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Synthesis and properties of large ri...

Stanford University.

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Synthesis and properties of large ring macromolecules.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Synthesis and properties of large ring macromolecules./
作者:	Jeong, Wonhee.
面頁冊數:	150 p.
附註:	Source: Dissertation Abstracts International, Volume: 69-10, Section: B, page: 6133.
Contained By:	Dissertation Abstracts International69-10B.
標題:	Chemistry, Organic. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3332845
ISBN:	9780549846055

Synthesis and properties of large ring macromolecules.
Jeong, Wonhee.

Synthesis and properties of large ring macromolecules. - 150 p.

Source: Dissertation Abstracts International, Volume: 69-10, Section: B, page: 6133.

Thesis (Ph.D.)--Stanford University, 2008.

The topological constraint of connecting the ends of a large macromolecule has a significant influence on its structure, dynamics, and properties. However, some properties of ring polymers are not firmly understood at the molecular level. This is primarily due to our inability to generate and characterize high molecular weight cyclic polymers in high purity. Thus, the development of versatile synthetic routes to large ring macromolecules of well-defined molecular weight is expected to fill the gaps in our understanding of the properties of cyclic polymers and guide us in generating new classes of polymeric materials.

ISBN: 9780549846055Subjects--Topical Terms:

516206
Chemistry, Organic.

Synthesis and properties of large ring macromolecules.
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245 1 0 $a Synthesis and properties of large ring macromolecules.
300 $a 150 p.
500 $a Source: Dissertation Abstracts International, Volume: 69-10, Section: B, page: 6133.
502 $a Thesis (Ph.D.)--Stanford University, 2008.
520 $a The topological constraint of connecting the ends of a large macromolecule has a significant influence on its structure, dynamics, and properties. However, some properties of ring polymers are not firmly understood at the molecular level. This is primarily due to our inability to generate and characterize high molecular weight cyclic polymers in high purity. Thus, the development of versatile synthetic routes to large ring macromolecules of well-defined molecular weight is expected to fill the gaps in our understanding of the properties of cyclic polymers and guide us in generating new classes of polymeric materials.
520 $a Chapter 1 summarizes current synthetic routes developed for the preparation of large ring macromolecules. This chapter contrasts solution and bulk properties of cyclic polymers distinct from linear polymers that have been theoretically predicted and experimentally observed.
520 $a Chapter 2 describes the zwitterionic ring-opening polymerization of lactide by using the N-heterocyclic carbene 1,3-dimesitylimidazol-2-ylidene. This synthetic route generates cyclic poly(lactide)s of defined molecular weight (Mw > 20 kg/mol) and narrow molecular weight distributions (polydispersity < 1.3). Mechanistic and kinetic investigations of these reactions implicate a mechanism that involves a slow initiation step (second order in monomer), and a propagation step (first order in monomer) that is much faster than cyclization and depropagation. Stochastic kinetic simulations based on the proposed mechanistic model yield reasonable agreement with the experimental data for evolution of molecular weight and polydispersity as a function of time. The proposed mechanism provides a useful framework to interpret the unusual behavior of these zwitterionic polymerizations and guides further studies to optimize these zwitterionic polymerizations as a strategy to generate well-defined cyclic polyesters.
520 $a Chapter 3 describes the generation of spirocyclic imidazolines derived from the saturated carbene 1,3-dimesitylimidazolin-2-ylidene and beta-lactones. These spirocyclics not only support the proposed nucleophilic mechanism, but also serve as competent initiators for the zwitterionic ring-expansion polymerization of beta-lactones to generate cyclic poly(beta-lactone)s of well-defined molecular weight. Mechanistic studies suggest a novel mechanism that involves the reversible collapse of zwitterionic intermediates to neutral imidazole spirocycles.
520 $a Chapter 4 describes the synthesis of high molecular weight cyclic poly(epsilon-caprolactone) (MW > 100 kg/mol) by the zwitterionic polymerization of epsilon-caprolactone initiated with 1,3,4,5-tetramethylimidazol-2-ylidene. Synchrotron small-angle X-ray scattering experiments show that crystallization of cyclic poly(epsilon-caprolactone) is faster than that of linear poly(epsilon-caprolactone), and that the equilibrium melting point of cyclic poly(epsilon-caprolactone) is estimated to be higher than that of linear poly(epsilon-caprolactone). These results suggest the significance of topological interactions in the bulk of cyclic polymers and merit further studies on the crystallization and dynamics of cyclic polymers in bulk.
590 $a School code: 0212.
650 4 $a Chemistry, Organic. $3 516206
650 4 $a Chemistry, Polymer. $3 1018428
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710 2 $a Stanford University. $3 754827
773 0 $t Dissertation Abstracts International $g 69-10B.
790 $a 0212
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3332845