The isothermal crystallization kinetics, spherulite morphology, and thermal behavior of the melt-crystallized optically active R and S polyenantiomers, their blends, and the stereoblock form of poly(epichlorohydrin) (PECH) and poly(propylene oxide) (PPrO) have been investigated using polarized light microscopy (PLOM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The novel optically pure polyenantiomers of PECH were synthesized from the optically active monomers using a triethylaluminum$ cdot$water (1:0.6) catalyst, which was also used in the polymerization of the racemic monomer to an isotactic crystalline stereoblock fraction. The optically pure polyenantiomers and the stereoblock form of PPrO were obtained by the quantitative dechlorination reaction of the corresponding PECH polymers, using LiAlH$ sb4$, with retention of configuration of the main chain chiral centers. / The spherulite radial growth rates of the melt-crystallized PECH equimolar polyenantiomer blend are depressed relative to those of either optically pure components over the range of crystallization temperatures from the glass transition temperature ($T sb{ rm g} = -26 sp circ$C) to the equilibrium melting temperature ($T sb{ rm m} sp circ = 138 sp circ$C), which were determined to be the same for all of the PECH polymers. A further marked reduction in growth rates is recorded for the stereoblock polymer. Conversion of the PECH polyenantiomers to PPrO results in an overall order of magnitude increase in the spherulite radial growth rates. The growth rates of the PPrO stereoblock are only slightly depressed relative to those of either optically pure polyenantiomer over the range of crystallization temperatures from $T sb{ rm g}({-}65 sp circ$C) to $T sb{ rm m} sp circ(82 sp circ$C), which were determined to be the same for all of the PPrO polymers. An analysis of the linear spherulite radial growth rates of the PECH polymers in terms of the Hoffman-Lauritzen treatment gives evidence of a rougher lamellar fold surface in the stereoblock polymer than in the polyenantiomers, but suggests similar surface free energies among the polyenantiomers and stereoblock form of PPrO. / The multiple melting behavior exhibited by the different forms of PECH is greatly dependent on DSC heating rate and isothermal crystallization time, for samples crystallized at low temperatures and high temperatures, respectively. The behavior is demonstrated to be due to reorganization during the DSC heating scan in the former case, and linked to the process of secondary crystallization in the latter. / The optically pure polyenantiomers, their equimolar blend, and the stereoblock form of PPrO exhibit regularly banded spherulites, observed using PLOM. In contrast, only the optically active polyenantiomers of PECH form banded spherulites, whereas the equimolar polyenantiomer blend and the stereoblock display nonbanded, coarser spherulites. The birefringent extinction banding pattern of the PECH optically pure polyenantiomer spherulites corresponds directly to the surface topography mapped by AFM: Regularly alternating concentric ridges and valleys indicate the edges and the fold surfaces, respectively, of the radiating helicoidal lamellae. The direction or "sense" of an apparent surface spiral pattern of a banded spherulite is directly dependent on the chiral sense of the constituent polyenantiomer. It is suggested that the effects of the backbone chirality are being transmitted to the level of the gross spherulite morphology. / On the basis of the observed differences in crystallization kinetics and spherulite morphology among the well characterized PECH polymers, a mechanism of stereospecific segregation at the growth front is proposed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40257 |
| Date | January 1996 |
| Creators | Singfield, Kathy L. (Kathy Lee) |
| Contributors | Brown, G. Ronald (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001499697, proquestno: NN12487, Theses scanned by UMI/ProQuest. |
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