Random Copolymer Blends Research Articles

Miscibility in blends of random copolymers of styrene and acrylontrile with block copolymers of styrene and methyl methacrylate

AbstractPhase behavior in blends of random copolymers of styrene and acrylonitrile with block copolymers of styrene and methyl methacrylate was studied by light scattering, light microscopy and glass transition temperature measurements. The results are compared with those of respective blends containing random copolymers of styrene and methyl methacrylate. In terms of macrophase separation, the block copolymers display a more extended miscibility domain with styrene/acrylonitrile copolymers than the random copolymers. However, the extent of the miscibility domain varies as a function of temperature. Unlike the random copolymer blends, all blends containing block copolymers exhibit lower critical solution temperature behavior. Finally, it is established that the systems studied here undergo spinodal decomposition leading to macrophase separation.

Miscibility, crystallization and melting behaviour, and morphology of binary blends of polycaprolactone with styrene- co-maleic anhydride copolymers

Blends of polycaprolactone (PCL) and random copolymers of styrene and maleic anhydride (SMA) with different maleic anhydride contents were prepared by the coprecipitation technique. The miscibility of both polymers in the melt and in the solid state was studied by means of optical microscopy, light transmission measurements and dynamic mechanical analysis. The crystallization behaviour of PCL in the miscible blends was examined using optical microscopy and the morphology of the semicrystalline PCL/SMA blends was investigated by means of small-angle X-ray diffraction measurements. Their melting behaviour was studied by differential scanning calorimetry. SMA containing 14 and 25 wt% MA was found to be miscible with PCL over the entire composition and temperature range (up to 200°C). SMA appears to segregate interlamellarly during the isothermal crystallization of PCL. The double melting behaviour of PCL in the blends was attributed to a secondary crystallization process and not to a partial melting-recrystallization-remelting process.

Liquid—Liquid Equilibrium in Polydisperse Random Copolymer Blends

Abstract Continuous thermodynamics is applied to the liquid‐liquid equilibrium in random copolymer blends. Two copolymers are mixed, each consisting of two different monomer units. Hence, up to four monomer units may be present in the system. Both copolymers are characterized by divariate distribution functions with respect to molecular weight (chain length) and chemical composition. The basic relations necessary for phase equilibrium calculations are derived. The influences of both polydispersities and of the different parameters included in the model for the excess Gibbs free energy are discussed by calculating cloud‐point curves and shadow curves. Applications to practical systems are given.

Miscibility study of low molecular weight polystyrene/styrene-methyl methacrylate random copolymer blend using DSC

Miscibility study of low molecular weight polystyrene/styrene-methyl methacrylate random copolymer blend using DSC

Effect of pressure on phase behavior in polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and poly(o-fluorostyrene-co-p-fluorostyrene) copolymers

The effect of pressure on miscibility and phase separation in blends of random copolymers of ortho- and para-fluorostyrene, P(o-FS-co-p-FS) and poly(2,6-dimethyl-1,4-phenylene oxide), PPO, has been studied by differential thermal analysis (DTA) at pressures up to 300 MPa. At 200 MPa the copolymers containing from 10 to 38 mol% p-FS are miscible with PPO below 230°C using the customary criterion of a single calorimetric glass transition temperature (Tg). Each blend undergoes phase separation upon annealing at higher temperatures at both atmospheric and elevated pressures indicating the presence of a lower critical solution temperature (LCST). When the phase behaviors of the 50/50 wt% blends are examined as a function of temperature and copolymer composition, a symmetric miscibility “window” can be observed in the resulting temperature-composition diagram with a maximum at about 22 mol% p-FS. In a complementary set of experiments, the pressure dependence of the phase boundary for the blend of PPO and P(o-FS-co-p-FS) in which the copolymer contained 29 mol% p-FS was studied. The temperature minimum of the phase boundary is at about 50 wt% PPO and is independent of pressure. The consolute temperature, Tc, increases at about 0.10°C/MPa up to 200 MPa and then becomes independent of pressure to reach an asymptotic value at around 270°C. Similar behavior is also observed for blends in which the copolymer composition contains either 16 or 23 mol% p-FS. In these blends the decrease of dTc/dP at higher pressures may indicate that the negative volume of mixing approaches zero above 200 MPa. This study shows therefore, that pressure no longer plays a role in increasing the miscibility above 200 MPa.

A study on the compatibility of poly(methyl methacrylate)/methyl methacrylate—styrene random copolymer blends

A study on the compatibility of poly(methyl methacrylate)/methyl methacrylate—styrene random copolymer blends

Viscoelastic properties of styrene n-butyl methacrylate blends

Viscoelastic properties of blends of styrene n-butyl methacrylate random copolymers, 65/35 in composition, varying in molecular weights, were determined using the Eccentric Rotating Disks device of the Rheometrics Mechanical Spectrometer. The complex modulus increased with increasing high molecular weight fraction, with relative differences diminishing at higher frequencies. The relaxation modulus gave maximum increase on the addition of 10% of high molecular-weight fraction. The various blending laws (including quadratic laws ofGraessley andBogue, Masuda, Einga andOnogi) were applied to the data and their limitations were shown.

Viscoelastic photoelastic behavior of copolymers of styrene and 2-methoxyethyl methacrylate. II. Blends of random copolymers

Abstract The viscoelastic photoelastic behavior of blends of random copolymers styrene/2-methoxyethyl methacrylate having the same mean content of styrene (27 wt %) was measured. Blends were prepared that differed in their chemical heterogeneity characterized by the variance of the chemical composition, between 10−6 and 10−1 (where Wi is the weight fraction of the i-th component in the blend and xi its chemical composition given by the weight fraction of styrene; x is the mean composition of the blend). It was found that the viscoelastic behavior in the main transition as well as in the rubberlike regions was very little affected by the chemical heterogeneity, if σw 2 ↬ 10−2; for example, the stress-optical coefficient in the rubberlike region increased with σw 2 by some 20%. For these samples the time-temperature superposition can be successfully used, and the time dependence of the superimposed curves does not practically depend on the heterogeneity of the blend. However, the sample with σw 2 ≅ 1−1 show...

Ionic membranes for water desalination. I. Charge mosaic membranes from blends of random copolymers

AbstractThe incompatibility of polymers was used in order to prepare films with regular phase separation. The conversion of the separate phases into polyelectrolytes of different charge should lead to the preparation of charge mosaic membranes for piezodialysis.Copolymers of suitable monomers with 20–45 mole‐% butadiene content were synthesized which could be cross‐linked with sulfur monochloride. The comonomers were: styrene, 2‐vinyl pyridine, 4‐vinyl pyridine, methacrylic acid, methyl methacrylate and 2‐chloroethyl methacrylate.After conversion into the ionic form cross‐linked films of these copolymers showed salt rejections in the range of 26–78 % and water permeabilities of 40–43 [1· mm· m−2· day−1], respectively. These films can be used as anion and cation exchange membranes for water desalination.Mixtures of poly (2‐vinyl pyridine‐co‐butadiene) and poly (styrene‐co‐butadiene) yielded films with regular phase separation. After cross‐linking and conversion into the ionic form these charge mosaic membranes were porous and had poor mechanical strength. Despite these unfavourable properties a salt enrichment of 4.8 % was found in one case.