title: 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 theta temperature. The aggregation behavior of the s-PMMA with weight-average molecular weight M(w) =6.06 x 10(5) g mol(-1) was studied by a combination of static and dynamic laser-light-scattering experiments. A solution of concentration 1.12 x 10(-4) g mL(-1) was quenched from 50 degrees C (above the theta temperature in n-BuCl, 35 degrees C to 12 degrees 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) approximately < R(g) > d(f) (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.
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, PR China.
authors.forename: Wenna
authors.initials: W
authors.lastname: Chen
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yong
authors.initials: Y
authors.lastname: Jiang
authors.forename: Dadong
authors.initials: D
authors.lastname: Yan
authors.forename: Charles C
authors.initials: CC
authors.lastname: Han
mesh_terms: D008027:Light; D018625:Microscopy, Atomic Force; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D012542:Scattering, Radiation; D012996:Solutions / Q000737:chemistry; D013997:Time Factors
chemical_list: D012996:Solutions; D019904:Polymethyl Methacrylate