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In linear polymers the individual polymer chains rarely have exactly the same degree of polymerization and molar mass, and there is always a distribution around an average value. The molar mass distribution (or molecular weight distribution) in a polymer describes the relationship between the number of moles of each polymer species (Ni) and the molar mass (Mi) of that species.〔I. Katime "Química Física Macromolecular". Servicio Editorial de la Universidad del País Vasco. Bilbao〕 The molar mass distribution of a polymer may be modified by polymer fractionation. == Definition of molar mass averages == Different average values can be defined depending on the statistical method that is applied. In practice four averages are used, representing the weighted mean taken with the mole fraction, the weight fraction, and two other functions which can be related to measured quantities: *Number average molar mass or Mn (also loosely referred to as Number Average Molecular Weight (NAMW)) *Mass average molar mass or Mw (w is for weight; also commonly referred to as weight average (Weight Average Molecular Weight (WAMW)) *Z average molar mass or Mz (z is for centrifugation; from the German Zentrifuge) *Viscosity average molar mass or Mv 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Molar mass distribution」の詳細全文を読む スポンサード リンク
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