Macromolecules show a wide range of properties which are quite different from thoes of respective monomers. They may be:
Elastic or rigid ,Hard or Soft, Transparent or opaque , Have strength of steel but can have very light weight, Soften on heating or can set to a hard mass on cooling the melt.
These properties may vary from one type of polymer to another and even among the same type.
The fundamental parameters which influence the Structure-Property Relationship are: Molecular Mass, Polarity, Crystallinity, Molecular Cohesion, Nature of polymeric chains, Stereochemistry of the molecules.
These properties like tensile strength, crystallinity, elasticity, resistance to chemicals, and wear and tear depend mostly on the polymer structure.
Examples:
? Stronger attractive forces between chains = Stronger , less flexible polymer.
? Chains able to slide past each other = flexible polymer.
? In straight chain and branched chain polymers the individual chains are held together by weak intermolecular force of attraction.
? Strength increases with increase in chain length(in turn increase in Mw.) as the long chains are entangled(anchored)better
? In cross-linked polymers, monomeric units are held together only by means of covalent forces
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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