Introduction to physical polymer science

1. Introduction to physical polymer science 高物兴趣小组：沈璟 高材093班

2. INDEX • 2.5 Common Types of Copolymers • 2.6 NMR in Modern Research • 2.7 Multi-component Polymers • 2.8 Conformational States in Polymers • 2.9 Analysis of Polymers during Mechanical Strain • 2.10 Photo-physics of polymers • 2.11 Configuration and Conformation

3. 2.5 Common Types of Copolymers • Polymers with two or more kinds of mers. • Different kinds of polymers have differentmers. • Combined in different ways obtain different materials.

4. Some copolymer terminology

5. Statistical copolymers • Random copolymers • Alternating copolymers • Periodic copolymers

6. 2.6 NMR in Modern Research • 2.6.1 dilute solution studies : mer distribution. • In reality, not statistical/random copolymer but significant nonrandomness. • The order or lack of order  the physical and mechanical behavior. • “a series of copolymers of ethylene and 1-hexene.”

7. E ---ethylene, H---hexene.

8. The run number • Def 1.the average number of like mersequences. • 2.”runs”occurring in a copolymer per 100 mers.

9. 2.6 NMR in Modern Research • 2.6.2 high-resolution NMR in the solid state • Dilute solution :classical Fourier transform • Solid-state: • 1.dipolar decoupling crosspolarization (CP) • 2.high-powered decoupling (DD) • 3.magic-angle spinning techniques (MAS)

10. 2.7 Multi-component Polymers • Monomericunit mer chainslarge polymer structures (polymer alloys , polymer blends , multicomponent polymers) • Statistical , random , alternating , periodic.

11. block,graft,AB-crosslinked, • interpenetrating polymer networks • Other polymer-polymer combinations • Separation and identification of multicomponent polymers

12. 2.7.1 Block copolymer • An especially important block copolymer:SBS • polystyrene-block-polybutadiene-block-polystyrene • poly(styrene-b-butadiene-b-styrene) • -g-  -graft-

13. 2.7.2 Graft copolymers • A backbone species, a side-chain species. • If they are the same ,then “branched”. • Backbone: used in graft copolymer nomenclature to describe the chain onto which the graft is formed • Side chain: grafted chain in a graft copolymer

14. 2.7.3 AB-Cross-linked copolymers • Graft copolymer  the ideal case • When polymer B grafted at both ends of A • It’s a network ,not soluble.

15. Other polymer-polymer combination Semi-interpenetrating polymer networks interpenetrating polymer networks Star polymer,Star block copolymer,etc.

16. Terms • Conterminous : at both ends or at points along the chain. • Interpenetrating polymer network : intimate combination of two polymers both in network form, at least one of which is synthesized and /or cross-linked in the immediate presence of the other. • Semi- Interpenetrating polymer network

17. 2.7.6 separation and identification • The blends : extraction techniques • The graft and block : dissolve and flow on heating above Tf and/or Tg. • Most of the multicomponent polymer :phase separation

18. 2.8 Conformational States in Polymers Rotational potential energy diagram The gauche minus The gauche plus The trans

19. One surprising finding • The transitions occur in pairs. • reduce the motion of the long tail chains attached to the rotating segment.

20. 2.9 Analysis of Polymers during Mechanical Strain • Strain extrusion , molding , spinning , in service , under load. • Solid-state NMR,FTIR.

21. St-polypropylene chains oriented on stretching • In favor of the trans

22. The actual stretching of covalent bonds • At high strains • The backbone carbon atom bond distances increase . • Can this be observed instrumentally?

24. 2.10 Photo-physics of polymers • Electromagnetic energy :absorption , transfer , localization , and emission . • NO chemical reactions

25. 1. the absorption of electromagnetic energy A + hv = A* A is the molecule to be excited A* represents the excited state

26. 2.energy migration • mimics that observed in the ordered chlorophyll regions of green • plant chloroplasts • “the antenna chlorophyll” • “antenna effect.”

27. 2.10.1 Quenching Phenomena • A* +B = A + B* (a) chemical reaction(cross-linking, degradation, and rearrangement.) (b) enhancement of nonradiativedecay

28. (c) electronic energy transfer(absorbed as heat, emitted via fluorescence or phosphorescence) (d) complex formation. • exciplex (AB) *excimer (AA) * • Excited complex (dimer)

29. 2.10.2 Excimer formation • A* +A = (AA)* • (AA)* = 2A + hvE

30. Red-shifted

31. Geometry of the naphthalene excimer

32. 2.10.3 Experimental Studies • 2.10.3.1 Microstructure of Polystyrene • In dilute solutions,intramolecular rather than intermolecular. adjacent phenyl groups • In the bulk state, neighboring chains. • In atactic polystyrene, tt conformation or the tg- or g-t isomers

33. the ratio of excimeremission to single mer emission , ID/IM, increased from 10 to 100 times with increasing degree of tacticity .

34. 2.10.3.2 Excimer Stability • substituent groups: t-butyl groups

35. the groups away from ideal positions • Blue-shifted • Less stable

36. 2.11 CONFIGURATION and CONFORMATION • The configurationalproperties: crystallizable or NOT melting temperature The conformational properties: rotations about single bonds overall shape and size of the chain many of its motions

37. Both conformation and configuration contribute, albeit in different ways, to the behavior of the polymer.

38. Thanks for listening 