Some natural polymers are composed of one kind of monomer. 0000001236 00000 n • More crystalline polymer - stronger and less flexible. Synthesis of Polymers •Nearly all polymers used in engineering are synthetic They are made by chemical processing •Polymers are synthesized by joining many small molecules together into very large molecules, called macromolecules, that possess a chain-like structure •The small units, called monomers, are generally Polymers are very large and very complicated systems; their character­ ization has to begin with the chemical composition, configuration, and con­ formation of the individual molecule. Also, there are polymers which instead of carbon have other elements in its backbone. %%EOF Polyethylene is a member of the important family of polyolefin resins. • Both amorphous and crystalline areas in same polymer. 0000000729 00000 n However, glassy polymers are difficult to self-heal at room temperature due to their frozen molecules. 0000001643 00000 n 0000188681 00000 n /ProcSet [/PDF /Text /ImageC /ImageI] Structure features of polymers Each bond angle between three adjacent C atoms is near 109.5º and the angle can be rotated freely in space. Glassy polymers are widely used as structural materials in aerospace vehicles, airplanes, automobiles, biomedical devices, and so on. When the number of monomers is very large, the compound is sometimes called a high polymer. endstream endobj 49 0 obj<. ������1_��#ڝ,���GޤUi$c} The molecular connectivity of polymer−metal−organic framework (polyMOF) hybrid materials was investigated using density functional theory calculations and solid-state NMR spectroscopy. For example, Nylon, which contains nitrogen atoms in the repeated unit backbone. cleavage of covalent bonds between them and bio erodible polymers bring about erosion of the polymer due to dissolution of linking chains without bringing about any change in chemical structure of the molecule [2]. /Im1 6 0 R>> The first chapter is devoted to this broad objective. unusual properties of high polymers are developed, it will be convenient to consider the chemical and structural aspects of polymers at three different levels: 1) The chemical structure (atomic composition) of the monomer (primary structure) 2) The single polymer chain (secondary level) 3) Aggregation of polymer chains (tertiary structure) 0000007635 00000 n 11 0 obj 0000003206 00000 n 68 0 obj<>stream Man-made polymers have been studied since 1832. endobj Polymers with conjugated π-electron (i. e. system have C=C conjugated bonds) backbones display unusual electronic properties such as low energy optical transition, low ionization potentials, and high electron affinities. 11 The length of of the polymeric molecule L = l m l: the length of a single bond in the backbone of the hydrocarbon chain m: the number of bonds Carbon is the most common element in polymers. CHEM 379 – W20 Physical Properties of Polymers 6-1 6. 0000002800 00000 n /Type /Page Poly(a lkenes) are chemically inert due to the strong C-C and C-H This leads to the important topic of the structure-property relations to which this book is devoted. The general structure of these polymers is shown in Fig. Polymers are not restricted to monomers of the same chemical composition or molecular weight and structure. 0000003874 00000 n The word polymer designates an unspecified number of monomer units. Introduction: Organic polymers are normally insulators, it can be presumed that conducting polymers must have an unusual structure. endobj These polymers have a similar structure to the polyamides, which have the urethane (carbamate) group as part of the polymer backbone. /F1 9 0 R /F2 10 0 R>> 0000004371 00000 n /MediaBox[0 0 842 595] 15. Polymers There are two types of polymerisation: addition and condensation Addition Polymerisation An addition polymer forms when unsaturated monomers react to form a polymer Monomers contain C=C bonds Chain forms when same basic unit is repeated over and over. The spectrum of applications of polymers is immense. Most of the polymers around us are made up of a hydrocarbon backbone. The word “Polymer” is derived from two Greek words, ‘Poly’ that means many (numerous) and ‘Mer’ which means units. 10. The length of the side chain influences the packing of these polymer chains in the melt or glassy state. /Parent 3 0 R What is Polymer? 0000001584 00000 n 0000007147 00000 n Cold-drawing • When a polymer is stretched a ‘neck’ forms. 0000001100 00000 n Vari-ous drugrelease mechanisms can be studied comparatively in Figure 3. 0000188918 00000 n G H I I J K L M N N O P Q R S T U V W X X Y Z [ \ ] ] ^ _ ` a b c d !e "e "f "g "h #h #i #j #k #l $l $m $n $o %p %q %r &s. Polymers are substances consisting of macromolecules and the high molecular weight and chain-like structure of the macromolecules are responsible for the unique properties of polymers. Polyethylene, light, versatile synthetic resin made from the polymerization of ethylene. The process by which the polymers are formed is called polymerisation. 0000004744 00000 n Low M High M • Polymers can have various lengths depending on the number of repeat units. As the side chain becomes longer, the average interchain distance increases.10 This increased spacing between chain 8 0 obj <> stream <]>> This means that Polymer Structure. xref Polymers and Polymerizations—Architecture 12 The number of complementary reactive sites and geometry of monomer determine /Resources<< polymer structures Each parameter is important to the properties Each parameter is important to Polymer Chemistry, Chem 466, Spring 2014, January 14, 2014 . These identical structures, we understand as a unit made up of two or more molecules, join together to form a long chain. Polymers are very useful materials because their structures can be altered and tailored to produce materials 1) with a range of mechanical properties 2) in a wide spectrum of colors and 3) with different transparent properties. Crystalline polymers • Areas in polymer where chains packed in regular way. 0000004619 00000 n 0000002050 00000 n Overview; What is a Polymer? Networked polymers are complex polymers that are heavily linked to form a complex network of three-dimensional linkages. There may be extensive van der Waals and hydrogen bonding between the chains. In basic terms, a polymer is a long-chain molecule that is composed of a large number of repeating units of identical structure. �2�~��e.>�sҔ?��`wuHy�r��&ep�D�HS�ǣS}�g��*��'y����B}(5�4=�C_\��e�M���U��0Y���MW͎K��$x� E6+ �َ��������[�ή(���>�3P�Ѐl%n^�dSA!�I�\�����������M H��ՂG�1�:�m���G6���Ok`�N�O7������y�5�ɽ�)���a{�ч�d��931�>]s���FZ�)cRw�c�J�4H 0000004116 00000 n structure. >> %PDF-1.6 %���� Polymers serving as drug carrier should 3.12. A Hydrocarbon backbone being a long chain of linked carbon and hydrogen atoms, possible due to the tetravalent nature of carbon.A few examples of a hydrocarbon backbone polymer are polypropylene, polybutylene, polystyrene. 0000000016 00000 n The subjects are logically combined because understanding how structure a ects properties, as measured in characterization, is a key element of polymer materials science and engineering. Classification based on polymer structure Structure of polymer Copolymers Isomerism (Structural Isomerism, Sequence Isomerism, Tacticity) Chain arrangement (Topology) Molecular weight in polymers Thermal transitions glass transition and melting Mechanical properties of polymer Topics: 8 Topic: Principle Characteristics of Polymers [1-7] Synthetic polymers are characterized by defined structures with flexibility of modification in terms of functionality and degradability and response to environmental fluctuation (chemical and biological response to stimuli), mechanical strength [29]. These metrics are regularly updated to reflect usage leading up to the last few days. Examples: polyethylene, PVC, nylon. Starch, cellulose, and rubber all possess polymeric properties. Polymers that are heavily linked to form a long chain a polymer a. 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