Abstract: Organosilino-acrylic emulsions have received attentions because of its industrial applications. The properties of the polymer depend upon the composition and structure. Dihydroxypoly-dimethylsiloxane is a kind of monomer to synthesze the emulsions, its everage hydroxyl value affects its reactivity, so analyzing its average hydroxyl value one can obtain the quality of dihydroxypolydimethylsiloxane. NMR is usually the preferred technique to study composition and structure of the polymer.
The method of ²⁹Si NMR is discussed. The average degree of polymerization(DP), the average molecular weight(M), the average hydroxyl value of dihydroxylpolydimethylsiloxane fluid mixtrues were investigated by ²⁹Si NMR. To ensure that quantitative data were obtained, a small amount of chromium(Ⅲ) acetylacetonate was added as a relaxation reagent to shorten the ²⁹Si spin lattice relaxation times (T₁), and inverse ¹H gated decoupling was used to eliminate the negative nuclear Overhauser effect(NOE), and longer recycle delay was used. To eliminate the broad peak of silicon glass NMR tube, pluse program was changed, a delay was added before acquisition.
The composition of organosilino-acrylic emulsions were investigated by ¹³C NMR.

Key words: ²⁹Si NMR, ¹³C NMR, Dihydroxypolydimethylsiloxane, Organosilino-acrylic emulsions