PMSE 36 |
| The purpose of this talk is to describe and discuss the outcome of a study of the crystallization of Nylon 66 from solutions of the polymer in glycerol. This study has led to the following observations: (i) Seeming counterparts of the unusual negatively birefringent spherulites and asymmetric objects which have long been known to form in bulk polymer as a result of isothermal melting and recrystallization in the temperature range ~255-265°C, can be grown from solution. (ii) The peripheral regions of these spherulitic and complex aggregates exhibit different but distinctly microfaceted lamellae. The microfaceting of these lamellae distinguishes them from the more familiar type of lamellar single crystals grown in the same preparations under the same conditions, which exhibit preferential growth parallel to the a-axis. (iii) Electron diffraction of all the species of lamellae observed indicate that in all cases the surfaces containing the chain folds (the upper and lower surfaces of the lamellae) are parallel to (001) planes. Considerations stemming from the observed diversity in the lateral growth habits of nylon 66 lamellae will be suggested in regard to: (a) Implications concerning the possibility of intrinsic chain folding differences [i.e. folding along different (hk0) planes or combination of (hk0) planes, where h,k equal 0 or1). (b) The origins of the negatively birefringent spherulitic and other melt grown structures mentioned above, as compared to the more common positively birefringent spherulites which form upon cooling nylon 66 from temperatures well above the polymer melting point e.g. >280°C |
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50 Years after the Discovery of Polymer Single Crystals: A Look Back, Current Discoveries and Future Opportunities
8:30 AM-11:55 AM, Sunday, August 19, 2007 Westin Boston Waterfront -- Alcott, Oral
Division of Polymeric Materials: Science & Engineering |