POLYMER STRUCTURE AND CHARACTERIZATION

1 POLYMERSTRUCTURE ANDCHARACTERIZATIONP rofessor John A. NairnFall 2007 TABLE OF CONTENTS1 Definitions of Terms .. Course Goals ..52 POLYMER MOLECULAR Introduction .. Number Average Molecular Weight .. Weight Average Molecular Weight .. Other Average Molecular Weights .. A Distribution of Molecular Weights .. Most Probable Molecular Weight Distribution .. 123 MOLECULAR Introduction .. Nomenclature .. Property Calculation .. Freely-Jointed Chain.

2 Chain Analysis .. on Freely-Jointed Chain .. Equivalent Freely Jointed Chain .. Vector Analysis of POLYMER Conformations .. Freely-Rotating Chain .. Hindered Rotating Chain .. More Realistic Analysis .. Theta ( ) Temperature .. Rotational Isomeric State Model .. 484 RUBBER Introduction .. Historical Observations .. Thermodynamics .. Mechanical Properties .. Making Elastomers .. Elastomers .. Elastomers.

3 Elastomers .. 705 AMORPHOUS Introduction .. The Glass Transition .. Free Volume Theory .. Physical Aging .. 736 SEMICRYSTALLINE Introduction .. Degree of Crystallization .. Structures .. 75 Chapter 1 INTRODUCTIONThe topic of POLYMER STRUCTURE and CHARACTERIZATION covers molecular STRUCTURE of POLYMER molecules,the arrangement of POLYMER molecules within a bulk POLYMER material, and techniques used to giveinformation about STRUCTURE or properties of polymers.

4 The subjects are logically combined becauseunderstanding how STRUCTURE affects properties, as measured in CHARACTERIZATION , is a key element ofpolymer materials science and engineering. The subject of POLYMER STRUCTURE and characterizationis typically a second course in POLYMER science. As such it will be assumed that all students havecompleted, as a prerequisite, an introduction to POLYMER materials choose to subdivide POLYMER STRUCTURE into two areas. The first area is analysis of individualpolymer molecules.

5 Molecular STRUCTURE involves the detailed description of POLYMER molecules, theirmolecular weights, and their molecular configurations and conformations. Polymers are random-coil molecules that can exist in a variety of lengths, configurations, and conformations. We canlearn much about POLYMER materials purely by theoretical analysis of their conformations. Manyof the theoretical results can be verified by experiment, but most of our insight is gained by theprocess of doing the theoretical analysis and not by learning about techniques used to verify theanalysis.

6 The second area is the study of how individual POLYMER molecules pack into a solidmaterial to make a bulk POLYMER . POLYMER solids are either amorphous or semicrystalline. Anamorphous POLYMER means a non-crystalline material. A semicrystalline POLYMER means a mixtureof POLYMER single crystals ( POLYMER lamellae) and amorphous POLYMER . These components combineinto supramolecular structures that pack into the bulk material. A POLYMER s properties are stronglyaffected by whether or not is is semicrystalline.

7 For semicrystalline polymers, the properties arestrongly affected by the amount of crystalline material and the arrangement of the CHARACTERIZATION involves measuring any kind of property of a POLYMER material. Itincludes both molecular CHARACTERIZATION , such as molecular weight, microstructural information,degree of crystallinity,etc., and macroscopic property measurement, such as thermal properties,12 CHAPTER 1. INTRODUCTION mechanical properties, microstructural information, time dependence of properties, Polymercharacterization is done with a variety of experimental approaches.

8 Molecular CHARACTERIZATION usescommon methods from physical chemistry and often involves POLYMER solutions. Sometimes spec-troscopic methods can be used. Some common spectroscopic techniques are UV-visible absorptionspectroscopy, infrared spectroscopy (IR), Raman spectroscopy, nuclear magnetic resonance (NMR),electron spin resonance (ESR), and mass spectrometry (MS). These techniques are usually aimedat getting information about the chemical STRUCTURE of POLYMER materials. Macroscopic propertymeasurement is what might be referred to as conventional POLYMER CHARACTERIZATION .

9 It involvestaking a macroscopic POLYMER specimen, often in the final solid form, and doing experiments thatgive information about properties of that POLYMER . Some of the more important properties includethermal properties, mechanical and failure properties, melt viscosity, viscoelasticity properties,friction and wear properties, and electrical Definitions of TermsThe most basic definition is that of a POLYMER . Apolymeris molecule formed by covalent chemicalbonds between atoms (or groups of atoms) to give a large STRUCTURE (linear chains, branched chains,or cross-linked networks).

10 The key word is large. The wordpolymeris usually reserved for highmolecular weight molecules. Historically, the fact that polymers are molecules with ordinary chem-ical bonds ( , with chemical bonds identical to those found in low molecular weight molecules)was not recognized and polymers were once thought to be a distinct state of matter. Becausethis old thinking was wrong and instead polymers are large molecules (or macromolecules), we willfind that most of the principles of chemistry ( , chemical reactions) and physics ( , physicalproperties) apply to polymers just as they do to conventional molecules.