Poly(ethyl α-chloroacrylates) of different tacticities have been investigated by nmr spectroscopy at 220 MHz. Tetrad assignments and relative intensities of the tetrads are reported. The results obtained indicate a s...
A study has been made of the mechanical‐relaxation behavior of an ethylene‐methacrylic acid copolymer containing 4.1 mole % acid units and its partially ionized sodium salts. Degrees of ionization, estimated from in...
A study has been made of the mechanical‐relaxation behavior of an ethylene‐methacrylic acid copolymer containing 4.1 mole % acid units and its partially ionized sodium salts. Degrees of ionization, estimated from infrared analysis, ranged from 0% to 78%. The weight‐percent crystallinity of the samples, determined by differential‐scanning calorimetry, varied from about 15 for the acid copolymer to about 7 for the 78% ionized copolymer. Four relaxation regions have been observed. They are labelled α, β′, β and γ, and each has been assigned to motions within the amorphous phase of the polymer. In plots of the logarithmic decrement against temperature (at 1 cps), the α peak for the annealed acid copolymer occurs at 50°C and shifts to higher temperatures with increasing degree of ionization. This trend is consistent with the increase in melt flow viscosity with increasing ionization and, on this basis, the α process is attributed to the long‐range diffusional motions of chain segments. The β′ peak occurs at 23°C for the annealed acid copolymer and decreases in magnitude with increasing ionization. Hence the β′ mechanism is attributed to the micro‐Brownian motions of chain segments involving the breaking and reforming of intermolecular hydrogen bonds between dimerized carboxylic‐acid groups. The latter assignment is supported by infrared studies of hydrogen bonding as a function of temperature. The β peak is absent for the acid copolymer but appears at −10°C for the ionized polymers and increases in height with increasing ionization. Thus, the β process is attributed to motions of branched chain segments including the ionic (carboxylate) side groups. The onset of the γ peak is observed at −120°C and is associated with the local motions of linear methylene sequences. The observation that the β peak is located at a temperature very close to the β peak (−20°C) for ordinary branched polyethylene, must cast considerable doubt on the widely held view that the ionic side groups
The study of the relationship between the structure, morphology and properties of polymer films has significantly progressed in recent years through the use of a number of phyiscal techniques - some new and some old. ...
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ISBN:
(数字)9781461589518
ISBN:
(纸本)9781461589532
The study of the relationship between the structure, morphology and properties of polymer films has significantly progressed in recent years through the use of a number of phyiscal techniques - some new and some old. These methods include small and large angle x-ray diffraction, bire fringence, light scattering, infrared dichroism, fluorescence polarization, light and electron microscopy and interferrometry. This collection of papers, most of which were presented at a symposium at the Boston American Chemical Society Meeting in April, 1972, represent a collection of recent studies using many of these methods by some of the leading scientists in their fields. It is evident that these various techniques permit the study of various aspects of film structure such as crystal structure and orientation, amorphous orientation, the interrelation of crystalline and amorphous regions in lamellar, fibrillar, and spherulitic superstructure and the relationshi. p of these structural variables to the mechanical and optical properties of the films. Film structure is sufficiently complex that a complete understanding of the relationship between structure and properties will come from the employment of a combination of several of these methods. vii CONTENTS Optical Studies of the Morphology of polymer Films ••• • • 1 Richard S. Stein Light Scattering by Oriented Native Cellulose Systems 25 R. H. Marchessault Superstructure in Films of Bio and Biorelated Small Angle polymers as Noted by 39 Light Scattering • • Garth L.
A sample of low-density polyethylene containing 1.4 long chain branches per 100 carbon atoms was chemically modified by the inclusion of phosphonic acid side groups. Dynamic mechanical and differential scanning calori...
An infrared spectroscopic investigation of ethylene-methacrylic acid copolymers and their sodium salts has been carried out. All the copolymers studied were based on a parent copolymer containing 4.1 mol % of methacry...
An infrared spectroscopic investigation of ethylene-methacrylic acid copolymers and their sodium salts has been carried out. All the copolymers studied were based on a parent copolymer containing 4.1 mol % of methacrylic acid groups. This was then neutralized to various extents (from 0 to 78%) with sodium hydroxide. The per cent ionization was determined from the integrated absorbance of the 1700 cm-1 un-ionized carbonyl stretching band. Temperature-dependent infrared studies showed that the behavior of the un-ionized acid groups over the entire range of ionization is quantitatively comparable to that of low molecular weight carboxylic acids in nonpolar solvents. A monomer-dimer equilibrium exists among the acid groups and they are almost completely in the form of hydrogen-bonded dimers at room temperature. The heat of dissociation of the dimers was found to be 11.6 kcal mol-1. Thus each hydrogen-bond has a bond strength of 5.8 kcal mol-1. Infrared dichroism studies established that there is a significant amount of crystallinity even at the highest degree of ionization, that the hydrogen bonds are intermolecular in nature, and that the ionized carboxylate groups have a preferred orientation out of the plane of the main chain of the copolymer.
A laser homodyne spectrometer has been used to study the power spectrum of light scattered from dilute polystyrene + 2-butanone solutions. From the measurements the translational diffusion constants for the macromolec...
A laser homodyne spectrometer has been used to study the power spectrum of light scattered from dilute polystyrene + 2-butanone solutions. From the measurements the translational diffusion constants for the macromolecules were determined as a function of molecular weight and solute concentration. The analysis of the data included an estimation of the unperturbed dimensions of the polymer.
A study has been made of the relaxation phenomena in three series of polyurethanes in the neighborhood of their glass transition temperatures and above. The technique of dynamic mechanical relaxation was used in the i...
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