《高分子化学》课程教学资源（参考材料）Lecture Notes in Chemistry Volume 82《Principles of Polymer Design and Synthesis》

2.3 Measurement of Molecular Weight 23 (a) Solvent (b) Solvent flow Sample injection Separation- 。● beginning Partially- separated Fully- Elution separated Detection Elution Fig.2.11 Simple illustrations of the principle of gel permeation chromatography (GPC)[9]. (Adapted from I.M.Campbell,Introduction to Synthetic Polymers,Oxford,1994,p.26 with permission) smallest size molecules will be detected last.From the elution time of different size molecule,the molecular weight of the polymer can be calculated through the calibration curves obtained from polystyrene standard. For example,the synthesis of diblock copolymer:poly(styrene)-b-poly(2- vinylpyridine)(PS-b-P2VP)can be monitored by the GPC.Styrene is initiated by sec-butyl lithium first and then the polystyrene anion formed until the styrene monomer is completely consumed.Followed by introducing the 2-vinyl pyridine,a PS-b-P2VP block copolymer is finally prepared(Fig.2.12).As shown in Fig.2.13, the GPC results show that the PS anion was prepared first with low PDI(1.08). After adding the 2-VP,the PS-b-P2VP block copolymer was analyzed by GPC again,the PDI remained low,but the molecular weight has been doubled.More detailed discussions of anionic polymerizations will be present in Chap.8

smallest size molecules will be detected last. From the elution time of different size molecule, the molecular weight of the polymer can be calculated through the calibration curves obtained from polystyrene standard. For example, the synthesis of diblock copolymer: poly(styrene)-b-poly(2- vinylpyridine) (PS-b-P2VP) can be monitored by the GPC. Styrene is initiated by sec-butyl lithium first and then the polystyrene anion formed until the styrene monomer is completely consumed. Followed by introducing the 2-vinyl pyridine, a PS-b-P2VP block copolymer is finally prepared (Fig. 2.12). As shown in Fig. 2.13, the GPC results show that the PS anion was prepared first with low PDI (1.08). After adding the 2-VP, the PS-b-P2VP block copolymer was analyzed by GPC again, the PDI remained low, but the molecular weight has been doubled. More detailed discussions of anionic polymerizations will be present in Chap. 8. Fig. 2.11 Simple illustrations of the principle of gel permeation chromatography (GPC) [9]. (Adapted from I.M. Campbell, Introduction to Synthetic Polymers, Oxford, 1994, p. 26 with permission) 2.3 Measurement of Molecular Weight 23

24 2 Polymer Size and Polymer Solutions sec-Butyl Lithium PS-PVP Fig.2.12 Synthesis of PS-b-P2VP via anionic polymerization Fig.2.13 GPC traces of PS 200 homo polymer and PS-b- PS PDI-1.08 Mn=30.000 P2VP block copolymer.The PS-PVP PDI-1.I Mn=60.000 150 right peak is PS.The peak of copolymer is shifted to the left due to the addition of 100 P2VP 50 0 -50 0 5 10152025 30 35 Elusion Time(mins) 2.4 Problems 1.A "model"of a linear polyethylene having a molecular weight of about 200,000 is being made by using a paper clip to represent one repeating unit. How many paper clips does one need to string together? 2.In general,the viscosity of polymer is reduced by increasing temperature. How might the magnitude of this effect compare for the polymer in a "poor" solvent or in a "good"solvent?(This is the basis for all weather multi vis- cosity motor oils.) 3.From the practical standpoint,is it better to use a "good"solvent or a "poor" solvent when measuring polymer molecular weight?Explain. 4.Discuss the value of knowledge of the molecular weight and distribution of a polymer to the polymer scientist and engineer.Which method would you use to obtain this information on a routine basis in the laboratory and in the production respectively?Why?Which method would you use to obtain this information for a new polymer type which is not previously known?Why? 5.What would be the number average,weight average molecular weight and polydispersity of a sample of polypropylene that consists of 5 mol of 1000 unit propylene and 10 mol of 10,000 unit propylene? 6.A 0.5000-g sample of an unsaturated polyester resin was reacted with excess acetic anhydride.Titration of the reaction mixture with 0.0102 M KOH required 8.17 mL to reach the end point.What is the number average

2.4 Problems 1. A ‘‘model’’ of a linear polyethylene having a molecular weight of about 200,000 is being made by using a paper clip to represent one repeating unit. How many paper clips does one need to string together? 2. In general, the viscosity of polymer is reduced by increasing temperature. How might the magnitude of this effect compare for the polymer in a ‘‘poor’’ solvent or in a ‘‘good’’ solvent? (This is the basis for all weather multi vis￾cosity motor oils.) 3. From the practical standpoint, is it better to use a ‘‘good’’ solvent or a ‘‘poor’’ solvent when measuring polymer molecular weight? Explain. 4. Discuss the value of knowledge of the molecular weight and distribution of a polymer to the polymer scientist and engineer. Which method would you use to obtain this information on a routine basis in the laboratory and in the production respectively? Why? Which method would you use to obtain this information for a new polymer type which is not previously known? Why? 5. What would be the number average, weight average molecular weight and polydispersity of a sample of polypropylene that consists of 5 mol of 1000 unit propylene and 10 mol of 10,000 unit propylene? 6. A 0.5000-g sample of an unsaturated polyester resin was reacted with excess acetic anhydride. Titration of the reaction mixture with 0.0102 M KOH required 8.17 mL to reach the end point. What is the number average 0 5 10 15 20 25 30 35 Elusion Time (mins) -50 0 50 100 150 200 Intensity PS PDI~1.08 Mn=30,000 PS-PVP PDI~1.1 Mn=60,000 Fig. 2.13 GPC traces of PS homo polymer and PS-b￾P2VP block copolymer. The right peak is PS. The peak of copolymer is shifted to the left due to the addition of P2VP sec-Butyl Lithium + PS￾Li+ + N PS-PVP Fig. 2.12 Synthesis of PS-b-P2VP via anionic polymerization 24 2 Polymer Size and Polymer Solutions

2.4 Problems 25 Elution time (min.) Intensity 13.0 0.5 13.5 6.0 14.0 25.7 14.5 44.5 15.0 42.5 15.5 25.6 16.0 8.9 16.5 2.2 molecular weight of the polyester?Would this method be suitable for deter- mining any polyester?Explain. 7.Explain how one might experimentally determine the Mark-Houwink-Saku- rada constants K and a for a given polymer.Under what conditions can you use [n]to measure oM?How canoM be used to measure chain branching? 8.The molecular weight of poly(methyl methacrylate)was measured by gel permeation chromatography in tetrahydrofuran at 25C and obtained the above data: The polystyrene standard (PDI ~1.0)under the same conditions gave a linear calibration curve with M=98,000 eluting at 13.0 min.and M=1,800 eluting at 16.5 min. a.Calculate M and M using the polystyrene calibration curve. b.If the PDI of polystyrene is larger than 1.0,what errors you will see in the M and Mw of poly(methyl methacrylate). c.Derive the equation that defines the type of molecular weight obtained in the "universal"calibration method in gel permeation chromatography. 9.Please explain why the gel permeation chromatography method can measure both M and Mw,but the osmotic pressure method can only measure the Mm and the light scattering method can only measure M. 10.Please calculate the end-to-end distance of a polymer with molecular weight of 1 million and intrinsic viscosity of 2.10 dl/g and assume =2.1 X 1021. What is the solution behavior of this polymer?[10] References 1.G.Odian,Principle of Polymerization,4th edn.(Wiley Interscience,New York,2004) 2.M.P.Stevens.Polymer Chemistry.3rd edn.(Oxford,New York,1999) 3.P.A.Small,J.Appl.Chem.3,71-80(1953)

molecular weight of the polyester? Would this method be suitable for deter￾mining any polyester? Explain. 7. Explain how one might experimentally determine the Mark-Houwink-Saku￾rada constants K and a for a given polymer. Under what conditions can you use ½ g to measure r2 0M 1 ? How can r2 0M 1 be used to measure chain branching? 8. The molecular weight of poly(methyl methacrylate) was measured by gel permeation chromatography in tetrahydrofuran at 25C and obtained the above data: The polystyrene standard (PDI * 1.0) under the same conditions gave a linear calibration curve with M = 98,000 eluting at 13.0 min. and M = 1,800 eluting at 16.5 min. a. Calculate M w and M n using the polystyrene calibration curve. b. If the PDI of polystyrene is larger than 1.0, what errors you will see in the M n and M w of poly(methyl methacrylate). c. Derive the equation that defines the type of molecular weight obtained in the ‘‘universal’’ calibration method in gel permeation chromatography. 9. Please explain why the gel permeation chromatography method can measure both M n and M w, but the osmotic pressure method can only measure the M n and the light scattering method can only measure M w. 10. Please calculate the end-to-end distance of a polymer with molecular weight of 1 million and intrinsic viscosity of 2.10 dl/g and assume U ¼ 2:1 X 1021. What is the solution behavior of this polymer? [10] References 1. G. Odian, Principle of Polymerization, 4th edn. (Wiley Interscience, New York, 2004) 2. M.P. Stevens, Polymer Chemistry, 3rd edn. (Oxford, New York, 1999) 3. P.A. Small, J. Appl. Chem. 3, 71–80 (1953) Elution time (min.) Intensity 13.0 0.5 13.5 6.0 14.0 25.7 14.5 44.5 15.0 42.5 15.5 25.6 16.0 8.9 16.5 2.2 2.4 Problems 25

26 2 Polymer Size and Polymer Solutions 4.K.L.Hoy,J.Paint Tech.42,76-118 (1970) 5.J.Brandrup,E.H.Immergut (eds.),Polymer Handbook,3rd edn.(Wiley,New York,1989) 6.A.F.M.von Barton,CRC Handbook of Polymer-Liquid Interaction Parameters and Solubility Parameters (CRC Press,Boca Raton.1990) 7.P.J.Flory,Principles of Polymer Chemistry.(Cornell University,Ithaca,1953) 8.F.W.Billmeyer,Jr..Textbook of Polymer Science,3rd edn.(Wiley,New York,1984) 9.I.M.Campbell,Introduction to Synthetic Polymers.(Oxford University Press,Oxford,1994) 10.K.A.Peterson,M.B.Zimmt,S.Linse,R.P.Domingue,M.D.Fayer,Macromolecules 20, 168-175(1987)

4. K.L. Hoy, J. Paint Tech. 42, 76–118 (1970) 5. J. Brandrup, E.H. Immergut (eds.), Polymer Handbook, 3rd edn. (Wiley, New York, 1989) 6. A.F.M. von Barton, CRC Handbook of Polymer-Liquid Interaction Parameters and Solubility Parameters (CRC Press, Boca Raton, 1990) 7. P.J. Flory, Principles of Polymer Chemistry. (Cornell University, Ithaca, 1953) 8. F.W. Billmeyer, Jr., Textbook of Polymer Science, 3rd edn. (Wiley, New York, 1984) 9. I.M. Campbell, Introduction to Synthetic Polymers. (Oxford University Press, Oxford, 1994) 10. K.A. Peterson, M.B. Zimmt, S. Linse, R.P. Domingue, M.D. Fayer, Macromolecules 20, 168–175 (1987) 26 2 Polymer Size and Polymer Solutions

Chapter 3 Structure Morphology Flow of Polymer The chemical composition,configuration and molecular arrangement determine the structure of polymer.The physical structure of polymer is the morphology of polymer.The nonpolar polyethylene chain can be folded into ordered structure to have high crystallinity and exhibit good physical properties of toughness,strength, etc.The polar polymers as shown in Fig.3.1 exhibit intermolecular interactions that result in high crystallinity and exhibits good physical properties as well.There are some factors which affect polymer flow,such as temperature (kinetic energy), molecular weight (molecular entanglement),and molecular structure.The high crystalline polymer is usually difficult to process due to its high viscosity.The liquid crystalline polymer is an exception.It exhibits both excellent physical properties and low viscosity at liquid state (discuss later).The crosslinked polymer is obtained either by chemically bonding or physically bonding.The polymer is not crosslinked and is in liquid form for the ease of processing but it becomes crosslinked to have good mechanical strength after processing. 3.1 Chemical and Molecular Structure of Polymer The geometrical arrangement of the atoms in a polymer chain can be divided into two categories.The first category is configurational arrangements which are fixed by the chemical bonding in the molecule.The configuration of a polymer chain cannot be altered unless chemical bonds are broken and reformed.The second category is conformational arrangements which arise from the rotation of single bonds.Examples involving conformations of polymer chains include trans versus gauche arrangement of consecutive carbon-carbon single bonds and the helical arrangements found in some polymer crystal structures.Polymer configurations include head-to-head,tail-to-tail and head-to-tail arrangements in vinyl polymers, several stereoregular arrangements of 1,2-and 1,4-addition cis or trans isomers,or d and forms,and arrangements around asymmetric carbon atoms. Stereo-isomerism in polymers arises from different spatial arrangements (configurations)of the atoms or substituents in a molecule.Tacticity is the regularity W.-F.Su,Principles of Polymer Design and Synthesis, 27 Lecture Notes in Chemistry 82.DOI:10.1007/978-3-642-38730-2 3. Springer-Verlag Berlin Heidelberg 2013

Chapter 3 Structure Morphology Flow of Polymer The chemical composition, configuration and molecular arrangement determine the structure of polymer. The physical structure of polymer is the morphology of polymer. The nonpolar polyethylene chain can be folded into ordered structure to have high crystallinity and exhibit good physical properties of toughness, strength, etc. The polar polymers as shown in Fig. 3.1 exhibit intermolecular interactions that result in high crystallinity and exhibits good physical properties as well. There are some factors which affect polymer flow, such as temperature (kinetic energy), molecular weight (molecular entanglement), and molecular structure. The high crystalline polymer is usually difficult to process due to its high viscosity. The liquid crystalline polymer is an exception. It exhibits both excellent physical properties and low viscosity at liquid state (discuss later). The crosslinked polymer is obtained either by chemically bonding or physically bonding. The polymer is not crosslinked and is in liquid form for the ease of processing but it becomes crosslinked to have good mechanical strength after processing. 3.1 Chemical and Molecular Structure of Polymer The geometrical arrangement of the atoms in a polymer chain can be divided into two categories. The first category is configurational arrangements which are fixed by the chemical bonding in the molecule. The configuration of a polymer chain cannot be altered unless chemical bonds are broken and reformed. The second category is conformational arrangements which arise from the rotation of single bonds. Examples involving conformations of polymer chains include trans versus gauche arrangement of consecutive carbon–carbon single bonds and the helical arrangements found in some polymer crystal structures. Polymer configurations include head-to-head, tail-to-tail and head-to-tail arrangements in vinyl polymers, several stereoregular arrangements of 1,2- and 1,4-addition cis or trans isomers, or d and l forms, and arrangements around asymmetric carbon atoms. Stereo-isomerism in polymers arises from different spatial arrangements (configurations) of the atoms or substituents in a molecule. Tacticity is the regularity W.-F. Su, Principles of Polymer Design and Synthesis, Lecture Notes in Chemistry 82, DOI: 10.1007/978-3-642-38730-2_3, Springer-Verlag Berlin Heidelberg 2013 27