Browsing by Author "Gong, ZH"

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Hyperbranched poly(aryl ether oxazole)s: Synthesis, characterization, and modification
(2000-11-14)
Gong, ZH
;
Leu, CM
;
Wu, FI
;
Shu, CF
;
應用化學系
In this paper the synthesis and characterization of a hyperbranched poly(aryl ether oxazoIe) with terminal phenolic groups are described. An ABB' monomer containing a pair of phenolic groups and an aryl fluoride which is activated toward displacement by the attached oxazole ring was prepared. The nucleophilic substitution of the fluoride with the phenolic group leads to the formation of ether linkage and subsequently the hyperbranched poly(aryl ether oxazole) P1. As determined by a combination of model compound studies and H-1 NMR integration experiments, the degree of branching of PI is approximately 50%. The polymer P1 is thermally stable and readily soluble in polar organic solvents. The terminal phenolic groups in P1 were easily functionalized, yielding hyperbranched polymers with a variety of functional chain ends. Physical properties, such as the glass transition temperature and the solubility of the hyperbranched poly(aryl ether oxazole)s, depended significantly on the nature of the chain ends.
Nonlinear optical chromophores with configuration-locked polyenes possessing enhanced thermal stability and chemical stability
(1998-11-01)
Shu, CF
;
Shu, YC
;
Gong, ZH
;
Peng, SM
;
Lee, GH
A synthetic strategy has been developed for preparation of NLO chromophores with all the pi-conjugated methine groups incorporated into plane-rigidified, fused, six-membered rings. The comparison of the rigidified chromophores to the analogous nonrigid chromophores shows that the configuration-locking methods provide a dramatic enhancement of molecular thermal stability. The data from W-vis spectroscopy and X-ray crystallography reveal that the rigidity of the annulated rings does not diminish the planarity and the electron delocalization efficiency of the polyenic chain.
Nonlinear optical chromophores with configuration-locked polyenes possessing enhanced thermal stability and chemical stability
(1998-11-01)
Shu, CF
;
Shu, YC
;
Gong, ZH
;
Peng, SM
;
Lee, GH
A synthetic strategy has been developed for preparation of NLO chromophores with all the pi-conjugated methine groups incorporated into plane-rigidified, fused, six-membered rings. The comparison of the rigidified chromophores to the analogous nonrigid chromophores shows that the configuration-locking methods provide a dramatic enhancement of molecular thermal stability. The data from W-vis spectroscopy and X-ray crystallography reveal that the rigidity of the annulated rings does not diminish the planarity and the electron delocalization efficiency of the polyenic chain.
Synthesis and characterization of nonlinear optical chromophores with conformationally locked polyenes possessing enhanced thermal stability
(1999-06-01)
Shu, YC
;
Gong, ZH
;
Shu, CF
;
Breitung, EM
;
McMahon, RJ
Dipolar NLO chromophores with an interposed conjugated tetraene segment in which all but four of the methine groups are incorporated into a tetrahydronaphthalene framework have been synthesized and characterized. This conformation-locking approach furnishes NLO chromophores possessing an enhanced thermal stability. X-ray crystallographic data indicate that the polyenic chain of these molecules exhibits a near-planar all-trans conformation in the solid state. EFISH measurements show that these conformationally locked tetraenic chromophores exhibit large second-order optical nonlinearities (mu.beta similar to 4000 x 10(-48) cm(6) at 1907 nm), although the nonlinearities of the corresponding "unlocked" analogues are slightly larger.