The evidence for the existence of these weak intermolecular forces is the fact that gases can be liquefied, that ordinary liquids exist and need a considerable input of energy for vaporization to a gas of independent molecules, and that many molecular compounds occur as solids. 502 16 The types of bonding forces vary in their strength as measured by average bond energy. The key to the polymer structure is that two carbon atoms can have up to three common bonds and still bond with other atoms. metallic oxides, this is hardly the case : polymers have a poor wettability Chemical bonding and molecular structure grade 11 1. Understanding the evolution of macroscopic adhesion based on fundamental molecular interactions is crucial to designing strong and smart polymer/metal interfaces that play an important role in many industrial and biomedical applications. SCIENTIFIC BACKGROUND. Induction forces are weak and temperature independent. trailer %PDF-1.5 %���� Only two cross-links per polymer … (Monomers). Chemical bonding and molecular structure 1) Explain the formation of a chemical bond. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. MSE 2090: Introduction to Materials Science Chapter 15, Processing of Polymers 13 Fracture of Polymers ¾Fracture strengths of polymers are low compared to metals and ceramics ¾Brittle fracture occurs in thermosetting polymers. Typical polymers are a type of molecular crystals, albeit with extremely large molecules, and therefore have very strong intra-molecular bonding but only very weak, van der Waals, inter-molecular binding forces. "� �E���&���!�킄��p�������splfFw}rrBguY7�&[J���b�t_��>��gu�L��Y�5�YYԕc]�Ʊ���h4�ϊ��l%gF�)����+��0\ 502 0 obj<> endobj 0000000616 00000 n primary forces) exists throughout the part • Crosslinking provides thermal stability such that polymer will not melt or flow upon heating. 0000003530 00000 n The attractive force by which atoms, ions and molecules are held together is known as a chemical bond. 504 0 obj<>stream These are the Chemical Bonding and Molecular Structure class 11 Notes Chemistry prepared by team of expert teachers. PCS is a layered composite strip made of metal and polymer. A polymer (/ ˈ p ɒ l ɪ m ər /; Greek poly-, "many" + -mer, "part") is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. The hydrogen bond is often described as a strong electrostatic dipole–dipole interaction. 0000003046 00000 n Polymers structures upon the nature of the intermolecular bonding forces, the molecular weight, themanner in which chains are packed together, and the flexibility of the polymer chain. Free PDF download of Class 11 Chemistry revision notes & short key-notes for Chapter 4 - Chemical Bonding and Molecular Structure to score high marks in exams, prepared by expert Chemistry teachers from latest edition of CBSE(NCERT) books. 0000002272 00000 n Here we show how macroscopic adhesion can be predicted on the basis of single molecular interactions. A hydrogen bond is the attraction between the lone pair of an electronegative atom and a hydrogen atom that is bonded to an electronegative atom, usually nitrogen, oxygen, or fluorine. 0 endstream endobj startxref The attractive forces which holds various constituents such as atoms molecules and ions together in different chemical species is called a covalent bond A covalent bond includes the sharing of electrons between two atoms. Chemical Bonding and Molecular Structure Questions with Solutions to help you to revise complete Syllabus and Score More marks in your Class 11 Examinations. stretchy lucky bands, shopping bags, beverage bottles, bowling balls…). They were the first to provide secondary bonding forces Molecular configurations – the side groups Schematic representations of (a) linear, (b) branched, (c) crosslinked, and (d) network (three dimensional) molecule structures. Polymers; Chemical Bonds; Physical Bond; Ionic Bond; Covalent Bond . At lower molecular weight, the polymer chains are loosely bonded by weak van der Waals forces and the chains can move easily, responsible for low strength,althoughcrystallinityispresent.Incaseoflargemolecularweight 5.5 INTERMOLECULAR FORCES A molecule is a group of atoms connected by covalent bonds. 8���O�$UJE���֤�Y[5/-ri>�e�r�y����F6���C�c�&m��]�rs�Z+u��j57�\{��&. The relatively simple band theory model must therefore be modified for polymers. Dispersion forces depend on the polarizability of a molecule. Larger molecules generally are more polarizable, so large polymers with high molecular weights can have significant dispersion forces. CHEMICAL BONDING AND MOLECULAR STRUCTURE 101 4.1 KÖSSEL-LEWIS APPROACH TO CHEMICAL BONDING In order to explain the for mation of chemical bond in terms of electrons, a number of attempts were made, but it was only in 1916 when Kössel and Lewis succeeded independently in giving a satisfactory explanation. Just as bonds can be polar, molecules can also be polar • Molecular polarity plays major role in: – solubility (like dissolves like), – reactivity (biochemical interactions) 1 POLYMERS Polymers are the high molecular weight compounds obtained by repeated union of simple molecules. ∞ is the tensile strength of the polymer with molecular weight of infinity. Molecular force and chemical bonding in Polymer. � 0000001256 00000 n h�b```f``�c`a`��� �� @ ��j�^�P��2��Z���Ǻ�=c�����u�ҭ�&G6000���9>�stt|""�$L΁��A���!����A��!����@��X���|@��ڛ������y��2 L拂ů�-N���ѣƸ����uy3�f�. 0000001473 00000 n • Secondary bonding exists between virtually all atoms or molecules, but its presence may be obscured if any of the three primary bonding types is present. Holds various constituents ( atoms or ions ) together in different chemical species here we show how macroscopic adhesion be! Ability to form chemical bonds ; physical bond ; Ionic bond ; covalent bond, so polymers. 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