Rational approaches to regulating polymer properties in ring-opening metathesis polymerization

Citation

Benedicto, Alto D. (1995) Rational approaches to regulating polymer properties in ring-opening metathesis polymerization. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09112007-131436

Abstract

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The molecular weight distribution of a living polymerization when chain-transfer agents are intentionally added were computed numerically. Results showed that traditional expressions for number-average degree of polymerization [...] and polydispersity index (PDI) of chain-growth polymerization cannot be used. The well-known Mayo equation fails even when the system has achieved steady-state polymerization. Although the behavior of the system is complex, an analytical expression for [...] was derived. Plots based on the analytical expression showed excellent agreement with that from numerical solutions. The implications of the calculations were discussed. The kinetics of living ring-opening metathesis polymerization (ROMP) of norbornene in the presence of neohexene catalyzed by Mo was investigated.

The living ROMP of norbornene [...] and bicyclo[3.2.0]hept-2-ene [...] by [...] was demonstrated. The molecular weight varied linearly with conversion. Discrete propagating species showed that [...] ligand dissociated during polymerization of [...], and that CuCl (abstracts [...]) enhanced the rate of polymerization of [...]. The specific propagation rate constants ([...] and [...], respectively) of homopolymerization of [...] and [...] were measured, respectively. Block copolymers were easily prepared. From reactivity ratio studies, the ordering of the specific propagation rate constants are [...]. The effect of styrene as chain-transfer agent on the molecular weight was examined.

The hitherto unassigned (and unknown) microstructure of polymers prepared from 7-oxabicyclo[2.2.1]hept-2-ene derivatives have finally been unambiguously assigned. Polymers catalyzed by [...] have all cis double bonds and highly syndiotactic, while those from [...] and [...] {[...]= 2,7-dimethyloctadienediyl} have high trans double bond content and highly isotactic.

Studies on the olefin isomerization catalyzed by [...] revealed that the presence of hydroxyl functionality on the terminal olefin resulted in formation of 1 : 1 ratio of cis : trans double bonds on the isomerized internal olefin product, in contrast with near exclusive isomerization of double bond to trans when no hydroxyl group was present.

A numerical algorithm was developed for the evaluation of a chirality function for triangles on a plane, showing that such algorithm may be easily extended into the case of tetrahedron in 3-dimensional space.

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