氯丁橡胶的长链支化分布和分子量表征

CHARACTERIZATION OF LONG CHAIN BRANCHING DISTRIBUTION AND MOLECULAR WEIGHT OF POLYCHLOROPRENE

在相同溶剂、相同温度下,测定长链支化高聚物(如氯丁橡胶)的特性粘数[η]和数字化GPC图谱,并用窄分布聚幕乙烯绘制GPC标准曲线[表示为ln([η]_iM_ni)=f(V_i)],此时高聚物的[η]与分子量的关系不再符合Mark-Houwink程,可用多项式ln[η]_i=lnK+alnM_(ni)+b(lnM_(ni))~2+c(lnM_(ni))~3来表示。当高聚物分子量较小、支化度较低时,可计算出每个分子的支化点平均值(?)_n((?)_n=∑(?)W_i/M_n(V))和分子中每500个单体单元的数均长支链数(?)_n((?)_n=500M_R∑B_n(V)W_i/M_n(V))以及(?)_w,(?)_n等。提出了一种合理而简便的测定长链支化高聚物的支化分布和分子量的新方法。

A molecular weight and branching distribution (MWBD) method is presented for measuring long chain branching (LCB) as a function of molecular weight in such polymers as polychloroprene . The method requires intrinsic viscosity [η] and size exclusion chromatography data on the polymer , and a polystyrene calibration determined under the same solvent and temperature . The MWBD method expresses the size separation with elution volume (V) as In ([η]( Mni)=f(Vi),and assumes [η] to be described by a polynomial equation:The number-average number of LCB points per molecule for the whole polymer can be obtained as:The number -average number of branch points per 500 repeat units for the whole polymer can be obtained as :