Showing papers in "Polymer Bulletin in 2008"

Synthesis and characterization of novel polyurethanes based on 4,4’-{1,4-phenylenebis[methylylidenenitrilo]}diphenol

Abstract: A series of novel segmented polyurethanes (PUs) containing imine units in the main chain were prepared by polyaddition reaction of various diisocyanates like 4,4’-diphenyl-methane diisocyanate, tolylene 2,4-diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate with 4,4’-{1,4-phenylenebis[methylylidenenitrilo]} diphenol based diol. The structure of the diol and segmented PUs were determined by Fourier transform infrared, ultraviolet-visible spectrometry and fluoroscence spectroscopy. PUs were soluble is polar aprotic solvents. Thermal properties were done by using differential scanning calorimetry (DSC) and thermogravimetric analysis. DSC data display the PUs having multiple endotherm peaks. MDI based PU show the more thermal stable compared to other PUs.

Amide II and Amide III Bands in Polyurethane Model Soft and Hard Segments

Abstract: Amide II and III bands in polyurethane (PU) have been often taken as two of the characteristic bands indicating the formation of urethane structure. Since these bands, however, are very complicated, further studies, especially the effect of H-bonds on amide II and III bands in PU, were seldom reported. In the present work, we report a new finding on the correlation of amide II and amide III bands with different H-bonding interactions in PU model soft and hard segments. The PU model soft segment (PUMSS) is based on poly(tetrahydrofuran) (PTHF) and diphenylmethane-4,4’-diisocyanate (MDI) whereas the PU model hard segment (PUMHS) is based on MDI and n-butanol (BO). FTIR results show that the H-bond is formed by NH...carbonyl (C=O) (Type I) in PUMHS while the H-bond is mainly formed by NH...ether(O) (Type II) in PUMSS; the amide II band, however, is more related to the Type II H-bonding interaction while amide III band is more dependent upon the Type I H-bonding interaction.

Mechanical Properties of Biodegradable Polyhydroxyalkanoates/Single Wall Carbon Nanotube Nanocomposite Films

Abstract: The nanocomposite films of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyoctanoate) (PHO) with single wall carbon nanotubes (SWCNTs), were prepared. The Optical microscopy showed that the crystalline size substantially decreased for PHB/SWCNTs nanocomposites with a 1 % weight fraction of SWCNTs relative to PHB (PHB/(1%)SWCNTs), indicating the effective nucleation of PHB crystallization by SWCNTs. Mechanical properties of the nanocomposite films were measured by nanoindentation. Both polymer nanocomposite films showed an increase in hardness (H) and Young’s modulus (E), with SWCNTs concentration. The PHB/SWCNTs nanocomposite films are found to be more brittle than neat PHB films.

Crystal morphology of rapidly cooled isotactic polypropylene: A comparative study by TEM and AFM

Abstract: The morphology of crystals, formed at the surface and in the bulk of rapidly cooled and subsequently at elevated temperature annealed films of isotactic polypropylene (iPP) was analyzed by transmission electron microscopy (TEM) and by atomic force microscopy (AFM). Both techniques show a lamellar crystals after melt-crystallization at 12 K s-1, and a nodules after melt-crystallization at 750 K s-1. The morphology of crystals is independent on the position of the investigated film of thickness of 100 μm, suggesting (a) that the crystallization at the surface is not affected by the use of a glass substrate for preparation, and (b) that the temperature-gradient during primary crystallization is sufficiently small to ensure identical structure at the surface and in the bulk. AFM suggests a larger size of crystals than TEM, in particular if the absolute size of objects approaches the dimensions of the used tip of the AFM. If the absolute size of objects is distinctly larger, then AFM and TEM yield nearly identical dimensional information.

Properties of hydrophilic chitosan network membranes by introducing binary crosslink agents

Abstract: In this investigation chitosan (CS) was crosslinked using mixtures of sulfosuccinic acid (SSA) and glutaraldehyde (GA) as the binary crosslinking agents to form hydrophilic chitosan network membranes. GA and SSA improve the tensile strength and contribute to hydrophilicity of the membranes, respectively. The membranes prepared by varying the crosslinking agent ratios are also characterized using FT-IR, X-ray diffraction, and tensile testing, and their swelling ratio and thermal properties were measured. Experimental results reveal that the contact angle of the membrane decreases from 84.54° to 69.83° and the maximum stress rises from 39.62 MPa to 133.66 MPa as the increase of the binary crosslinking agent content. These resultant membranes not only maintain its hydrophilicity and but also enhance the mechanical strength.

Synthesis and Characterization of Injectable Photocrosslinking Poly (ethylene glycol) Diacrylate based Hydrogels

Abstract: The poly (ethylene glycol) diacrylate (PEGDA)-based hydrogels were prepared by UV radiation under nitrogen, using PEGDA and 2-hydroxyethyl methacrylate (HEMA) as precursors. The PEGDA and HEMA precursors were respectively added into distilled water at a predetermined feed ratio. 2-Hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure2959) was used as a photoinitiator. The PEGDA-based hydrogels were characterized by FT-IR spectra, interior morphology, equilibrium swelling ratio, and Dynamic contact angle (DCA). The results showed: (1) -C=C- bonds of PEGDA and HEMA disappeared after photocrosslinking, which indicated hydrogel formation by consuming -C=C- bonds; (2) swelling ratio of the hydrogels were greatly influenced by the additive precursor ratios and microporous net; (3) with HEMA content increasing in PEGDA-based hydrogels, equilibrium water content (EWC) increased and the contact angle decreased, which resulted from the strong H-bonding interactions of HEMA between the polymer and water.

Effect of Morphology on the Biodegradation of Thermoplastic Starch in LDPE/TPS Blends

Abstract: In this study, thermoplastic starch (TPS) was mixed with low density polyethylene with different melt flow indexes in a one-step extrusion process to produce LDPE/TPS blends varied from 32% to 62% by weight of TPS. The influence of starch content and LDPE viscosity on morphology, biodegradation and tensile properties of LDPE/TPS blends were evaluated. Starch continuity and biodegradability were studied by hydrolytic, enzymatic and bacterial degradation. The LDPE viscosity had a considerable effect on the morphology and the connectivity of the starch particles. Evaluation of hydrolytic extraction showed that blends having TPS content above 50 wt% possessed a full connectivity. Studies of biodegradation indicated that the bacterial attack on starch resulted in weight loss of TPS of 92%, 39% and 22%, for PE1/TPS having 62% and 32% TPS, and PE2/TPS (31% TPS), respectively. Comparatively, the weight loss was more significant at 100%, 66% and 31% by hydrolytic extraction. Differences between these two techniques were discussed in terms of the accessibility of starch domains to microorganisms. Tensile properties (eb and E) decreased with increasing exposure time to activated sludge. Changes in tensile properties were highly dependent on the biodegradation rate. PE1/TPS blends having 32% starch remained ductile after 45 days of exposure to bacterial attack.

Synergic Effect of Acrylate Liquid Rubber and Bisphenol A on Toughness of Epoxy Resins

Abstract: The synergic effect of acrylate liquid rubber with pendant epoxy group and bisphenol A on the toughness of epoxy resins was presented in this paper. The addition of bisphenol A enhances the impact strength and elongation at break of epoxy resin and actually increases the ductibility of epoxy resin matrix. Much higher toughness efficiency can be achieved for the ALR modified epoxy resins by the incorporation of bisphenol A at the same time. The synergic promotion effect of acrylate liquid rubber and bisphenol A on the toughness efficiency of epoxy resins is attributed to the two-phase morphology and high ductibility of matrix, and the resultant large stress white zones and high shear yielding during the fracture process.

Preparation and characterization of poly(methyl methacrylate) nanocomposites containing octavinyl polyhedral oligomeric silsesquioxane

Abstract: A series of poly(methyl methacrylate) (PMMA) containing octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) nanocomposites were synthesized by solution polymerization. The products were characterized by FTIR, 1H NMR, GPC, TEM, DSC and TGA. The actual contents of OV-POSS in the obtained products and the reaction degree of the vinyl groups in the POSS were calculated on the basis of FTIR, TGA and 1H NMR data respectively. The DSC and TGA results indicate that the incorporation of POSS molecules could improve the thermal properties of PMMA nanocomposites significantly. The glass transition temperature (Tg) and thermal decomposition temperature (Tdec1) of the nanocomposite with 12.27 wt % of OV-POSS were increased by 23 °C and 93 °C correspondingly. In our experiment, the improved thermal properties were largely attributed to the nanoreinforcement effect of POSS cages and the formation of star-shaped structures with cubic silsesquioxane core.

The Effect of MMT/Modified MMT on the Structure and Performance of the Superabsorbent Composite

Abstract: A series of superabsorbent composites containing Montmorillonite (MMT), modified- Montmorillonite (OMMT) and sodium acrylate were synthesized by free-radical polymerization in aqueous solution. The structure of composites was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the results showed that the polymer chains were grafted onto the edge and the surface of MMT or OMMT. At the same time, the equilibrium swelling ratio of the composites was investigated as a function of the clay content and the results showed that the equilibrium swelling ratio of composites was improved by the introduction of clay. The maximum equilibrium swelling ratio of composite in distilled water and 0.9 wt% sodium chloride solutions were up to 2450 g/g and 118 g/g, respectively. Finally, the result of thermogravimetric analysis (TGA) suggested that the introduction of clay and modified clay could improve the thermal stability of superabsorbent composites.

Temperature and pH sensitive hydrogels composed of chitosan and poly(ethylene glycol)

Abstract: Chitosan based semi-interpenetrating polymer network (semi-IPN) hydrogels containing different amounts of poly(ethylene glycol) (PEG) were prepared. The crosslinking of the hydrogels was achieved by using a naturally occurring nontoxic cross-linking agent genipin. The swelling behaviour of these hydrogels was studied by immersing the films in deionized water at 25, 37 and 45 °C and in media of different pHs at 37 °C. Swelling was found to be dependent on temperature, pH of the medium and the amount of PEG in the gel. States of water in the hydrogels swollen in deionized water at 37 °C were determined using Differential Scanning Calorimetry (DSC). The equilibrium water content and the amount of freezing water in the swollen hydrogels increased with the increase in PEG concentration in the gels.

Effect of cooling rate on melt-crystallization of random propylene-ethylene and propylene-1-butene copolymers

Abstract: The effect of variation of the rate of cooling on melt-crystallization of random copolymers of isotactic polypropylene with low amount of either ethylene or 1-butene is evaluated using X-ray techniques, atomic force microscopy, and calorimetry. Slow non-isothermal melt-crystallization mainly results in formation of monoclinic α-crystals of lamellar geometry. The presence of comonomers leads to a decrease of the degree of crystallinity, and of the thickness of lamellae. These changes are proportional to the concentration of co-units, and are more distinct in propylene-ethylene copolymers. Rapid cooling of propylene-1-butene copolymers leads to formation of non-lamellar mesomorphic domains, independent of the concentration of co-units within the investigated range of concentrations. In quenched propylene-ethylene copolymers, in contrast, the formation of mesomorphic structure partially is replaced by formation of monoclinic α-crystals of still non-lamellar geometry.

Characterization of ionic conduction and electrode polarization relaxation processes in ethylene glycol oligomers

Abstract: The complex relative dielectric function, dielectric loss tangent, electric modulus, alternating current electrical conductivity and impedance spectra of ethylene glycol oligomers (EGOs) i.e., ethylene glycol, diethylene glycol and poly(ethylene glycol)s of average molecular weight 200, 300, 400 and 600 g mol-1 have been investigated in the frequency range 20 Hz to 1 MHz at 25 °C. These EGOs show the low frequency dielectric/electrical dispersion due to electrode polarization and ionic conduction effects. The ‘master curves representation’ of the real and imaginary parts of the intensive dielectric/electrical functions were used to evaluate the relaxation times corresponding to these effects processes. The comparative dielectric study of EGOs confirms that the values of low frequency relaxation times and direct current electrical conductivity are influenced by the chain flexibility and its random coiling.

Biodegradable Composites: Ramie Fibre Reinforced PLLA-PCL Composite Prepared by in Situ Polymerization Process

Abstract: Thermoplastic biodegradable composites based on ramie fibre (RF) and a poly(l-lactic acid)-poly(e-caprolactone) (PLLA-PCL) matrix was manufactured using the in situ polymerization method. In order to improve the compatibility and strengthen the interface in natural fibre composite materials, the RF was firstly treated by coupling agents. Then the RF reinforced thermoplastic PLLA-PCL composite was prepared by in situ polymerization of PLLA oligomer with NCO-terminated PCL prepolymer. The effect of fibre length and fibre content on tensile strength and impact strength of this natural-fibre-reinforced biodegradable composite (PLLA-PCL/RF) was discussed, including the influence of the use of silane coupling agent (KH550) for improved interfacial adhesion. The results showed that the tensile strength and impact strength of PLLA-PCL/RF were highest when the RF length was 5-6mm, RF content was 45% and with KH550 as surface treatment agent of RF.

Efficient allylation of cellulose in dimethyl sulfoxide/tetrabutylammonium fluoride trihydrate

Abstract: The cellulose solvent dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF) was successfully applied as reaction medium for the synthesis of allyl cellulose by conversion of the polymer with allyl chloride in the presence of solid NaOH. Samples with degree of substitution from 0.50 to 2.98 were accessible by varying the molar ratio anhydroglucose unit:allyl chloride:NaOH and reaction time. DMSO/TBAF was found to be an efficient reaction medium for the preparation of highly functionalized samples from spruce sulfite pulp with degree of polymerization of about 500 even in a scale of 50 g. The allyl cellulose samples were characterized by means of FTIR- and NMR spectroscopy. Size exclusion chromatography revealed negligible polymer degradation during synthesis and purification of the samples.

Preparation of Mono-Dispersed Polyurea-Urea Formaldehyde Double Layered Microcapsules

Abstract: A new method to prepare a kind of double layered microcapsules was developed. Polyurea (PU) microcapsules were firstly fabricated by interfacial polymerization as inner layer, on which urea-formaldehyde (UF) resin was coated to form a protective outer layer by in-situ polymerization. Environmental scanning electron microscope, optical image analyzer, Fourier transform infrared spectrophotometer and thermo gravimetric analysis were employed to investigate their characteristics for the morphologies, particle size, materials structures and thermal properties. The prepared double layered PU-UF microcapsules are mono-dispersed with ultra-thick capsule wall and improved thermal stability.

Dielectric properties of polymer/ceramic composites based on thermosetting polymers

Abstract: A series of thermosetting polymer/ceramic composites were prepared Three kinds of thermosetting polymers, ie cyanate resin, bismaleimide resin, and epoxy resin, were used as matrixes, and BaTiO3 particles were as fillers The dielectric properties of these composites were investigated Experimental data of the dielectric constants were fitted to several theoretical equations in order to obtain the best-fitting equations of the dielectric constants of these composites The result indicates that the dielectric constants of composites all increase with the increase of BaTiO3 content Using bismaleimide resin and epoxy resin as matrixes, the dielectric losses both increase obviously as the amount of BaTiO3 particles is increased, but the dielectric loss of cyanate/BaTiO3 composite decreases With the increase of the frequency, the variation ranges of the dielectric constant and dielectric loss of cyanate/BaTiO3 composite are both the smallest The predications of the effective dielectric constants by Lichterecker mixing rule are in good agreement with experiment data

Synthesis and photochromic property of nanoparticles with spiropyran moieties via one-step miniemulsion polymerization

Abstract: Photochromic nanoparticles with spiropyran moieties were prepared by a facile one-step miniemulsion polymerization. The nanoparticle dispersion was obtained by mixing the monomers, spiropyran-containing molecules and hydrophobe, dispersing them into an aqueous solution with surfactant, subjecting the dispersion to ultrasonification and polymerizing the monomers by using a water soluble initiator. The shape and size of the nanoparticles was determined with the atomic force microscope (AFM) and dynamic light scattering (DLS), and the determined average diameter of the nanoparticles ranges from 30 nm to 60 nm. The absorption and fluorescence spectra for the nanoparticles dispersions reveal that the spiropyran molecules were successfully incorporated in the polymer nanoparticles. Moreover, the nanoparticle dispersions were found to exhibit enhanced photo-reversibility, photo-stability and relatively fast photo-responsive property compare to the same species in aqueous solution.

Saline solution absorbency and structure study of poly (AA-AM) water superabsorbent by inverse microemulsion polymerization

Abstract: A series of novel copolymer superabsorbents based on acrylamide (AM), acrylic acid(AA) were prepared by inverse microemulsion copolymerization using ammonium persulfate (APS) as the initiator and N,N-methylenebisacrylamide (MBA) as the crosslinking agent and OP-10 and SDS as complex surfactants. The synthetic variables (amount of crosslinking agent and initiator, water/oil ratio, monomer/surfactant ratio and AA/ Am ratio) and their effects on the absorbencies of the synthesized superabsorbents were investigated. The experimental results of superabsorbent polymers (SAPs) showed the maximum saline solution absorbency of 130 g/g within 75 min, and the saline solution absorbency of 111 g/g within 30 min. FTIR indicated the structure of the acrylic acid and acrylamide copolymer. SEM indicated that the particles prepared with higher crosslinker content (0.03%) showed smaller pore sizes and less porous structures compared with those with less crosslinker content (0.01%) and the number of the micropores largely decreased with the water/oil ratio increasing from 8% to 14%.

New Interpenetrating Polymer Networks of N-isopropylacrylamide/ N-acryloxysuccinimide: Synthesis and Characterization

Abstract: Interpenetrating polymer networks (IPNs) based on poly (N-isopropylacrylamide), PNIPAAm, and poly (N-acryloxysuccinimide), PNAS, were prepared by a sequential method; the PNIPAAm which was polymerized and crosslinked by gamma irradiation, was swelled in a solution of PNAS/polylysine, which function as crosslinking agent for this monomer and as anchoring element of vesicles. The thermosensitivity properties (limit swelling time, lower critical solution temperature (LCST) and water retention), chemical composition (FTIR and elemental analysis), thermal properties (DSC and TGA) and morphology (SEM) were studied to characterize the IPNs.

Morphology development and non isothermal crystallization behaviour of drawn blends and microfibrillar composites from PP and PET

Abstract: Microfibrillar composites (MFC) were prepared from the blends of polypropylene (PP) and poly (ethylene terephthalate) (PET) at a fixed weight ratio of 85/15. The blending of the mixture was carried out in a single screw extruder, followed by continuous drawing at a stretch (draw) ratio 5. The stretched blends were converted into MFC by injection moulding. Scanning electron microscopy (SEM) studies showed that the extruded blends were isotropic, but both phases possessed highly oriented fibrils in the stretched blends, which were generated insitu during drawing. The PET fibrils were found to be randomly distributed in the PP matrix after injection moulding. The non isothermal crystallization behaviour of the as extruded blend, stretched blend and MFC was compared. The analysis of the crystallization temperature and time characteristics revealed that the PET fibrils in the stretched blend had a greater nucleating effect for the crystallization of PP than the spherical PET particles in the as extruded blend and short PET fibrils in the MFC.

Effect of the polymer matrix on the thermal behaviour of a furan-maleimide type adduct in the molten state

Abstract: The effect of three different polymer matrices on the stability of the exo-adduct formed from N-Phenylmaleimide (PM) and furfuryl alcohol (FAl) toward retro Diels-Alder reaction was studied. First, a stereospecific synthesis of the exo-adduct was carried out at the condensed state and for a best understanding, its thermal properties was reported. The temperature of the rDA reaction of the exo-adduct in polyolefins (a low density polyethylene and a random copolymer of ethylene and glycidyl methacrylate) was found similar to the pure exo-adduct rDA reaction temperature. In a poly(vinylacetate)-g-polycaprolactone matrix this temperature was distinctly lower. In this last matrix, the reversibility of the rDA reaction was proved by the formation of the endo-adduct FAlPM during cooling.

Radiation Synthesis of Polyampholytic and Reversible pH-Responsive Hydrogel and Its Application as Drug Delivery System

Abstract: Graft copolymerization of acrylic acid (AA) and acrylamide (AAm) onto chitosan (CS) was carried out using gamma irradiation. Their swelling behavior was investigated. The hydrogels before and after alkaline hydrolysis were confirmed by FTIR spectroscopic studies. The hydrogels show ampholytic and reversible pH-responsiveness characteristics. The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. The ability of the prepared copolymer to be used as gastric antibiotic delivery system was estimated using amoxicillin trihydrate as a model drug. Release of amoxicillin trihydrate from these investigated hydrogels was studied. For non-ionized drugs, such as amoxicilin trihydrate, the electrostatic polymer/ polymer interactions take place between the cationic groups from CS and the anionic ones from PAA resulting in entrapping the drug into the mesh space of the hydrogel. The non-ionized amoxicillin release was controlled by the swelling/eroding ratio.

Synthesis and characterization of new aromatic polyesters and poly(ester-imide)s containing phosphorous cyclic bulky groups

Abstract: New phosphorous-containing polyesters were prepared by polycondensation of 2-(6-oxido-6H-dibenz oxaphosphorin-6-yl)-1,4-naphthalene diol, 1, with different aromatic dicarboxylic acids using a SOCl2/pyridine condensing agent. Two poly(ester-imide)s were prepared by polycondensation in solution at high temperature of the same aromatic bisphenol 1, with diacid chlorides containing preformed imide rings. The most of the polymers were easily soluble in polar organic solvents such as N-methylpyrrolidone, N,N-dimethylformamide and chloroform. They showed high thermal stability, the decomposition temperature being in the range of 330-442 °C and glass transition in the temperature range of 193-226 °C. One of these polymers exhibited thermotropic liquid crystalline behavior. Due to the presence of phosphorus the polymers gave high char yield in termogravimetric analysis, hence good flame retardant properties.

In-situ nanofabrication via electrohydrodynamic jetting of countercharged nozzles

Abstract: Methods to in-situ construct nanostructures are the key tools of nanotechnology. Herein, for the enforced combination of two nanomaterials, an in-situ combination technique, ‘electrohydrodynamic jetting of countercharged nozzles (EJC)’, was explored. EJC used an attraction force between negative and positive surface charges generated by electrohydrodynamic spinning and spraying. The obtained nanostructures were dependent on the types of materials and jetting conditions. Poly(methyl methacrylate) nano- or micro-fibers were uniformly combined with polystyrene nano- or microparticles. When lipoic acid (an antioxidant drug) was used instead of polystyrene, composite structures of fibers and surface nanodots resulted. The method could also enforce gold nanoparticles stick onto the surface of fibers. EJC is an efficient technique to fabricate composite nanostructures using materials with a wide range of properties.

Synthesis and Flocculation Characteristics of Konjac Glucomannan-g-Polyacrylamide

Abstract: A flocculant was synthesized by graft copolymerization of acrylamide onto konjac glucommannan using potassium permanganate/thiourea redox system as an initiator. The effects of the concentration of monomer, initiator, H2SO4, as well as reaction time and temperature on the graft copolymerization were studied. The optimum synthesis conditions were: the concentrations of acrylamide, KMnO4 and H2SO4 were 2.0 mol.L-1, 20 mmol.L-1and 3.0 mmol.L-1, respectively, and the molar ratio of KMnO4/thiourea was 2/1 at 60 °C for 3 h. Compared with polyacrylamide, the graft copolymer had better flocculating effect on the kaolin suspensions, as well as the local Qinjiang river water and the machine water in paper making.

Cationic Graft Polymerization onto Silica Nanoparticle Surface in a Solvent-Free Dry-System

Abstract: For the purpose of the prevention of the environmental pollution and the simplification of reaction process, the scale-up synthesis of polymer-grafted silica nanoparticle by surface initiated cationic ring-opening graft polymerization of 2-methyl-2-oxazoline (MeOZO) in a solvent-free dry-system was investigated. The introduction of iodopropyl groups onto the silica surface as initiating group was carried out by the reaction of silanol groups with 3-iodopropyl- trimethoxysilane in a solvent-free dry-system. The graft polymerization of MeOZO onto silica nanoparticle surface in a solvent-free dry-system was initiated by spraying the monomer onto the surface having iodopropyl groups and the polymerization was conducted in powder fluid system under nitrogen. After the polymerization, unreacted MeOZO was readily removed under high vacuum. It was found that the cationic ring-opening polymerization of MeOZO was successfully initiated in the solvent-free dry-system to give polyMeOZO-grafted silica nanoparticles. The maximum grafting of polyMeOZO obtained from the polymerization initiated by iodopropyl groups on the surface reached 47.7 %. The percentage of grafting and grafting efficiency during the cationic ring-opening graft polymerization in the solvent-free dry-system were considerably larger than those in solution system. This suggests that chain transfer reaction from surface growing cation to monomer was effectively inhibited in the solvent-free dry-system.

Determination of Flory interaction parameters between polyimide and organic solvents by HSP theory and IGC

Abstract: Flory-Huggins interaction parameter χ12 is an important parameter used for characterizing the interaction intensity between polymer and solvent. In this work, two methods were used to calculate the χ12 values of a polyimide (HQDPA-DMMDA) and twelve organic solvents. One method was inverse gas chromatography (IGC) technique, another was Hansen Solubility Parameters (HSP) theory. For the IGC experiment, χ12 was measured with an extrapolation method for the carrier gas when the temperature was changed from 50circC to 80°C. For the HSP approach, the Beerbower group contribution method was used to calculate the HSP values of the polyimide. It was found that the χ12 values of the polyimide and the organic solvents calculated from the two methods were similar. Consequently, the Beerbower group contribution method can be used to calculate HSP, and the HSP can be used to rapidly estimate the Flory–Huggins interaction parameter χ12.

Semi-IPN hydrogels based on Poly(vinyl alcohol) for controlled release studies of chemotherapeutic agent and their Swelling characteristics

Abstract: Poly (vinyl alcohol)/poly(acryl amide-co-acrylamidoglycolic acid) (PVA/Poly(Am-co-AGA) based pH sensitive semi interpenetrating (semi-IPN) hydrogels were prepared by free radical polymerization in aqueous solution using N, N-methelene-bis-acryl amide (MBA) as a crosslinker. Different hydrogels with different compositions of AGA and MBA were prepared and characterized by Fourier transform infrared spectroscopy. The developed hydrogels were used for controlled release of 5-fluorouracil (5-FU). The drug entrapment efficiency up to 55% was achieved. The 5-FU loaded gels were characterized by X- ray diffraction and differential scanning calorimetric techniques, to understand the nature of drug in the polymeric matrix. The release of 5-FU through the semi-IPN was completed with in ∼12 h. Swelling studies performed in water have been analyzed with the help of an empirical equation to investigate the diffusion mechanism.

Structure-property relationships of hydroxy-terminated polyether based polyurethane network

Abstract: In the present work, the effect of crosslink density on HTPE networks has been studied in swelling, thermal and mechanical properties. The solubility parameters of HTPE PUs were obtained by swelling test. They depended on the molar ratio of N-100 and IPDI and equivalent ratio. It was decreased as the content of N-100 was lowered. The thermal characteristics of the network polymer were examined by DSC results. Thermal behavior of HTPE PU network depended on by dangling chain and chain folding in the series using N-100, with NCO/OH ratio as 1.0, 0.8, 0.6. However, when we performed experiment with IPDI and N-100, with NCO/OH ratio as 1.0, the thermal properties depended on Mc. Moreover, using IPDI with N-100 showed enhanced volume specific energy than using only N-100 in tensile test due to strain induced crystallization.