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Chemical modification of polymers and properties of functionalized polymers

by Su, Zhaohui

Abstract (Summary)
The work presented in this thesis is divided into four chapters. Chapter I describes the control of the crystallization behavior of syndiotactic polystyrene (sPS) by chemical modification of sPS using sulfonation. In Chapter II, preparation of wood-ceramic composites through sol-gel processes is described. Chapter III describes the end-functionalization of poly(ethylene oxide)s (PEOs), and the interfacial properties of the functionalized PEOs. Finally, the distribution of chain conformation of PEO in the liquid state is discussed in Chapter IV. Direct sulfonation of highly stereoregular syndiotactic polystyrene (sPS) has been accomplished in chloroform. The degree of sulfonation can be effectively controlled. The crystallization behavior of sulfonated sPS is considerably different than the unmodified polymer. The crystallinity and the crystallization kinetics of sPS decrease with increasing extent of modification. Wood-ceramic composites were prepared by introducing a ceramic component into pine, a softwood, through sol-gel processes. Several ceramic precursors, including SiCl$\sb4$, Si(OCH$\sb3)\sb4$, and CH$\sb3$SiCl$\sb3$, were used. The ceramic content introduced into the wood structure can be controlled by varying the reaction time and the moisture content of wood. The modification of wood by CH$\sb3$SiCl$\sb3$ in supercritical CO$\sb2$ penetrated the entire wood structure, generating a macroscopically uniform distribution of the ceramic component in wood. Samples with one or both ends of monodisperse PEO functionalized with perfluorodecanoyl groups (PEO$\sp{\rm F}$ or PEO$\sp{\rm F2}$) were synthesized and blends of these end-capped PEOs with PEOs of the same molecular weight (M$\sb{\rm n}$$\sim$2000 - $\sim$16000) were prepared as cast films. Due to the lower surface energy of the fluorocarbon end groups, the modified PEOs preferentially adsorb to the free polymer surface. The surface concentration of the perfluoroalkyl end groups was measured by XPS which indicates that perfluoroalkyl chain ends adsorb to the polymer surface in a reasonably close-packed fashion (at all molecular weights) and leave a zone depleted of fluorine immediately beneath the highly fluorinated surface region. There is only a slight effect of molecular weight on surface fluorine content indicating a "stretched brush" conformation for the higher molecular weight samples. The adsorption of these polymers at the air-water interface was studied as well. The packing density and the orientation angle of the fluorinated chain end segregated at the interface were assessed by external reflectance IR. Isotropic Raman spectra of PEO in aqueous solution and in the melt were simulated by superposing calculated spectra resulting from a series of normal coordinate calculations performed for an ensemble of conformers, and compared with the corresponding experimental results. The conformational distribution for poly(ethylene oxide) in the molten state favors the tgg' conformer, and the aqueous solution of poly(ethylene oxide) contains mostly tgt conformers. The results for PEO were supported by measurements and computations made using 1,2-dimethoxyethane as a model.
Bibliographical Information:

Advisor:

School:University of Massachusetts Amherst

School Location:USA - Massachusetts

Source Type:Master's Thesis

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ISBN:

Date of Publication:01/01/1997

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