APS Content Research Articles

Preparation and properties of Polyvinyl alcohol (PVA) composite films by incorporation of γ- aminopropyltriethoxysilane(APTES) modified mesoporous silica (SBA-15) as filler

In this work, a mesoporous silica (SBA-15) was synthesized using a hydrothermal method and the surface of the SBA-15 was further modified by utilizing the organosilane compound γ- aminopropyltriethoxysilane(APTES); FT-IR testing confirmed the successful grafting of these organic groups onto the surface of the SBA-15, the result being the AP-S. Composite films were subsequently prepared through a casting method, with SBA-15 and AP-S serving as the inorganic filler particles, and PVA acting as the matrix material. These films were characterized by tensile texts, dynamic mechanical analysis, scanning electron microscopy, and dielectric measurements. The results showed that the tensile modulus, loss modulus and dielectric properties of the modified AP-S/PVA composite films were improved compared with those of SBA-15/PVA, with the tensile strength being the largest at 145.25 MPa when the AP-S content was 2%. This result combined with the SEM analysis, shows that the incorporation of SBA-15 modified by APTES into PVA films can effectively improve the dispersion of SBA-15 in the PVA films, which can also explain the performance enhancement.

Polystyrene: A Self-Dispersing, Ultralow Loading Additive for Improving the Breakdown Strength of Polypropylene for High Voltage Power Cable Applications

Voltage stabilizers (VSs) with benzene derivatives have received great interest as high-performance additives for improving the electrical durability of polypropylene (PP)-based insulation materials for high voltage (HV) power cable applications. In this work, atactic polystyrene (aPS) was first used as a thermoplastic VS (TVS) to efficiently dope the benzene units into isotactic PP (iPP). The aPS TVS was incorporated in the iPP matrix through melt-mixing, and the domain size of immiscible aPS decreased with the decrease of aPS content. The smaller amount of aPS doping increased the direct current (DC) breakdown strength (BDS) of iPP, even at ultralow loading levels below 0.01 phr. The enhancement ratio of the BDS value of iPP with 0.001 phr of aPS was higher compared to the results obtained for other types of additives reported in the previous literature.

Oxidation-Responsive Emulsions Stabilized with Poly(Vinyl Pyrrolidone-co-allyl Phenyl Sulfide).

Oxidation-responsive emulsions were obtained by stabilizing mineral oil droplets using amphiphilic poly(vinyl pyrrolidone-co-allyl phenyl sulfide) (P(VP-APS)). 1H nuclear magnetic resonance (NMR) spectroscopy revealed that P(VP-APS) whose APS content was 0%, 3.28%, 3.43% and 4.58% were successfully prepared by free radical reaction and the sulfide of APS was oxidized by H2O2 treatment. X-ray Photoelectron Spectroscopy (XPS) also disclosed that the sulfide of APS was oxidized to sulfone by the oxidizing agent. The optical density of copolymer solutions and the interfacial activity of the copolymers markedly decreased by H2O2 treatment possibly because the sulfide of APS was oxidized and the amphiphilicity of the copolymers were weakened. The increase rate of the oil droplet diameter of the emulsions was outstandingly promoted when H2O2 solution (10%, v/v) was used as an aqueous phase. The phase separation of the emulsions was also expedited by the oxidizing agent. The oxidation of APS and the weakened interfacial activity were thought to be a main reason for the demulsification of P(VP-APS)-stabilized emulsions.

In situ preparation of Ag nanoparticles on silicon wafer as highly sensitive SERS substrate.

An intensive surface enhanced Raman scattering (SERS) effect is realized by ordered Ag nanoparticles (NPs) in situ grown on silicon wafer directly using (3-aminopropyl) trimethoxysilane (APS) as both the surface modifier and reducing agent. The as-prepared ordered Ag NPs based SERS substrate shows excellent performance in detecting glycerin (an important integration in liquid super lubricating system) as well as conventional Rhodamine 6G (R6G, a kind of dye organic pollutant). The enhancement factor (EF) achieves 4-fold for glycerin and 10-fold for R6G (allowing for detecting as low as 10−11 M aqueous R6G), confirming the high sensitivity. The limited relative standard deviations (RSD) of the enhancement factors are within 15% for both glycerin and R6G, indicating the excellent uniformity. This remarkable progress is ascribed to the advantages of APS in improving adsorption and modulating distribution of Ag NPs on silicon, which results in a large local electric field to enhance the Raman signals. The SEM and UV-visible absorption spectrum characterization verified the contribution of APS in SERS improvement by investigating the influence of APS content and reduction time during the preparation process. All these advances imply that the SERS substrates prepared by Ag NPs in situ grown on silicon wafer have great potential application in real-time interface state tracing and sensitive detection.

Mathematical modeling for the prediction of the overall swelling profile from poly (AM-co-AA-co-HEA) hydrogels: effect of glycidyl methacrylate and ammonium per sulphate

In the present investigation, a series of hydrogels based on poly (AM-co-AA-co-HEA) from the constant weight ratio (1/1/1) of acrylamide (AM), acrylic acid (AA), and hydroxy ethyl acrylate (HEA) monomers were synthesized by solution polymerization to optimize the reaction conditions. The reaction conditions were optimized by varying the reaction temperature, reaction time, crosslinker and initiator concentration, and amount of solvent. At optimized reaction conditions, two different sets of hydrogels were synthesized by varying the concentrations of cross-linker (glycidyl methacrylate, GMA) from 1 to 4 % and initiator (ammonium per sulphate, APS) from 1 to 4 %, to study the effects of crosslinker variation as well as initiator variation on swelling ratio by Flory’s equations. The three mathematical models (early time, late time and etters model) were fitted on experimental swelling data to investigate the entire swelling profile of all the hydrogels prepared with various amounts of GMA and APS content. Values of swelling transport exponents showed that the swelling mechanism was shifted from diffusion to relaxation controlled in case of increasing APS content, while only diffusion mechanism was followed for increasing GMA content. The proportionality constant (k) was calculated by two different models (1) power law and (2) Baker and Lonsdale to confirm the validity of early-time model fitting on experimental swelling data.

Synthesis and characterization of CuO nanoparticles, DBSA doped PANI and PANI/DBSA/CuO hybrid composites for diode and solar cell device development

Pure CuO, PANI and PANI/CuO hybrid composites are prepared by chemical synthesis method. The samples were characterized by structural, optical, morphological and electrical studies. FT-IR spectra of PANI/CuO hybrid composites are found to be shifted toward higher wave number compared with pure PANI. XRD spectrum confirms the formation of CuO nanoparticles and PANI/CuO hybrid composites. Morphological change has been observed in PANI–CuO hybrid composites formed at different weight % of APS. PANI samples show spherical and smooth morphology, whereas PANI–CuO hybrid composites with aggregated morphology as per the SEM results. TEM morphology shows the formation of evenly distributed DBSA and CuO doped composite nanoparticles in the polymer matrix. The PANI/CuO composites exhibit relatively high photoluminescence intensity in violet and green–yellow region of visible spectrum along with high electrical conductivity compared with pure PANI. The composites show semiconducting nature and the conductivity decreases with increasing of APS content due to the formation of new conduction pathways. The effect of APS content on the structural, electrical and optical properties of the composites are presented. Moreover, the device based on the ITO/PANI/CuO/APSx composites was fabricated and its I–V behavior was studied.

Grafting molecularly imprinted poly(2-acrylamido-2-methylpropanesulfonic acid) onto the surface of carbon microspheres

Poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) was grafted on the surface of carbon microspheres (CMSs), which were modified in prior by a mixed acid (HNO3 and H2SO4) oxidation and 3-methacryloxypropyl trimethoxysilane silanization. Then, the molecularly imprinting polymerization was carried out towards the macromolecule PAMPS grafted on the surface of CMSs using dibenzothiophene (DBT) as template, ethylene dimethacrylate as cross-linking agent and (NH4)2S2O8 (APS) as initiator to prepare surface molecularly imprinted polymer (MIP-PAMPS/CMSs) for adsorbing DBT. The optimized conditions of grafting PAMPS, including AMPS dosage, APS content, reaction temperature and reaction time, were emphasized in this paper. The morphology of the samples was characterized by field emission scanning electron microscopy. The functional groups were analyzed qualitatively by Fourier transform infrared spectrometry. The grafting degree of PAMPS was investigated by thermogravimetry. The results show that the preferable AMPS dosage, APS content, reaction temperature and time were 5g, 0.15g, 70°C and 12h, respectively, for preparing PAMPS/CMSs composite on the basis of 1.0g of silanized-CMSs. The absorbing characteristic of MIP-PAMPS/CMSs toward DBT was studied preliminarily with dynamic adsorption. In the experiment of dynamic adsorption, MIP-PAMPS/CMSs and non-imprinted polymer (NIP-PAMPS/CMSs) were compared with respect to their rapid adsorption in 1mmol/L of DBT solution in n-hexane. When the first 1mL of 1mmol/L DBT solution was injected and flowed through a column packed with 0.1g of MIP-PAMPS/CMSs, the content of DBT reduced to 0.265mmol/L, that is, decreased significantly from 279 to 74ppm. When 3mL of DBT solution was flowed through the packed column, the adsorption of MIP-PAMPS/CMSs toward DBT reached saturation with the maximum adsorption amount of 1.38×10−2mmol/g and the overall adsorption efficiency of 46%, while NIP-PAMPS/CMSs adsorbed only 1.66×10−3mmol/g of DBT. It is suggested that the MIP-PAMPS/CMSs had much better adsorption property towards DBT than NIP-PAMPS/CMSs.

Fabrication of Polyaniline: Nail/Spindle‐Shaped Morphology

AbstractNail/spindle‐shaped polyaniline is synthesized by chemically oxidizing aniline with ammonium persulfate in a near‐neutral aqueous medium using PVP as the stabilizing agent. The type of dispersing agent, APS content and aniline concentration have obvious impacts on the morphology of the resulting polyaniline. Typically, in the concentration ranges of 1.5–6 × 10−4 M PVP and 0.02–0.05 M aniline and for molar ratios [APS]:[aniline] of 0.4:1 to 0.8:1, nail/spindle‐shaped polyaniline can be obtained. A possible mechanism is proposed to elucidate the formation process.magnified image

A comparative study on the dispersion stability of aminofunctionalised silica nanoparticles made from sodium silicate

A method to prevent the irreversible agglomeration of silica nanoparticles prepared from sodium silicate, which occurs upon treatment with trialkoxy silanes, is presented. Electrostatic stabilisation is maintained by using mixtures of 3-aminopropyltrimethoxysilane and the cationic derivative N-trimethoxysilylpropyl- N , N , N -trimethylammoniumchloride (TMAPS), which gives rise to stable dispersions of aminofunctionalised particles with unusually high amine content. The particles can be isolated and redispersed without significant increase in particle size. However, an increase in the dispersed particle-size was observed on increasing the APS content in the reaction mixture. This was least pronounced for the 9 nm particles prepared from sodium silicate and more pronounced for the 30 nm particles, for which gel and/or precipitate formation occurred at high APS contents.

Clathrate (δ) Form Crystal Transitions of Syndiotactic Polystyrene in Atactic Polystyrene Networks

Syndiotactic polystyrene (sPS) δ crystals within atactic polystyrene (aPS) and atactic polystyrene networks (aPSNW) were prepared. The polymorphism behaviors of sPS within aPS and aPSNW were studied by in-situ wide-angle X-ray diffraction (WAXD) and differential scanning calorimeter (DSC). The sPS δ crystals transfer into γ and then α form crystals during the gradually heating process. The transition temperature of the δ to γ form crystals decreases with the increase in the aPS and aPSNW content in all samples. By contrast, the transition temperature of γ-to-α form crystals increases with the rising aPSNW content, whereas it is independent of the content of aPS. Meanwhile, the transition temperatures of δ to γ and γ to α in aPSNW are higher than those in linear aPS blends. When the samples were annealed at a temperature above 150 °C, the sPS δ form is not favorable to transform into the β form in aPSNW. The results indicate that polymorphism behaviors of sPS are disturbed within aPS networks.

Thermal and structural properties of blends of isotactic with atactic polystyrene

Blends of isotactic polystyrene (iPS) with non-crystallizable atactic polystyrene (aPS) were studied by differential scanning calorimetry and small angle X-ray scattering. The iPS/aPS blends, prepared by solution casting, were found to be miscible in the melt over the entire composition range. Both quenched amorphous and semicrystalline blends exhibit a single, composition-dependent glass transition temperature, depressed from that of either of the homopolymer components. Addition of aPS causes a decrease in crystallinity and in the rigid amorphous fraction, and suppression of the reorganization/recrystallization of iPS during thermal scanning: only one melting peak is observed for blends with larger aPS content. Formation and devitrification of the rigid amorphous fraction of iPS are also affected by aPS addition. The annealing peak, which is due to the relaxation of rigid amorphous fraction in parallel with melting of a tiny amount of crystals, is retarded with an increase of the composition of aPS, resulting in the slow devitrification of RAF in parallel with the melting of large amount of crystals. X-ray scattering shows that the long period in the iPS/aPS blends is greater than in the iPS homopolymer, and long period increases slightly as aPS content increases. Comparison of the volume fraction of phase 1 with the volume fraction crystallinity from DSC suggests that more and more amorphous phase is rejected outside the lamellar stacks as aPS content increases. The effect of aPS addition is to reduce the confinement of the amorphous phase chains. The cooperativity length, ξA, which is calculated from thermal analysis of the Tg region, increases with aPS addition. The interlamellar and extra-lamellar amorphous chains both contribute to the glass transition relaxation process.

Competitive influence of atactic polystyrene and supercritical carbon dioxide on the conformation of syndiotactic polystyrene

AbstractThe crystallization behavior of miscible syndiotactic polystyrene (sPS) and atactic polystyrene (aPS) blends with different sPS/aPS weight ratios was investigated in supercritical CO2 by using Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Supercritical CO2 and aPS exhibited different effects on the conformational change of sPS and competed with each other. Increasing the content of amorphous aPS in the blends made its effect on the conformational change of sPS gradually surpass that of supercritical CO2. Supercritical CO2 favored the formation of the helical conformation of sPS in lower temperature range and the all trans planar conformation in higher temperature range, instead of forming the latter one only in higher temperature range in ambient atmosphere. However, increasing aPS content in the blends pushed the range for forming the helical conformation to lower temperature and made the all trans planar conformation dominant in aPS/sPS 25/75 blend after treating in supercritical CO2 above 60 °C. The all trans planar zigzag conformation was more favorable than the helical conformation after mixing aPS in sPS in supercritical CO2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1755–1764, 2007

The Role of γ -Aminopropyltriethoxysilane (γ -APS) on Thermal Stability of TEOS-PDMS Ormosils

The degradation process of TEOS-PDMS Ormosils containing different amounts of γ -APS has been studied by means of DTA, TG, FTIR and 29Si-NMR measurements. It has been found that the amount of γ -APS improved the thermal properties of Ormosil materials. The increase in γ -APS content causes the increment on the decomposition temperatures and activation energies of the studied Ormosils. These results have been attributed to the favourable effect of γ -APS in the copolymerisation reaction between TEOS and PDMS molecules. 29Si-NMR analyses have shown that the incorporation of γ -APS increases the concentration of D(Q) units in the Ormosil structure, i.e., increases the number of TEOS molecules bonded to PDMS ones. Initial decomposition temperature (IDT), temperature of maximum weight loss rate (T max), integral procedure decomposition temperature (IPDT) and activation energy values (E) were calculated from different equations which described the degradation of these materials. Addition of 10 wt% γ -APS produced an increase of 63∘C in the IDT and of 115 and 110∘C, respectively, for T max and IPDT (up to 478 and 610∘C) compared to the free γ -APS Ormosil. Activation energy values also rise up to 69.4 kJ⋅ mol−1 by introducing 10 wt% of γ -APS.

Crystallization, Melting and Morphology of Syndiotactic/Atactic Polystyrene Blends: Molecular Weight Effects of Atactic Polystyrene

AbstractSummary: Molecular weight (MW) effects of atactic polystyrene (aPS) on the morphologies and crystallization kinetics of syndiotactic polystyrene (sPS) blends have been investigated, and miscibility was confirmed for all the sPS/aPS blends. Addition of aPS(M) or aPS(L) leads to a significant increase in the entropy of mixing and gives rise to a pronounced decrease in the equilibrium melting temperature of the blends. On heating from the glassy state, the crystallization peak temperature of the sPS/aPS(H) blend increased with increasing aPS content due to a dilution effect, whereas those of sPS/aPS(M) and sPS/aPS(L) decreased mainly due to enhanced chain mobility. On cooling from the melt state, the crystallization peak temperature decreased with increasing aPS content regardless of the aPS MW. A higher activation energy is required for the sPS component transport from the miscible melt to the growth front in the sPS/aPS(L), suggesting that extra energy is required for the demixing process. Interspherulitic segregation of aPS diluents was evident in the sPS/aPS(L) blends, while interfibrillar segregation morphology was obtained in the sPS/aPS(H) as well as the sPS/aPS(U) blends.SEM images of sPS/aPS blends 50/50(L) at 230 °C (C) and 70/30(L) at 250 °C (D).magnified imageSEM images of sPS/aPS blends 50/50(L) at 230 °C (C) and 70/30(L) at 250 °C (D).

Miscible blends of syndiotactic polystyrene and atactic polystyrene. Part 2. Depolarized light scattering studies and crystal growth rates

Crystallization kinetics and morphology in miscible blends of syndiotactic polystyrene (sPS) and atactic postyrene (aPS) have been investigated by means of time-resolved depolarized light scattering (DPLS), polarized optical microscopy (POM) and scanning electron microscopy (SEM). Two different weight-average molecular weight of aPS, i.e. M w=100k and 4.3k, were used to prepare the blends and denoted sPS/aPS(H) and sPS/aPS(M), respectively. Owing to a dilution effect, addition of aPS reduces the crystal growth rate and the overall crystallization rate of sPS; the reduction is more significant in sPS/aPS(M) of which a depression of equilibrium melting temperature is found due to the enhanced mixing entropy. Linear crystal growth is always observed in sPS/aPS(H) at the temperatures studied (240–269 °C) and results in an interfibrillar segregation morphology revealed by SEM, whereas sPS/aPS(M) with high aPS content exhibits non-linear growth behavior at low supercooling and gives an interspherulitic segregation morphology. Based on the Lauritzen–Hoffman theory, the fold surface free energies ( σ e) of sPS lamellae derived from DPLS and POM are in fair agreement, being 15.1 erg/cm 2 from the former and 12.6 erg/cm 2 from the latter. The peculiarly low values of σ e and the derived work of chain folding are discussed briefly. On addition of aPS, the lateral surface free energy of lamellae remains intact (9.9 erg/cm 2) regardless of aPS molecular weight used, which is ascribed to the absence of specific interaction between sPS and aPS components. Moreover, it seems that the activation energy for sPS chains to diffuse from the miscible melt to the crystal growth front is slightly increased in sPS/aPS(M), plausibly attributable to the extra energy required for the demixing process.

Ultradrawing and crystallization of isotactic polystyrene and blends with atactic polystyrene

AbstractPure isotactic polystyrene (iPS, Mw = 8.89 × 104, Mw/Mn = 4.89) and its blends with an atactic polystyrene (aPS, Mw = 3.9 × 105, Mw/Mn < 1.13) were subjected to draw by solid state coextrusion at 127°C within polyethylene. The content of amorphous iPS in these blends was varied from 100 to 24.4 wt %. The extent of draw‐induced crystallization was found to depend on the draw ratio and on iPS concentration. The blend with 24.4% iPS was coextruded in two stages. The highest effective draw ratio (EDR) was 7.6 and 13.7 for one‐ and two‐stage draw, respectively. The highest crystallinity of 33.2% was obtained for pure iPS at the maximum EDR of 7.6. Considerable crystallinity was induced in blends, requiring successively higher draw ratio to reach similar crystallinity with increased aPS content. The tensile modulus increased from 1.5 to 3.2 GPa, independent of iPS concentration. Thermal shrinkage results indicate that the elastic recovery of draw in the blends is near quantitative for an EDR < 8. For pure iPS, extrudate elastic recovery was dramatically altered by the draw‐induced crystallinity.