Formation and properties of triol‐based polyester networks

Networks have been prepared by reacting polyoxypropylene triols with sebacoyl chloride at equal concentrations of hydroxyl and acid chloride groups. The reactions were allowed to go to completion to form the networks studied. The gel points of the reaction mixtures were also determined and used as a basis for the correlation of the properties of the networks formed at complete reaction. Reactions were carried out at 27°C, in bulk and in diglyme as solvent, and the shear moduli of networks formed, in the dry state and at equilibrium swelling in diglyme, were measured at the same temperature using uniaxial compression. Deviations from Gaussian behaviour wer found to decrease as the dilution of the reaction mixture forming the network increased. For apparent values of the molecular mass between junction points (Mc) greater than about 104, essentially Gaussian stress‐strain behaviour was observed. For the triols used, such values of Mc may be obtained from dilute reaction systems. Values of Mc increased with pre‐gel intramolecular reaction and indicate that in the limit of a perfect gelling system, a perfect network is formed. The values of Mc found are generally larger than those expected for the perfect network (M ), irrespective of whether phantom or affine behaviour is assumed, and are consistent with network imperfections being elastically ineffective loops, caused by pre‐gel intramolecular reaction, rather than entanglements.