Distribution of molecular weight and of branching in high molecular weight polymers from bisphenol a and epichlorohydrin

The molecular weight distributions and long‐chain branching distributions of three samples of Bisphenol A poly(hydroxy ether) have been investigated. The samples were fractionated and the fractions characterized by solution viscosity and light‐scattering measurements. A log‐log plot of intrinsic viscosity and M̄w for fractions of all three resins yields a straight line up to molecular weights of about 70,000 (approximately 80% by weight of each polymer) described by [η] = 1.48 × 10−4 M̄w. Beyond this molecular weight the viscosities fall increasingly below the straight line whose constants are representative of those expected for linear fractions in a good solvent. It is evident that long‐chain branching does not occur appreciably in the lower fractions but does begin abruptly at 70,000 molecular weight and increases continuously above that point. Comparison of both the branching and molecular weight distributions with those predicted from Beasley's random branching mechanism confirms the nonrandom nature of the branching mechanism in these poly(hydroxy ethers). The numbers of branches calculated using the Zimm‐Kilb theory reach impossibly high values, while those calculated from the Zimm‐Stockmayer theory appear more reasonable. No correlation was found between the Huggins' k′ and molecular weight or branching. The highest molecular weight sample possesses a longer and more highly branched high molecular weight tail, which is reflected in differences in physical properties.