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.
A series of polybutadiene "combs" with polydispersities less than 1.2 have been synthesized using anionic polymerization techniques. Control was exerted over the average number and length of branches but not on their placement along the polybutadiene backbone. Hydrogenation of the materials resulted in the formation of the corresponding poly(ethylene-co-butene) combs. The effects of branching on the solution properties of the polybutadiene combs have been examined. As predicted using the BerryOrofino model, the "shrinking factor" g′ decreases with increasing branch length. The effect of branching on the Zimm-Stockmayer parameter, g, has also been investigated.
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