Sailendra N. Bhattacharyya

Analogue calorimetry of polymer blends: poly(styrene-co-acrylonitrile) and poly(phenyl acrylate) or poly(vinyl benzoate)

Abstract Unlike poly(phenyl acrylate) (PPA), its isomer poly(vinyl benzoate) (PVBZ) is immiscible with poly(styrene- co -acrylonitrile) (SAN). The difference in miscibility behaviour of PPA and PVBZ towards SAN is also reflected in the heats of mixing ( ΔH m ) of the low-molecular-weight analogues of the respective blend components at compositions corresponding to o SAN = 0.92 in the blend. It turns out that propionitrile, the hydrogenated monomer of polyacrylonitrile (PAN), is very unsuitable as an analogue of the latter. In contrast, acetonitrile, having a solubility parameter closer to PAN, is a fairly acceptable analogue of PAN as far as miscibility of the latter with PPA is concerned in the PAN-rich region, o PAN > 0.7.

Novel polyaniline dispersions using poly(vinyl methyl ether) stabilizer

Abstract Oxidative dispersion polymerization of aniline using poly(vinyl methyl ether) (PVME) dispersant in water or aqueous alcohol media yields dispersions of submicronic conducting polyaniline (PANI) particles which have rice grain morphology. The conductivity of the particles in pressed pellet form ranged between 0.03–5 S cm−1 depending on the synthesis condition. Dispersion polymerization is best effected in aqueous alcohol (50–70% v/v alcohol). Using 50% ethanol as the polymerization medium dispersions containing 5 wt% PANI were prepared.

Dispersion polymerization of pyrrole using poly(vinyl methyl ether) as stabilizer

Abstract Polypyrrole (PPy) dispersions are prepared at room temperature by oxidative polymerization using FeCl3 oxidant in the presence of poly(vinyl methyl ether) (PVME) as stabilizer, and ethanol or aqueous ethanol as the dispersion medium. With water as dispersion medium, lower temperatures are required when the solvent property of water towards the PVME stabilizer becomes good enough to effect steric stabilization. PPy prepared in 50% ethanol or in water exhibits high specific conductivity, about 10 S cm−1, while PPy prepared in ethanol under similar conditions has a conductivity two to four decades lower, depending on the FeCl3 concentration and temperature used in the preparation. Transmission electron micrographs of PPy reveal that the particles are spherical but polydisperse.

Co-nonsolvent systems for poly(ϵ-caprolactone) and poly(methyl methacrylate)

Abstract The cloud points for the co-nonsolvent systems (i) pyridine (PY) + formic acid (FA) towards poly(ϵ-caprolactone) (PCL) or poly(methyl methacrylate) (PMMA) and (ii) pyridine + acetic acid (AA) towards PCL have been experimentally determined as a function of solvent composition at fixed polymer concentrations. Heats of mixing for the (FA + PY) system have also been measured. The single liquid approximation model correctly predicts for the (PY + FA) system the solvent composition at which the solvent power of the mixture is the poorest, provided it is recognized that the solvent system is comprised of pyridinium formate (PYFA) as one component and either PY or FA (depending on which is present in excess over 1:1 mole ratio) as the other. With the other co-nonsolvent system, the prediction is not as good. A possible reason for the discrepancy has been given.

Miscibility of poly(styrene‐co‐butyl acrylate) with poly(ethyl methacrylate): Existence of both UCST and LCST

A miscible homopolymer–copolymer pair viz., poly(ethyl methacrylate) (PEMA)–poly(styrene-co-butyl acrylate) (SBA) is reported. The miscibility has been studied using differential scanning calorimetry. While 1 : 1 (w/w) blends with SBA containing 23 and 34 wt % styrene (ST) become miscible only above 225 and 185 °C respectively indicating existence of UCST, those with SBA containing 63 wt % ST is miscible at the lowest mixing temperature (i.e., Tgs) but become immiscible when heated at ca 250 °C indicating the existence of LCST. Miscibility for blends with SBA of still higher ST content could not be determined by this method because of the closeness of the Tgs of the components. The miscibility window at 230 °C refers to the two copolymer compositions of which one with the lower ST content is near the UCST, while the other with the higher ST content is near the LCST. Using these compositions and the mean field theory binary interaction parameters between the monomer residues have been calculated. The values are χST-BA = 0.087 and χEMA-BA = 0.013 at 230 °C.

Conducting polypyrrole particles dispersible in both aqueous and non-aqueous media

Dispersion polymerization of pyrrole in absolute alcohol or water–alcohol mixtures using poly(vinyl methyl ether)(PVME) dispersant and FeCl3 initiator–dopant yields conducting polypyrrole (PPy) particles which after isolation and purification can be redispersed in water as well as in many common organic solvents to give submicronic stable dispersions.

Some observations on the magnetic field effect on photoinitiated emulsion polymerization of styrene

Abstract The photo-emulsion polymerization of styrene using benzoin or dibenzyl ketone as photoinitiator, with or without magnetic field, has been followed with time. The magnetic field effect is best seen at low rates of radical generation. The field shortens the particle nucleation period to a small extent so that the polymerization in the absence of the field is delayed by that small time. At the lowest light intensity (lowest radical generation rate) used in this work, the steady state Rp increases by 80% with the application of a field of 1000 G. The field effect on molecular weight is discernible only at low conversions. Molecular weights increase greatly with conversion both with and without the field so that the field effect, if any, on molecular weights in the later stages of reaction is masked.