Browsing by Author "Liu, WP"

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Effect of hydrolysis on the strength of hydrogen bonds and T-g of poly(vinylphenol-co-acetoxystyrene)
(2003-07-15)
Kuo, SW
;
Liu, WP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A series of poly(vinylphenol-co-acetoxystyrene) (PVPh-co-PAS) copolymers were prepared by partial hydrolyses of poly(acetoxystyrene) (PAS) in acidic and basic solutions. Higher glass transition temperature, higher fraction of hydrogen-bonded carbonyl group, and higher interassociation equilibrium constant were observed for copolymers with same composition prepared from the acidic hydrolysis than from the basic hydrolysis because the sequence distribution of the former is relatively more random than the latter. Infrared spectra provide positive evidence in terms of sequence distribution, glass transition temperature, and hydrogen-bonding strength in poly(vinylphenol-co-acetoxystyrene) by prepared these two hydrolysis methods.
Miscibility enhancement on the immiscible binary blend of poly(vinyl phenol) and poly(acetoxy styrene) with poly(ethylene oxide)
(2005-11-14)
Kuo, SW
;
Liu, WP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The miscibility and hydrogen-bonding behaviors of ternary polymer blends of poly(ethylene oxide) (PEO)/ poly(vinyl phenol) (PVPh)/poly(acetoxystyrene) (PAS) were investigated by using DSC and Fourier transform infrared spectroscopy (FTIR). The PEO is miscible with both PVPh and PAS based on the observed single T-g over the entire composition range. FTIR was used to Study the hydrogen-bonding interactions between PEO with PAS and PVPh, respectively. Quantitative analyses show that the strength of hydrogen-bonding strength is of the order of the hydroxyl-ether inter-association of PVPh/PEO blend > the hydroxyl-hydroxyl self-association of pure PVPh > the hydroxyl-carbonyl inter-association PVPh/PAS blend at room temperature. Furthermore, the addition of PEO is able to enhance the I miscibility of immiscible PVPh/PAS binary blends at lower (20 wt.-%) or higher (60 and 80 wt.-%) PEO content. However, there exists a closed iminiscibility loop in the phase diagram at 40 wt.-% PEO content due to the "Delta chi" and "Delta K" effects in this hydrogen-bonded ternary polymer system. Therefore, an interesting and unusual sandwich phase diagram has been observed in this ternary polymer blend.
Two theorems of instability with application to gimbal walk
(1999-06-01)
Ge, ZM
;
Liu, WP
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機械工程學系
;
Department of Mechanical Engineering
Two theorems of instability, different from the traditional Chetaev's instability theorem are developed. The theorems determine the instability of autonomous and non-autonomous dynamical systems by means of investigating the higher-order' derivatives of the Lyapunov function. Using the first theorem of these theorems, the walk of a free gyroscope, which has not been verified by traditional stability theorem, can be solved by our theorem. Furthermore, several dynamical systems are presented as examples of application of these two theorems. They are the motion of a symmetric gyroscope with steady precession, the steady rotations of a rigid body around the intermediate axis of its ellipsoid of inertia, the equilibrium of the equations of Lotka-Volterra model of competition between two species, etc.