Investigation of nanodispersion in polystyrene-montmorillonite nanocomposites by solid state NMR

Nanocomposites result from combinations of materials with vastly different properties in the nanometer scale. These materials exhibit many unique properties such as improved thermal stability, reduced flammability, and improved mechanical properties. Many of the properties associated with polymer–clay nanocomposites are a function of the extent of exfoliation of the individual clay sheets or the quality of the nanodispersion. This work demonstrates that solid-state NMR can be used to characterize, quantitatively, the nanodispersion of variously modified montmorillonite (MMT) clays in polystyrene (PS) matrices. The direct influence of the paramagnetic Fe3, embedded in the aluminosilicate layers of MMT, on polymer protons within about 1 nm from the clay surfaces creates relaxation sources, which, via spin diffusion, significantly shorten the overall proton longitudinal relaxation time (T1 H). Deoxygenated samples were used to avoid the particularly strong contribution to the T1 H of PS from paramagnetic molecular oxygen. We used T1 H as an indicator of the nanodispersion of the clay in PS. This approach correlated reasonably well with X-ray diffraction and transmission electron microscopy (TEM) data. A model for interpreting the saturation-recovery data is proposed such that two parameters relating to the dispersion can be extracted. The first parameter, f, is the fraction of the potentially available clay surface that has been transformed into polymer–clay interfaces. The second parameter is a relative measure of the homogeneity of the dispersion of these actual polymer–clay interfaces. Finally, a quick assay of T1 H is reported for samples equilibrated with atmospheric oxygen. Included are these samples as well as 28 PS/MMT nanocomposite samples prepared by extrusion. These measurements are related to the development of highthroughput characterization techniques. This approach gives qualitative indications about dispersion; however, the more time-consuming analysis, of a few deoxygenated samples from this latter set, offers significantly greater insight into the clay dispersion. A second, probably superior, rapid-analysis method, applicable to oxygen-containing samples, is also demonstrated that should yield a reasonable estimate of the f parameter. Thus, for PS/MMT nanocomposites, one has the choice of a less complete NMR assay of dispersion that is significantly faster than TEM analysis, versus a slower and more complete NMR analysis with sample times comparable to TEM, information rivaling that of TEM, and a substantial advantage that this is a bulk characterization method. © 2003 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys 41: 3188–3213, 200

Further 13C NMR evidence for the coexistence of two crystalline forms in native cellulose

"September, 1987.""This manuscript is based on results of collaboration between The Institute of Paper Chemistry and the National Bureau of Standards, and has been submitted for inclusion in the Symposium on solid State Characterization of Cellulose, R.H. Atalla, Editor, to be published in the ACS Symposium Series.

Studies on the structure of cellulose using Raman spectroscopy and solid state C NMR

"November, 1988.""This manuscript is based on results obtained in IPC research and has been submitted for consideration for publication in the Journal of Applied Polymer Science.

Studies on the structure of cellulose using Raman spectroscopy and solid state 13C NMR

"January, 1987.""This manuscript is based on results obtained in IPC Project 3288 and is to be presented at the International Symposium on Wood and Pulping Chemistry in Paris, France on April 26-30, 1987.

Pulping processes project advisory committee meeting

"October 18-19, 1988."Copy 2 includes handouts.Fine structure of wood pulp fibers: project 3288 / R. H. Atalla ; Raman microprobe investigation of molecular structure and organization in the native state of woody tissue: project 3521-2 / R. H. Atalla ; The resolved Raman microprobe system / R. H. Atalla ; Smelt water explosions: project 3456-2 / T. M. Grace ; Energy conversion and scaling rules for steam explosions / T. M. Grace, N. T. Shiang, J. R. Hopenfeld ; Fundamental processes in alkali recovery furnaces: project 3473-1 / T.M. Grace ; Fundamental studies of black liquor combustion: project 3473-6 / T. M. Grace, A. Macek ; In-situ fume particle size and number density measurement from synthetic smelt: project 3473-6 / Jay C. L. Hsu, David T. Clay, Cary Presser ; Improved process for bleached pulp: project 3474 / T. J. McDonough ; Fundamentals of selectivity in pulping and bleaching: project 3475 / D. R. Dimmel ; Development and application of analytical techniques: project 3477 / D. B. Easty ; Fundamentals of brightness stability: project 3524 / U. P. Agarwal ; Strong, intact high yield fibers: project 3566 / T. J. McDonough, S. Aziz ; Computer model of recovery furnace: project 3605 / T. M. Grace -- Handout

Pulping processes project advisory committee meeting

"March 22-23, 1988."Fine structure of wood pulp fibers: project 3288 / R. H. Atalla ; Smelt-water explosions: project 3456-2 / T. M. Grace ; Fundamental processes in alkali recovery furnaces: project 3473-1 / T. M. Grace, J. H. Cameron, D. T. Clay ; Improved processes for bleached pulp: project 3474 / T. J. McDonough, B. Bihani ; Fundamentals of selectivity in pulping and bleaching: project 3475 / D. R. Dimmel ; Development and application of analytical techniques: project 3477 / D. B. Easty ; Raman microprobe investigation of molecular structure and organization in the native state of woody tissue: project 3521-2 / R. H. Atalla ; Fundamentals of brightness stability: project 3524 / U. P. Agarwal ; Exploratory research: project 3534 / Division 20 ; Strong, intact high yield fibers: project 3566 / T. J. McDonough, S. Aziz ; Computer model of recovery furnace: project 3605 / T. M. Grace ; Excerpts from midrange plan for Institute of paper chemistry / R. A. Yeske -- Handout

High Throughput Methods for Polymer Nanocomposites Research: Extrusion, NMR Characterization and Flammability Property Screening

A large number of parameters influence polymer-nanocomposite performance and developing a detailed understanding of these materials involves investigation of a large volume of the associated multi-dimensional property space. This multi-dimensional parameter space for polymer-nanocomposites consists of the obvious list of different material types under consideration, such as polymer and nano-additive, but also includes interphase surface chemistry, and processing conditions. This article presents combinatorial library design and high-throughput screening methods for polymer nanocomposites intended as flame-resistant materials. Here, we present the results of using a twin-screwn extruder to create composition-gradient library strips of polymer nanocomposites that are screened with a solid-state NMR method to rapidly evaluate the optimal processing conditions for achieving nanocomposite dispersion. In addition, we present a comparison of a new rapid Cone calorimetry method to conventional Cone calorimetry and to the gradient heat-flux flame spread method