Polystyrene

About: Polystyrene is a research topic. Over the lifetime, 28444 publications have been published within this topic receiving 508696 citations. The topic is also known as: PS & Poly(styrene).

The glass temperature and related properties of polystyrene. Influence of molecular weight

Abstract: Experimental results on the molecular weight dependence of the glass temperature (To), bulk viscosity g, viscosity-temperature coeficient (ET), and specific volume (v) for fractionated polystyrenes were presented in previous publications.' Subsequently, it was shown that the relationship used to calculate the molecular weights ( M ) of the fractions from their intrinsic viscosities in benzene a t 30\" was in error for values of M < 30,000.293 The data are therefore re-examined here and the previously reported empirical equations relating the above properties to molecular weight and temperature are re-expressed in terms of a revised molecular weight scale. The results of more recent investigations are also discussed. Molecular weights of the polystyrene fractions were calculated previously from their intrinsic viscosities, [g], at 30\" in freshly distilled benzene, using the relationship of E ~ a r t : ~ log Mu = (log [g] + 4.013)/0.74 ( M > 3 X lo4) (1)

Studies on the preparation and characterisation of monodisperse polystyrene laticee: III. Preparation without added surface active agents

Abstract: Preparative methods have been developed in order to obtain monodisperse polystyrene latices in the absence of added surface active agents. By suitable adjustment of the ionic strength of the aqueous phase the initiator concentration and the polymerisation temperature it was found possible to obtain a range of particle sizes, ca. 0.1 to 1.0 ,um, by single-stage reactions. The total initial ionic strength of the aqueous phase was found to play a critical function in determining particle size. A formula has been derived from the experimental data which enables the preparative conditions required to form a latex, containing particles of a particular size, to be predicted.

Influence of molecular weight and degree of crosslinking on the specific volume and glass temperature of polymers

Abstract: On the basis of simple assumptions, equations are derived for predicting the specific volume-temperature-molecular weight (v-T-M) relationships for a homologous series of polymers from the v-T curves for the monomer and the polymer of infinite molecular weight. Analogous v-T-ρ relationships (where ρ is the degree of crosslinking) are similarly obtained. The result, that v decreases linearly with decreasing 1/M and with increasing ρ, conforms with the picture that either the removal of two chain ends (as M increases) or the introduction of a crosslinkage involves, between two polymer segments, the exchange of a van der Waals bond for a shorter covalent bond. The validity of these equations is illustrated by comparison with the observed data for polymers covering a wide range in M, T, and chemical type. For several polymer series the extrapolated value of v at 0°K (v0) is the same for all members of the series, indicating that at this temperature the average length of the van der Waals and covalent bonds between polymer segments are the same. Assuming that the form of the linear relationship observed for polystyrene between the specific volume (vg) at the glass temperature and the value (Tg) of the latter is valid for other polymer series, equations are derived which predict Tg as a function of M from the limiting value of the glass temperature for a chain of infinite length, and from the v-T curves in the liquid state for the monomer and for the polymer of M = ∞. Analogous Tg-ρ relationships are similarly obtained. According to these equations, a linear relationship between 1/Tg and 1/M should be obtained, which reduces at high M to a linear dependence of Tg on 1/M. Similarly, a linear dependence of Tg on ρ is predicted at low ρ. These predictions are in satisfactory agreement with data on polystyrene fractions and on crosslinked copolymers of styrene with divinylbenzene. The conclusion that Tg for polystyrenes represent a state of iso-free volume irrespective of M is shown to be an approximation that is valid, within experimental error, only for large values of M.

Fabrication of Tunable Superhydrophobic Surfaces by Nanosphere Lithography

Abstract: With trimming of the diameter of the well-ordered polystyrene arrays using oxygen plasma treatment and modification of these surfaces with gold and alkylthiols, the water contact angles on these su...

Ordered nanoporous polymers from polystyrene-polylactide block copolymers.

Abstract: Nanoporous polystyrene monoliths were prepared from polystyrene−polylactide (PS−PLA) block copolymers that form hexagonally packed nanocylinders of PLA in a PS matrix. A morphology diagram was developed to determine the range in composition and molecular weight over which this morphology existed. Macroscopic alignment of these materials gave anisotropic monoliths that were subjected to mild degradation conditions leading to the chemical etching of the PLA. The resulting nanoporous monoliths consisted of a polystyrene matrix containing hexagonally close-packed, oriented, and continuous nanoscopic channels (pore size was tunable through synthesis or blending) lined with chemically accessible hydroxyl functional groups. Both the precursors and the porous materials were analyzed moleculary (size-exclusion chromatography and proton nuclear magnetic resonance spectroscopy) and structurally (small-angle X-ray scattering, scanning electron microscopy, and differential scanning calorimetry). In addition, the surfa...