【摘要】 对聚二甲基硅氧烷-溴代环己烷θ溶液（28℃）体系进行了沉降速度法测定分子量分布及沉降系数压力改正的研究。提出了一种新的直接测定沉降系数的压力改正的方法,即在沉降池中加入不同量的溶液以得到不同的液柱高来改变静压,测定溶液界面在不同静压下的浮升速度计算压力系数。所得适用 于静压为200大气压以下的沉降系数的压力改正系数α=1.44×10^-3_大气压^-1。从沉降系数分布、（?）_ω、[η]_θ及[η]_甲苯的测定,订定了聚二甲基硅氧烷在28℃θ条件下的s-M,[η]_θ-M及在甲苯（25℃,良溶剂）中的[η]-M单分散关系为。 s₁=6.30×10¹⁶M^0.50（溴代环己烷,28℃） [η]=7.41×10^-2M^0.50（溴代环己烷,28℃） [η]=9.53×10^-3M^0.71（甲苯,25℃）更多还原

【Abstract】 The molecular weight distribution by sedimentation velocity measurements and hydrostatic pressure correction for the sedimentation coefficient of the floating system poly-dimethylsiloxane-bromocyclohexane at θ-temperature (28 ℃) have been studied. A new method for the experimental evaluation of the hydrostatic pressure correction of the sedimentation coefficient is proposed. By using different quantities of the solution added to the sedimentation cell, so as to give different heights of the liquid column, it is possible to determine the influence of the hydrostatic pressure on the sedimentation coefficient. Assuming a linear relation between the sedimentation coefficient and the hydrostatic pressure, the authors found that the pressure coefficient of the system studied is 1.44×10-3 (atm)-1 for hydrostatic pressures less than 200 atm.From the distribution of sedimentation coefficients, and the values of Mw, [η]θ, and [η] toluene of a polydimethylsiloxane fraction the monodisperse relationships s-M, [η]θ-M, in the θ-solvent at 28℃ and [η]tolucne-M at 25℃ are obtained:s1 = 6.30 × 10-16M0.50 (bromocyclohexane, 28℃) [η]θ = 7.41 × 10-2 M0.50 (bromocyclohexane, 28℃) [η] = 9.53 × 10-3 M0.71 (toluene, 25℃)更多还原