Styrene-acrylonitrile Random Copolymer Research Articles

Comparison of structural, spectral and magnetic properties of NiO nanofibers obtained by sol–gel electrospinning from two different polymeric binders

NiO is a p-type semiconductor with wide band gap energy. In this study, nickel oxide nanofibers were fabricated by sol–gel electrospinning followed by high temperature calcination, using two sacrificial polymeric binders. Poly(2-ethyl-2-oxazoline) (PEtOx) in water and styrene-acrylonitrile random copolymer (SAN) in N,N- dimethylformamide (DMF) along with nickel (II) acetate tetrahydrate (NATH), as metal oxide precursor, were the two distinct polymeric systems used in this study. The morphological and structural properties of NiO fibers obtained from the aforementioned systems were compared with each other. The degradation behavior of the sacrificial polymeric binder imparted a significant effect on the properties of the obtained NiO fibers. The grain sizes and the activation energies for grain growth of NiO fibers from two systems were different. The non-stoichiometric NiO fibers obtained from the SAN/NATH system had a better ferromagnetic behavior as compared with that produced from the PEtOx/NATH system. This non-stoichiometry made a difference also in the optical band gap energies of the NiO nanofibers.

Poly(styrene–isoprene–butadiene- g -SAN) graft copolymers: Size-controllable synthesis and their toughening properties

The poly(styrene–isoprene–butadiene) (PSIB) latexes with large particle diameters were synthesized in a seed-emulsion polymerization or followed by agglomerating with amphiphilic block copolymers, and their granularity uniformities were also investigated through the determination of PSIB grain-size distribution. Resultant PSIB latexes were functionalized with styrene–acrylonitrile random copolymers (SAN) which the chemical graft modification had been investigated as well. The large particle diameter of PSIB latex via a seed-emulsion polymerization showed a continuous and normal distribution, which was improved greatly with the dosages of emulsifier and seed-emulsion concentration. A bimodal PSIB latex with large-sized particles were also prepared by the agglomerating process with a hydrophilic polymer of poly(butylacrylate-methacrylic) acid after the radical emulsion polymerization and was greatly affected with addition of poly(butylacrylate-methacrylic) acid. Moreover, the higher value of graft yield of SAN copolymer onto PSIB latex was observed as compared to the PB latex and the following factors controlled the grafting degree of the particles: (i) the composition of monomers; (ii) the initiator's content; (iii) the conditions for grafting copolymerization. Poly(styrene–isoprene–butadiene-g-SAN) graft copolymers (PSIB-g-SAN) were blended with SAN resins and their toughening properties were tested respectively. The effects of the composite polymer particles and the properties of PSIB-g-SAN particles were also discussed.

Thermodynamic Interactions and Phase Behavior of Multicomponent Blends Containing Supercritical Carbon Dioxide, Styrene–Acrylonitrile Random Copolymer, and Deuterated Poly(methyl methacrylate)

Small-angle neutron scattering (SANS) was used to probe the phase behavior of multicomponent mixtures of supercritical carbon dioxide (scCO2), styrene–acrylonitrile random copolymer, and deuterated poly(methyl methacrylate). Ternary mixtures were homogeneous at low carbon dioxide pressures (PCO2) but phase separated as PCO2 was increased at constant temperature (T). Phase separation pressure was found to be a nonmonotonic function of T with a minimum at T = 60 °C. An expression based on the multicomponent random phase approximation was used to determine the interaction parameters between polymer and scCO2 from a combination of SANS experiments on homogeneous ternary mixtures and measurements of scCO2 uptake by the neat polymers. Interaction parameters that underlie the nonmonotonic phase behavior described above collapse onto a straight line when plotted as a function of scCO2 density.

Fabrication of styrene–acrylonitrile random copolymer nanofiber membranes from N,N-dimethyl formamide by electrospinning

Ultrafine styrene–acrylonitrile random copolymer (SAN) nanofiber-based membranes were produced from N,N-dimethyl formamide solution by electrospinning. The purpose of this study was to find the optimum values of the electrospinning parameters and the influence of major significant parameters on the electrospun fiber morphology and the average fiber diameter ( Davg) and its standard deviation using design of experiment. A backward elimination model for multiple regression analysis was employed to obtain quantitative interactions among selected electrospinning parameters and the final fiber diameter. The dependence of the Davg and morphology on the critical entanglement concentration was also studied. Morphology of the electrospun nanofiber mats were examined by scanning electron microscopy. Davg of electrospun SAN fibers increased considerably with increasing solution concentration. Fibers with diameters ranging from 40 to 650 nm were obtained. Analysis of variance was utilized to identify the statistically significant parameters ( p < 0.05) and error variance.

Solution electrospinning of styrene-acrylonitrile random copolymer from dimethyl sulfoxide

Electrospinning is an efficient and versatile technique for the fabrication of ultrafine fibers having diameters ranging from nano to sub-micron level for various potential applications. In this study, we have investigated the influence of process and solution parameters, such as solution concentration, flow rate and applied voltage, on the morphology of electrospun poly(styrene-co-acrylonitrile) (SAN) fibers. Morphology and average diameter (Davg.) of the electrospun SAN fibers were characterized by scanning electron microscopy (SEM). The SEM results reveal that concentration, applied voltage and flow rate of solution are strongly associated with formation of defects, such as beads, in the fibers. Ultrafine SAN fibers with Davg. in the range of 96–872 nm were obtained by controlling the experimental parameters. The Davg. of electrospun fibers increased with increasing solution concentration, applied voltage and flow rate. Also, the Davg. exhibits a power law relationship with the solution concentration.

Characterization of Polymer Interfaces by Energy-Filtering TEM

Energy-Filtering TEM (EFTEM) was performed for the investigation of polymer interfaces. Polymer-polymer adhesion with various interfacial thicknesses formed between styrene-acrylonitrile random copolymer (SAN) and poly(methyl methacrylate) (PMMA) was studied by oxygen and nitrogen mapping and electron-energy-loss spectroscopy (EELS). Polymers brushes grafted on silica nanoparticles and organic dyes adsorbed on silica nanoparticles have been successfully characterized by high-resolution carbon mapping with contamination-free TEM.

Nanoporous carbon produced from a styrene-acrylonitrile random copolymer/carbon nanotube composite

A new type of nanoporous carbon material by pyrolysis of styrene-acrylonitrile random copolymer (SAN)/multiwalled carbon nanotube (MWCNT) composite was prepared. The thermal decomposable styrene component of the SAN could act as a soft template to form abundant nanopores with the help of the pristine nanotubular framework of the MWCNT. The measured Brunauer–Emmett–Teller surface area of the SAN/MWCNT-based carbon was up to 376 m2/g with a MWCNT content of 10 wt%, 11 and 14 times as large as those of SAN-based and polyacrylonitrile/MWCNT-based carbons, respectively. As a result, the highest specific capacitance of an as-prepared SAN/MWCNT-based carbon reached 118 F/g, which is much higher than those of the latter two.

Viscoelastic properties of silica‐grafted poly(styrene–acrylonitrile) nanocomposites

AbstractThe melt state viscoelastic properties of styrene–acrylonitrile random copolymers grafted to silica nanoparticles and prepared by in situ atom transfer radical polymerization are examined. Linear dynamic oscillatory viscoelastic measurements indicate that nanocomposites with silica contents as low as 1.2 vol % exhibit solid‐like response. Steady shear results in considerable alteration to the mesoscale structure and results in the failure of the Cox‐Merz rule. Flow reversal studies confirm the elastic nature of the mesoscale structure and demonstrate that the relaxation of the flow altered structure is slow, non‐Brownian, and possibly cooperative. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2014–2023, 2006

Novel application of reactive blending: tailoring morphology of PBT/SAN blends

Reactive blending has been usually utilized to stabilize morphology and to improve the properties of multi-component polymer blends by generating copolymers in situ at the interface. However, the present study on blends composed of poly(butylene terephthalate) (PBT) and functionalized styrene–acrylonitrile random copolymer (SAN) demonstrates another possibility for this method, i.e. tailoring morphology and thereby controlling the properties of polymer blends. By varying reaction conditions it was demonstrated that blends could be formed having the same ratio of [PBT]/[SAN] but which possessed completely different microstructural forms: a sea–island morphology with and without micelles, a corded dispersed phase morphology, and a highly oriented, layer-like morphology.

Synthesis of styrene–acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

Synthesis of styrene–acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

Synthesis of styrene-acrylonitrile random copolymers (SAN) and polyarylate block copolymers and the control of their mechanical properties by morphology generation

The idea of repulsion in random copolymers was applied to the miscibility modification between polystyrene (PS) and polyarylate (PAr) segments of PS–PAr block copolymer (PAr–PS–PAr). Acrylonitrile (AN), which has a large positive interaction parameter against styrene, was used as a miscibility modifier toward PAr segments. AN was introduced into the carboxyl terminated telechelic-PS at AN wt % ranging from 12 to 37 wt %. Based on these telechelic acrylonitrile–styrene random copolymers (SANx's where x represents AN wt %), SANx and PAr block copolymers (PAr–SANx–PAr's) were synthesized. The miscibility of SANx and PAr segments was estimated from the results of DSC with Fox's equation and spin–spin relaxation time measured by pulsed NMR. These results evidenced that the miscibility between PS and PAr segments can be modified by introducing AN into PS segments. The estimated volume fraction of the interfacial layer between SANx and PAr segments was increased as x was increased toward 24 wt %, around which the predicted miscibility reaches a maximum. Above that AN wt %, it began to decrease. The flexural strength increased as the miscibility between SANx and PAr segments increased. In particular, when x was between 20 and 30 wt %, PAr–SANx–PAr exhibited three times larger flexural strength than PAr–PS–PAr. The fracture behavior changed from brittle to ductile, even though the telechelic SANx by themselves exhibited almost the same fracture strength as the telechelic PS. The results of dynamic mechanical measurements and the percolation model suggested that around these AN wt % the continuum matrices in PAr–SANx–PAr changed from SANx phase to a cocontinuous phase of SANx and PAr. From these results, PAr–SANx–PAr was explained to perform such a high flexural strength by this phase change in the continuum matrices. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 127–137, 2000

Estimation of the Surface Properties of Styrene-Acrylonitrile Random Copolymers from Contact Angle Measurements

The surface free energy per unit area of a solid, γS, is a fundamental property of materials and determines their surface and interfacial behavior in processes like wetting and adhesion. In this study the γS of a series of styrene–acrylonitrile random copolymers is evaluated. Three different approaches are used to determine the components in which the surface free energy can be decomposed. Using the geometric and the harmonic mean approach, the dispersive, γd, and polar, γp, components of the solid surface free energy were determined and compared to the Lifshitz–van der Waals, γLW, and acid–base, γAB, components using the approach developed by C. J. van Oss et al. (1987, Adv. Colloid Interface Sci. 28, 35). The acid–base approach was also used to evaluate the work of adhesion of the test liquids: water, glycerol, and thiodiglycol. It was found that the contact angles of these liquids follow closely the predictions of Cassie equation. The evaluation of the surface free energy components on one hand and the relative magnitude of the work of adhesion components on the other hand, suggest that below 50% of acrylonitrile the polystyrene repeating units are preferentially at the surface. Above 50% of acrylonitrile the segregation of the low-energy homopolymer at the surface decreases.

Studies on miscibility in polycarbonate/poly(styrene-co-acrylonitrile) blends by ellipsometry

The interfacial thickness between immiscible polymers, bisphenol A polycarbonate (PC) and styrene–acrylonitrile random copolymers (SAN), was measured by ellipsometry as a function of temperature and acrylonitrile content in SAN, in order to study the miscibility between PC and SAN. Both the temperature and copolymer composition (AN content) dependence of the interfacial thickness in the equilibrium state indicated a maximum. Using the values of the interfacial thickness, it is possible to calculate the polymer–polymer interaction parameter χAB between PC and SAN. The χAB exhibited the lowest positive value at about 200°C for each copolymer composition due to the maximum of the interfacial thickness, i.e. at low temperature range, χAB decreased with increasing temperature, then χAB increased at high temperature range. This behaviour implies the possibility of the coexistent behaviour of upper and lower critical solution temperature (UCST and LCST) in the phase diagram of the mixture consisting of polymers with suitable molecular weight. This coexistent behaviour of UCST and LCST was confirmed by measuring cloud point curves of the mixtures having lower molecular weight PC. On the other hand, the copolymer composition dependence of χAB also has a minimum in a certain copolymer composition, which leads to the miscibility window behaviour. From these results, it was shown that there appeared to be a loop-type miscibility window (`miscibility egg') in the miscibility diagram of copolymer composition versus temperature of PC/SAN. From the calculation based on these results, it has also been shown that all three segmental interaction parameters χi/j of PC/SAN, i.e. χS/C, χAN/C and χS/AN, decreased with increasing temperature monotonically. It was predicted that the LCST behaviour in PC/SAN mixtures could occur due to the remarkable decrease of interaction χS/AN between comonomers in SAN at high temperature, without the free volume contribution.

Shear effect on the phase behavior and morphology in pmma/san-29.5 blend

The effect of simple shear flow on the miscibility and morphology of blends of poly(methyl methacrylate) (PMMA) and a styrene-acrylonitrile random copoly-mer with 29.5 wt% acrylonitrile (SAN-29.5) has been investigated using shear apparatus and transmission electron microscopy (TEM). The obtained data showed that only shear-induced mixing was observed for all of the composition ratios. The increase of the cloud point (or homogenization temperature) ΔT(γdot; = T(γdot;) - T(0) was investigated as a function of shear rate γdot;; in addition, the normalized shift in the cloud point ΔT(γdot;)/T(0) versus γdot; was also studied and compared with that of simple liquid mixtures and polymer solutions. The results showed that the polymer blends were more sensitive to the shear rate than both simple-liquid mixtures and polymer solutions. The morphology of the PMMN SAN(= 75/25) blend (the critical composition) indicated that shear-induced phase mixing occurred at a critical shear rate value, below which the two phases were highly oriented and elongated in the flow direction. Three regimes, depending on the applied shear rate values, were detected that were in good agreement with the literature data for polymer solutions. The effect of relaxation times after shear cessation showed a decrease in the orientation of the elongated particles, but it did not completely vanish even for 10 min after the shear cessation.

Studies on miscibility in homopolymer/ random copolymer blends by equation of state theory

The miscibility of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile random copolymers (SAN) blends was investigated on the basis of the Flory—Orwoll—Vrij equation of state theory. To obtain the equation of state parameters ( P∗, V∗ sp , T∗: characteristic parameters ), the pressure—volume—temperature ( PVT) behaviour was measured for PMMA and a series of SANs with various acrylonitrile contents. The exchange energy parameter X ij was also calculated by fitting the theory to some phase diagrams of PMMA/SAN blends. The Flory—Huggins interaction parameter χ was separated into two contributions based on the equation of state theory for mixtures: the exchange energy term χ inter and the free volume term χ free. Both the temperature and copolymer composition dependences of χ inter and χ free were estimated by calculations using the equation of state parameters. There exists a region in which χ inter is negative, leading to a miscibility window in PMMA/SAN blends. However, the immiscibility at high temperatures in the blends cannot be explained only by χ inter; it is caused by the free volume contribution, χ free. The miscibility window behaviour in PMMA/SAN blends may be explained within the framework of the equation of state theory.

Molecular weight polydispersity effects on the melt viscoelasticity of styrene-acrylonitrile random copolymers

A series of polydisperse SAN (styrene-co-acrylonitrile) random copolymers was studied by means of oscillatory rheometry in the rubbery plateau zone and in the terminal zone. The plateau modulus, the Newtonian viscosity, and the critical frequencies for the onset of non-Newtonian behavior were extracted from the experimental data. All these viscoelastic quantities consistently indicate that the tail of molecular weights below approximately Me (the entanglement spacing) acts as a solvent for the rest of the polymer with M>Me.

Reactions of organolithium compounds with poly(vinyl chloride), poly(methyl methacrylate) and poly(styrene-co-acrylonitrile) as labelling pathways with fluorescent chromophores

This paper reports pathways to attach anthracene and naphthalene to preformed poly(vinyl chloride) (PVC), poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile random copolymer (SAN). The addition of 9-methylanthryl Li(1) or α-methyl-naphthyl Li(2) on the carbonyl of ester groups is an efficient means of labelling PMMA. The SN 2 nucleophilic substitution of the secondary chlorine atoms by (1) and (2) works well when Li is the counter-anion. The alkylation of SAN by 9-methylanthryl chloride in the presence of NLi diisopropylamide is another appropriate labelling pathway.

Styrene-acrylonitrile random copolymer in ethyl acetate

Styrene-acrylonitrile random copolymer in ethyl acetate

Gradient adsorptin thin-layer chromatography of styrene—acrylonitrile random copolymers

The compositional inhomogeneity of styrene—acrylonotrile random copolymers has been investigated by gradient adsorption thi-layer chromatography. The compositional distributions obtained this way are in good agreement with those calculated from the kinetics of the copolymerization.

Comparison between Successive Precipitation and Column Elution Methods in Compositional Fractionation of Copolymers

Abstract In order to compare the efficiencies of successive precipitation and column elution methods in compositional fractionation, mixtures of two styrene-acrylonitrile random copolymers with different chemical compositions were fractionated by the two methods by using the methyl ethyl ketone-cyclohexane system. The compositional distribution curve determined by each method was compared with the curve calculated from a theory on compositional fractionation. The value of a parameter K, which shows the efficiency of compositional fractionation, was determined to have the best agreement between the experimental and calculated curves. It was found that the column elution method is more effective than the successive precipitation method.