Differential refractometry and light scattering on nylon-6 and poly(methyl acrylate) in mixed solvents

Investigations have been made of solvent systems for potential use in characterizing nylon-6/poly (methyl acrylate) copolymers. To this end, measurements involving differential refractometry (at constant composition and also constant chemical potential of solvents) and light scattering have been conducted on solutions of nylon-6, poly(methyl acrylate) and a mixture of these two polymers. From refractometric and solubility considerations the most suitable solvents are binary mixtures of o-chlorophenol (o-CP) and 2, 2′, 3, 3′-tetrafluoropropanol. In particular, the binary solvent containing 73% (by volume) of o-CP yields the molecular weight of the nylon-6 constituent of the polymer mixture directly, since the light scattering from the other polymer constituent is thereby eliminated. Preferential adsorption of o-CP occurs to both polymers, the maximum extents corresponding to 1 mol $\text{o-}\text{CP}\text{1.4}$ segments nylon and 1 mol $\text{o-}\text{CP}\text{5.7}$ segments poly(methyl acrylate). This is attributed to a breakdown of intramolecular hydrogen-bonding in o-CP and subsequent formation of hydrogen bonds with the carbonyl groups in the polymers.