Chain aggregation in dilute solutions of poly(methyl methacrylate) below the phase-separation temperature.
Chain aggregation in dilute solutions of poly(methyl methacrylate) below the phase-separation temperature.
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低于相分离温度的聚甲基丙烯酸甲酯稀溶液中的链聚集。
DOI：
10.1103/physreve.63.031803
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
M. Nakata
中科院分区：
文献类型：
--
作者：
T. Nakagawa;Y. Nakamura;N. Sasaki;M. Nakata
对分子量为M(w)=4.4 × 10(6)的聚甲基丙烯酸甲酯与醋酸异戊酯的稀溶液，采用静态光散射法研究了相分离过程。将浓度范围为1.4 × 10(-4) ~ 3.8 × 10(-4) g/cm(3)的稀溶液淬至低于相分离温度约16k，在数小时内测量聚合物链的聚集过程。通过Guinier图分析光散射数据，确定了聚合物链簇的重量平均分子量(w)和z平均平方半径（1/2）(z)作为时间t（min）和浓度c （g/cm(3)）的函数。簇的生长以指数形式(w)/M(0)=e（gct）和(z)/R(2)(0)=e（hct）作为ct的函数表示，其中M(0)和R2(0)为t=0时的值，确定常数g和h分别为g=11.6和h=7.5。(w)与（1/2）(z)的双对数图得到一条斜率为D=3.06+/-0.02的直线。将这些链聚集过程的特征特征与i-mer和j-mer具有碰撞核（i+j）的簇-簇聚集的Smoluchowski方程进行了比较。观察到的团簇生长缓慢归因于反应限制的团簇聚集。簇内链密度随簇大小的增加而增加，导致斜率D大于3。
For dilute solutions of poly(methyl methacrylate) in isoamyl acetate with the molecular weight M(w)=4.4 x 10(6), the phase-separation process was studied by static light-scattering measurements. The dilute solutions in the concentration range from 1.4 x 10(-4) to 3.8 x 10(-4) g/cm(3) were quenched to about 16 K below the phase-separation temperature, and the aggregation processes of polymer chains were measured over a period of several hours. By analyzing the light-scattering data with the Guinier plot, the weight-averaged molecular weight (w) and z-averaged square radius (1/2)(z) for clusters of polymer chains were determined as a function of time t(min) and concentration c (g/cm(3)). The growth of clusters was represented by the exponential forms (w)/M(0)=e(gct) and (z)/R(2)(0)=e(hct) as a function of ct, where M(0) and R2(0) were the values at t=0, and the constants g and h were determined to be g=11.6 and h=7.5. A double-logarithmic plot of (w) versus (1/2)(z) yielded a straight line with the slope D=3.06+/-0.02. These characteristic features of the chain aggregation process were compared with the Smoluchowski equation for cluster-cluster aggregation with the collision kernel (i+j) for i-mer and j-mer. The observed slow growth of clusters was attributed to the reaction- limited cluster aggregation. The chain density in a cluster was found to increase with an increase of the cluster size, resulting in the slope D exceeding 3.