Crystal structure of isotactic poly(methyl methacrylate)

Abstract

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.

Copolymerization of acrylic acid and 2-hydroxyethyl methacrylate onto poly(N-vinylpyrrolidone): Template influence on comonomer reactivity

“…[14][15][16][17][18][19][20][21][22][23] For instance, the polymerization of acrylic acid is influenced by the presence of poly(N-vinylpyrrolidone) as the template. [24][25][26] Dilatometry and conductimetry were used to investigate the kinetics of the reaction.…”

Time-Resolved Emission Anisotropy of Anthracene Fluorophore in the Backbone of Stereoregular Poly(methyl methacrylate)

“…The double-stranded helical structure of PMMA stereocomplex proposed by Bosscher et al [2] was an impetus to compare this stereocomplex with the DNA molecule. Sasaki and Yamamoto [15] estimated the torsion rigidity of the stereocomplex formed by i-PMMA and s-PMMA in toluene using time-resolved fluorescence emission anisotropy data.…”

“…The torsional rigidity (a) of the stereocomplex of PMMA was evaluated according to Equation (5) and the value of the friction factor c was determined from Equation (6); the viscosity of DMF and 1,4-dioxane at 30 8C is 7.58 6 10 -4 Pa N s and 1.073 6 10 -3 Pa N s, respectively. The other quantities characterizing dimensions of the stereocomplex proposed by Bosscher et al [2] were taken from ref. [15] In this case, the subunit rod consists of one monomer unit of i-PMMA and two monomer units of s-PMMA.…”

“…Solvents are classified according to their tendency to stimulate the stereocomplex formation: solvents enabling the stereocomplex formation (weakly and strongly complexing solvents) and solvents where the stereocomplex does not form (non-complexing solvents). [1] From X-ray diffraction data and conformational energy calculation, Bosscher et al [2] proposed that the stereocomplex is formed by a double-stranded helix in which the helix of an isotactic chain with a small radius (30/4 helical conformation) is surrounded by a syndiotactic chain with a large radius (60/4 helical conformation). Recently, Schomaker and Challa [3] proposed another double-stranded helix model with 9/1 helical symmetry.…”

On-Line SEC-NMR Analysis of the Stereocomplex of Uniform Isotactic and Uniform Syndiotactic Poly(methyl methacrylate)s

“…[1,2] This phenomenon is interesting from the viewpoint of molecular "recognition" of simple synthetic polymers. Of particular interest is the plausible structure of PMMA stereocomplex [3,4] which is in some respects analogous to the double-stranded helical structures of biological macromolecules.…”