourier transform infrared (FTIR) and nuclear magnetic resonace (NMR) spectroscopy as well as dynamic mechanical analysis. FTIR and NMR data confirmed the occurrence of hydrogen-bonding and ester-interchange reactions. Thermal properties and changes in crystallinity of the blends were examined with differential scanning calorimetry and X-ray diffraction. A considerable increase in crystallinity was shown by the blend system containing BIONOLLE/PCL. The morphology of the blends was observed and correlated to the improved mechanical properties of the blend system. Results revealed an intermediate multiphase system in which a significant degree of mixing was achieved through the chemical interaction of the functional groups present, while using the twin-screw extruder. Significant improvement in mechanical properties of some blends was observed, and information about the miscibility of these polyesters is provided. (C) 2002 Wiley Periodicals, Inc.

Modified soy-based vegetable oil polyols were successfully incorporated as a replacement for conventional polyols to produce flexible slabstock polyurethane foams. The oil was characterized for its hydroxyl value and fatty acid composition. The modified oils had higher hydroxyl values and lower unsaturated acids than regular unmodified oils. Three different modified polyols were used to investigate the reactivity with isocyanates. The effects on the foaming reaction of two different isocyanates, namely TDI and MDI, were investigated. The reactions were also carried out with a mixture of polyols containing synthetic polyols and vegetable oil-based polyols to delineate the effect of each component. FTIR technique was used to identify the sequence of chemical reactions during the foaming process. The effect of water levels and isocyanate content on the kinetics of the foaming reaction was investigated. Information regarding the formation of hard and soft segments with the varying compositions was obtained. As the water content increased, the amount of the hard segment and urea formation increased in both soy oil polyols and synthetic polyols. Increased synthetic polyols in the mixture increased the rate of reaction and phase mixing due to the availability of primary hydroxyl groups. Scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) were used to probe the morphology. As the water content increased, the cell size increased. At lower water content a more uniform cell structure was evident and at higher water levels hard domain size increased. (C) 2002 Wiley Periodicals, Inc.

The functionalization of poly(butylene terephthalate) (PBT) has been accomplished in a twin screw extruder by grafting maleic anhydride (MA) using a free radical polymerization technique. The resulting PBT-g-MA was successfully used as a compatibilizer for the binary blends of polyester (PBT) and polyamide (PA66). Enhanced mechanical properties were achieved for the blend containing a small amount (as low as 2.5%) of PBT-g-MA compared to the binary blend of unmodified PET with PA66. Loss and storage moduli for blends containing compatibilizer were higher than those of uncompatibilized blends or their respective polymers. The grafting and compatibilization reactions were confirmed using FTIR and C-13 NMR spectroscopy. The properties of these blends were studied in detail by varying the amount of compatibilizer, and the improved mechanical behaviour was correlated with the morphology with the help of scanning electron microscopy. Morphology studies also revealed the interfacial interaction in the blend containing grafted PET. The improvement in the properties of these blends can be attributed to the effective interaction of grafted maleic anhydride groups with the amino group in PA66. The results indicate that PBT-g-MA acts as an effective compatibilizer for the immiscible blends of PET and PA66. (C) 2000 Society of Chemical Industry.

Styrene-divinylbenzene copolymer with 5% and 15% cross linked were synthesised by suspension polymerization, chloromethylated and treated with 1,2-diaminopropane for the introduction of the ligand. The polymer beads modified with ligand was kept in contact with PdCl2 to form the metal complex on the surface of the polymer. The catalysts thus prepared were characterized by various techniques such as FTIR, reflectance UV–vis spectroscopy, SEM, EPR, TGA and ESCA. Physico-chemical properties such as moisture content, bulk density, surface area by BET method and swelling with different solvents were studied. The catalytic activity of synthesised catalysts was tested for hydrogenation of cyclohexene as a model reaction. Kinetic studies were carried out by varying different parameters. Energy of activation as well as entropy of activation was calculated. The recycling efficiency of the catalysts was also studied. A probable reaction mechanism was proposed.

The compatibilizing effect of anhydride groups attached to a polyester was examined while blending soy protein and a biodegradable polyester. Three different polyesters grafted with anhydride functional groups were used as compatibilizers for blending with soy protein concentrate, soy flour, and soy isolate. The processing conditions for these blends in a twin screw extruder and injection-molding machine were evaluated and the physical and mechanical properties of these blends were determined. The concentrations of soy protein and compatibilizer were varied to achieve optimum mechanical properties, exploring the various limits of operating conditions. The dynamic mechanical properties were determined using a rheometric mechanical spectrometer (RMS-800). The enthalpy of fusion was determined using a differential scanning calorimeter. Blends containing compatibilizer gave enhanced tensile strength when compared to blends without compatibilizer. The morphology of these blends was investigated with the help of an optical microscope and X-ray diffraction was used for crystallinity studies. Water and oil absorption by these blends were determined for a period of 25 days. (C) 1999 Society of Chemical Industry.

Different compositions of wheat gluten (65% and 75%) and polycaprolactone (PCL) were melt blended in a twin screw extruder. PCL was modified to incorporate a functional group that could interact with the functional groups on the protein. These samples were then injection moulded to obtain test samples whose tensile and flexural properties were obtained. Results indicate that a small amount of anhydride modified polycaprolactone in the blend improved the physical properties of these blends over those of simple mixtures of wheat gluten and polycaprolactone. These blends have a narrow window of processability. Up to 75% by weight of wheat gluten could be incorporated into the blends without adversely affecting the tensile properties. However, elongations decreased significantly at these levels of gluten. Weldline strengths ranged between 50 and 75% of the non-weldline strengths and decreased with increase in gluten content. Storage at high humidity and low temperature (freezer), or dry and elevated temperature conditions (oven), did not affect the physical properties of the blends. They could be re-ground and reused without any appreciable loss in properties. Dynamic mechanical spectroscopy was used to obtain information on the respective phases and the significance of G′ and G″ as a function of temperature and frequency are discussed. Both G′ and G″ for the compatible blends were an order of magnitude higher than blends containing simple mixtures. Morphology of the blends using an optical microscope indicate a two-phase system with PCL as the continuous phase and gluten as the dispersed phase. At such high gluten content the moulded samples absorbed around 40% by weight of water within 7 days. The mechanism of water uptake is discussed. Average oil absorption was less than 0.5% for a 20-day period. The samples were found to be biodegradable under aerobic conditions.

Anti-depressants have been reported to be useful in the management of the Irritable Bowel syndrome. We studied the efficacy of amitriptyline for 12 weeks in a randomized double-blind placebo-controlled trial. Forty patients who met predefined criteria entered the trial. They received 25 mg amitriptyline for the first week, 50 mg for the second week and 75 mg nightly thereafter until the end of the 12th week. The drug and placebo groups were comparable in all major pretreatment variables. Amitriptyline was found to be significantly more effective than placebo in producing global improvement, increasing feelings of well-being, reducing abdominal pain and increasing satisfaction with bowel movements. Younger age and increasing extroversion predicted a better response to amitriptyline. Severity of depressive and anxiety symptoms and other personality variables did not influence outcome.

A twin-screw extruder was used to graft oxazoline reactive group onto polycaprolactone (PCL) by free radical initiation reaction. A low-volatility oxazoline compound was used to facilitate a high-temperature grafting reaction. The effect of melt temperature, screw speed, and initiator and monomer concentrations on graft content were evaluated. The graft content ranged from 0.7 to 2.6%. Increased melt temperature and reduced screw speed increased the graft content. Molecular weight and molecular weight distribution evaluated with the help of intrinsic viscosity and gel permeation chromatography measurements gave values that were close to that of the unmodified PCL. The oxazoline-grafted polyester gave considerable increase in the tensile force when compared with that of pure PCL. The grafting reaction was confirmed using Fourier transform infrared spectroscopy and nuclear magnetic resonance techniques. A probable reaction mechanism for the grafting reaction is proposed. (C) 1998 John Wiley & Sons, Inc.

Styrene-divinylbenzene copolymer with 2 and 5% crosslinking was chloromethylated by HCl and HCHO using AlCl3 as the catalyst. Polymer-bound Ru(III) complex catalysts were synthesized by sequential attachment of 1,2-diaminopropane to the copolymer beads followed by treatment with a metal salt. The catalysts were characterized by using various techniques: FT-IR, SEM, EPR, NMR, ESCA, TGA, and UV-Vis reflectance spectroscopy. Other physicochemical properties were determined: surface area by the BET method, swelling studies with different solvents, and moisture content. The catalytic behavior of the prepared catalysts was tested for hydrogenation of cyclohexene as a model reaction. The influence on catalytic behavior of various parameters was studied: temperature, concentration of catalyst and substrate, quantity of solvent, and the use of various solvents. The recycling efficiency of the catalysts was also studied. A probable reaction mechanism is proposed.

Polymer bound Ru (III) complexes were synthesised by sequential attachment of chloromethyl group, 1,2-diaminopropane (DAP) as a ligand End metal chloride to styrene-divinyl benzene copolymer with 8% and 15% cross-linking. Synthesised catalysts were characterised by different techniques such as FTIR, reflectance UV-Vis spectroscopy, SEM, TGA, ESR, NMR and ESCA. Various physico chemical properties such as moisture content, bulk density, surface area and swelling behaviour in different solvents were also studied. The corresponding homogeneous complex [RuDAPCl(2)] Cl was also synthesised. Catalytic activity of these catalysts was tested for oxidation of cyclohexane by varying the temperature of the system as well as concentration of substrate and catalyst. Values of energy of activation and entropy of activation have been evaluated from the kinetic data. A probable reaction mechanism has been proposed.

Polycaprolactone-graft-maleic anhydride (PCL-g-MA) copolymer was prepared by grafting maleic anhydride onto PCL in a batch mixer and in an extruder using dicumyl peroxide as the initiator. The graft content was determined with the volumetric method by converting the anhydride functions to acid groups and then titrating with ethanolic potassium hydroxide. The grafted polymer was extracted with xylene to remove any unreacted monomer before the estimation step. The effect of temperature and the various concentrations of the initiator and monomer used for the grafting reaction were investigated. The presence of residual initiator in the reaction product was checked using thin-layer chromatography. Molecular weight determination was carried out for the pure and grafted polymer using gel permeation chromatography to determine if chain scission was present. Results indicate that maleic anhydride is grafted onto PCL using free radical initiators. The grafting reaction was confirmed by FTIR and NMR techniques. FTIR spectra showed absorption bands around 1785 and 1858 cm(-1). NMR spectra gave signals for methine proton at 3.47 ppm. For a given peroxide level, a higher temperature or residence (reaction) time gave higher percentage of grafted MA. There was an optimum temperature and initiator concentration after which the percentage of MA grafted on PCL decreased. The number-average molecular weight, tensile strength, and the percent elongation of PCL-g-MA were comparable to those of PCL before grafting. (C) 1997 John Wiley & Sons, Inc.

The interaction of the protein product of the H-ras oncogene with a series of nucleoside di- and triphosphates has been examined to investigate the tolerance of the active site to departures from the GTP or GDP structures. Nucleotides which bind relatively strongly could be used as competitors of GDP in a simple filter binding assay to give semiquantitave estimates of their affinities. For more weakly binding nucleotides or to obtain quantitative data, a transient kinetic method was used which was based on determination of the association and dissociation rate constants. The results obtained indicate that substantial modification of the sugar or phosphate structure is tolerated with little or moderate loss of affinity, but that large losses in affinity occur on modification of the base structure. In particular, replacing the guanine by an adenine residue leads to a dramatic loss of affinity. Thus, discrimination against ATP and ADP is very high (relative affinities of ATP and GTP 1:10(7)). This is due not only to loss of positive (stabilizing) interactions, but especially to the introduction of negative ones.