Polyoxazoline segmented

The dried polyoxazoline-modified silica gel was immersed into distilled water. The adsorption property of the resulting gel was estimated by the water content. The water uptake was calculated from an expression of (W -W)jW, where Wis the weight of dried gel and W is the weight of water-absorbed gel. The modified gel showed a higher water-adsorption property than that of untreated silica gel, which absorbed 10.8 multiples of water. The water uptake of modified gel was up to 13.7 multiples of the weight of dried gel. Thus, silica gel has been made more hydrophilic by a polyoxazoline segment. 

The obtained gels were purified by Soxhlet extraction with chloroform to remove the unreacted polyoxazoline. Table 6 summarizes the results of the preparation of polymer hybrids together with their water adsorptions. In comparison with the silica gel without polyoxazoline segments, the modified silica with 50% polyoxazoline was found to show higher water adsorption. 

The core-first method, which uses an active multifimctional core to initiate growth of polymer chains, was apphcable to make hybrid POSS-core star-shaped polyoxazohnes that showed an increase in Tg, compared to that of polyoxazohne initiated by methyl p-toluenesulfonate (MeOTs) with poly(2-methyl-2-oxazohne) (POZO) [76]. Other hybrid star-shaped polyoxazohnes initiated by cube-OTs or cube-benzyl revealed the same phenomenon. This was attributed to the reduction of segmental mobifity of POZO in starshaped polyoxazolines, which was caused by the incorporation of hard, compact POSS moiety to the core of star polymer with the core-first technique. The conclusions were drawn that the thermal stabilities of star-shaped polymers increased as the POSS wt % was increased, and this was used as a measure of the effect of the inorganic POSS unit on polymer thermal properties. 

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