| Summary: | 碩士 === 國立臺灣大學 === 化學學系 === 82 === A series of low molecular weight (Mn<10.6k), high phenyl
content (>50 mol%) polydiphenylsiloxane/polydimethylsiloxane
(PDPS/PDMS) random copolymers were synthesized through a living
anionic polymerization from hexamethylcyclotrisiloxane(D3) and
hexaphenylcyclotrisiloxane(P3), using phenyllithium as
initiator, THF as solvent, diphenylmethylsilane (or
dimethylphenylsilane) as terminator. Characterization of these
copolymers was carried out by GPC, 1H-NMR and 29Si-NMR
spectroscopy. The reactivity ratio of the monomers under this
anionic polymerization condition and the sequence distribution
of these copolymer's products were studied in detail. The
relationship between the physical properties and the phenyl
content of the copolymers was also investigated. The reaction
rate initiated by phenyllithium was slower than by n-
butyllithium in D3 polymerization and D3/P3 copolymerization .
In the D3/P3 copolymerization the reactivity ratio was obtained
by using Fineman-Ross eq.. Combined the reactivity ratio with
the Skeist's equation and Bovey's pentad model, the
differential sequence distribution and integrated sequence
distribution as a function of conversion% were calculated.
29Si-NMR, as well as 1H-NMR spectroscopy, was also use to
analyze the sequence distribution of the random copolymers
(Mn=4.5k). Characteristic thermal properties such as glass
transition temperature(Tg), crystal liquid-crystal transition
temperature (Tcl) and the Heat of Tcl transition of these
copolymers were carried out by DSC (differential scanning
calorimeter). Study on the phenyl content and the degree of
polymerization of the copolymers in relation to these thermal
properties was discussed in detail. The solubility behavior of
these copolymers was also described. The effect on the physical
properties of the copolymers using different initiator
(phenyllithium and n-butyllithium) was investigated.
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