Small-angle neutron scattering studies of low-polarity telechelic ionomer solutions. 1. Total scattering

Abstract

The overall structure and thermodynamic interactions that take place in low-polarity ionomer solutions have been investigated via the technique of small-angle neutron scattering for two Na-neutralized carboxy-telechelic polystyrene model ionomer systems that differ in the length of the polymer backbone. The strong interchain association that is evidenced in the viscometric measurements of the ionomers compared to the ester forms is apparent in the scattering profiles of the ionomers that show a characteristic upturn that extends in the low-q regime and increases with increasing polymer concentration. The apparent molecular weight and size of the aggregated particles show a significant increase over a small concentration range, while the ionic content seems to not affect the degree of association in the concentration regime studied. The supramolecular structure of the ionomer solutions is revealed by fitting the scattering data to a scaling law in the intermediate qRg regime that supports a percolation type of behavior for the ionomer clusters for both systems studied. The fractal dimension of the aggregates is 1.76 for both ionomer systems which provides evidence for a rather extended configuration and high polydispersity of the clusters in solution. The molecular weight of the associating particles is observed to rapidly approach infinity with increasing polymer concentration, indicating the approach to a gel transition. The scattering data of the ionomer solutions were fitted to the de Gennes model based on the random-phase approximation theory. The Flory-Huggins interaction parameter of the ionomer solutions determined using this model shows a strong concentration dependence with a quite unexpected increase with decreasing polymer concentration. The thermodynamic interactions in the ionomer solutions were changed dramatically by the association as revealed by a significant decrease of the second virial coefficient.

Small-Angle Neutron Scattering Studies of Low Polarity Telechelic Ionomer Solutions. 2. Single Chain Scattering

“…This study focuses on the behavior of halato carboxy−telechelic polystyrene ionomers neutralized with sodium. The telechelic ionomers have been synthesized according to the synthetic procedures described in the first part of this series . The polymers based on either hydrogenous styrene (99%, Aldrich, USA) or styrene- d 8 monomer (98+atom% D, Aldrich, Belgium) were synthesized via anionic polymerization to produce a narrow molecular weight distribution.…”

“…The solutions were placed in quartz cells of thickness 2 mm, which was determined based on the known coherent and incoherent atomic cross sections to give sample transmissions within 0.5 to 0.8. , The scattering data from each solution and the solvent were corrected for the scattering from the empty cell and background (using a 6 Li blocked beam), and the corrected scattering from the solvent was subtracted from the corrected solution scattering to obtain the scattering from the polymer alone. The transmission measurements and the corrections for the detector response have been made as described previously . As none of the samples exhibited anisotropy, the scattering data were radially averaged and placed on an absolute scale by measuring the scattering from a 1 mm thickness silica gel standard that has a zero cross section of (d∑/dΩ) (0) = 32 ± 1 cm -1 .…”

“…In the first part of this series the technique of small-angle neutron scattering was applied to obtain the total scattering function of the telechelic ionomer solutions …”

Viscoelasticity of Potassium Neutralized Telechelic Poly(ethylene-butylene) Ionomer in Non-polar Solvent

“…[1][2][3][4][5][6][7][8][9] Although structures and properties of telechelic ionomers in bulk have been studied extensively, relatively little effort has been made to develop an understanding of their solution behavior. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Especially, there seems to be no report dealing with the association process of ionomers in a wide concentration range from dilute to concentrated regime.…”

Viscoelasticity of Potassium Neutralized Telechelic Poly(ethylene–butylene) Ionomer in Non-polar Solvent. II

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] It seems well established that telechelic ionomers are aggregated even at very dilute concentration in anhydrous solvent, grow in aggregate size with increasing polymer concentration C and then form weak viscoelastic networks at certain C Ã depending on a kind of metallic ions used followed by development of stronger networks with ion clusters as crosslinking points up to the bulk. Here, adjectives ''weak'' and ''strong'' are only conventionally used to differentiate two networks with that there are large differences in magnitudes of viscosity and plateau modulus characteristic of the viscoelastic network.…”