Effect of molecular weight on the refractive index increments of polystyrene, poly(ethylene glycol), poly(propylene glycol), and poly(dichlorophenylene oxide) in solution

Abstract

Abstract The variation of refractive index increments with molecular weight has been studied using solutions of polystyrene (2.2 × 10 3 < M w < 1.8 × 10 6 ), poly(ethylene glycol) (1.0 × 10 3 < M w < 2.0 × 10 4 ), and poly(dichlorophenylene oxide) (3.3 × 10 3 < M w < 4.8 × 10 5 ) in toluene and poly(propylene glycol) (1.2 × 10 3 < M w < 4.0 × 10 3 ) in benzene. The refractive index increments of polyglycols containing aliphatic ether moieties are negative in these solvents. However, poly(dichlorophenylene oxide) polymers, which contain aromatic ether moieties, give positive values. Linear and branched halogenated poly(phenylene oxide)s show an asymptotic approach of the refractive index increment to the same limiting value, but the approach is more rapid for the branched polymer.