Nakagawa T, Nakamura Y, Sasaki N, Nakata M. Chain aggregation in dilute solutions of poly(methyl methacrylate) below the phase-separation temperature.
PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001;
63:031803. [PMID:
11308670 DOI:
10.1103/physreve.63.031803]
[Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2000] [Indexed: 05/23/2023]
Abstract
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 <M>(w) and z-averaged square radius <R2>(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 <M>(w)/M(0)=e(gct) and <R2>(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 <M>(w) versus <R2>(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.
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