Diisocyanate‐linked polymers. I. Dilute‐solution properties of toluene diisocyanate‐extended polypropylene glycol

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Abstract
A study was made of the dilute solution properties and the molecular weight distribution of a polyurethane polymer prepared from polypropylene glycol 2025 and toluene‐2,4‐diisocyanate by a bulk polymerization under anhydrous conditions at 60°C. Such conditions were chosen to minimize possible side reactions which could produce branching. The polymer, which had a weight‐average molecular weight of 36,500, was separated into fourteen fractions by fractional precipitation from a benzene solution with isooctane as precipitant. The fractions were characterized by light scattering measurements on methanol solutions and by dilute solution viscosities in methanol, benzene, and a theta‐solvent. The molecular weight distribution of the unfractionated polymer and the relations between molecular weight and intrinsic viscosity in the various solvents were determined. Polymer configurations and interaction parameters are discussed.

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