Surface Area Of Polymer Research Articles

Influence of electropolymerization conditions on the morphological and electrical properties of PEDOT film

ABSTRACT In this work the effects of electropolymerization conditions on the morphological properties and conductivity of poly(3,4-ethylenedioxythiophene) (PEDOT) film have been studied. PEDOT films were electrochemically synthesized in a one step process from acetonitrile solution containing 3,4-ethylenedioxythiophene (EDOT) and lithium perchlorate. Based on atomic force microscopy, scanning electron microscopy, cyclic voltammetry and impedance spectroscopy measurements, the morphological properties such as the of structure, double layer capacitance and thus the polymer surface area have been determined. It was shown that depending on the deposition conditions applied, different structures and film surface area could be obtained. Impedance measurements performed during deposition showed different resistance behavior and conductivity. The relationship between structure and conductivity of PEDOT film obtained under different deposition conditions has been discussed.

Carboxylated dithiafulvenes and tetrathiafulvalene vinylogues: synthesis, electronic properties, and complexation with zinc ions.

A class of carboxyl and carboxylate ester-substituted dithiafulvene (DTF) derivatives and tetrathiafulvalene vinylogues (TTFVs) has been synthesized and their electronic and electrochemical redox properties were characterized by UV–vis spectroscopic and cyclic voltammetric analyses. The carboxyl-TTFV was applied as a redox-active ligand to complex with Zn(II) ions, forming a stable Zn-TTFV coordination polymer. The structural, electrochemical, and thermal properties of the coordination polymer were investigated by infrared spectroscopy, cyclic voltammetry, powder X-ray diffraction, and differential scanning calorimetric analyses. Furthermore, the microscopic porosity and surface area of the Zn-TTFV coordination polymer were measured by nitrogen gas adsorption analysis, showing a BET surface of 148.2 m2 g−1 and an average pore diameter of 10.2 nm.

Polymeric Implants for the Delivery of Green Tea Polyphenols

Polymeric implants (millirods) have been tested for local delivery of chemotherapeutic agents in cancer treatment. Modeling of drug release profiles is critical as it may provide theoretical insights on rational implant design. In this study, a biodegradable poly (ε-caprolactone) (PCL) polymeric implant delivery system was tested to deliver green tea polyphenols (GTPs), both in vitro and in vivo. Factors including polymer compositions, supplements, drug loads, and surface area of implants were investigated. Our data showed that GTPs were released from PCL implants continuously for long durations, and drug load was the main determining factor of GTPs release. Furthermore, rates of in vitro release and in vivo release in the rat model followed similar kinetics for up to 16 months. A mathematical model was deduced and discussed. GTP implants have the potential to be used systemically and locally at the tumor site as an alternative strategy.

Enzymatic surface modification of polyacrylonitrile and its copolymers: Effects of polymer surface area and protein adsorption

Polyacrylonitrile (PAN) is a widely used polymer in the textile industry. PAN contains cyano groups on the surface due to which it possess low hydrophilicity and limits its application. Thus, there is a need to modify the functional groups on the surface of PAN for its industrial demand to improve moisture uptake, dyeability with ionic dyes, without affecting mechanical properties. A number of strategies such as chemical treatment, plasma treatment, enzymatic treatment etc. have been applied for the surface modification of polymer but enzymatic treatment are advantageous over plasma treatment and chemical treatment. In enzymatic treatment, reaction is limited to polymer surface only, and provides milder condition with less damage to polymer. In present study, it was found that enzyme system of Amycolatopsis sp.IITR215 was effective enzyme system for modification of surface nitrile groups of polyacrylonitrile. PAN powder was treated with the cell free extract of Amycolatopsis sp.IITR215 and it was found that the nitrile metabolizing enzymes of this strain were efficiently able to transform -CN to -COOH groups present on the surfaces of PAN powder. The formation of carboxyl group was quantified by ammonia released and dye binding assay. Further, confirmation of carboxyl group on polymer was done by FTIR and XPS. This study indicates that, specific adsorption of enzyme probably plays an important role in the enzymatic surface modification of polymer.

High-aspect-ratio conducting polymer microtube synthesis by light-activated electropolymerization on microstructured silicon

Synthesis of conducting polymer (CP) microtubes with characteristic size and period of a few micrometers, height from 5 to 50 micrometers, and aspect-ratio from 1 to 10, is demonstrated by light-activated electropolymerization on microstructured silicon for poly(3,4-ethylendioxythiophene), poly(3-methylthiophene) and polythiophene. Electrochemical characterization by cyclic voltammetry demonstrates that the entire surface of microstructured CPs is electroactive and can be effectively exploited in electrochemical processes without detaching CP films from the silicon substrate, thus directly and easily taking advantage of the increased polymer surface area. Such a successful merging of CP and silicon microstructuring technologies would break new grounds in different analytical/technological fields connected to microstructured CPs.

Effective removal of effluent organic matter (EfOM) from bio-treated coking wastewater by a recyclable aminated hyper-cross-linked polymer

Effluent organic matter (EfOM) is a complex matrix of organic substance mainly from bio-treated sewage effluent and is considered as the main constraint to further advanced treatment. Here a recyclable aminated hyper-cross-linked polymeric adsorbent (NDA-802) featured with aminated functional groups, large specific surface area, and sufficient micropore region was synthesized for effective removal of EfOM from the bio-treated coking wastewater (BTCW), and its removal characteristics was investigated. It was found that hydrophobic fraction was the main constituent (64.8% of DOC) in EfOM of BTCW, and the hydrophobic-neutral fraction had the highest SUVA level (7.06 L mg−1 m−1), which were significantly different from that in the domestic wastewater. Column adsorption experiments showed that NDA-802 exhibited much higher removal efficiency of EfOM than other polymeric adsorbents D-301, XAD-4, and XAD-7, and the efficiency could be readily sustained according to continuous 28-cycle batch adsorption–regeneration experiments. Moreover, dissolved organic matter (DOM) fractionation and excitation-emission matrix (EEM) fluorescence spectroscopy study indicated that NDA-802 showed attractive adsorption preference as well as high removal efficiency of hydrophobic and aromatic compounds. Possibly ascribed to the presence of functional aminated groups, relatively large specific surface area and micropore region of the unique polymer, NDA-802 possesses high and sustained efficiency for the removal of EfOM, and provides a potential alternative for the advanced treatment.

Thermally Enhancing the Surface Areas of Yamamoto-Derived Porous Organic Polymers

Thermal treatment of highly stable porous organic polymers based upon the Yamamoto polymerization of 2,2′,7,7′-tetrabromo-9,9′-spirobifluorene was done. The polymers are shown to be thermally and chemically stable. Upon thermal treatment the polymers are shown to have BET surface areas of ca. 2,000 m2/g and 2,500 m2/g respectively.

Preparation and Application Study on the Coalmine Wastewater Flocculant - PAM/OMMT

The modified polyacrylamide/organic montmorillonite (PAM/OMMT) flocculant was prepared by in-situ intercalation polymerization with acrylamide monomer and OMMT under CO2 inert atmosphere. The OMMT was synthesized with MMT and cetyl trimethyl ammonium bromide (CTAB) as intercalation agent by cationic exchange reaction. This flocculant was used to deal with coalmine wastewater. The effects of the flocculant dose on turbidity removal rate and settling time, the influent of pH value, temperature on turbidity removal rate and the comparison with PAM was studied. Experimental results show that PAM/OMMT is a kind of high efficient compound flocculating agent, the formation of hydrophobic micro in polymer surface area has strong adsorption ability and dispersing capability. Then MMT increased the quality of flocculant body so that flocculating settling time is shorter. Its turbidity removal rate can be as high as 95.5%. Compared with PAM, PAM/OMMT presents many advantages with higher turbidity removal rate, higher settling velocity, lower relatively sludge water content and lower sensitivity of temperature and pH in wastewater treatment process. Flocculant dosage in 10 to 20 mg/L is the optimal flocculation condition. Sludge water content treated by PAM/OMMT (63.4%) is relatively lower than PAM (80.2%).

Nanostructured Synthetic Carbons Obtained by Pyrolysis of Spherical Acrylonitrile/Divinylbenzene Copolymers

Novel carbon materials have been prepared by the carbonization of acrylonitrile (AN)/divinylbenzene (DVB) suspension porous copolymers having nominal crosslinking degrees in the range of 30–70% and obtained in the presence of various amounts of porogens. The carbons were obtained by pre-oxidation of AN/DVB copolymers at 250−350°C in air followed by pyrolysis at 850°C in an N2 atmosphere. Both processes were carried out in one furnace and the resulting material needed no further activation. Resulting materials were characterized by XPS and low temperature nitrogen adsorption/desorption. It was found that maximum pyrolysis yield was ca. 50% depending on the oxidation conditions but almost independent of the crosslinking degree of the polymers. Porous structure of the carbons was characterized for the presence of micropores and macropores, when obtained from highly crosslinked polymers or polymers oxidized at 350°C and meso- and macropores in all other cases. The latter pores are prevailing in the structure of carbons obtained from less porous AN/DVB resins. Specific surface area (BET) of polymer derived carbons can vary between 440 m2/g and 250 m2/g depending on the amount of porogen used in the synthesis of the AN/DVB polymeric precursors.

Effects of SiO2 and Al2O3 nanofillers on polyethylene properties

AbstractPolymers filled with inorganic nanoparticles have become interesting materials as dielectrics because of their improved mechanical and electrical properties compared with the unfilled polymers and with polymer microcomposites. These improvements are mainly due to the large surface area of nanoparticles and new polymer–nanofiller interface characteristics. In the present work, polyethylene nanocomposites with SiO2 and Al2O3 nanoparticles were prepared by melt mixing. Mechanical and electrical properties of these composites were determined and morphological aspects were revealed by scanning electron microscopy, wide‐angle X‐ray diffraction, and atomic force microscopy. The effect of nanostructure and the importance of nanofiller dispersion were analyzed in connection with mechanical and electrical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Development and In Vitro-In Vivo Evaluation of Polymeric Implants for Continuous Systemic Delivery of Curcumin

The introduction of curcumin into clinics is hindered by its low water solubility and poor bioavailability. To overcome these limitations, we developed curcumin implants using poly (ε-caprolactone) as the polymeric matrix. Implants were prepared by melt-extrusion method; in vitro drug release was optimized for effects of polymer composition, drug load, surface area and water-soluble additives. Implants were also tested under in vivo conditions for cumulative curcumin release, and liver concentration was correlated with its efficacy to modulate selected xenobiotic-metabolizing enzymes (CYP1A1 and GSTM). Drug release from implants followed biphasic release pattern with Higuchi kinetics and was proportional to the surface area of implants. Drug release increased proportionately from 2 to 10% (w/w) drug load, and incorporation of 10% (w/w) of water-soluble additives (F-68, PEG 8000 and cyclodextrin) did not significantly alter the drug release. In vivo drug release was found to be ~1.8 times higher than in vitro release. Curcumin was detected at 60 ± 20 ng/g in the liver after four days of implantation and was almost constant (8-15 ng/g) for up to 35 days. This time-dependent drop in curcumin level was found to be due to induction of CYP1A1 and GSTM (μ) enzymes which led to increased metabolism of curcumin. Our data showed that these implants were able to release curcumin for long duration and to modulate liver phase I and phase II enzymes, demonstrating curcumin's biological efficacy delivered via this delivery system.

A kinetic theory and benchmark predictions for polymer-dispersed, semi-flexible macromolecular rods or platelets

The goals of this paper are: to present a mean-field kinetic theory for the hydrodynamics of macromolecular high aspect ratio rods or platelets dispersed in a polymeric solvent; and, to apply the formalism to predict the impact due to a polymeric versus viscous solvent on the classical Onsager isotropic–nematic equilibrium phase diagram and on the monodomain response to imposed steady shear. The kinetic theory coupling between the nanoscale rods or platelets and the polymeric solvent is incorporated through a mean-field potential that reflects the enormous particle–polymer surface area and the particle–polymer interactions across this interfacial area. To determine predictions of this theory on the equilibrium and sheared monodomain phase diagrams, we present a reduction procedure which approximates the coupled Smoluchowski equations for the polymer chain probability distribution function (PDF) and the nano-particle orientational PDF in favor of a coupled system of equations for the rank 2 second-moment tensors for each PDF. The reduced model consists of an 11-dimensional dynamical system, which we solve using continuation software (AUTO) to predict the modified Onsager equilibrium phase diagram and the modified Doi–Hess shear phase diagram due to the physics of polymer–particle surface interactions.

Modifications in the morphology of poly(styrene-co-divinylbenzenes) induced by gamma-ray irradiation

Abstract The possibility of increasing the apparent specific surface area of macroreticular styrenic polymers crosslinked to different extent by gamma-ray irradiation was investigated. In order to overcome the protective action of benzene rings and simultaneously minimize the negative effect of chain scission competing with the desired additional crosslinking, it was necessary to optimize both the irradiation dose and the content of divinylbenzene. The best conditions for the radiation-induced post-crosslinking of polymers were assessed on the basis of the resultant apparent BET surface area. Useful morphological changes both in the dry and swollen state were possible to be generated.

Heavy metal ion adsorption onto polypyrrole-impregnated porous carbon

Polypyrrole-impregnated porous carbon was readily synthesized using vapor infiltration polymerization of pyrrole monomers. The results show that the functionalized polymer layer was successfully coated onto the pore surface of carbon without collapse of mesoporous structure. The modified porous carbon exhibited an improved complexation affinity for heavy metal ions such as mercury, lead, and silver ions due to the amine group of polypyrrole. The introduced polypyrrole layer could provide the surface modification to be applied for heavy metal ion adsorbents. Especially, polymer-impregnated porous carbon has an enhanced heavy metal ion uptake, which is 20 times higher than that of adsorbents with amine functional groups. Furthermore, the relationship between the coated polymer amount and surface area was also investigated in regard to adsorption capacity.

The effect of molecular imprinting on the pore size distribution of polymers

Molecular imprinting techniques are becoming an increasingly important domain of porous polymers generally, to achieve molecule specific recognition through morphology or stereochemistry of cavities. Imprinting is sought to increase both selectivity and sensitivity where the polymer may be present as particulate, membrane or thin film forms. Here, we detail mechanisms involved in the formation, stability and adsorption of binding sites, through the influence of polymerisation conditions and templates on the porosity of highly crosslinked molecularly imprinted polymers (MIPs). Environmental control represents an important area for porous polymers, here we focus on two template fungicides, iprodione and pyrimethanil, for ethylene glycol dimethacrylate (EGDMA) based polymers. In general, control of the pre-polymerisation interactions were able to vary the surface areas of polymers from 40–60 m2 g−1 to 300–436 m2 g−1 while pore sizes fell into distributions (a) close to the micropore region at ∼3.8 nm, (b) in the 10 to 20 nm mesopore region and (c) in the 20 to 50 nm mesopore region. The importance of intermolecular interactions and aggregation in the pre-polymerisation solution to the Brunauer, Emmett, Teller (BET) surface areas and pore size distribution of final polymers has been demonstrated by systematic variation of chemical functionality. These effects confirm recent molecular dynamic simulation studies of MIP formation and cavity stability.

Biodegradation of biphenyl in a solid–liquid two-phase partitioning bioreactor

Biphenyl was successfully degraded by Burkholderia xenovorans LB400, initially described as Pseudomonas sp. LB400, in a solid–liquid two-phase partitioning bioreactor (TPPB). Solid–liquid TPPBs are comprised of an aqueous, cell containing phase, and a solid polymeric phase that partitions toxic and/or poorly soluble substrates (in this case biphenyl) based on maintaining a thermodynamic equilibrium. The employed polymer was Hytrel™, a thermoplastic polyester elastomer. The surface area available for mass transfer of biphenyl was limiting and resulted in mass transfer limited growth, as demonstrated experimentally by employing two different geometric shapes (cylinders with different aspect ratios) of the polymer phase with different specific surface area, while keeping all other parameters constant. The linear microbial growth rates were substantially higher when more polymer surface area was provided. The mass transfer coefficient of biphenyl from Hytrel™ to water was measured under experimental conditions, which allowed predicting the release rate based on the biphenyl concentration gradient. The partitioning behaviour of biphenyl between Hytrel™ and culture medium was measured as well, which allowed the development of a simple mechanistic model describing microbial growth based on known microbial properties in combination with substrate delivery from the solid polymer phase. The model was capable of describing the experimental data well and can be used to predict degradation rates for other geometric shapes of a solid delivery phase such as sheets or rods, which might be of operational advantage in various applications of TPPBs to the controlled uptake and release of other recalcitrant molecules.

Surfactant assisted polymerization of tetrafluoroethylene in supercritical carbon dioxide with a pilot scale batch reactor

Chain-free radical polymerization of tetrafluoroethylene (TFE) was carried out in supercritical carbon dioxide (scCO2), at 50 °C and 121–133 bar, with tertiary-amyl-per-pivalate as a free radical initiator, using a 5-L pilot scale batch reactor. Experiments were carried out both in the absence and in the presence of perfluoropolyether (PFPE) carboxylate surfactants. Stabilizers were employed under the free acid form and as sodium and calcium salts. An expanded fibrillated poly(TFE) was obtained in all experiments. In the case of surfactant-free polymerizations, the product was mainly constituted by irregular shape macroparticles having size in the range 200–500 μm. Quite interestingly, when the free acid surfactant was used, a clear acceleration of the polymerization rate was observed and smaller polymer particles with more regular quasi-spherical morphology were obtained. Melt fusion crystallinity of as-polymerized poly(TFE) seemed not substantially affected by the presence of the stabilizers and was rather high (80–86%) suggesting that polymerization mainly occurs at polymer particle surface. All these elements suggest that FLUOROLINK® 7004H PFPE carboxylic acid decreases coagulation of primary polymer particles leading to an increase in polymer surface area. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 257–266, 2008

Specifics of change in the surface area of amorphous poly(vinyl chloride) during its inelastic deformation

A direct microscopic observation procedure was used to study the processes of deformation and shrinkage of poly(vinyl chloride) above its glass transition temperature. Prior to stretching or contraction of the polymer, its surface was decorated with a thin (10–15 nm) metal layer. As a result of subsequent deformation (shrinkage), the decoration underwent structural rearrangements, which were detected by means of direct microscopic examination. These rearrangements contain information on the mechanism of deformation of the polymer substrate. In particular, the procedure makes it possible to characterize the process of development of the interface in the polymer during deformation and the reverse process of interface contraction during the shrinkage of the material. It was found that, in the case of an increase in the interfacial area, its growth is accompanied by a growth in imperfection of the polymer surface layer. These defects can concentrate mechanical stress, thus strongly affecting the fragmentation of the metal decoration on the polymer surface. It was shown that the surface defects could be eliminated by annealing of the polymer above its glass transition temperature. The introduction of a plasticizer that decreases the glass transition temperature below the deformation temperature likewise prevents the development of these defects during an increase in the surface area of the polymer in the process of its inelastic deformation.

The potential of organic polymer-based hydrogen storage materials

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.

Macroporous condensed poly(tetrafluoroethylene). I. In vivo inflammatory response and healing characteristics

This study was designed to determine whether the novel spatial geometry of macroporous condensed poly(tetrafluoroethylene) (cPTFE) favorably affects the in vivo repair process. Specifically, the macroporous surface geometry and the reduced material thickness contribute to better healing characteristics. For this purpose, three other materials used for abdominal wall repair were selected, expanded poly(tetrafluoroethylene) (ePTFE), low-weight poly(propylene) (lwPP), and high-weight poly(propylene) (hwPP). Samples of each material (1 x 2 cm, n = 4) were implanted subcutaneously in rats for 7, 28, or 56 days. After sacrificing the animals, at each time point, the tissue implant sites were subjected to morphometric analysis and evaluation of inflammatory and wound-healing tissue characteristics. Although the fibrous capsule thickness did not significantly vary among the four materials (p > 0.05), cPTFE consistently led to the most mature fibrous capsule. However, ePTFE showed the greatest tissue-material integration. Both PP materials presented various levels of tissue integration, but they were characterized by significant early inflammation and increased foreign body reaction around the mesh openings, especially for hwPP. In contrast, cPTFE did not induce extensive inflammation or elevated foreign body reaction around its mesh openings. We conclude that cPTFE combines the inherent PTFE biocompatibility with low polymer surface area (large mesh openings, reduced material thickness) leading to a better inflammatory and wound healing response compared to available materials used in abdominal wall reconstruction.