Light‐Scattering Study of the Aggregation of Syndiotactic Poly(methyl methacrylate) in Solution

Abstract

Syndiotactic poly(methyl methacrylate) (s‐PMMA) may undergo aggregation in n‐butyl chloride (n‐BuCl) at temperatures below the θ temperature. The aggregation behavior of the s‐PMMA with weight‐average molecular weight M_w=6.06×10⁵ g mol⁻¹ was studied by a combination of static and dynamic laser‐light‐scattering experiments. A solution of concentration 1.12×10⁻⁴ g mL⁻¹ was quenched from 50 °C (above the θ temperature in n‐BuCl, 35 °C) to 12 °C, and the aggregation process was measured over 60 h. The time dependence of M_w, the root‐mean‐square z‐average radius of gyration <R_g>, and the average hydrodynamic radius <R_h> were used to monitor the growth of the aggregates, with the result M_w∼<R_g> (where d_f=1.98±0.02), which implies the formation of a fractal aggregate. The observed fractal dimension, d_f, is close to that expected for a reaction‐limited cluster aggregation for which d_f=2.1. In addition, atomic force microscopy was used to image the aggregates.