Allowance for polymolecularity in polymer structure‐property relationships

Relations between molar mass M and molar mass dependent properties E of polymers are mostly strictly valid only for monomolecular samples i: For polymolecular polymer samples the corresponding averages Mav and Eav must be applied: Provided the kind of average (number‐, weight‐ or any general average) of e.g. Mav is known, the corresponding average Eav is given by. Eqs. (1a, b). This is demonstrated for the relationships of van't Hoff and Mark‐Houwink, frequently used for the determination of molar masses of polymers. It is also shown that the four different relations for the expansion factor α by Flory‐Stockmayer, Fixman, Ptitsyn, and by Yamakawa‐Tanaka can be applied to polymolecular polymer samples (i.e. without fractionation), provided the corresponding averages[η]av and Mav from the Mark‐Houwink relationship are taken for the evaluation of the parameters KΘ and B′.