Macromolecules 1982,15,[1364][1365][1366][1367][1368] used to generate the correct selection from the q~ array for integration segments of this type. References and Notes(1) The most recent review of the properties of this phase is: Leute, U.; Dollhopf, W. Colloid Polym.ABSTRACT The structure of isotactic poly(methy1 methacrylate) (it-PMMA) has been determined by X-ray analysis and energy calculations. X-ray diffraction photographs were taken from an oriented sample of high crystallinity and the intensities and positions of the observed reflections were measured. The results indicate that the unit cell is triclinic although the unit-cell parameters are only slightly different from those of the orthorhombic cells reported in the literature. Favorable conformations are calculated by energy minimization, applying the virtual bond method. Our results support the suggestion of Tadokoro that it-PMMA crystallizes in a double-stranded 10/1 helix with a stabilization energy of 12.4 kJ/(base mol). ABSTRACT: The dielectric relaxation spectra of solid solutions of bisphenol A polycarbonate/bisphenolA bis(cumylpheny1) carbonate have been obtained-as a function of composition. Tg varies continuously with composition and can be described by either a Tg-M,-I or polymer-diluent correlation. The former indicates that the low molecular weight material is a better model system for polycarbonate than bisphenol A diphenyl carbonate studied previously. Up to 87.5 wt % small molecule, the T relaxations are Arrhenius activated.The T activation energy is composition independent above 25 wt % smal! molecule. This observation correlates with t i e disappearance of the 0 relaxation of the polymer and indicates that localized motion of the polymer backbone is intimately related to the energetics of longer chain motion at Tg.

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Monodisperse zinc sulfide particles were prepared by homogeneous precipitation from zinc sulfate solutions. Particle size could be adjusted in the range of 1 to 5 microns by changing the viscosity of the reaction medium. From electron micrographs of particles prepared in high viscosity media subparticles up to 50 nm in diameter could be observed. From these results it was concluded that particle growth took place predominantly by Brownian coagulation.Furthermore, it was established that stirring the reactor content during the initial phase of particle formation alone did not influence particle size, nor did it promote coagulation of micron-sized spheres. We were able to prepare this material in amounts up to 2 kg of solid material from a reactor with a working volume of 36 1.

The aim of this research was to prepare a monodisperse polystyrene latex without surfactants adsorbed at the particle surface. Conventional polymerization formulations usually lead to large amounts of oligomers. Furthermore, they are characterized by a low reproducibility with respect to particle size. This was overcome by using a seed latex that was crosslinked in order to overcome dissolution in the monomer phase. By adjusting the seed concentration, any desired particle size in the range 0.5-1.2 #m could be obtained. The monodispersity was very good.

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