Backbone Carbon Atoms Research Articles

Sequence Length and Crystallinity in Alpha-Olefin Terpolymers

Abstract The minimum sequence length for crystallization in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers. Copolymers and terpolymers of ethylene, propylene, and but-1-ene were prepared with a Ziegler—Natta catalyst system. Compositions of feeds and polymers were analyzed, and kinetic reactivity parameters were calculated using both the Fine—Ross and Alfrey—Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane-soluble, rubbery polymers even using a catalyst system which normally produced blocky materials. Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallization did not occur was estimated; this length was approximately 20 backbone carbon atoms.

Sequence length and crystallinity in alpha‐olefin terpolymers

AbstractThe minimum sequence length for crystallisation in a polymer was determined by a novel kinetic approach using sequence analysis of a series of blocky terpolymers.Copolymers and terpolymers of ethylene, propylene, and but‐l‐ene were prepared with a Ziegler–Natta catalyst system. Compositions of feeds and polymers were analysed, and kinetic reactivity parameters were calculated using both the Fineman–Ross and Alfrey–Goldfinger approaches. The parameters were then applied to determine the sequence length distribution of each component in the terpolymers. Also, deliberate control of sequence lengths enabled synthesis of heptane‐soluble, rubbery polymers even using a catalyst system which normally produced blocky materials.Crystalline contents of the terpolymers were determined experimentally by nitric acid digestion. A critical comparison of the measured crystallinities with the calculated sequence length distributions was thereby made possible. From this comparison a minimum sequence length of monomer below which crystallisation did not occur was estimated; this length was approximately 20 backbone carbon atoms.

Diffusion in Amorphous Polymers

Abstract Diffusion and solubility coefficients are presented for He, Ne, Ar, and N2 in three ethylene propylene copolymers, two styrene butadiene copolymers and a cis-polybutadiene at five temperatures in the range 0–50° C. The data were obtained by using a slightly modified Dow Gas Transmission Cell and analyzed by a new modified time lag technique which properly accounts for the increase in pressure on the downstream side of the cell. Activation energies were calculated for the twenty-four diffusion systems and correlated with polymer intermolecular forces and gas molecule sizes by using a cell theory for amorphous polymers which employs a potential energy depth parameter, ε*, a range parameter, ρ*, the number of degrees of freedom per structural unit (center), 3Cm, and the number of centers per unit cell, n. The first three parameters were evaluated from thermodynamic data, while n was evaluated from the diffusion data. It is believed that n is an indication of the number of backbone carbon atoms active in polymer segmental motion. The values obtained here (5–9) agree well with existing values estimated from polymer viscous flow data. A correlation for the solubility data is shown and a linear free energy relationship is discussed.

The infra-red absorption characteristics of syndiotactic poly(methyl methacrylate) from 1050 cm −1 to 1300 cm −1

There are five (i.e. v 1 to v 5) infra-red absorption peaks associated with the ester group of s-poly(methyl methacrylate) while simple esters (i.e. methyl acetate) exhibit only one. These multiple absorption peaks do not arise because of specific intermolecular interactions because they persist in dilute solution. The multiple absorption peaks do arise because of specific intramolecular interactions because they disappear in copolymers of styrene. The implication being that a single ester group can be found in either one of two or perhaps four different rotational positions, each position is to be associated with a different force constant. The absorption characteristics could be described by the sum of seven Lorenz type dispersion functions each associated with a single absorption peak. From the Lorenz parameters the variation of integrated intensity (which is related to the population density in each environment) can be determined as a function of temperature. The integrated intensity was independent of temperature for all four peaks below the glass temperature: above the glass temperature they varied with temperature. However, the sum of the integrated intensities for peaks v 1 and v 2 as well as v 3 and v 4 was found to be independent of temperature over the entire experimental range. The implication is that the ester group can rotate from the environments associated with v 1 to v 2 or from v 4 to v 3 only above the glass temperature. Further experimental evidence indicates that the high temperature population distribution can be supercooled to room temperature. In addition, the dilute solution behaviour near room temperature is similar to the behaviour above the glass temperature for the solid polymer. The location, relative intensity, polarization and sensitivity to polymer chain tacticity indicates that peaks v 6, v 7 may be associated with a planar zig-zag arrangement of the backbone carbon atoms.

Diffusion in amorphous polymers

AbstractDiffusion and solubility coefficients are presented for He, Ne, Ar, and N2 in three ethylene‐propylene copolymers, two styrene‐butadiene copolymerg and a cis‐poly‐butadiene for five temperature levels in the range 0–50°C. The data were obtained by using a slightly modified Dow Gas Transmission Cell and analyzed by a new modified time‐lag technique which properly accounts for the increase in pressure on the downstream side of the cell. Activation energies were calculated for the twenty‐four diffusion systems and correlated with the polymer intermolecular forces and the gas molecule sizes by using ii cell theory for amorphous polymers which employs a potential energy depth parameter, ϵ*, a range parameter, p*, the number of degrees of freedom per structural unit (center), 3Cm, and the number of centers per unit cell, n. The first three parameters were evaluated from thermodynamic data, while n was evaluated from the diffusion data. It is believed that n is an indication of the number of backbone carbon atoms active in polymer segmental motion. The values obtained here (5–9) agree well with existing values estimated from polymer viscous flow data. A correlation for the solubility data is shown and a linear free energy relationship is discussed.