A thermally sensitive copolymer, poly(N-isopropylacrylamide-co-styrene) [P(NIPAM-co-St)] (M n =9.5×10 5 g/mol and M w /M n =1.51) was synthesized by soap-free emulsion polymerization. The phase separation of the copolymer in water was investigated by Rayleigh scattering (RS) technique. The RS spectra revealed the transition of molecular conformation and the aggregation of molecular chains in the course of phase separation. The coil-to-globule and globule-to-coil transitions of P(NIPAM-co-St) chains were found in one heating-and-cooling cycle. By means of Avrami formula, apparent activation energy of phase separation of P(NIPAM-co-St) aqueous solutions was estimated. Moreover, a model was proposed to describe the phase separation process.
The ultrafine bio-glass powder of Si-Al-Ca-P-F-polynary system was prepared by sol-gel method with organic and inorganic compounds such as Si (OC2H5)4, (C2H5)3PO4, Ca (NO3)2·4H2O, Al (NO3)3·9H2O and NH4F. The powder was heat-treated at the different temperature in the range from 200 to 900°C and its crystallized transition was ascertained. The morphology, composition, structure state and crystallized behavior of the glassy powder were characterized by means of TEM, XRD, EDS, DSC-TG, FT-IR etc methods and compared with the glassy powder of the same system by melting-quenching and liquid precipitation. The results show that the powder containing elements Si, Al, Ca, P, F and O belongs to typical amorphous state, and is composed of the near spherical particles with the size from 100 to 400nm; The transition temperature of glass was about 580°C, and the crystallized phase CaF2precipitate firstly above 600°C; A series of crystallized phases Ca5(PO4)3F and Ca5(PO4)2SiO4were separated sequentially with increasing temperature; The network structure of glass is similar to that of melt-quenching or liquid precipitation glass.
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